Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

FIP200, a ULK-interacting protein, is required for autophagosome formation in mammalian cells

FIP200, a ULK-interacting protein, is required for autophagosome formation in mammalian cells JCB: ARTICLE FIP200, a ULK-interacting protein, is required for autophagosome formation in mammalian cells 1 1 1 2 2 3 Taichi Hara , Akito Takamura , Chieko Kishi , Shun-ichiro Iemura , Tohru Natsume , Jun-Lin Guan , 1,4 and Noboru Mizushima Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8549, Japan Biological Information Research Center, National Institutes of Advanced Industrial Science and Technology, Kohtoh-ku, Tokyo 135-0064, Japan Department of Internal Medicine-MMG, University of Michigan Medical School, Ann Arbor, MI 48109 Solution Oriented Research for Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan utophagy is a membrane-mediated intracellular identifi ed the focal adhesion kinase family interacting degradation system. The serine/threonine kinase protein of 200 kD (FIP200), which regulates diverse cellu- A Atg1 plays an essential role in autophagosome lar functions such as cell size, proliferation, and migra- formation. However, the role of the mammalian Atg1 ho- tion. We found that FIP200 was redistributed from the mologues UNC-51 – like kinase (ULK) 1 and 2 are not yet cytoplasm to the isolation membrane under starvation well understood. We found that murine ULK1 and 2 local- conditions. In FIP200-defi cient cells, autophagy induction ized to autophagic isolation membrane under starvation by various treatments was abolished, and both stability conditions. Kinase-dead alleles of ULK1 and 2 exerted a and phosphorylation of ULK1 were impaired. These results dominant-negative effect on autophagosome formation, suggest that FIP200 is a novel mammalian autophagy fac- suggesting that ULK kinase activity is important for auto ph- tor that functions together with ULKs. agy. We next screened for ULK binding proteins and Introduction Autophagy is a primary route by which cytoplasmic contents The molecular mechanism of autophagy has been revealed are directed to the lysosome to be degraded ( Cuervo, 2004 ; by genetic analyses performed in yeast ( Klionsky, 2005 ; Suzuki Levine and Klionsky, 2004 ; Rubinsztein, 2006 ; Mizushima, and Ohsumi, 2007 ), in which 31 autophagy-related ATG genes 2007 ; Mizushima et al., 2008 ). There are three types of auto ph- have been identifi ed so far. Among these genes, Atg1 – 10, 12 – 14, agy: macroautophagy, microautophagy, and chaperone-mediated 16 – 18, 29, and 31 (collectively called AP-Atg) are required for autophagy. Among them, only macroautophagy (referred to autophagosome formation. In yeast, autophagosomes are generated as autophagy hereafter) is mediated by the autophagosome. at a special site near the vacuolar membrane, called the preauto ph - Upon induction of autophagy, a membrane cisterna called the agosomal structure (PAS), where most AP-Atg proteins are re- isolation membrane (also termed the phagophore) enwraps a cruited ( Kim et al., 2001a ; Suzuki et al., 2001 ; Suzuki and Ohsumi, portion of cytoplasm to generate an autophagosome. The au- 2007 ). Although autophagy requires only these AP-Atg proteins, tophagosome then fuses with an endosome and, fi nally, with the an autophagy-related pathway called cytoplasm-to-vacuole tar- lysosome, leading to degradation of cytoplasm-derived mate- geting (Cvt) pathway, which delivers two vacuolar enzymes, amino - rials sequestered inside the autophagosome. Although auto ph- peptidase 1 and  -mannosidase 1, from the cytoplasm to the agy occurs at low levels under normal conditions ( Hara et al., vacuole, requires almost all Atg proteins except Atg17, 29, and 31. 2006 ; Komatsu et al., 2006 ), autophagy is extensively activated AP-Atg proteins are classifi ed into six functional groups: under starvation conditions ( Mizushima and Klionsky, 2007 ). the Atg1 protein kinase complex; the Atg2 – Atg18 complex; the Atg8 conjugation system; the Atg12 conjugation system; Correspondence to Noboru Mizushima: nmizu.phy2@tmd.ac.jp the Atg14 – phosphatidylinositol 3-kinase complex; and Atg9 Abbreviations used in this paper: Cvt, cytoplasm-to-vacuole targeting; E, embry- ( Suzuki et al., 2007 ). Among these functional units, the Atg1 onic day; FIP200, FAK family – interacting protein of 200 kD; MEF, mouse embry- complex has a unique feature: it apparently receives the starva- onic fi broblast; mTOR, mammalian target of rapamycin; PAS, preautophagosomal structure; PE, phosphatidylethanolamine; ULK, UNC-51 – like kinase. tion signals. Atg1 is a serine/threonine protein kinase, and its The online version of this paper contains supplemental material. kinase activity can be up-regulated after autophagy-inducible © 2008 Hara et al. The Rockefeller University Press $30.00 J. Cell Biol. Vol. 181 No. 3 497–510 JCB 497 www.jcb.org/cgi/doi/10.1083/jcb.200712064 THE JOURNAL OF CELL BIOLOGY treatments such as nutrient starvation or rapamycin treatment tinct partners. Indeed, C. elegans UNC-51 interacts with UNC-14, ( Kamada et al., 2000 ). The kinase activity of Atg1 is believed to a protein involved in coordinated movement ( Ogura et al., be required for autophagy, although there have been debates 1997 ). In mammals, ULK1 interacts with SynGAP, a negative ( Kamada et al., 2000 ; Abeliovich et al., 2003 ; Kabeya et al., regulator of Ras, and Syntenin, a Rab5-interacting protein 2005 ; Cheong et al., 2008 ). The Atg1 complex includes Atg13, ( Tomoda et al., 2004 ). These interactions have been suggested Atg17 ( Kamada et al., 2000 ), Atg29 ( Kawamata et al., 2008 ), to be important for axon guidance/elongation. Another recent Atg31/Cis1 ( Kabeya et al., 2007 ), Atg11/Cvt9 ( Kim et al., 2001b ), paper also suggested that ULK1 is recruited to the TrkA – NGF Atg24/Cvt13 ( Nice et al., 2002 ), Atg20/Cvt20 ( Nice et al., 2002 ), receptor complex by p62 and regulates non – clathrin-coated and Vac8 ( Scott et al., 2000 ). Atg17 ( Kamada et al., 2000 ), 29 endocytosis in growth cones, fi lopodia extension, and branching ( Kawamata et al., 2005 ), and 31 ( Kabeya et al., 2007 ) are specifi - ( Zhou et al., 2007 ). However, homologues of the yeast Atg1- cally involved in autophagy, whereas Atg11, Atg20, Atg24, and interacting autophagy proteins have not been reported in higher Vac8 are specifi cally required for the Cvt pathway. Atg13 and 1 eukaryotes (except for plant Atg13; Hanaoka et al., 2002 ). are involved in both pathways. A recent systematic analysis re- To better understand the role of the Atg1/ULK family, we vealed that Atg17 and 11 are essential for PAS organization, and screened for ULK-interacting proteins and identifi ed the FAK Atg17 has been suggested to behave as a scaffold protein ( Suzuki family – interacting protein of 200 kD (FIP200), which is also et al., 2007 ). The Atg1 – Atg17 interaction largely depends on called RB1CC1 (retinoblastoma 1 – inducible coiled-coil 1). Atg13 ( Cheong et al., 2005 ; Kabeya et al., 2005 ), but a yeast two- FIP200 was reported to interact with multiple proteins, including hybrid analysis suggested that Atg1 and 17 can also directly FAK ( Abbi et al., 2002 ), Pyk2 ( Ueda et al., 2000 ), TSC1 ( Gan interact with each other ( Cheong et al., 2005 ). Interactions be- et al., 2005 ), p53 ( Melkoumian et al., 2005 ), ASK1, and TRAF2 tween Atg13, 1, and 17 are enhanced by starvation treatment, and ( Gan et al., 2006 ), thereby regulating a variety of cellular func- both Atg13 and 17 are important for proper regulation of Atg1 tions such as cell migration, proliferation, cell size, and apopto- kinase activity ( Kamada et al., 2000 ; Kabeya et al., 2005 ). sis. FIP200 was also independently identifi ed as a novel inducer The function of the Atg17 – Atg13 – Atg1 complex has yet of RB1. We found that ULK1, ULK2, and FIP200 are present on to be fully understood. Although Atg1 and 13 sense nutrient con- autophagic isolation membrane. Using FIP200 mouse embry- ditions, this complex does not appear to function as a simple onic fi broblasts (MEFs), we revealed that FIP200 is a novel mam- transducer of starvation signaling. For example, Atg1 is required malian autophagy factor that functions together with ULKs. for a late step of micropexophagy in Pichia pastoris ( Mukaiyama et al., 2002 ) and for the Cvt pathway, which is a constitutive bio- Results synthetic pathway proceeding under nutrient-rich conditions ( Kamada et al., 2000 ; Abeliovich et al., 2003 ). Furthermore, ULK1 and ULK2 localize on the isolation Atg1 is known to be important for retrieval of Atg9 and 23 from membrane (phagophore) PAS ( Reggiori et al., 2004 ). We found four ULK homologues in the mouse database. Homologues of Atg1 have been found in other species Although ULK1 and 2 are closely related to C. elegans UNC51, such as Dictyostelium discoideum ( Otto et al., 2004 ), Cae- ULK3 and 4 show similarity to UNC51 only in the kinase norhabditis elegans ( Ogura et al., 1994 ; Melendez et al., 2003 ), domain (Fig. S1, available at http://jcb.org/cgi/content/full/jcb Drosophila melanogaster ( Scott et al., 2004 ), Arabidopsis thali- .200712064/DC1). We therefore analyzed the role of ULK1 ana ( Hanaoka et al., 2002 ), and mammals ( Yan et al., 1998, and 2 in autophagosome formation. We fi rst determined the sub- 1999 ). Mutants of Atg1 in the species examined thus far indeed cellular distribution of ULK1 and 2 using NIH3T3 cells stably exhibit autophagy-defective phenotypes ( Melendez et al., 2003 ; expressing ULKs fused with GFP at the N terminus (GFP-ULK1 Otto et al., 2004 ; Scott et al., 2004 ; Chan et al., 2007 ). and GFP-ULK2). Under nutrient-rich conditions, GFP-ULK1 In metazoa, however, the role of Atg1 seems not to be and GFP-ULK2 were mostly found to distribute evenly through- limited to macroautophagy. C. elegans Atg1 is known as UNC out the cytoplasm, with few punctuate dots ( Fig. 1, A and B , (uncoordinated movement)-51. The unc-51 mutants show neuro- complete). We occasionally observed GFP-ULK1 and -ULK2 at logical abnormalities such as paralysis and defects in axonal the ruffl ed membrane in some cells (Fig. S2). After amino acid elongation ( Ogura et al., 1994 ). In mammals, two Atg1 homo- and serum starvation, GFP-ULK1 and -ULK2 localized to punc- logues have been reported: UNC-51 – like kinase (ULK) 1 (also tuate structures ( Fig. 1, A and B , starvation). These punctuate known as Unc51.1; Yan et al., 1998 ; Tomoda et al., 1999 ) and structures immediately disappeared after replenishment with nu- ULK2 (also known as Unc51.2; Tomoda et al., 1999 ; Yan et al., trient medium ( Fig. 1, A and B , starvation → complete). As previ- 1999 ). RNAi-mediated suppression of ULK1 expression alone ously reported ( Chan et al., 2007 ), these data suggest that ULK1 is suffi cient to inhibit autophagy ( Chan et al., 2007 ) and re- and 2 are targeted to autophagy-related structures. We then ex- distribution of mAtg9 from the TGN to endosomes ( Young amined the localization of GFP-ULK in more detail and found that et al., 2006 ). In addition to the autophagy phenotype, a dominant- both ULK1 and 2 colocalized with endogenous Atg16L1 almost negative form of ULK1, K46R, suppresses neurite extension of completely ( Fig. 1, C and D ). Because Atg16L1, together with cerebellar granular neurons ( Tomoda et al., 1999 ), which is con- the Atg12 – Atg5 conjugate, specifi cally localizes to elongating sistent with the neurological phenotype of the unc-51 worm. isolation membrane (also called the phagophore; Mizushima The observations that Atg1 is a multifunctional protein et al., 2001 ), these data suggest that both ULK1 and 2 are tar- suggest that Atg1 should function in concert with several dis- geted to the isolation membrane. 498 JCB • VOLUME 181 • NUMBER 3 • 2008 Figure 1. ULK1 and 2 localize to the isola- tion membrane (phagophore) under starvation conditions. (A and B) NIH3T3 cells stably ex- pressing GFP-ULK1 (A) and -ULK2 (B) were cul- tured in complete or starvation medium for 30 min. They were then cultured in fresh complete medium for an additional 30 min (starvation → complete). (C and D) NIH3T3 cells stably ex- pressing GFP-ULK1 (C) and -ULK2 (D) were cul- tured in starvation medium for 120 min. The cells were fi xed, permeabilized, and subjected to immunofl uorescence microscopy using anti- Atg16L1 antibody and Alexa Fluor 660 – con- jugated secondary antibody. More than 90% of GFP-ULKs dots were positive for Atg16L1. (E – H) Wild-type (E and G) and Atg5 (F and H) MEFs were transfected with retroviral vectors encoding GFP-ULK1 and -ULK2. MEFs stably expressing GFP-ULK1 (E and F) and -ULK2 (G and H) were cultured in complete or starvation medium for 120 min. The cells were fi xed and examined by fl uorescence micros- copy. Bars, 20 μ m. In yeast, Atg1 localizes to the PAS independently of Atg5 Kinase-dead ULK mutants inhibit autophagy ( Suzuki et al., 2007 ). Although it is not clear whether mamma- In yeast, Atg1 kinase activity is up-regulated during autophagy lian cells have a similar PAS, we examined whether the puncta induced by nitrogen starvation or Tor inactivation ( Kamada formation of ULKs was independent of Atg5. Wild-type and et al., 2000 ). However, it is not known whether this is the case in Atg5 MEFs were transfected with retroviral vectors encod- mammalian cells. We therefore determined ULK kinase activity ing GFP-ULK1 ( Fig. 1, E and F ) and -ULK2 ( Fig. 1, G and H ) in MEFs under nutrient-rich and starved conditions. Endog- and observed after starvation. Although both GFP-ULK1 and enous ULK1 was precipitated with anti-ULK1 antibody, and -ULK2 puncta were formed in wild-type MEFs ( Fig. 1, E and G ), the resultant immunoprecipitate was analyzed by an in vitro these dots were never observed in Atg5 MEFs ( Fig. 1, F and H ). kinase assay using myelin basic protein as a model substrate. These results suggest that ULK puncta formation is dependent The ULK1 kinase activity level under the starvation condition is on Atg5 in mammalian cells. increased 1.3-fold relative to the nutrient-rich condition ( Fig. 2 A ). ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 499 Although this change was modest, these data suggest that the increase in ULK1 kinase activity might be important for the in- duction of autophagosome formation. We next examined the importance of the ULK kinase activ- ity using ULK kinase-dead mutants. Overexpression of kinase- dead Atg1 mutants inhibits autophagy in D. discoideum ( Tekinay et al., 2006 ) and D. melanogaster ( Scott et al., 2007 ), whereas overexpression of wild-type Atg1 accelerates autophagy in D. melanogaster ( Scott et al., 2007 ). However, in mammalian cells, both wild-type and kinase-dead ULK1 suppress autophagy, as judged by the LC3 conversion assay ( Chan et al., 2007 ). We therefore carefully examined the effect of wild-type and kinase- dead mutants of ULK1 and 2 on Atg16L1 puncta formation. In transient transfection experiments, moderate expression of K46N K39T kinase-dead HA-ULK1 ( Yan et al., 1998 ) and HA-ULK2 ( Yan et al., 1999 ) effi ciently suppress the starvation-induced Atg16L1 puncta formation ( Fig. 2 C ), whereas wild-type ULK1 and 2 showed almost no effect ( Fig. 2 B ; note that HA-ULK dots are not as clear as those in stable transformants [ Fig. 1 ] because of high cytoplasmic signals caused by overexpression). In con- trast, when overexpressed in higher levels, both wild-type and kinase-dead ULKs suppressed Atg16L1 puncta formation (un- published data). The shape of wild-type ULK-overexpressing cells was abnormal (Fig. S3, available at http://jcb.org/cgi/content/full/ jcb.200712064/DC1), as previously demonstrated by Chan et al. (2007) . The cells generated protrusions and, fi nally, detached from the culture dish, which is consistent with the previous results in D. melanogaster that Atg1 overexpression caused apoptotic cell death ( Scott et al., 2007 ). However, these abnormalities were not observed in cells overexpressing kinase-dead ULK1 and 2 (Fig. S3). Therefore, the effects of overexpression of wild-type and kinase-dead ULKs are different. The kinase-dead mutants indeed act as dominant-negative mutants, whereas wild-type overexpres- sion may cause cytotoxicity by some other mechanism. Collec- tively, these data suggest that the kinase activity is important for the involvement of ULKs in autophagy. We also generated NIH3T3 cells stably expressing GFP- K46N K39T ULK1 and GFP-ULK2 . Although both Atg16L1 and GFP-ULKs formed puncta in wild-type NIH3T3 cells after star- vation, these puncta were only very rarely observed in NIH3T3 K46N K39T cells stably expressing GFP-ULK1 or GFP-ULK2 ( Fig. 2 D ), confi rming that kinase-dead ULKs function as a dominant- negative mutant in autophagosome formation. We next measured this effect by the LC3 conversion as- say. Conversion of cytosolic LC3 (LC3-I) to membrane-bound phosphatidylethanolamine (PE) – conjugated LC3 (LC3-II) oc- curs during autophagy, and the amount of LC3-II is correlated with the number of autophagosomes ( Kabeya et al., 2000 ). This Figure 2. The kinase-dead ULK mutants inhibit autophagy. (A) In vitro LC3 conversion during starvation was markedly suppressed in kinase assay of endogenous ULK1. MEFs were cultured in complete or K46N NIH3T3 cells stably expressing ULK1 ( Fig. 2 E ), as recently starvation medium for 60 min. ULK1 kinase activity was determined as de- scribed in Materials and methods. Relative kinase activity is shown. Data are the mean ± SE of fi ve independent experiments. (B and C) NIH3T3 cells were transiently transfected with HA-ULK1, HA-ULK2, or their kinase- dead mutants and subjected to immunofl uoresence microscopy using cultured in starvation medium for 120 min. The cells were subjected to monoclonal anti-HA and polyclonal anti-Atg16L1 antibodies for primary immunofl uorescence microscopy using anti-Atg16L1 antibody. Bar, 20 μ m. staining and Alexa Fluor 488 – conjugated goat anti – mouse IgG and (E) NIH 3T3 cells were transfected with the retroviral vectors encoding HA- K46N Alexa Fluor 568 – conjugated goat anti – rabbit IgG antibodies for second- ULK1 or with the corresponding empty retrovirus (mock). They were ary antibodies. Transfected cells are indicated by arrows. Bars, 20 μ m. cultured in complete or starvation medium for 120 min. Cell lysates were K46N K39T (D) NIH3T3 cells stably expressing GFP-ULK1 and GFP-ULK2 were then analyzed by immunoblot analysis with the indicated antibodies. 500 JCB • VOLUME 181 • NUMBER 3 • 2008 Figure 3. ULK1 interacts with FIP200. (A) HEK293T cells were cotransfected with FLAG-FIP200 and HA-ULKs. Cell lysates were subjected to immuno- precipitation (IP) using antibodies against FLAG. The resulting precipitates were examined by immunoblot (IB) analysis with the indicated antibodies. The as- terisk indicates nonspecifi c band. (B) Lysates of MEFs were immunoprecipitated with anti-ULK1 or anti-FIP200 antibody or preimmune rabbit serum, and the resulting precipitates were subjected to immunoblot analysis with antibodies against ULK1 and FIP200. (C) Schematic representation of ULK1 mutants used in D. (D) HEK293T cells were cotransfected with FLAG-FIP200 and various ULK1 mutants and analyzed as in A using anti-HA and anti-FLAG antibodies. (E) NIH3T3 cells stably expressing GFP-ULK1 (left) and GFP-ULK1 (right) were cultured in starvation medium for 120 min. Bar, 20 μ m. reported by Chan et al. (2007) . Another assay was conducted the role of ULK, we searched for additional ULK-interacting to monitor autophagy fl ux. Because p62 (SQSTM1/sequesto- proteins. Mouse ULK1-FLAG and FLAG-ULK2 were expressed some 1) can bind LC3, p62 is preferentially incorporated into in HEK293 cells and immunoprecipitated with an anti-FLAG autophagosomes and degraded by autophagy ( Bj ø rk ø y et al., antibody. We analyzed the immunoprecipitates by highly sensi- 2005 ; Mizushima and Yoshimori, 2007 ). The amount of p62 can tive direct nanofl ow liquid chromatography/tandem mass spec- therefore serve as a good indicator of autophagic activity. The trometry ( Natsume et al., 2002 ) and identifi ed FIP200, which K46N base level of p62 was up-regulated in ULK1 -transfected is also called RB1CC1, in both the ULK1 and 2 precipitates. cells compared with mock-transfected cells. Although the level We confi rmed the interaction of FIP200 with ULK1 and 2 by of p62 decreased during starvation in mock-transfected cells, immunoprecipitation analysis using HEK293T cells coexpress- K46N the decrease was modestly suppressed in ULK1 -transfected ing FLAG-FIP200 and either HA-ULK1 or -ULK2 ( Fig. 3 A ). cells. These data suggest that autophagic fl ux was attenuated by Furthermore, we generated antibody against FIP200 and detected expression of the kinase-dead ULKs. the interaction between endogenous ULK1 and FIP200 in wild- type MEFs ( Fig. 3 B ). This coprecipitation was not observed Identifi cation of FIP200 if we performed the same experiments using FIP200 MEFs. as a ULK-interacting protein The interaction between ULK1 and FIP200 was not affected by In yeast, Atg1 forms a complex with multiple proteins including nutrient conditions, suggesting that ULK1 and FIP200 physically Atg13 and 17. However, a different set of ULK-interacting pro- interact with each other under both nutrient-rich and starvation teins has been reported in mammals that includes GABARAP, conditions ( Fig. 3 B ). GATE-16 ( Okazaki et al., 2000 ), SynGAP, and Syntenin ( Tomoda We next determined which region of ULK1 is required et al., 2004 ) but not other Atg homologues. To better understand for the interaction with FIP200, using several ULK1 mutants ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 501 Figure 4. FIP200 localizes to phagophore after starvation treatment. (A) NIH3T3 cells stably ex- pressing GFP-FIP200 were cultured in complete or starvation medium for 120 min and the GFP signal was observed. (B) NIH3T3 cells stably expressing GFP-FIP200 were cultured in starvation medium for 120 min and then subjected to immunofl uorescence microscopy using anti-Atg16L1 antibody and Alexa Fluor 568 – conjugated secondary antibody. Bars, 20 μ m. More than 90% of GFP-FIP200 dots were positive for Atg16L1. (C) NIH3T3 cells stably expressing GFP- ULK1 were starved for 120 min and then subjected to immunofl uorescence microscopy using anti-FIP200 antibody and Alexa Fluor 568 – conjugated secondary antibody. Black squares indicate the enlarged areas shown in insets. Bar, 20 μ m. K46N ( Fig. 3 C ). Although kinase-dead ULK1 could interact with acid and serum starvation, however, the number of these dots 1 – 427 FIP200, the C-terminal deletion mutants (ULK1 and increased. These GFP-FIP200 – positive dots were almost com- 1 – 828 ULK1 ) could not ( Fig. 3 D ). The C-terminal deletion mu- pletely colocalized with Atg16L1 ( Fig. 4 B ). Furthermore, we 1 – 828 tant ULK1 also failed to accumulate to punctuate dots ( Fig. observed almost complete colocalization between GFP-ULK1 3 E ). Thus, the C-terminal region (829 – 1051 aa) of ULK1 is re- and endogenous FIP200 ( Fig. 4 C ). All these data suggest that quired for both ULK-FIP200 interaction and puncta formation. FIP200 localizes to elongating isolation membrane together with ULKs. FIP200 localizes to the isolation membrane FIP200, a ubiquitously expressed protein ( Bamba et al., 2004 ), FIP200 is required for autophagy was originally identifi ed as a Pyk2 (proline-rich tyrosine kinase The isolation membrane localization of FIP200 prompted us to 2)-interacting protein ( Ueda et al., 2000 ). FIP200 binding in- further examine its role in autophagy. FIP200 is known to be hibits Pyk2 kinase activity, thereby inhibiting Pyk2-induced essential for embryonic development. FIP200 mice show apoptosis. FIP200 also associates with FAK as a negative regula- embryonic lethality between embryonic day (E) 13.5 and 16.5 tor ( Abbi et al., 2002 ). Additionally, FIP200 interacts with multi- because of defective heart and liver development ( Gan et al., ple proteins such as TSC1 ( Gan et al., 2005 ), p53 ( Melkoumian 2006 ). We therefore examined the autophagic activity of MEFs et al., 2005 ), ASK1, and TRAF2 ( Gan et al., 2006 ). FIP200 also derived from FIP200 embryos. In wild-type MEFs, 1 h of induces RB1 expression ( Chano et al., 2002a ). Therefore, FIP200 amino acid and serum starvation induced LC3 conversion, is a multifunctional protein that is involved in cell migration, which was restored by an additional 1-h incubation in com- proliferation, cell size regulation, cell death, and tumor suppres- plete DME supplemented with 10% FCS ( Fig. 5 A ). In con- sion. However, its involvement in autophagy or membrane traf- trast, the starvation-induced LC3 conversion was almost fi cking has not been reported. completely abolished in FIP200 MEFs. Furthermore, p62 To investigate the functional relevance of FIP200 in accumulated in FIP200 MEFs, suggesting that autophagy autophagosome formation, we fi rst examined the subcellular is profoundly suppressed in the absence of FIP200. It should localization of FIP200. FIP200 has been previously reported to be noted, however, that a small amount of LC3-II was detected localize to the nucleus ( Chano et al., 2002a ), cytoplasm ( Ueda in FIP200 MEFs irrespective of nutrient conditions. This et al., 2000 ), and focal contacts in the cell periphery ( Abbi et al., phenotype was quite different from that of Atg5 MEFs, in 2002 ). When we observed NIH3T3 cells transfected with a retro- which LC3-II was never detected ( Fig. 5 A ). These results sug- virus vector encoding GFP-fused FIP200 under nutrient-rich gest either that low-level autophagy constitutively occurs in conditions, most GFP signals were detected diffusely in the FIP200 MEFs or that LC3 conversion occurs independently cytoplasm, with only a few punctate dots ( Fig. 4 A ). After amino of autophagy. 502 JCB • VOLUME 181 • NUMBER 3 • 2008 +/+  /  +/+  / Figure 5. FIP200 is required for autophagy. (A) FIP200 , FIP200 , Atg5 , and Atg5 MEFs were cultured in complete or starvation medium for 60 min. In the recovery experiments, starved MEFs were cultured in fresh complete medium for an additional 60 min (replenishment). The cell lysates were subjected to immunoblot analysis with the indicated antibodies. (B) Wild-type and FIP200 MEFs were cultured in the complete or starvation medium for indicated time with or without 100 nM bafi lomycin A . The cell lysates were subjected to immunoblot analysis with anti-LC3 antibody. (C) Wild-type and FIP200 MEFs were transfected with retroviral vectors encoding GFP-Atg5 or GFP-LC3. Resulting cells were cultured in the starvation medium for 120 min. The cells were fi xed and examined by fl uorescence microscopy. Bar, 20 μ m. (D – G) Wild-type (D and E) and FIP200 (F and G) MEFs were cultured in complete (D and F) or starvation (E and G) medium for 120 min and then fi xed and subjected to EM analysis. Autophagosome-like structures (open arrowheads), and autolysosomes (closed arrowheads) are indicated. Bar, 1 μ m. (H) The ratio of total area of autophagosomes (AP) and autolysosomes (AL) to total cytoplasmic area in D – G was determined by morphometric analysis. To monitor the autophagic ability of FIP200 MEFs toring the redistribution of cytosolic GFP-Atg5 and GFP-LC3 more precisely, we determined the autophagy fl ux in these cells to membrane structures. After a 2-h culture in amino acid- by the LC3 turnover assay ( Tanida et al., 2005 ; Mizushima and and serum-deprived medium, several GFP-Atg5 and GFP- Yoshimori, 2007 ). Because LC3-II is present on both outer and LC3 dots were observed in wild-type MEFs ( Fig. 5 C , left). inner autophagosome membranes, LC3-II itself is degraded after In FIP200 cells, however, these GFP-Atg5 – positive dots autophagosome-lysosome fusion. If autophagosome-lysosome were completely absent ( Fig. 5 C , right, top). The number of fusion is blocked with the vacuolar H ATPase inhibitor bafi lo- GFP-LC3 dots was greatly reduced, but several GFP-LC3 – mycin A ( Yamamoto et al., 1998 ), autophagic degradation of positive dots were still observed in FIP200 cells ( Fig. 5 C , LC3-II should be suppressed. This treatment indeed caused ac- right, bottom). However, these dots were irregular in shape, cumulation of LC3-II in 2-h and 4-h starved wild-type MEFs and their number did not change after starvation treatment ( Fig. 5 B ). However, this effect of bafi lomycin A was not ob- (unpublished data). These structures therefore likely represent served in FIP200 MEFs e ven after 4-h starvation, suggesting some aberrant structures or aggregates of GFP-LC3 protein that autophagic degradation is suppressed almost completely in caused by FIP200 defi ciency. To further confi rm the effect of these cells. loss of FIP200 on autophagosome formation, we performed We also examined autophagy induction in wild-type and EM analysis. In wild-type MEFs after a 2-h starvation, we FIP200 MEFs stably expressing GFP-Atg5 (isolation mem- could detect numerous autophagic vacuoles, which occupied brane marker) or GFP-LC3 (autophagosome marker) by moni-  3% of the total cytoplasmic volume (  2% autophagosomes ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 503 +/   / Figure 6. FAK is not required for autophagy. (A) FAK and FAK MEFs were cultured in the complete or starvation medium for the indicated times +/   / with or without 100 nM bafi lomycin A . The cell lysates were subjected to immunoblot analysis with the indicated antibodies. (B) FAK and FAK MEFs stably expressing GFP-LC3 were cultured in complete or starvation medium for 120 min. The cells were fi xed and examined by fl uorescence microscopy. (C) Wild-type MEFs stably expressing GFP-FAK were cultured in complete or starvation medium for 120 min. The cells were fi xed and subjected to immuno- fl uorescence microscopy using anti-Atg16 antibody. Black squares indicate the enlarged areas shown in insets. Bars, 20 μ m. and  1% autolysosomes; Fig. 5, D, E, and H ). In contrast, auto - FIP200 functions downstream of ph agosome-like structures were hardly observed in FIP200 mammalian target of rapamycin (mTOR) in MEFs even under amino acid and serum starvation conditions autophagosome formation ( Fig. 5, F, G, and H ). These results demonstrate that FIP200 is FIP200 interacts with TSC1 and inhibits its function ( Gan et al., required for autophagosome formation. 2005 ). The TSC1-TSC2 heterodimer inhibits mTOR function through Rheb inactivation ( Inoki and Guan, 2006 ; Wullschleger The role of FIP200 in autophagy is et al., 2006 ; Guertin and Sabatini, 2007 ). As autoph agy is nega- independent of FAK tively regulated by mTOR signaling ( Meijer and Codogno, FIP200 can bind FAK and inhibit FAK function. FAK is one of 2004 ), we investigated whether the autophagy defect of FIP200 the focal adhesion components that include multiple proteins MEFs is a result of aberrant TSC-mTOR signaling. If this were such as vinculin, paxillin, and talin ( Carragher and Frame, the case, autophagy should be induced by treatment with the 2004 ). In addition, while we were preparing this manuscript, it mTOR inhibitor rapamycin. In wild-type MEFs, rapamycin was reported that paxillin also acts as a regulator of autophagy induced LC3 conversion both in the absence and presence of ( Chen et al., 2007 ). On that basis, we investigated the potential bafi lomycin A . However, the LC3 conversion induced by rapa- /   / role of FAK in autophagy using FAK MEFs ( Ilic et al., 1995 ). mycin was still impaired in FIP200 MEFs ( Fig. 7 A ). We also As far as we tested, FAK MEFs demonstrated no abnormal- observed that rapamycin was able to induce GFP-Atg5 and ities related to autophagy. Starvation-induced LC3 conversion GFP-LC3 dot formation in wild-type MEFs but not in FIP200 with and without bafi lomycin A and starvation-induced p62 MEFs ( Fig. 7 B ). Furthermore, mTOR appeared to be normally degradation in the lysosome were normal ( Fig. 6 A ). There was suppressed in FIP200 MEFs after serum and amino acid also no difference in starvation-induced GFP-LC3 dot forma- starvation, as judged by 4E-BP1 dephosphorylation, despite the +/   / tion between FAK and FA K MEFs ( Fig. 6 B ). Addition- suppression of autophagy ( Fig. 5 A ). Collectively, these data ally, GFP-fused FAK localized to focal adhesions but not to the suggest that the defect in autophagosome formation of FIP200 Atg16L1-positive autophagy-related structure ( Fig. 6 C ). These MEFs is caused by loss of FIP200 function downstream of results suggest that FAK is not involved in auto ph agy and that mTOR and not by aberrant nutrient signaling including the the role of FIP200 in autophagy is independent of FAK. TSC complex. 504 JCB • VOLUME 181 • NUMBER 3 • 2008 Figure 8. FIP200 is required for membrane targeting and proper function +/   / of ULK. (A) FIP200 and FIP200 MEFs stably expressing GFP-ULK1 or -ULK2 were cultured in starvation medium for 120 min. The cells were +/+ fi xed and examined by fl uorescence microscopy. Bar, 20 μ m. (B) FIP200 and FIP200 MEFs were cultured in complete medium. The cell lysates were subjected to immunoblot analysis with antibodies against ULK1 or +/+ HSP90 (loading control). (C) Phosphatase sensitivity of ULK1. FIP200 Figure 7. FIP200 functions downstream of mTOR in autophagosome for- and FIP200 MEFs were cultured in complete medium. ULK1 was mation. (A) Wild-type and FIP200 MEFs were treated with 100 ng/ml immunoprecipitated from cell lysates and treated with  phosphatase for rapamycin (rapa) or vehicle (DMSO) for 120 min in the presence or ab- 30 min at 30 ° C in the absence or presence of phosphatase inhibitors sence of 100 nM bafi lomycin A . The cell lysates were subjected to immuno- (1 mM Na VO , 50 mM KF, 15 mM Na P O , and 1 mM EGTA). 1 2 4 4 2 7 blot analysis with anti-LC3 antibody. (B) Wild-type and FIP200 MEFs stably expressing GFP-Atg5 or GFP-LC3 were cultured in the presence of 100 ng/ml rapamycin for 120 min. The formation of GFP-Atg5 (top) and ment of isolation membrane formation in the absence of FIP200, GFP-LC3 (bottom) puncta was examined by fl uorescence microscopy. Bar, /  because even GFP-Atg5 dot formation was suppressed in 20 μ m. (C) Wild-type and FIP200 MEFs were treated with 10 mM lithium chloride for 24 h or 100 μ M C -ceramide for 2 h. FIP200 MEFs ( Fig. 5 C ). To explore more direct functional connections between ULK and FIP200, we next examined the expression status of ULK1 in wild-type and FIP200 MEFs. /   / FIP200 MEFs were also resistant to various auto phagy- The expression level of ULK1 in FIP200 MEFs was much inducing reagents such as lithium chloride ( Sarkar et al., lower than in wild-type MEFs under both nutrient rich ( Fig. 2005 ) and ceramide ( Fig. 7 C ; Scarlatti et al., 2004 ). Because 8 B ) and starvation (not depicted) conditions. The ULK1 mRNA the effect of lithium is independent of mTOR ( Sarkar et al., expression was enhanced after starvation, but there was no dif- 2005 ), FIP200 should function in both mTOR-dependent and ference between wild-type and FIP200 cells (Fig. S4 A, -independent autophagy. available at http://jcb.org/cgi/content/full/jcb.200712064/DC1). However, we observed faster decay of ULK1 protein in FIP200 FIP200 is required for ULK puncta cells after cycloheximide treatment, suggesting that ULK1 is formation and is important for the stability destabilized in the absence of FIP200 (Fig. S4 B). Additionally, and proper phosphorylation of ULK we found that ULK1 was detected as a smeared band with faster Given that FIP200 interacts with ULK1 and 2, we postulated mobility in FIP200 MEFs. As previously reported ( Yan K46N that ULKs and FIP200 function together. We fi rst examined the et al., 1998, 1999 ), we observed that mobility of ULK1 is membrane targeting of ULKs in wild-type and FIP200 faster than that of wild-type ULK1, suggesting that ULK1 is MEFs. As we demonstrated in Fig. 1 , GFP-ULK puncta were autophosphorylated ( Fig. 3 D ). Consistent with this, when we formed in wild-type MEFs during starvation. These puncta rep- treated ULK1 immunoprecipitated from wild-type cells with resent the isolation membrane ( Fig. 8 A , left). However, these  phosphatase, ULK1 migrated to a lower position that was dots were never observed in FIP200 MEFs, suggesting that suppressed in the presence of phosphatase inhibitors, confi rming puncta formation of ULK1 and 2 depends on FIP200 ( Fig. 8 A , that ULK1 is phosphorylated ( Fig. 8 C ). Likewise, the phospha- right). However, this observation may simply refl ect impair- tase treatment of ULK1 from FIP200 cell lysates produced a ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 505 band with the same mobility ( Fig. 8 C , compare lanes 2 and 5), MEFs ( Gan et al., 2005 ). We also failed to detect clear defect in indicating that the faster migration of endogenous ULK1 in this pathway as we tested the phosphorylation levels of 4E-BP1 FIP200 MEFs represents reduced phosphorylation rather ( Fig. 5 A ). There might be adaptation to the FIP200-defi cient than other modifi cations such as protein processing. Therefore, conditions in permanently knocked out cells. However, our FIP200 is likely important for maintenance of the ULK1 kinase present study does not exclude the possibility that FIP200 func- activity. All these results suggest that FIP200 and ULK1 are tions with the TSC complex. FIP200 may function both up- functionally connected and that this complex plays an important stream and downstream of mTOR, but the downstream effect role in autophagosome formation. can be dominant when we analyze autophagy. As FIP200 interacts with ULK1 and 2 and is essential for autophagy, one might speculate that this protein is a counterpart Discussion of yeast Atg13 or 17. Indeed, although FIP200 (1594 aa) is We have identifi ed a novel ULK-interacting protein, FIP200, much larger than Atg17 (417 aa), FIP200 shares several features and demonstrated that ULK1, ULK2, and FIP200 localize to the with yeast Atg17. First, both Atg17 and FIP200 have multiple isolation membrane. Because FIP200-defi cient cells displayed coiled-coil domains. Second, just as Atg17 is required for Atg1 virtually no autophagosomes, we propose that the ULK – FIP200 kinase activity ( Kamada et al., 2000 ; Kabeya et al., 2005 ), the complex is essential for an early step, not a later or completion phosphorylation status of ULK1 is reduced in FIP200-defi cient step, of autophagosome formation. cells, which may indicate diminished ULK1 activity ( Fig. 8 ). It is therefore likely that Atg17 and FIP200 can support the function Comparison between yeast Atg1 and of Atg1 and ULKs, respectively. We also found that ULK1 mammalian ULK in the autophagy pathway kinase activity per cell was reduced in FIP200 cells (unpub- Although yeast Atg1 and mammalian ULK possess several lished data). However, as ULK1 expression level itself was also common features, there are some differences. One difference is lower in FIP200 cells than in wild-type cells ( Fig. 8 ), we that although both proteins target to autophagic structures, pre- could not conclude how much specifi c activity of ULK1 re- cise localization may not be the same. Yeast Atg1 is known to duced in the absence of FIP200. Third, the C-terminal region of localize to the PAS ( Suzuki et al., 2007 ). However, because ULK1 is essential for both FIP200 interaction and ULK1 puncta Atg1 is delivered to the vacuole ( Suzuki et al., 2001 ), it should formation ( Fig. 3 ; Chan et al., 2007 ), suggesting that interaction be present on the inner membrane of autophagosomes or cap- with FIP200 is important for membrane targeting. This is con- tured inside autophagosomes. In contrast, we detected ULK1 sistent with the previous fi nding that yeast Atg17 is required and 2 only on the isolation membrane, which suggests that for PAS targeting of Atg1, which is particularly apparent in ULK1 and 2 associate primarily with the outer membrane of the atg11 mutant ( Suzuki et al., 2007 ; Cheong et al., 2008 ; autophagosomes like the Atg12 – Atg5 conjugate ( Mizushima Kawamata et al., 2008 ). Fourth, FIP200 has multiple binding et al., 2001 ). Accordingly, both ULK1 and FIP200 are not de- partners other than ULK1 and 2. Similarly, systematic analyses graded in lysosome because expression levels of these proteins of yeast protein interactions by two-hybrid analysis and mass did not change after treatments of bafi lomycin A1 (Fig. S5, spectrometry identifi ed many potential Atg17-interacting pro- available at http://jcb.org/cgi/content/full/jcb.200712064/DC1). teins, some of which are unrelated to autophagy ( Ho et al., Another difference is the Atg5 dependency of Atg1/ULK 2002 ; Gavin et al., 2006 ; Krogan et al., 2006 ). Therefore, both dot formation. Although PAS targeting of yeast Atg1 does not Atg17 and FIP200 may function as a scaffold for multiple pro- depend on Atg5 ( Suzuki et al., 2007 ), puncta formation of teins. Finally, homologues of Atg17 are present in Kluyveromyces ULK1 and 2 depends on Atg5 in mammalian cells ( Fig. 1 ). One lactis and Eremothecium gossypii , where FIP200 homologue possible explanation of this apparent discrepancy between yeast is missing. On the other hand, FIP200 homologues are found in and mammalian Atg1/ULK would be that the PAS-equivalent Homo sapiens , Mus musculus , Gallus gallus , and D. melano- structure is not visible in mammalian cells, and localization of gaster , where Atg17 homologues are absent, but not in Saccha- Atg1/ULK to isolation membrane should be dependent on Atg5 romyces cerevisiae. This mutual exclusiveness suggests that both in yeast and mammals. Dissection of PAS and the isolation these two groups of proteins may serve similar functions for membrane in yeast would clarify this issue. which one, but not both, proteins are required. Identifi cation We did not observe any difference between ULK1 and 2 and analysis of a functional homologue of mammalian Atg13, a in the present study, although ULK2 has been reported to be critical factor of this complex, will further clarify the functional dispensable for autophagy ( Young et al., 2006 ; Chan et al., relationship between yeast and mammalian Atg1 complex. 2007 ). The function of ULK2 thus remains unclear. Examina- tion of endogenous ULK2 will be required. LC3 conversion in FIP200 cells One notable fi nding in this study is that signifi cant amounts of FIP200, a possible counterpart of yeast LC3-II, which is the most widely used autophagy indicator, are Atg17? detectable in FIP200-defi cient cells. This may indicate that It w as previously shown that FIP200 interacted with TSC1, and a very low level of autophagy occurs even in the absence of phosphorylation of S6 kinase after amino acid stimulation was FIP200, which is consistent with the fi nding that small autopha- impaired in cells treated with FIP200 siRNA ( Gan et al., 2005 ). gosomes are occasionally generated in yeast atg17 mutant cells However, this effect was observed only moderately in FIP200 ( Cheong et al., 2005 ; Kabeya et al., 2005 ). However, this leaky 506 JCB • VOLUME 181 • NUMBER 3 • 2008 phenotype is likely mediated by Cvt-specifi c Atg11, which is for autophagy, suggesting that the focal adhesion complex per absent in mammalian cells ( Suzuki et al., 2007 ; Cheong et al., se is not involved in autophagy. FAK-independent communica- 2008 ; Kawamata et al., 2008 ). Indeed, the autophagy fl ux anal- tion between FIP200 and paxillin will be the subject of future ysis of FIP200 cells suggested that autophagic degradation studies in both autophagy and focal adhesion. is nearly completely abolished ( Fig. 5 B ). Thus, the small Given that at least three of the focal adhesion components amount of LC3-II detected in FIP200 cells may be generated function in autophagy, it is possible that ULKs also plays a role in an autophagy-independent manner. In yeast, Atg8 – PE is gen- in cell adhesion that is independent of its function in autophagy. erated even in atg17 mutant cells as well as in several other Indeed, GFP-ULK1 and -ULK2 were occasionally detected at autophagy mutants such as atg1 , 2 , 6 , 9 , 13 , 14 , and 16 mutants the cell periphery (Fig. S2), and overexpression of wild-type ( Suzuki et al., 2001 ). Atg8 – PE conjugation is severely affected ULKs caused abnormal cell morphology such as cell rounding only in atg5 , 10 , and 12 mutant cells and is completely blocked and protrusion (Fig. S3). So far, several studies have suggested in atg3 , 4 , and 7 mutant cells ( Suzuki et al., 2001 ). The Atg12 – autophagy-independent roles of Atg1/ULK in various species, Atg5 conjugate was recently reported to have an E3-like en- such as axonal elongation and branching in C. elegans ( Ogura zyme activity for the Atg8 – PE conjugation reaction ( Hanada et al., 1994 ) and mammals ( Tomoda et al., 1999 ; Zhou et al., et al., 2007 ). Therefore, the Atg8 – PE conjugation can take place 2007 ). These functions may be related to the role of Atg1 in fo- in an autophagy-independent manner. The Atg knockout mam- cal adhesion. /   / malian cells reported so far are Atg5 and Atg7 . Although In conclusion, we have identifi ed a novel ULK-interacting LC3-II formation is absent in these cells, this is probably caused protein, FIP200, which is functionally similar to yeast Atg17. by defi ciency of Atg12 and 8 conjugation and not simply au- The ULK – FIP200 complex is essential for autophagy, but the tophagy defi ciency. As observed in FIP200 cells, Beclin 1 precise role of this complex is unknown. Identifi cation of physi- silencing blocks autophagosome formation but does not cause ologically relevant substrates of Atg1 – ULK is one of the most complete suppression of the LC3 conversion ( Zeng et al., 2006 ; straightforward approaches, although it has not been successful Matsui et al., 2007 ). Therefore, it is not contradictory that thus far in any species studied ( Deminoff and Herman, 2007 ). FIP200 cells show some LC3-II, even if the autophagic Searching for additional interacting proteins will also facilitate activity is virtually suppressed. Rather, these data suggest that understanding of the role of Atg1 – ULK complex and the regu- we should measure the autophagy fl ux, not the absolute amount lation of autophagy induction and autophagosome formation. of LC3-II, to monitor autophagy ( Tanida et al., 2005 ; Mizushima and Yoshimori, 2007 ). Materials and methods ULK/Atg1 and focal adhesion components Plasmids IMAGE Consortium cDNA clones (GenBank accession no. BC017556) We have demonstrated that FIP200 localizes to the autophagic encoding human RB1CC1/FIP200 were obtained from Invitrogen. The isolation membrane and is essential for autophagy. We do not cDNA encoding FIP200 was cloned into p3 × FLAG CMV10 (Sigma- think that FIP200 is an autophagy-specifi c protein. The most Aldrich). Expression constructs for wild-type and kinase-dead mouse ULK1 and 2 were gifts from N. Okazaki (Kazusa DNA Research Institute, striking evidence for this is that FIP200 mice die between Kisarazu, Japan) and M. Muramatsu (Tokyo Medical and Dental Univer- E13.5 and 16.5 with defective heart and liver development ( Gan sity, Tokyo, Japan). The kinase-dead ULK1 mutant (with conserved ATP /   / et al., 2006 ), whereas autophagy-defi cient Atg5 and Atg7 binding Lys 46 replaced with Asn) and the kinase-dead mutant ULK2 (with Lys 39 to Thr replacement) were previously described ( Yan et al., 1998, mice survive embryogenesis (although they die within one day 1999 ). FAK cDNA constructs were provided by S. Hanks (Vanderbilt Uni- of birth). Indeed, FIP200 involvement has been suggested in versity, Nashville, TN). various cellular processes, such as inhibition of Pyk2-induced Cell culture and transfection signaling ( Ueda et al., 2000 ), inhibition of cell migration /   /  +/ Atg5 ( Kuma et al., 2004 ), FIP200 ( Gan et al., 2006 ), and FAK , through FAK inhibition ( Abbi et al., 2002 ), tumor suppression  / FAK (gift from S. Aizawa, Institute of Physical and Chemical Research, ( Chano et al., 2002b ), induction of RB expression ( Chano et al., Kobe, Japan; Ilic et al., 1995 ) MEFs were generated previously. MEFs and HEK293T cells were cultured in DME supplemented with 10% FBS and 2002a ), cell size regulation through inhibition of the TSC com- 50 μ g/ml penicillin and streptomycin (complete medium) in a 5% CO plex ( Gan et al., 2005 ; Chano et al., 2006 ), inhibition of p53- incubator. Bovine calf serum was used instead of FBS for NIH3T3 cells. mediated G1-S progression ( Melkoumian et al., 2005 ), and For starvation, cells were washed with PBS and incubated in amino acid – free DME without FBS (starvation medium). Fugene 6 reagent (Roche) inhibition of TNF-induced apoptosis, probably through inhibition and lipofectamine 2000 reagent (Invitrogen) were used for transfection. with ASK1 and TRAF2 ( Gan et al., 2006 ). These data suggest that FIP200 is a multifunctional protein. Antibodies and reagents Polyclonal antibodies against FIP200 or ULK1 were generated in rabbits by An important question is whether FIP200 alone or FIP200 standard procedures with fragments of recombinant human FIP200 (resi- and its interacting proteins are involved in autophagy. While we dues 200 – 413 and 1 – 633) or mouse ULK1 (residues 738 – 1052) as anti- were preparing this manuscript, a D. melanogaster genetic anal- gens. Polyclonal anti-LC3 ( Hosokawa et al., 2006 ) and anti-Atg16L1 antibodies ( Mizushima et al., 2003 ) were described previously. Polyclonal ysis revealed a genetic interaction between Atg1 and paxillin, a anti-ULK1 antibody (A7481) and monoclonal anti-FLAG (M2) and anti – cytoskeletal scaffolding protein ( Chen et al., 2007 ). The study -tubulin (DM1A) were purchased from Sigma-Aldrich. Another polyclonal further demonstrates that paxillin and vinculin redistribute from anti-ULK1 antibody was purchased from Santa Cruz Biotechnology, Inc. A monoclonal anti-HA antibody (HA11) was purchased from Covance. focal adhesions to intracellular structures under starvation con- Monoclonal anti-HSP90 and anti-HSP70 antibodies were purchased from ditions and that paxillin-defi cient MEFs are defective in autoph- BD Biosciences. Polyclonal antibodies to 4E-BP1 were purchased from Cell agy. In contrast, our analysis showed that FAK is not required Signaling Technology. Polyclonal antibodies to p62 were purchased from ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 507 American Research Products, Inc. Alexa Fluor 488 – , 568 – , and 660 – conju- 5  -TGGGGAGAAGGTGTGTAGGG-3  ; and mouse  -actin forward, gated goat anti – rabbit IgG (H + L) antibodies (Invitrogen) were used for 5  -CTGGGTATGGAATCCTGTGG-3  ; and reverse, 5  -GTACTTGCGCT- immunochemistry. Rapamycin and lithium chloride were purchased from CAGGAGGAG-3  . Amplicon expression in each sample was normalized Sigma-Aldrich. Bafi lomycin A was purchased from Wako Pure Chemical to its  -actin mRNA content. Industries, Ltd. C -ceramide was purchased from EMD. Online supplemental material Fig. S1 shows the structural comparison of murine ULK homologues (ULK1 – 4). EM Fig. S2 shows the peripheral localization pattern of ULK1 and 2. Fig. S3 MEFs were fi xed in 2.5% glutaraldehyde in 0.1 M sodium phosphate buf- shows the aberrant cell morphology of cells overexpressing wild-type ULK fer, pH 7.4, for 2 h. The cells were washed three times in phosphate buffer but not in kinase-dead ULK. Fig. S4 shows the ULK1 mRNA expression and containing 1 mM glycine and were postfi xed in 1% OsO in 0.1 M phos- protein turnover in wild-type and FIP200 MEFs. Fig. S5 shows endog- phate buffer, pH 7.4, for 1 h. The cells were further dehydrated with a enous expression of ULK1 and FIP200 in MEFs in the presence or absence graded series of ethanol and were embedded in epoxy resin. Ultrathin sec- of 100 nM bafi lomycin A . Online supplemental material is available at tions were doubly stained with uranyl acetate and lead citrate and observed 1 http://jcb.org/cgi/content/full/jcb.200712064/DC1. using an electron microscope (7100; Hitachi). For morphometric analysis, at least 20 sections of each sample were analyzed using MetaMorph image We thank Dr. Shinichi Aizawa (Institute of Physical and Chemical Research) for analysis software (version 6.2; MDS Analytical Technologies). providing FAK MEFs, Dr. Steven K. Hanks (Vanderbilt University) for FAK cDNA, and Dr. Toshio Kitamura (The University of Tokyo) for the retroviral vec- Retroviral expression system tors and Plat E cells. K46N  C cDNAs encoding human FIP200, wild-type mouse ULK1, ULK1 , ULK1 , This work was supported in part by Grants-in-aid for Scientifi c Research K39T ULK2, ULK2 , Atg5, and FAK, and rat LC3 were N-terminally fused to the from the Ministry of Education, Culture, Sports, Science and Technology of K46N GFP fragment. A cDNA encoding mouse ULK1 was N-terminally tagged Japan. The authors also thank the Kato Memorial Bioscience Foundation and with the HA epitope. These cDNAs were subcloned into pMXs-puro or the Toray Science Foundation for fi nancial support. pMXs-IP (provided by T. Kitamura, University of Tokyo, Tokyo, Japan). The resulting vectors were used to transfect Plat E cells and thereby generate Submitted: 12 December 2007 recombinant retroviruses. MEFs and NIH 3T3 cells were infected with the Accepted: 2 April 2008 recombinant retroviruses and selected in medium containing 1 μ g/ml puromycin. Cells stably expressing the recombinant proteins were pooled for experiments ( Kamura et al., 2004 ). References Immunoprecipitation and immunoblotting Abbi , S. , H. Ueda , C. Zheng , L.A. Cooper , J. Zhao , R. Christopher , and J.L. Cell lysates were prepared in a lysis buffer (50 mM Tris-HCl, pH 7.5, 150 Guan . 2002 . Regulation of focal adhesion kinase by a novel protein in- mM NaCl, 1 mM EDTA, 0.5% Triton X-100, 1 mM PMSF, 1 mM Na VO , 3 4 hibitor FIP200. Mol. Biol. Cell . 13 : 3178 – 3191 . and protease inhibitor cocktail [Complete EDTA-free protease inhibitor; Abeliovich , H. , C. Zhang , W.A. Dunn Jr ., K.M. Shokat , and D.J. Klionsky . 2003 . Roche]). The lysates were clarifi ed by centrifugation at 15,000 rpm for 15 min Chemical genetic analysis of Apg1 reveals a non-kinase role in the induc- and were subjected to immunoprecipitation using specifi c antibodies in tion of autophagy. Mol. Biol. Cell . 14 : 477 – 490 . combination with protein G – Sepharose (GE Healthcare). Precipitated immuno- Bamba , N. , T. Chano , T. Taga , S. Ohta , Y. Takeuchi , and H. Okabe . 2004 . complexes were washed fi ve times in lysis buffer and boiled in sample buffer. Expression and regulation of RB1CC1 in developing murine and human Samples were subsequently separated by SDS-PAGE and transferred to tissues. Int. J. Mol. Med. 14 : 583 – 587 . Immobilon-P polyvinylidene difl uoride membranes (Millipore). Immunoblot Bj ø rk ø y , G. , T. Lamark , A. Brech , H. Outzen , M. Perander , A. Ø vervatn , H. analysis was performed with the indicated antibodies and visualized Stenmark , and T. Johansen . 2005 . p62/SQSTM1 forms protein aggregates with SuperSignal West Pico Chemiluminescent substrate (Thermo Fisher Sci- degraded by autophagy and has a protective effect on huntingtin-induced entifi c). The signal intensities were analyzed using an imaging analyzer cell death. J. Cell Biol. 171 : 603 – 614 . (LAS-3000mini; Fujifi lm) and Multi Gauge software (version 3.0; Fujifi lm). Carragher , N.O. , and M.C. Frame . 2004 . Focal adhesion and actin dynamics: a Contrast and brightness adjustment was applied to the whole images using place where kinases and proteases meet to promote invasion. T rends Cell Photoshop 7.0.1 (Adobe). Biol. 14 : 241 – 249 . Chan , E.Y. , S. Kir , and S.A. Tooze . 2007 . siRNA screening of the kinome iden- Fluorescence microscopy tifi es ULK1 as a multidomain modulator of autophagy. J. Biol. Chem. MEF or NIH3T3 cells expressing protein fused to GFP were directly ob- 282 : 25464 – 25474 . served with a fl uorescence microscope (IX81; Olympus) equipped with a Chano , T. , S. Ikegawa , K. Kontani , H. Okabe , N. Baldini , and Y. Saeki . 2002a . charge-coupled device camera (ORCA ER; Hamamatsu Photonics). A 60 × Identifi cation of RB1CC1, a novel human gene that can induce RB1 in PlanAPO oil immersion lens (1.42 NA; Olympus) was used. Images were various human cells. Oncogene . 21 : 1295 – 1298 . acquired using MetaMorph image analysis software version. For examina- Chano , T. , K. Kontani , K. Teramoto , H. Okabe , and S. Ikegawa . 2002b . Truncating tion by immunofl uorescence microscopy, cells grown on gelatinized cover- mutations of RB1CC1 in human breast cancer. Nat. Genet. 31 : 285 – 288 . slips were fi xed and stained with an anti-Atg16L1, anti-FIP200, or anti-HA Chano , T. , M. Saji , H. Inoue , K. Minami , T. Kobayashi , O. Hino , and H. Okabe . antibody as previously described ( Mizushima et al., 2001 ). 2006 . Neuromuscular abundance of RB1CC1 contributes to the non-pro- liferating enlarged cell phenotype through both RB1 maintenance and Kinase assay TSC1 degradation. Int. J. Mol. Med. 18 : 425 – 432 . Cells were washed with PBS and then lysed in an extraction buffer (20 mM Chen , G.C. , J.Y. Lee , H.W. Tang , J. Debnath , S.M. Thomas , and J. Settleman . Tris-HCl, pH7.5, 150 mM NaCl, 10 mM  -glycerophosphate, 5 mM 2007 . Genetic interactions between Drosophila melanogaster Atg1 and EGTA, 1 mM sodium pyrophosphate, 5 mM NaF, 1 mM Na VO , and 3 4 paxillin reveal a role for paxillin in autophagosome formation. A utophagy . 0.5% Triton X-100) supplemented with protease inhibitors (10 μ g/ml each 4 : 37 – 45 . of pepstatin A, chymostatin, leupeptin, and E64 [Peptide Institute, Inc.]). Cheong , H. , T. Yorimitsu , F. Reggiori , J.E. Legakis , C.W. W ang , and D.J. ULK1 was immunoprecipitated with anti-ULK1 antibody, and an in vitro Klionsky . 2005 . Atg17 regulates the magnitude of the autophagic re- protein kinase assay was performed for 30 min at 30 ° C in the presence of sponse. Mol. Biol. Cell . 16 : 3438 – 3453 . -[ P]ATP (GE Healthcare) and myelin basic protein (Millipore). The reac- Cheong , H. , U. Nair, J. Geng , and D.J. Klionsky . 2008 . The Atg1 kinase complex tion products were separated by SDS-PAGE and the intensities of the P- is involved in the regulation of protein recruitment to initiate sequestering labeled myelin basic protein bands were visualized with a BAS image vesicle formation for nonspecifi c autophagy in Saccharomyces cerevi- siae. Mol. Biol. Cell . 19 : 668 – 681 . analyzer (Fujifi lm). The signal intensities were quantifi ed using Multi Gauge software. The amount of immunoprecipitated ULK1 was monitored by im- Cuervo , A.M. 2004 . Autophagy: in sickness and in health. Trends Cell Biol. munoblot analysis using ULK1 antibody (Santa Cruz Biotechnology, Inc.). 14 : 70 – 77 . Deminoff , S.J. , and P .K. Herman . 2007 . Identifying atg1 substrates: four means Real-time PCR to an end. Autophagy . 3 : 667 – 673 . Real-time PCR was performed on a Thermal Cycler Dice (Takara) using Gan , B. , Z.K. Melkoumian , X. Wu , K.L. Guan , and J.L. Guan . 2005 . Identifi cation SYBR premix EX Taq (Takara). The primer sets used were as follows: of FIP200 interaction with the TSC1 – TSC2 complex and its role in regu- mouse ULK1 forward, 5  -TTACCAGCGCATCGAGCA-3  ; and reverse, lation of cell size control. J. Cell Biol. 170 : 379 – 389 . 508 JCB • VOLUME 181 • NUMBER 3 • 2008 Gan , B. , X. Peng , T. Nagy , A. Alcaraz , H. Gu , and J.L. Guan . 2006 . Role of Levine , B. , and D.J. Klionsky . 2004 . Development by self-digestion: mo- FIP200 in cardiac and liver development and its regulation of TNF  and lecular mechanisms and biological functions of autophagy. De v. Cell . TSC – mTOR signaling pathways. J. Cell Biol. 175 : 121 – 133 . 6 : 463 – 477 . Gavin , A.C. , P. Aloy , P. Grandi , R. Krause , M. Boesche , M. Marzioch , C. Rau , Matsui , Y. , H. Takagi , X. Qu , M. Abdellatif , H. Sakoda , T. Asano , B. Levine , and L.J. Jensen , S. Bastuck , B. Dumpelfeld , et al . 2006 . Proteome survey re- J. Sadoshima . 2007 . Distinct roles of autophagy in the heart during ische- veals modularity of the yeast cell machinery. Natur e . 440 : 631 – 636 . mia and reperfusion: roles of AMP-activated protein kinase and Beclin 1 in mediating autophagy. Circ. Res. 100 : 914 – 922 . Guertin , D.A. , and D.M. Sabatini . 2007 . Defi ning the role of mTOR in cancer. Meijer , A.J. , and P. Codogno . 2004 . Regulation and role of autophagy in mam- Cancer Cell . 12 : 9 – 22 . malian cells. Int. J. Biochem. Cell Biol. 36 : 2445 – 2462 . Hanada , T. , N.N. Noda , Y. Satomi , Y. Ichimura , Y. Fujioka , T. Takao , F. Melendez , A. , Z. Tall ó czy , M. Seaman , E.-L. Eskelinen , D.H. Hall , and B. Inagaki , and Y. Ohusmi . 2007 . The ATG12-ATG5 conjugate has a Levine . 2003 . Autophagy genes are essential for dauer development and novel e3-like activity for protein lipidation in autophagy. J. Biol. Chem. life-span extension in C. elegans. Science . 301 : 1387 – 1391 . 282 : 37298 – 37302 . Melkoumian , Z.K. , X. Peng , B. Gan , X. Wu , and J.L. Guan . 2005 . Mechanism Hanaoka , H. , T. Noda , Y. Shirano , T. Kato , H. Hayashi , D. Shibata , S. Tabata , of cell cycle regulation by FIP200 in human breast cancer cells. Cancer and Y. Ohsumi . 2002 . Leaf senescence and starvation-induced chlorosis Res. 65 : 6676 – 6684 . are accelerated by the disruption of an Arabidopsis autophagy gene. Plant Physiol. 129 : 1181 – 1193 . Mizushima , N. 2007 . Autophagy: process and function. Genes Dev. 21 : 2861 – 2873 . Hara , T. , K. Nakamura , M. Matsui , A. Yamamoto , Y. Nakahara , R. Suzuki- Mizushima , N. , and D.J. Klionsky . 2007 . Protein turnover via autophagy: impli- Migishima , M. Yokoyama , K. Mishima , I. Saito , H. Okano , and N. cations for metabolism. Annu. Rev. Nutr. 27 : 19 – 40 . Mizushima . 2006 . Suppression of basal autophagy in neural cells causes Mizushima , N. , and T . Yoshimori . 2007 . How to interpret LC3 immunoblotting. neurodegenerative disease in mice. Nature . 441 : 885 – 889 . Autophagy . 3 : 542 – 545 . Ho , Y. , A. Gruhler , A. Heilbut , G.D. Bader, L. Moore , S.L. Adams , A. Millar, P. Mizushima , N. , A. Yamamoto , M. Hatano , Y. Kobayashi , Y. Kabeya , K. Suzuki , Taylor , K. Bennett , K. Boutilier, et al . 2002 . Systematic identifi cation of T. Tokuhisa , Y. Ohsumi , and T. Yoshimori . 2001 . Dissection of autopha- protein complexes in Saccharomyces cerevisiae by mass spectrometry. gosome formation using Apg5-defi cient mouse embryonic stem cells. Nature . 415 : 180 – 183 . J. Cell Biol. 152 : 657 – 667 . Hosokawa , N. , Y. Hara , and N. Mizushima . 2006 . Generation of cell lines with Mizushima , N. , A. Kuma , Y. Kobayashi , A. Yamamoto , M. Matsubae , T. Takao , tetracycline-regulated autophagy and a role for autophagy in controlling T. Natsume , Y. Ohsumi , and T. Yoshimori . 2003 . Mouse Apg16L, a novel cell size. FEBS Lett. 580 : 2623 – 2629 . WD-repeat protein, targets to the autophagic isolation membrane with the Ilic , D. , Y. Furuta , S. Kanazawa , N. Takeda , K. Sobue , N. Nakatsuji , S. Nomura , Apg12-Apg5 conjugate. J . Cell Sci. 116 : 1679 – 1688 . J. Fujimoto , M. Okada , T. Yamamoto , and S. Aizawa . 1995 . Reduced cell Mizushima , N. , B. Levine , A.M. Cuervo , and D.J. Klionsky . 2008 . Autophagy motility and enhanced focal adhesion contact formation in cells from fi ghts disease through cellular self-digestion. Natur e . 451 : 1069 – 1075 . FAK-defi cient mice. Natur e . 377 : 539 – 544 . Mukaiyama , H. , M. Oku , M. Baba , T. Samizo , A.T. Hammond , B.S. Glick , N. Inoki , K. , and K.L. Guan . 2006 . Complexity of the TOR signaling network. Kato , and Y. Sakai . 2002 . Paz2 and 13 other PAZ gene products regu- Trends Cell Biol. 16 : 206 – 212 . late vacuolar engulfment of peroxisomes during micropexophagy. Genes Kabeya , Y. , N. Mizushima , T. Ueno , A. Yamamoto , T. Kirisako , T. Noda , E. Cells . 7 : 75 – 90 . Kominami , Y. Ohsumi , and T. Yoshimori . 2000 . LC3, a mammalian ho- Natsume , T. , Y. Yamauchi , H. Nakayama , T. Shinkawa , M. Yanagida , N. mologue of yeast Apg8p, is localized in autophagosome membranes after Takahashi , and T. Isobe . 2002 . A direct nanofl ow liquid chromatogra- processing. EMBO J . 19 : 5720 – 5728 . phy-tandem mass spectrometry system for interaction proteomics. Anal. Kabeya , Y. , Y. Kamada , M. Baba , H. Takikawa , M. Sasaki , and Y. Ohsumi . 2005 . Chem. 74 : 4725 – 4733 . Atg17 functions in cooperation with Atg1 and Atg13 in yeast autophagy. Nice , D.C. , T.K. Sato , P.E. Stromhaug , S.D. Emr , and D.J. Klionsky . 2002 . Mol. Biol. Cell . 16 : 2544 – 2553 . Cooperative binding of the cytoplasm to vacuole targeting pathway Kabeya , Y. , T. Kawamata , K. Suzuki , and Y. Ohsumi . 2007 . Cis1/Atg31 is proteins, Cvt13 and Cvt20, to phosphatidylinositol 3-phosphate at the required for autophagosome formation in Saccharomyces cerevisiae. pre-autophagosomal structure is required for selective autophagy. J . Biol. Biochem. Biophys. Res. Commun. 356 : 405 – 410 . Chem. 277 : 30198 – 30207 . Kamada , Y. , T. Funakoshi , T. Shintani , K. Nagano , M. Ohsumi , and Y. Ohsumi . Ogura , K. , C. Wicky , L. Magnenat , H. Tobler, I. Mori , F. Muller , and Y. 2000 . Tor-mediated induction of autophagy via an Apg1 protein kinase Ohshima . 1994 . Caenorhabditis elegans unc-51 gene required for complex. J . Cell Biol. 150 : 1507 – 1513 . axonal elongation encodes a novel serine/threonine kinase. Genes Dev. 8 : 2389 – 2400 . Kamura , T. , T. Hara , M. Matsumoto , N. Ishida , F. Okumura , S. Hatakeyama , M. Yoshida , K. Nakayama , and K.I. Nakayama . 2004 . Cytoplasmic ubiqui- Ogura , K. , M. Shirakawa , T.M. Barnes , S. Hekimi , and Y. Ohshima . 1997 . tin ligase KPC regulates proteolysis of p27(Kip1) at G1 phase. Nat. Cell The UNC-14 protein required for axonal elongation and guidance in Biol. 6 : 1229 – 1235 . Caenorhabditis elegans interacts with the serine/threonine kinase UNC-51. Genes Dev. 11 : 1801 – 1811 . Kawamata , T. , Y. Kamada , K. Suzuki , N. Kuboshima , H. Akimatsu , S. Ota , M. Ohsumi , and Y. Ohsumi . 2005 . Characterization of a novel auto phagy- Okazaki , N. , J. Yan , S. Yuasa , T. Ueno , E. Kominami , Y. Masuho , H. Koga , and specifi c gene, ATG29. Bioc hem. Biophys. Res. Commun. 338 : 1884 – 1889 . M. Muramatsu . 2000 . Interaction of the Unc-51-like kinase and micro- tubule-associated protein light chain 3 related proteins in the brain: pos- Kawamata , T. , Y. Kamada , Y. Kabeya , T. Sekito , and Y. Ohsumi . 2008 . Organization sible role of vesicular transport in axonal elongation. Brain Res. Mol. of the pre-autophagosomal structure responsible for autophagosome for- Brain Res. 85 : 1 – 12 . mation. Mol. Biol. Cell . DOI:10.1091/mbc.E07-10-1048. Otto , G.P. , M.Y. Wu , N. Kazgan , O.R. Anderson , and R.H. Kessin . 2004 . Kim , J. , W.-P. Huang , and D.J. Klionsky . 2001a . Membrane recruitment of Aut7p Dictyostelium macroautophagy mutants vary in the severity of their de- in the autophagy and cytoplasm to vacuole targeting pathways requires velopmental defects. J . Biol. Chem. 279 : 15621 – 15629 . Aut1p, Aut2p, and the autophagy conjugation complex. J . Cell Biol. 152 : 51 – 64 . Reggiori , F. , K.A. Tucker , P.E. Stromhaug , and D.J. Klionsky . 2004 . The Atg1- Atg13 complex regulates Atg9 and Atg23 retrieval transport from the pre- Kim , J. , Y. Kamada , P.E. Stromhaug , J. Guan , A. Hefner-Gravink , M. Baba , S.V. autophagosomal structure. Dev. Cell . 6 : 79 – 90 . Scott , Y. Ohsumi , W.A. Dunn Jr ., and D.J. Klionsky . 2001b . Cvt9/Gsa9 functions in sequestering selective cytosolic cargo destined for the vacuole. Rubinsztein , D.C. 2006 . The roles of intracellular protein-degradation pathways J. Cell Biol. 153 : 381 – 396 . in neurodegeneration. Nature . 443 : 780 – 786 . Klionsky , D.J. 2005 . The molecular machinery of autophagy: unanswered ques- Sarkar , S. , R.A. Floto , Z. Berger , S. Imarisio , A. Cordenier , M. Pasco , L.J. Cook , tions. J. Cell Sci. 118 : 7 – 18 . and D.C. Rubinsztein . 2005 . Lithium induces autophagy by inhibiting inositol monophosphatase. J. Cell Biol. 170 : 1101 – 1111 . Komatsu , M. , S. Waguri , T. Chiba , S. Murata , J.I. Iwata , I. Tanida , T. Ueno , M. Koike , Y. Uchiyama , E. Kominami , and K. Tanaka . 2006 . Loss of auto phagy Scarlatti , F. , C. Bauvy, A. Ventruti , G. Sala , F. Cluzeaud , A. Vandewalle , R. in the central nervous system causes neurodegeneration in mice. Nature . Ghidoni , and P . Codogno . 2004 . Ceramide-mediated macroautophagy 441 : 880 – 884 . involves inhibition of protein kinase B and up-regulation of beclin 1. J. Biol. Chem. 279 : 18384 – 18391 . Krogan , N.J. , G. Cagney , H. Yu , G. Zhong , X. Guo , A. Ignatchenko , J. Li , S. Pu , N. Datta , A.P. Tikuisis , et al . 2006 . Global landscape of Scott , R.C. , O. Schuldiner , and T.P. Neufeld . 2004 . Role and regulation of protein complexes in the yeast Saccharomyces cerevisiae . Nature . starvation-induced autophagy in the Drosophila fat body. Dev. Cell . 440 : 637 – 643 . 7 : 167 – 178 . Kuma , A. , M. Hatano , M. Matsui , A. Yamamoto , H. Nakaya , T. Yoshimori , Y. Scott , R.C. , G. Juhasz , and T.P. Neufeld . 2007 . Direct induction of autophagy Ohsumi , T. Tokuhisa , and N. Mizushima . 2004 . The role of autophagy by Atg1 inhibits cell growth and induces apoptotic cell death. Curr. Biol. during the early neonatal starvation period. Nature . 432 : 1032 – 1036 . 17 : 1 – 11 . ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 509 Scott , S.V. , D.C. Nice III , J.J. Nau , L.S. Weisman , Y. Kamada , I. Keizer-Gunnink , T. Funakoshi , M. Veenhuis , Y. Ohsumi , and D.J. Klionsky . 2000 . Apg13p and Vac8p are part of a complex of phosphoproteins that are required for cytoplasm to vacuole targeting. J. Biol. Chem. 275 : 25840 – 25849 . Suzuki , K. , and Y. Ohsumi . 2007 . Molecular machinery of autophagosome for- mation in yeast, Saccharomyces cerevisiae. FEBS Lett. 581 : 2156 – 2161 . Suzuki , K. , T. Kirisako , Y. Kamada , N. Mizushima , T. Noda , and Y. Ohsumi . 2001 . The pre-autophagosomal structure organized by concerted func- tions of APG genes is essential for autophagosome formation. EMBO J. 20 : 5971 – 5981 . Suzuki , K. , Y. Kubota , T. Sekito , and Y. Ohsumi . 2007 . Hierarchy of Atg proteins in pre-autophagosomal structure organization. Genes Cells . 12 : 209 – 218 . Tanida , I. , N. Minematsu-Ikeguchi , T. Ueno , and E. Kominami . 2005 . Lysosomal turnover, but not a cellular level, of endogenous LC3 is a marker for autophagy. Autophagy . 1 : 84 – 91 . Tekinay , T. , M.Y. Wu , G.P. Otto , O.R. Anderson , and R.H. Kessin . 2006 . Function of the Dictyostelium discoideum Atg1 kinase during autophagy and development. Eukaryot. Cell . 5 : 1797 – 1806 . Tomoda , T. , R.S. Bhatt , H. Kuroyanagi , T. Shirasawa, and M.E. Hatten . 1999 . A mouse serine/threonine kinase homologous to C. elegans UNC51 func- tions in parallel fi ber formation of cerebellar granule neurons. Neur on . 24 : 833 – 846 . Tomoda , T. , J.H. Kim , C. Zhan , and M.E. Hatten . 2004 . Role of Unc51.1 and its binding partners in CNS axon outgrowth. Genes De v. 18 : 541 – 558 . Ueda , H. , S. Abbi , C. Zheng , and J.L. Guan . 2000 . Suppression of Pyk2 kinase and cellular activities by FIP200. J . Cell Biol. 149 : 423 – 430 . Wullschleger , S. , R. Loewith , and M.N. Hall . 2006 . TOR signaling in growth and metabolism. Cell . 124 : 471 – 484 . Yamamoto , A. , Y. Tagawa , T. Yoshimori , Y. Moriyama , R. Masaki , and Y. Tashiro . 1998 . Bafi lomycin A prevents maturation of autophagic vacuoles by in- hibiting fusion between autophagosomes and lysosomes in rat hepatoma cell line, H-4-II-E cells. Cell Struct. Funct. 23 : 33 – 42 . Yan , J. , H. Kuroyanagi , A. Kuroiwa , Y. Matsuda , H. Tokumitsu , T. Tomoda , T. Shirasawa , and M. Muramatsu . 1998 . Identifi cation of mouse ULK1, a novel protein kinase structurally related to C. elegans UNC-51. Biochem. Biophys. Res. Commun. 246 : 222 – 227 . Yan , J. , H. Kuroyanagi , T. Tomemori , N. Okazaki , K. Asato , Y. Matsuda , Y. Suzuki , Y. Ohshima , S. Mitani , Y. Masuho , et al . 1999 . Mouse ULK2, a novel member of the UNC-51-like protein kinases: unique features of functional domains. Oncogene . 18 : 5850 – 5859 . Young , A.R. , E.Y. Chan , X.W. Hu , R. Kochl , S.G. Crawshaw , S. High , D.W. Hailey , J. Lippincott-Schwartz , and S.A. Tooze . 2006 . Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. J . Cell Sci. 119 : 3888 – 3900 . Zeng , X. , J.H. Overmeyer , and W.A. Maltese . 2006 . Functional specifi city of the mammalian Beclin-Vps34 PI 3-kinase complex in macroautophagy versus endocytosis and lysosomal enzyme traffi cking. J. Cell Sci. 119 : 259 – 270 . Zhou , X. , J.R. Babu , S. da Silva , Q. Shu , I.A. Graef , T. Oliver , T. T omoda , T. Tani , M.W. Wooten , and F. Wang . 2007 . Unc-51-like kinase 1/2-medi- ated endocytic processes regulate fi lopodia extension and branching of sensory axons. Proc. Natl. Acad. Sci. USA . 104 : 5842 – 5847 . 510 JCB • VOLUME 181 • NUMBER 3 • 2008 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Cell Biology Pubmed Central

FIP200, a ULK-interacting protein, is required for autophagosome formation in mammalian cells

The Journal of Cell Biology , Volume 181 (3) – May 5, 2008

Loading next page...
 
/lp/pubmed-central/fip200-a-ulk-interacting-protein-is-required-for-autophagosome-4lS86v565w

References (86)

Publisher
Pubmed Central
Copyright
© 2008 Hara et al.
ISSN
0021-9525
eISSN
1540-8140
DOI
10.1083/jcb.200712064
Publisher site
See Article on Publisher Site

Abstract

JCB: ARTICLE FIP200, a ULK-interacting protein, is required for autophagosome formation in mammalian cells 1 1 1 2 2 3 Taichi Hara , Akito Takamura , Chieko Kishi , Shun-ichiro Iemura , Tohru Natsume , Jun-Lin Guan , 1,4 and Noboru Mizushima Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8549, Japan Biological Information Research Center, National Institutes of Advanced Industrial Science and Technology, Kohtoh-ku, Tokyo 135-0064, Japan Department of Internal Medicine-MMG, University of Michigan Medical School, Ann Arbor, MI 48109 Solution Oriented Research for Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan utophagy is a membrane-mediated intracellular identifi ed the focal adhesion kinase family interacting degradation system. The serine/threonine kinase protein of 200 kD (FIP200), which regulates diverse cellu- A Atg1 plays an essential role in autophagosome lar functions such as cell size, proliferation, and migra- formation. However, the role of the mammalian Atg1 ho- tion. We found that FIP200 was redistributed from the mologues UNC-51 – like kinase (ULK) 1 and 2 are not yet cytoplasm to the isolation membrane under starvation well understood. We found that murine ULK1 and 2 local- conditions. In FIP200-defi cient cells, autophagy induction ized to autophagic isolation membrane under starvation by various treatments was abolished, and both stability conditions. Kinase-dead alleles of ULK1 and 2 exerted a and phosphorylation of ULK1 were impaired. These results dominant-negative effect on autophagosome formation, suggest that FIP200 is a novel mammalian autophagy fac- suggesting that ULK kinase activity is important for auto ph- tor that functions together with ULKs. agy. We next screened for ULK binding proteins and Introduction Autophagy is a primary route by which cytoplasmic contents The molecular mechanism of autophagy has been revealed are directed to the lysosome to be degraded ( Cuervo, 2004 ; by genetic analyses performed in yeast ( Klionsky, 2005 ; Suzuki Levine and Klionsky, 2004 ; Rubinsztein, 2006 ; Mizushima, and Ohsumi, 2007 ), in which 31 autophagy-related ATG genes 2007 ; Mizushima et al., 2008 ). There are three types of auto ph- have been identifi ed so far. Among these genes, Atg1 – 10, 12 – 14, agy: macroautophagy, microautophagy, and chaperone-mediated 16 – 18, 29, and 31 (collectively called AP-Atg) are required for autophagy. Among them, only macroautophagy (referred to autophagosome formation. In yeast, autophagosomes are generated as autophagy hereafter) is mediated by the autophagosome. at a special site near the vacuolar membrane, called the preauto ph - Upon induction of autophagy, a membrane cisterna called the agosomal structure (PAS), where most AP-Atg proteins are re- isolation membrane (also termed the phagophore) enwraps a cruited ( Kim et al., 2001a ; Suzuki et al., 2001 ; Suzuki and Ohsumi, portion of cytoplasm to generate an autophagosome. The au- 2007 ). Although autophagy requires only these AP-Atg proteins, tophagosome then fuses with an endosome and, fi nally, with the an autophagy-related pathway called cytoplasm-to-vacuole tar- lysosome, leading to degradation of cytoplasm-derived mate- geting (Cvt) pathway, which delivers two vacuolar enzymes, amino - rials sequestered inside the autophagosome. Although auto ph- peptidase 1 and  -mannosidase 1, from the cytoplasm to the agy occurs at low levels under normal conditions ( Hara et al., vacuole, requires almost all Atg proteins except Atg17, 29, and 31. 2006 ; Komatsu et al., 2006 ), autophagy is extensively activated AP-Atg proteins are classifi ed into six functional groups: under starvation conditions ( Mizushima and Klionsky, 2007 ). the Atg1 protein kinase complex; the Atg2 – Atg18 complex; the Atg8 conjugation system; the Atg12 conjugation system; Correspondence to Noboru Mizushima: nmizu.phy2@tmd.ac.jp the Atg14 – phosphatidylinositol 3-kinase complex; and Atg9 Abbreviations used in this paper: Cvt, cytoplasm-to-vacuole targeting; E, embry- ( Suzuki et al., 2007 ). Among these functional units, the Atg1 onic day; FIP200, FAK family – interacting protein of 200 kD; MEF, mouse embry- complex has a unique feature: it apparently receives the starva- onic fi broblast; mTOR, mammalian target of rapamycin; PAS, preautophagosomal structure; PE, phosphatidylethanolamine; ULK, UNC-51 – like kinase. tion signals. Atg1 is a serine/threonine protein kinase, and its The online version of this paper contains supplemental material. kinase activity can be up-regulated after autophagy-inducible © 2008 Hara et al. The Rockefeller University Press $30.00 J. Cell Biol. Vol. 181 No. 3 497–510 JCB 497 www.jcb.org/cgi/doi/10.1083/jcb.200712064 THE JOURNAL OF CELL BIOLOGY treatments such as nutrient starvation or rapamycin treatment tinct partners. Indeed, C. elegans UNC-51 interacts with UNC-14, ( Kamada et al., 2000 ). The kinase activity of Atg1 is believed to a protein involved in coordinated movement ( Ogura et al., be required for autophagy, although there have been debates 1997 ). In mammals, ULK1 interacts with SynGAP, a negative ( Kamada et al., 2000 ; Abeliovich et al., 2003 ; Kabeya et al., regulator of Ras, and Syntenin, a Rab5-interacting protein 2005 ; Cheong et al., 2008 ). The Atg1 complex includes Atg13, ( Tomoda et al., 2004 ). These interactions have been suggested Atg17 ( Kamada et al., 2000 ), Atg29 ( Kawamata et al., 2008 ), to be important for axon guidance/elongation. Another recent Atg31/Cis1 ( Kabeya et al., 2007 ), Atg11/Cvt9 ( Kim et al., 2001b ), paper also suggested that ULK1 is recruited to the TrkA – NGF Atg24/Cvt13 ( Nice et al., 2002 ), Atg20/Cvt20 ( Nice et al., 2002 ), receptor complex by p62 and regulates non – clathrin-coated and Vac8 ( Scott et al., 2000 ). Atg17 ( Kamada et al., 2000 ), 29 endocytosis in growth cones, fi lopodia extension, and branching ( Kawamata et al., 2005 ), and 31 ( Kabeya et al., 2007 ) are specifi - ( Zhou et al., 2007 ). However, homologues of the yeast Atg1- cally involved in autophagy, whereas Atg11, Atg20, Atg24, and interacting autophagy proteins have not been reported in higher Vac8 are specifi cally required for the Cvt pathway. Atg13 and 1 eukaryotes (except for plant Atg13; Hanaoka et al., 2002 ). are involved in both pathways. A recent systematic analysis re- To better understand the role of the Atg1/ULK family, we vealed that Atg17 and 11 are essential for PAS organization, and screened for ULK-interacting proteins and identifi ed the FAK Atg17 has been suggested to behave as a scaffold protein ( Suzuki family – interacting protein of 200 kD (FIP200), which is also et al., 2007 ). The Atg1 – Atg17 interaction largely depends on called RB1CC1 (retinoblastoma 1 – inducible coiled-coil 1). Atg13 ( Cheong et al., 2005 ; Kabeya et al., 2005 ), but a yeast two- FIP200 was reported to interact with multiple proteins, including hybrid analysis suggested that Atg1 and 17 can also directly FAK ( Abbi et al., 2002 ), Pyk2 ( Ueda et al., 2000 ), TSC1 ( Gan interact with each other ( Cheong et al., 2005 ). Interactions be- et al., 2005 ), p53 ( Melkoumian et al., 2005 ), ASK1, and TRAF2 tween Atg13, 1, and 17 are enhanced by starvation treatment, and ( Gan et al., 2006 ), thereby regulating a variety of cellular func- both Atg13 and 17 are important for proper regulation of Atg1 tions such as cell migration, proliferation, cell size, and apopto- kinase activity ( Kamada et al., 2000 ; Kabeya et al., 2005 ). sis. FIP200 was also independently identifi ed as a novel inducer The function of the Atg17 – Atg13 – Atg1 complex has yet of RB1. We found that ULK1, ULK2, and FIP200 are present on to be fully understood. Although Atg1 and 13 sense nutrient con- autophagic isolation membrane. Using FIP200 mouse embry- ditions, this complex does not appear to function as a simple onic fi broblasts (MEFs), we revealed that FIP200 is a novel mam- transducer of starvation signaling. For example, Atg1 is required malian autophagy factor that functions together with ULKs. for a late step of micropexophagy in Pichia pastoris ( Mukaiyama et al., 2002 ) and for the Cvt pathway, which is a constitutive bio- Results synthetic pathway proceeding under nutrient-rich conditions ( Kamada et al., 2000 ; Abeliovich et al., 2003 ). Furthermore, ULK1 and ULK2 localize on the isolation Atg1 is known to be important for retrieval of Atg9 and 23 from membrane (phagophore) PAS ( Reggiori et al., 2004 ). We found four ULK homologues in the mouse database. Homologues of Atg1 have been found in other species Although ULK1 and 2 are closely related to C. elegans UNC51, such as Dictyostelium discoideum ( Otto et al., 2004 ), Cae- ULK3 and 4 show similarity to UNC51 only in the kinase norhabditis elegans ( Ogura et al., 1994 ; Melendez et al., 2003 ), domain (Fig. S1, available at http://jcb.org/cgi/content/full/jcb Drosophila melanogaster ( Scott et al., 2004 ), Arabidopsis thali- .200712064/DC1). We therefore analyzed the role of ULK1 ana ( Hanaoka et al., 2002 ), and mammals ( Yan et al., 1998, and 2 in autophagosome formation. We fi rst determined the sub- 1999 ). Mutants of Atg1 in the species examined thus far indeed cellular distribution of ULK1 and 2 using NIH3T3 cells stably exhibit autophagy-defective phenotypes ( Melendez et al., 2003 ; expressing ULKs fused with GFP at the N terminus (GFP-ULK1 Otto et al., 2004 ; Scott et al., 2004 ; Chan et al., 2007 ). and GFP-ULK2). Under nutrient-rich conditions, GFP-ULK1 In metazoa, however, the role of Atg1 seems not to be and GFP-ULK2 were mostly found to distribute evenly through- limited to macroautophagy. C. elegans Atg1 is known as UNC out the cytoplasm, with few punctuate dots ( Fig. 1, A and B , (uncoordinated movement)-51. The unc-51 mutants show neuro- complete). We occasionally observed GFP-ULK1 and -ULK2 at logical abnormalities such as paralysis and defects in axonal the ruffl ed membrane in some cells (Fig. S2). After amino acid elongation ( Ogura et al., 1994 ). In mammals, two Atg1 homo- and serum starvation, GFP-ULK1 and -ULK2 localized to punc- logues have been reported: UNC-51 – like kinase (ULK) 1 (also tuate structures ( Fig. 1, A and B , starvation). These punctuate known as Unc51.1; Yan et al., 1998 ; Tomoda et al., 1999 ) and structures immediately disappeared after replenishment with nu- ULK2 (also known as Unc51.2; Tomoda et al., 1999 ; Yan et al., trient medium ( Fig. 1, A and B , starvation → complete). As previ- 1999 ). RNAi-mediated suppression of ULK1 expression alone ously reported ( Chan et al., 2007 ), these data suggest that ULK1 is suffi cient to inhibit autophagy ( Chan et al., 2007 ) and re- and 2 are targeted to autophagy-related structures. We then ex- distribution of mAtg9 from the TGN to endosomes ( Young amined the localization of GFP-ULK in more detail and found that et al., 2006 ). In addition to the autophagy phenotype, a dominant- both ULK1 and 2 colocalized with endogenous Atg16L1 almost negative form of ULK1, K46R, suppresses neurite extension of completely ( Fig. 1, C and D ). Because Atg16L1, together with cerebellar granular neurons ( Tomoda et al., 1999 ), which is con- the Atg12 – Atg5 conjugate, specifi cally localizes to elongating sistent with the neurological phenotype of the unc-51 worm. isolation membrane (also called the phagophore; Mizushima The observations that Atg1 is a multifunctional protein et al., 2001 ), these data suggest that both ULK1 and 2 are tar- suggest that Atg1 should function in concert with several dis- geted to the isolation membrane. 498 JCB • VOLUME 181 • NUMBER 3 • 2008 Figure 1. ULK1 and 2 localize to the isola- tion membrane (phagophore) under starvation conditions. (A and B) NIH3T3 cells stably ex- pressing GFP-ULK1 (A) and -ULK2 (B) were cul- tured in complete or starvation medium for 30 min. They were then cultured in fresh complete medium for an additional 30 min (starvation → complete). (C and D) NIH3T3 cells stably ex- pressing GFP-ULK1 (C) and -ULK2 (D) were cul- tured in starvation medium for 120 min. The cells were fi xed, permeabilized, and subjected to immunofl uorescence microscopy using anti- Atg16L1 antibody and Alexa Fluor 660 – con- jugated secondary antibody. More than 90% of GFP-ULKs dots were positive for Atg16L1. (E – H) Wild-type (E and G) and Atg5 (F and H) MEFs were transfected with retroviral vectors encoding GFP-ULK1 and -ULK2. MEFs stably expressing GFP-ULK1 (E and F) and -ULK2 (G and H) were cultured in complete or starvation medium for 120 min. The cells were fi xed and examined by fl uorescence micros- copy. Bars, 20 μ m. In yeast, Atg1 localizes to the PAS independently of Atg5 Kinase-dead ULK mutants inhibit autophagy ( Suzuki et al., 2007 ). Although it is not clear whether mamma- In yeast, Atg1 kinase activity is up-regulated during autophagy lian cells have a similar PAS, we examined whether the puncta induced by nitrogen starvation or Tor inactivation ( Kamada formation of ULKs was independent of Atg5. Wild-type and et al., 2000 ). However, it is not known whether this is the case in Atg5 MEFs were transfected with retroviral vectors encod- mammalian cells. We therefore determined ULK kinase activity ing GFP-ULK1 ( Fig. 1, E and F ) and -ULK2 ( Fig. 1, G and H ) in MEFs under nutrient-rich and starved conditions. Endog- and observed after starvation. Although both GFP-ULK1 and enous ULK1 was precipitated with anti-ULK1 antibody, and -ULK2 puncta were formed in wild-type MEFs ( Fig. 1, E and G ), the resultant immunoprecipitate was analyzed by an in vitro these dots were never observed in Atg5 MEFs ( Fig. 1, F and H ). kinase assay using myelin basic protein as a model substrate. These results suggest that ULK puncta formation is dependent The ULK1 kinase activity level under the starvation condition is on Atg5 in mammalian cells. increased 1.3-fold relative to the nutrient-rich condition ( Fig. 2 A ). ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 499 Although this change was modest, these data suggest that the increase in ULK1 kinase activity might be important for the in- duction of autophagosome formation. We next examined the importance of the ULK kinase activ- ity using ULK kinase-dead mutants. Overexpression of kinase- dead Atg1 mutants inhibits autophagy in D. discoideum ( Tekinay et al., 2006 ) and D. melanogaster ( Scott et al., 2007 ), whereas overexpression of wild-type Atg1 accelerates autophagy in D. melanogaster ( Scott et al., 2007 ). However, in mammalian cells, both wild-type and kinase-dead ULK1 suppress autophagy, as judged by the LC3 conversion assay ( Chan et al., 2007 ). We therefore carefully examined the effect of wild-type and kinase- dead mutants of ULK1 and 2 on Atg16L1 puncta formation. In transient transfection experiments, moderate expression of K46N K39T kinase-dead HA-ULK1 ( Yan et al., 1998 ) and HA-ULK2 ( Yan et al., 1999 ) effi ciently suppress the starvation-induced Atg16L1 puncta formation ( Fig. 2 C ), whereas wild-type ULK1 and 2 showed almost no effect ( Fig. 2 B ; note that HA-ULK dots are not as clear as those in stable transformants [ Fig. 1 ] because of high cytoplasmic signals caused by overexpression). In con- trast, when overexpressed in higher levels, both wild-type and kinase-dead ULKs suppressed Atg16L1 puncta formation (un- published data). The shape of wild-type ULK-overexpressing cells was abnormal (Fig. S3, available at http://jcb.org/cgi/content/full/ jcb.200712064/DC1), as previously demonstrated by Chan et al. (2007) . The cells generated protrusions and, fi nally, detached from the culture dish, which is consistent with the previous results in D. melanogaster that Atg1 overexpression caused apoptotic cell death ( Scott et al., 2007 ). However, these abnormalities were not observed in cells overexpressing kinase-dead ULK1 and 2 (Fig. S3). Therefore, the effects of overexpression of wild-type and kinase-dead ULKs are different. The kinase-dead mutants indeed act as dominant-negative mutants, whereas wild-type overexpres- sion may cause cytotoxicity by some other mechanism. Collec- tively, these data suggest that the kinase activity is important for the involvement of ULKs in autophagy. We also generated NIH3T3 cells stably expressing GFP- K46N K39T ULK1 and GFP-ULK2 . Although both Atg16L1 and GFP-ULKs formed puncta in wild-type NIH3T3 cells after star- vation, these puncta were only very rarely observed in NIH3T3 K46N K39T cells stably expressing GFP-ULK1 or GFP-ULK2 ( Fig. 2 D ), confi rming that kinase-dead ULKs function as a dominant- negative mutant in autophagosome formation. We next measured this effect by the LC3 conversion as- say. Conversion of cytosolic LC3 (LC3-I) to membrane-bound phosphatidylethanolamine (PE) – conjugated LC3 (LC3-II) oc- curs during autophagy, and the amount of LC3-II is correlated with the number of autophagosomes ( Kabeya et al., 2000 ). This Figure 2. The kinase-dead ULK mutants inhibit autophagy. (A) In vitro LC3 conversion during starvation was markedly suppressed in kinase assay of endogenous ULK1. MEFs were cultured in complete or K46N NIH3T3 cells stably expressing ULK1 ( Fig. 2 E ), as recently starvation medium for 60 min. ULK1 kinase activity was determined as de- scribed in Materials and methods. Relative kinase activity is shown. Data are the mean ± SE of fi ve independent experiments. (B and C) NIH3T3 cells were transiently transfected with HA-ULK1, HA-ULK2, or their kinase- dead mutants and subjected to immunofl uoresence microscopy using cultured in starvation medium for 120 min. The cells were subjected to monoclonal anti-HA and polyclonal anti-Atg16L1 antibodies for primary immunofl uorescence microscopy using anti-Atg16L1 antibody. Bar, 20 μ m. staining and Alexa Fluor 488 – conjugated goat anti – mouse IgG and (E) NIH 3T3 cells were transfected with the retroviral vectors encoding HA- K46N Alexa Fluor 568 – conjugated goat anti – rabbit IgG antibodies for second- ULK1 or with the corresponding empty retrovirus (mock). They were ary antibodies. Transfected cells are indicated by arrows. Bars, 20 μ m. cultured in complete or starvation medium for 120 min. Cell lysates were K46N K39T (D) NIH3T3 cells stably expressing GFP-ULK1 and GFP-ULK2 were then analyzed by immunoblot analysis with the indicated antibodies. 500 JCB • VOLUME 181 • NUMBER 3 • 2008 Figure 3. ULK1 interacts with FIP200. (A) HEK293T cells were cotransfected with FLAG-FIP200 and HA-ULKs. Cell lysates were subjected to immuno- precipitation (IP) using antibodies against FLAG. The resulting precipitates were examined by immunoblot (IB) analysis with the indicated antibodies. The as- terisk indicates nonspecifi c band. (B) Lysates of MEFs were immunoprecipitated with anti-ULK1 or anti-FIP200 antibody or preimmune rabbit serum, and the resulting precipitates were subjected to immunoblot analysis with antibodies against ULK1 and FIP200. (C) Schematic representation of ULK1 mutants used in D. (D) HEK293T cells were cotransfected with FLAG-FIP200 and various ULK1 mutants and analyzed as in A using anti-HA and anti-FLAG antibodies. (E) NIH3T3 cells stably expressing GFP-ULK1 (left) and GFP-ULK1 (right) were cultured in starvation medium for 120 min. Bar, 20 μ m. reported by Chan et al. (2007) . Another assay was conducted the role of ULK, we searched for additional ULK-interacting to monitor autophagy fl ux. Because p62 (SQSTM1/sequesto- proteins. Mouse ULK1-FLAG and FLAG-ULK2 were expressed some 1) can bind LC3, p62 is preferentially incorporated into in HEK293 cells and immunoprecipitated with an anti-FLAG autophagosomes and degraded by autophagy ( Bj ø rk ø y et al., antibody. We analyzed the immunoprecipitates by highly sensi- 2005 ; Mizushima and Yoshimori, 2007 ). The amount of p62 can tive direct nanofl ow liquid chromatography/tandem mass spec- therefore serve as a good indicator of autophagic activity. The trometry ( Natsume et al., 2002 ) and identifi ed FIP200, which K46N base level of p62 was up-regulated in ULK1 -transfected is also called RB1CC1, in both the ULK1 and 2 precipitates. cells compared with mock-transfected cells. Although the level We confi rmed the interaction of FIP200 with ULK1 and 2 by of p62 decreased during starvation in mock-transfected cells, immunoprecipitation analysis using HEK293T cells coexpress- K46N the decrease was modestly suppressed in ULK1 -transfected ing FLAG-FIP200 and either HA-ULK1 or -ULK2 ( Fig. 3 A ). cells. These data suggest that autophagic fl ux was attenuated by Furthermore, we generated antibody against FIP200 and detected expression of the kinase-dead ULKs. the interaction between endogenous ULK1 and FIP200 in wild- type MEFs ( Fig. 3 B ). This coprecipitation was not observed Identifi cation of FIP200 if we performed the same experiments using FIP200 MEFs. as a ULK-interacting protein The interaction between ULK1 and FIP200 was not affected by In yeast, Atg1 forms a complex with multiple proteins including nutrient conditions, suggesting that ULK1 and FIP200 physically Atg13 and 17. However, a different set of ULK-interacting pro- interact with each other under both nutrient-rich and starvation teins has been reported in mammals that includes GABARAP, conditions ( Fig. 3 B ). GATE-16 ( Okazaki et al., 2000 ), SynGAP, and Syntenin ( Tomoda We next determined which region of ULK1 is required et al., 2004 ) but not other Atg homologues. To better understand for the interaction with FIP200, using several ULK1 mutants ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 501 Figure 4. FIP200 localizes to phagophore after starvation treatment. (A) NIH3T3 cells stably ex- pressing GFP-FIP200 were cultured in complete or starvation medium for 120 min and the GFP signal was observed. (B) NIH3T3 cells stably expressing GFP-FIP200 were cultured in starvation medium for 120 min and then subjected to immunofl uorescence microscopy using anti-Atg16L1 antibody and Alexa Fluor 568 – conjugated secondary antibody. Bars, 20 μ m. More than 90% of GFP-FIP200 dots were positive for Atg16L1. (C) NIH3T3 cells stably expressing GFP- ULK1 were starved for 120 min and then subjected to immunofl uorescence microscopy using anti-FIP200 antibody and Alexa Fluor 568 – conjugated secondary antibody. Black squares indicate the enlarged areas shown in insets. Bar, 20 μ m. K46N ( Fig. 3 C ). Although kinase-dead ULK1 could interact with acid and serum starvation, however, the number of these dots 1 – 427 FIP200, the C-terminal deletion mutants (ULK1 and increased. These GFP-FIP200 – positive dots were almost com- 1 – 828 ULK1 ) could not ( Fig. 3 D ). The C-terminal deletion mu- pletely colocalized with Atg16L1 ( Fig. 4 B ). Furthermore, we 1 – 828 tant ULK1 also failed to accumulate to punctuate dots ( Fig. observed almost complete colocalization between GFP-ULK1 3 E ). Thus, the C-terminal region (829 – 1051 aa) of ULK1 is re- and endogenous FIP200 ( Fig. 4 C ). All these data suggest that quired for both ULK-FIP200 interaction and puncta formation. FIP200 localizes to elongating isolation membrane together with ULKs. FIP200 localizes to the isolation membrane FIP200, a ubiquitously expressed protein ( Bamba et al., 2004 ), FIP200 is required for autophagy was originally identifi ed as a Pyk2 (proline-rich tyrosine kinase The isolation membrane localization of FIP200 prompted us to 2)-interacting protein ( Ueda et al., 2000 ). FIP200 binding in- further examine its role in autophagy. FIP200 is known to be hibits Pyk2 kinase activity, thereby inhibiting Pyk2-induced essential for embryonic development. FIP200 mice show apoptosis. FIP200 also associates with FAK as a negative regula- embryonic lethality between embryonic day (E) 13.5 and 16.5 tor ( Abbi et al., 2002 ). Additionally, FIP200 interacts with multi- because of defective heart and liver development ( Gan et al., ple proteins such as TSC1 ( Gan et al., 2005 ), p53 ( Melkoumian 2006 ). We therefore examined the autophagic activity of MEFs et al., 2005 ), ASK1, and TRAF2 ( Gan et al., 2006 ). FIP200 also derived from FIP200 embryos. In wild-type MEFs, 1 h of induces RB1 expression ( Chano et al., 2002a ). Therefore, FIP200 amino acid and serum starvation induced LC3 conversion, is a multifunctional protein that is involved in cell migration, which was restored by an additional 1-h incubation in com- proliferation, cell size regulation, cell death, and tumor suppres- plete DME supplemented with 10% FCS ( Fig. 5 A ). In con- sion. However, its involvement in autophagy or membrane traf- trast, the starvation-induced LC3 conversion was almost fi cking has not been reported. completely abolished in FIP200 MEFs. Furthermore, p62 To investigate the functional relevance of FIP200 in accumulated in FIP200 MEFs, suggesting that autophagy autophagosome formation, we fi rst examined the subcellular is profoundly suppressed in the absence of FIP200. It should localization of FIP200. FIP200 has been previously reported to be noted, however, that a small amount of LC3-II was detected localize to the nucleus ( Chano et al., 2002a ), cytoplasm ( Ueda in FIP200 MEFs irrespective of nutrient conditions. This et al., 2000 ), and focal contacts in the cell periphery ( Abbi et al., phenotype was quite different from that of Atg5 MEFs, in 2002 ). When we observed NIH3T3 cells transfected with a retro- which LC3-II was never detected ( Fig. 5 A ). These results sug- virus vector encoding GFP-fused FIP200 under nutrient-rich gest either that low-level autophagy constitutively occurs in conditions, most GFP signals were detected diffusely in the FIP200 MEFs or that LC3 conversion occurs independently cytoplasm, with only a few punctate dots ( Fig. 4 A ). After amino of autophagy. 502 JCB • VOLUME 181 • NUMBER 3 • 2008 +/+  /  +/+  / Figure 5. FIP200 is required for autophagy. (A) FIP200 , FIP200 , Atg5 , and Atg5 MEFs were cultured in complete or starvation medium for 60 min. In the recovery experiments, starved MEFs were cultured in fresh complete medium for an additional 60 min (replenishment). The cell lysates were subjected to immunoblot analysis with the indicated antibodies. (B) Wild-type and FIP200 MEFs were cultured in the complete or starvation medium for indicated time with or without 100 nM bafi lomycin A . The cell lysates were subjected to immunoblot analysis with anti-LC3 antibody. (C) Wild-type and FIP200 MEFs were transfected with retroviral vectors encoding GFP-Atg5 or GFP-LC3. Resulting cells were cultured in the starvation medium for 120 min. The cells were fi xed and examined by fl uorescence microscopy. Bar, 20 μ m. (D – G) Wild-type (D and E) and FIP200 (F and G) MEFs were cultured in complete (D and F) or starvation (E and G) medium for 120 min and then fi xed and subjected to EM analysis. Autophagosome-like structures (open arrowheads), and autolysosomes (closed arrowheads) are indicated. Bar, 1 μ m. (H) The ratio of total area of autophagosomes (AP) and autolysosomes (AL) to total cytoplasmic area in D – G was determined by morphometric analysis. To monitor the autophagic ability of FIP200 MEFs toring the redistribution of cytosolic GFP-Atg5 and GFP-LC3 more precisely, we determined the autophagy fl ux in these cells to membrane structures. After a 2-h culture in amino acid- by the LC3 turnover assay ( Tanida et al., 2005 ; Mizushima and and serum-deprived medium, several GFP-Atg5 and GFP- Yoshimori, 2007 ). Because LC3-II is present on both outer and LC3 dots were observed in wild-type MEFs ( Fig. 5 C , left). inner autophagosome membranes, LC3-II itself is degraded after In FIP200 cells, however, these GFP-Atg5 – positive dots autophagosome-lysosome fusion. If autophagosome-lysosome were completely absent ( Fig. 5 C , right, top). The number of fusion is blocked with the vacuolar H ATPase inhibitor bafi lo- GFP-LC3 dots was greatly reduced, but several GFP-LC3 – mycin A ( Yamamoto et al., 1998 ), autophagic degradation of positive dots were still observed in FIP200 cells ( Fig. 5 C , LC3-II should be suppressed. This treatment indeed caused ac- right, bottom). However, these dots were irregular in shape, cumulation of LC3-II in 2-h and 4-h starved wild-type MEFs and their number did not change after starvation treatment ( Fig. 5 B ). However, this effect of bafi lomycin A was not ob- (unpublished data). These structures therefore likely represent served in FIP200 MEFs e ven after 4-h starvation, suggesting some aberrant structures or aggregates of GFP-LC3 protein that autophagic degradation is suppressed almost completely in caused by FIP200 defi ciency. To further confi rm the effect of these cells. loss of FIP200 on autophagosome formation, we performed We also examined autophagy induction in wild-type and EM analysis. In wild-type MEFs after a 2-h starvation, we FIP200 MEFs stably expressing GFP-Atg5 (isolation mem- could detect numerous autophagic vacuoles, which occupied brane marker) or GFP-LC3 (autophagosome marker) by moni-  3% of the total cytoplasmic volume (  2% autophagosomes ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 503 +/   / Figure 6. FAK is not required for autophagy. (A) FAK and FAK MEFs were cultured in the complete or starvation medium for the indicated times +/   / with or without 100 nM bafi lomycin A . The cell lysates were subjected to immunoblot analysis with the indicated antibodies. (B) FAK and FAK MEFs stably expressing GFP-LC3 were cultured in complete or starvation medium for 120 min. The cells were fi xed and examined by fl uorescence microscopy. (C) Wild-type MEFs stably expressing GFP-FAK were cultured in complete or starvation medium for 120 min. The cells were fi xed and subjected to immuno- fl uorescence microscopy using anti-Atg16 antibody. Black squares indicate the enlarged areas shown in insets. Bars, 20 μ m. and  1% autolysosomes; Fig. 5, D, E, and H ). In contrast, auto - FIP200 functions downstream of ph agosome-like structures were hardly observed in FIP200 mammalian target of rapamycin (mTOR) in MEFs even under amino acid and serum starvation conditions autophagosome formation ( Fig. 5, F, G, and H ). These results demonstrate that FIP200 is FIP200 interacts with TSC1 and inhibits its function ( Gan et al., required for autophagosome formation. 2005 ). The TSC1-TSC2 heterodimer inhibits mTOR function through Rheb inactivation ( Inoki and Guan, 2006 ; Wullschleger The role of FIP200 in autophagy is et al., 2006 ; Guertin and Sabatini, 2007 ). As autoph agy is nega- independent of FAK tively regulated by mTOR signaling ( Meijer and Codogno, FIP200 can bind FAK and inhibit FAK function. FAK is one of 2004 ), we investigated whether the autophagy defect of FIP200 the focal adhesion components that include multiple proteins MEFs is a result of aberrant TSC-mTOR signaling. If this were such as vinculin, paxillin, and talin ( Carragher and Frame, the case, autophagy should be induced by treatment with the 2004 ). In addition, while we were preparing this manuscript, it mTOR inhibitor rapamycin. In wild-type MEFs, rapamycin was reported that paxillin also acts as a regulator of autophagy induced LC3 conversion both in the absence and presence of ( Chen et al., 2007 ). On that basis, we investigated the potential bafi lomycin A . However, the LC3 conversion induced by rapa- /   / role of FAK in autophagy using FAK MEFs ( Ilic et al., 1995 ). mycin was still impaired in FIP200 MEFs ( Fig. 7 A ). We also As far as we tested, FAK MEFs demonstrated no abnormal- observed that rapamycin was able to induce GFP-Atg5 and ities related to autophagy. Starvation-induced LC3 conversion GFP-LC3 dot formation in wild-type MEFs but not in FIP200 with and without bafi lomycin A and starvation-induced p62 MEFs ( Fig. 7 B ). Furthermore, mTOR appeared to be normally degradation in the lysosome were normal ( Fig. 6 A ). There was suppressed in FIP200 MEFs after serum and amino acid also no difference in starvation-induced GFP-LC3 dot forma- starvation, as judged by 4E-BP1 dephosphorylation, despite the +/   / tion between FAK and FA K MEFs ( Fig. 6 B ). Addition- suppression of autophagy ( Fig. 5 A ). Collectively, these data ally, GFP-fused FAK localized to focal adhesions but not to the suggest that the defect in autophagosome formation of FIP200 Atg16L1-positive autophagy-related structure ( Fig. 6 C ). These MEFs is caused by loss of FIP200 function downstream of results suggest that FAK is not involved in auto ph agy and that mTOR and not by aberrant nutrient signaling including the the role of FIP200 in autophagy is independent of FAK. TSC complex. 504 JCB • VOLUME 181 • NUMBER 3 • 2008 Figure 8. FIP200 is required for membrane targeting and proper function +/   / of ULK. (A) FIP200 and FIP200 MEFs stably expressing GFP-ULK1 or -ULK2 were cultured in starvation medium for 120 min. The cells were +/+ fi xed and examined by fl uorescence microscopy. Bar, 20 μ m. (B) FIP200 and FIP200 MEFs were cultured in complete medium. The cell lysates were subjected to immunoblot analysis with antibodies against ULK1 or +/+ HSP90 (loading control). (C) Phosphatase sensitivity of ULK1. FIP200 Figure 7. FIP200 functions downstream of mTOR in autophagosome for- and FIP200 MEFs were cultured in complete medium. ULK1 was mation. (A) Wild-type and FIP200 MEFs were treated with 100 ng/ml immunoprecipitated from cell lysates and treated with  phosphatase for rapamycin (rapa) or vehicle (DMSO) for 120 min in the presence or ab- 30 min at 30 ° C in the absence or presence of phosphatase inhibitors sence of 100 nM bafi lomycin A . The cell lysates were subjected to immuno- (1 mM Na VO , 50 mM KF, 15 mM Na P O , and 1 mM EGTA). 1 2 4 4 2 7 blot analysis with anti-LC3 antibody. (B) Wild-type and FIP200 MEFs stably expressing GFP-Atg5 or GFP-LC3 were cultured in the presence of 100 ng/ml rapamycin for 120 min. The formation of GFP-Atg5 (top) and ment of isolation membrane formation in the absence of FIP200, GFP-LC3 (bottom) puncta was examined by fl uorescence microscopy. Bar, /  because even GFP-Atg5 dot formation was suppressed in 20 μ m. (C) Wild-type and FIP200 MEFs were treated with 10 mM lithium chloride for 24 h or 100 μ M C -ceramide for 2 h. FIP200 MEFs ( Fig. 5 C ). To explore more direct functional connections between ULK and FIP200, we next examined the expression status of ULK1 in wild-type and FIP200 MEFs. /   / FIP200 MEFs were also resistant to various auto phagy- The expression level of ULK1 in FIP200 MEFs was much inducing reagents such as lithium chloride ( Sarkar et al., lower than in wild-type MEFs under both nutrient rich ( Fig. 2005 ) and ceramide ( Fig. 7 C ; Scarlatti et al., 2004 ). Because 8 B ) and starvation (not depicted) conditions. The ULK1 mRNA the effect of lithium is independent of mTOR ( Sarkar et al., expression was enhanced after starvation, but there was no dif- 2005 ), FIP200 should function in both mTOR-dependent and ference between wild-type and FIP200 cells (Fig. S4 A, -independent autophagy. available at http://jcb.org/cgi/content/full/jcb.200712064/DC1). However, we observed faster decay of ULK1 protein in FIP200 FIP200 is required for ULK puncta cells after cycloheximide treatment, suggesting that ULK1 is formation and is important for the stability destabilized in the absence of FIP200 (Fig. S4 B). Additionally, and proper phosphorylation of ULK we found that ULK1 was detected as a smeared band with faster Given that FIP200 interacts with ULK1 and 2, we postulated mobility in FIP200 MEFs. As previously reported ( Yan K46N that ULKs and FIP200 function together. We fi rst examined the et al., 1998, 1999 ), we observed that mobility of ULK1 is membrane targeting of ULKs in wild-type and FIP200 faster than that of wild-type ULK1, suggesting that ULK1 is MEFs. As we demonstrated in Fig. 1 , GFP-ULK puncta were autophosphorylated ( Fig. 3 D ). Consistent with this, when we formed in wild-type MEFs during starvation. These puncta rep- treated ULK1 immunoprecipitated from wild-type cells with resent the isolation membrane ( Fig. 8 A , left). However, these  phosphatase, ULK1 migrated to a lower position that was dots were never observed in FIP200 MEFs, suggesting that suppressed in the presence of phosphatase inhibitors, confi rming puncta formation of ULK1 and 2 depends on FIP200 ( Fig. 8 A , that ULK1 is phosphorylated ( Fig. 8 C ). Likewise, the phospha- right). However, this observation may simply refl ect impair- tase treatment of ULK1 from FIP200 cell lysates produced a ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 505 band with the same mobility ( Fig. 8 C , compare lanes 2 and 5), MEFs ( Gan et al., 2005 ). We also failed to detect clear defect in indicating that the faster migration of endogenous ULK1 in this pathway as we tested the phosphorylation levels of 4E-BP1 FIP200 MEFs represents reduced phosphorylation rather ( Fig. 5 A ). There might be adaptation to the FIP200-defi cient than other modifi cations such as protein processing. Therefore, conditions in permanently knocked out cells. However, our FIP200 is likely important for maintenance of the ULK1 kinase present study does not exclude the possibility that FIP200 func- activity. All these results suggest that FIP200 and ULK1 are tions with the TSC complex. FIP200 may function both up- functionally connected and that this complex plays an important stream and downstream of mTOR, but the downstream effect role in autophagosome formation. can be dominant when we analyze autophagy. As FIP200 interacts with ULK1 and 2 and is essential for autophagy, one might speculate that this protein is a counterpart Discussion of yeast Atg13 or 17. Indeed, although FIP200 (1594 aa) is We have identifi ed a novel ULK-interacting protein, FIP200, much larger than Atg17 (417 aa), FIP200 shares several features and demonstrated that ULK1, ULK2, and FIP200 localize to the with yeast Atg17. First, both Atg17 and FIP200 have multiple isolation membrane. Because FIP200-defi cient cells displayed coiled-coil domains. Second, just as Atg17 is required for Atg1 virtually no autophagosomes, we propose that the ULK – FIP200 kinase activity ( Kamada et al., 2000 ; Kabeya et al., 2005 ), the complex is essential for an early step, not a later or completion phosphorylation status of ULK1 is reduced in FIP200-defi cient step, of autophagosome formation. cells, which may indicate diminished ULK1 activity ( Fig. 8 ). It is therefore likely that Atg17 and FIP200 can support the function Comparison between yeast Atg1 and of Atg1 and ULKs, respectively. We also found that ULK1 mammalian ULK in the autophagy pathway kinase activity per cell was reduced in FIP200 cells (unpub- Although yeast Atg1 and mammalian ULK possess several lished data). However, as ULK1 expression level itself was also common features, there are some differences. One difference is lower in FIP200 cells than in wild-type cells ( Fig. 8 ), we that although both proteins target to autophagic structures, pre- could not conclude how much specifi c activity of ULK1 re- cise localization may not be the same. Yeast Atg1 is known to duced in the absence of FIP200. Third, the C-terminal region of localize to the PAS ( Suzuki et al., 2007 ). However, because ULK1 is essential for both FIP200 interaction and ULK1 puncta Atg1 is delivered to the vacuole ( Suzuki et al., 2001 ), it should formation ( Fig. 3 ; Chan et al., 2007 ), suggesting that interaction be present on the inner membrane of autophagosomes or cap- with FIP200 is important for membrane targeting. This is con- tured inside autophagosomes. In contrast, we detected ULK1 sistent with the previous fi nding that yeast Atg17 is required and 2 only on the isolation membrane, which suggests that for PAS targeting of Atg1, which is particularly apparent in ULK1 and 2 associate primarily with the outer membrane of the atg11 mutant ( Suzuki et al., 2007 ; Cheong et al., 2008 ; autophagosomes like the Atg12 – Atg5 conjugate ( Mizushima Kawamata et al., 2008 ). Fourth, FIP200 has multiple binding et al., 2001 ). Accordingly, both ULK1 and FIP200 are not de- partners other than ULK1 and 2. Similarly, systematic analyses graded in lysosome because expression levels of these proteins of yeast protein interactions by two-hybrid analysis and mass did not change after treatments of bafi lomycin A1 (Fig. S5, spectrometry identifi ed many potential Atg17-interacting pro- available at http://jcb.org/cgi/content/full/jcb.200712064/DC1). teins, some of which are unrelated to autophagy ( Ho et al., Another difference is the Atg5 dependency of Atg1/ULK 2002 ; Gavin et al., 2006 ; Krogan et al., 2006 ). Therefore, both dot formation. Although PAS targeting of yeast Atg1 does not Atg17 and FIP200 may function as a scaffold for multiple pro- depend on Atg5 ( Suzuki et al., 2007 ), puncta formation of teins. Finally, homologues of Atg17 are present in Kluyveromyces ULK1 and 2 depends on Atg5 in mammalian cells ( Fig. 1 ). One lactis and Eremothecium gossypii , where FIP200 homologue possible explanation of this apparent discrepancy between yeast is missing. On the other hand, FIP200 homologues are found in and mammalian Atg1/ULK would be that the PAS-equivalent Homo sapiens , Mus musculus , Gallus gallus , and D. melano- structure is not visible in mammalian cells, and localization of gaster , where Atg17 homologues are absent, but not in Saccha- Atg1/ULK to isolation membrane should be dependent on Atg5 romyces cerevisiae. This mutual exclusiveness suggests that both in yeast and mammals. Dissection of PAS and the isolation these two groups of proteins may serve similar functions for membrane in yeast would clarify this issue. which one, but not both, proteins are required. Identifi cation We did not observe any difference between ULK1 and 2 and analysis of a functional homologue of mammalian Atg13, a in the present study, although ULK2 has been reported to be critical factor of this complex, will further clarify the functional dispensable for autophagy ( Young et al., 2006 ; Chan et al., relationship between yeast and mammalian Atg1 complex. 2007 ). The function of ULK2 thus remains unclear. Examina- tion of endogenous ULK2 will be required. LC3 conversion in FIP200 cells One notable fi nding in this study is that signifi cant amounts of FIP200, a possible counterpart of yeast LC3-II, which is the most widely used autophagy indicator, are Atg17? detectable in FIP200-defi cient cells. This may indicate that It w as previously shown that FIP200 interacted with TSC1, and a very low level of autophagy occurs even in the absence of phosphorylation of S6 kinase after amino acid stimulation was FIP200, which is consistent with the fi nding that small autopha- impaired in cells treated with FIP200 siRNA ( Gan et al., 2005 ). gosomes are occasionally generated in yeast atg17 mutant cells However, this effect was observed only moderately in FIP200 ( Cheong et al., 2005 ; Kabeya et al., 2005 ). However, this leaky 506 JCB • VOLUME 181 • NUMBER 3 • 2008 phenotype is likely mediated by Cvt-specifi c Atg11, which is for autophagy, suggesting that the focal adhesion complex per absent in mammalian cells ( Suzuki et al., 2007 ; Cheong et al., se is not involved in autophagy. FAK-independent communica- 2008 ; Kawamata et al., 2008 ). Indeed, the autophagy fl ux anal- tion between FIP200 and paxillin will be the subject of future ysis of FIP200 cells suggested that autophagic degradation studies in both autophagy and focal adhesion. is nearly completely abolished ( Fig. 5 B ). Thus, the small Given that at least three of the focal adhesion components amount of LC3-II detected in FIP200 cells may be generated function in autophagy, it is possible that ULKs also plays a role in an autophagy-independent manner. In yeast, Atg8 – PE is gen- in cell adhesion that is independent of its function in autophagy. erated even in atg17 mutant cells as well as in several other Indeed, GFP-ULK1 and -ULK2 were occasionally detected at autophagy mutants such as atg1 , 2 , 6 , 9 , 13 , 14 , and 16 mutants the cell periphery (Fig. S2), and overexpression of wild-type ( Suzuki et al., 2001 ). Atg8 – PE conjugation is severely affected ULKs caused abnormal cell morphology such as cell rounding only in atg5 , 10 , and 12 mutant cells and is completely blocked and protrusion (Fig. S3). So far, several studies have suggested in atg3 , 4 , and 7 mutant cells ( Suzuki et al., 2001 ). The Atg12 – autophagy-independent roles of Atg1/ULK in various species, Atg5 conjugate was recently reported to have an E3-like en- such as axonal elongation and branching in C. elegans ( Ogura zyme activity for the Atg8 – PE conjugation reaction ( Hanada et al., 1994 ) and mammals ( Tomoda et al., 1999 ; Zhou et al., et al., 2007 ). Therefore, the Atg8 – PE conjugation can take place 2007 ). These functions may be related to the role of Atg1 in fo- in an autophagy-independent manner. The Atg knockout mam- cal adhesion. /   / malian cells reported so far are Atg5 and Atg7 . Although In conclusion, we have identifi ed a novel ULK-interacting LC3-II formation is absent in these cells, this is probably caused protein, FIP200, which is functionally similar to yeast Atg17. by defi ciency of Atg12 and 8 conjugation and not simply au- The ULK – FIP200 complex is essential for autophagy, but the tophagy defi ciency. As observed in FIP200 cells, Beclin 1 precise role of this complex is unknown. Identifi cation of physi- silencing blocks autophagosome formation but does not cause ologically relevant substrates of Atg1 – ULK is one of the most complete suppression of the LC3 conversion ( Zeng et al., 2006 ; straightforward approaches, although it has not been successful Matsui et al., 2007 ). Therefore, it is not contradictory that thus far in any species studied ( Deminoff and Herman, 2007 ). FIP200 cells show some LC3-II, even if the autophagic Searching for additional interacting proteins will also facilitate activity is virtually suppressed. Rather, these data suggest that understanding of the role of Atg1 – ULK complex and the regu- we should measure the autophagy fl ux, not the absolute amount lation of autophagy induction and autophagosome formation. of LC3-II, to monitor autophagy ( Tanida et al., 2005 ; Mizushima and Yoshimori, 2007 ). Materials and methods ULK/Atg1 and focal adhesion components Plasmids IMAGE Consortium cDNA clones (GenBank accession no. BC017556) We have demonstrated that FIP200 localizes to the autophagic encoding human RB1CC1/FIP200 were obtained from Invitrogen. The isolation membrane and is essential for autophagy. We do not cDNA encoding FIP200 was cloned into p3 × FLAG CMV10 (Sigma- think that FIP200 is an autophagy-specifi c protein. The most Aldrich). Expression constructs for wild-type and kinase-dead mouse ULK1 and 2 were gifts from N. Okazaki (Kazusa DNA Research Institute, striking evidence for this is that FIP200 mice die between Kisarazu, Japan) and M. Muramatsu (Tokyo Medical and Dental Univer- E13.5 and 16.5 with defective heart and liver development ( Gan sity, Tokyo, Japan). The kinase-dead ULK1 mutant (with conserved ATP /   / et al., 2006 ), whereas autophagy-defi cient Atg5 and Atg7 binding Lys 46 replaced with Asn) and the kinase-dead mutant ULK2 (with Lys 39 to Thr replacement) were previously described ( Yan et al., 1998, mice survive embryogenesis (although they die within one day 1999 ). FAK cDNA constructs were provided by S. Hanks (Vanderbilt Uni- of birth). Indeed, FIP200 involvement has been suggested in versity, Nashville, TN). various cellular processes, such as inhibition of Pyk2-induced Cell culture and transfection signaling ( Ueda et al., 2000 ), inhibition of cell migration /   /  +/ Atg5 ( Kuma et al., 2004 ), FIP200 ( Gan et al., 2006 ), and FAK , through FAK inhibition ( Abbi et al., 2002 ), tumor suppression  / FAK (gift from S. Aizawa, Institute of Physical and Chemical Research, ( Chano et al., 2002b ), induction of RB expression ( Chano et al., Kobe, Japan; Ilic et al., 1995 ) MEFs were generated previously. MEFs and HEK293T cells were cultured in DME supplemented with 10% FBS and 2002a ), cell size regulation through inhibition of the TSC com- 50 μ g/ml penicillin and streptomycin (complete medium) in a 5% CO plex ( Gan et al., 2005 ; Chano et al., 2006 ), inhibition of p53- incubator. Bovine calf serum was used instead of FBS for NIH3T3 cells. mediated G1-S progression ( Melkoumian et al., 2005 ), and For starvation, cells were washed with PBS and incubated in amino acid – free DME without FBS (starvation medium). Fugene 6 reagent (Roche) inhibition of TNF-induced apoptosis, probably through inhibition and lipofectamine 2000 reagent (Invitrogen) were used for transfection. with ASK1 and TRAF2 ( Gan et al., 2006 ). These data suggest that FIP200 is a multifunctional protein. Antibodies and reagents Polyclonal antibodies against FIP200 or ULK1 were generated in rabbits by An important question is whether FIP200 alone or FIP200 standard procedures with fragments of recombinant human FIP200 (resi- and its interacting proteins are involved in autophagy. While we dues 200 – 413 and 1 – 633) or mouse ULK1 (residues 738 – 1052) as anti- were preparing this manuscript, a D. melanogaster genetic anal- gens. Polyclonal anti-LC3 ( Hosokawa et al., 2006 ) and anti-Atg16L1 antibodies ( Mizushima et al., 2003 ) were described previously. Polyclonal ysis revealed a genetic interaction between Atg1 and paxillin, a anti-ULK1 antibody (A7481) and monoclonal anti-FLAG (M2) and anti – cytoskeletal scaffolding protein ( Chen et al., 2007 ). The study -tubulin (DM1A) were purchased from Sigma-Aldrich. Another polyclonal further demonstrates that paxillin and vinculin redistribute from anti-ULK1 antibody was purchased from Santa Cruz Biotechnology, Inc. A monoclonal anti-HA antibody (HA11) was purchased from Covance. focal adhesions to intracellular structures under starvation con- Monoclonal anti-HSP90 and anti-HSP70 antibodies were purchased from ditions and that paxillin-defi cient MEFs are defective in autoph- BD Biosciences. Polyclonal antibodies to 4E-BP1 were purchased from Cell agy. In contrast, our analysis showed that FAK is not required Signaling Technology. Polyclonal antibodies to p62 were purchased from ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 507 American Research Products, Inc. Alexa Fluor 488 – , 568 – , and 660 – conju- 5  -TGGGGAGAAGGTGTGTAGGG-3  ; and mouse  -actin forward, gated goat anti – rabbit IgG (H + L) antibodies (Invitrogen) were used for 5  -CTGGGTATGGAATCCTGTGG-3  ; and reverse, 5  -GTACTTGCGCT- immunochemistry. Rapamycin and lithium chloride were purchased from CAGGAGGAG-3  . Amplicon expression in each sample was normalized Sigma-Aldrich. Bafi lomycin A was purchased from Wako Pure Chemical to its  -actin mRNA content. Industries, Ltd. C -ceramide was purchased from EMD. Online supplemental material Fig. S1 shows the structural comparison of murine ULK homologues (ULK1 – 4). EM Fig. S2 shows the peripheral localization pattern of ULK1 and 2. Fig. S3 MEFs were fi xed in 2.5% glutaraldehyde in 0.1 M sodium phosphate buf- shows the aberrant cell morphology of cells overexpressing wild-type ULK fer, pH 7.4, for 2 h. The cells were washed three times in phosphate buffer but not in kinase-dead ULK. Fig. S4 shows the ULK1 mRNA expression and containing 1 mM glycine and were postfi xed in 1% OsO in 0.1 M phos- protein turnover in wild-type and FIP200 MEFs. Fig. S5 shows endog- phate buffer, pH 7.4, for 1 h. The cells were further dehydrated with a enous expression of ULK1 and FIP200 in MEFs in the presence or absence graded series of ethanol and were embedded in epoxy resin. Ultrathin sec- of 100 nM bafi lomycin A . Online supplemental material is available at tions were doubly stained with uranyl acetate and lead citrate and observed 1 http://jcb.org/cgi/content/full/jcb.200712064/DC1. using an electron microscope (7100; Hitachi). For morphometric analysis, at least 20 sections of each sample were analyzed using MetaMorph image We thank Dr. Shinichi Aizawa (Institute of Physical and Chemical Research) for analysis software (version 6.2; MDS Analytical Technologies). providing FAK MEFs, Dr. Steven K. Hanks (Vanderbilt University) for FAK cDNA, and Dr. Toshio Kitamura (The University of Tokyo) for the retroviral vec- Retroviral expression system tors and Plat E cells. K46N  C cDNAs encoding human FIP200, wild-type mouse ULK1, ULK1 , ULK1 , This work was supported in part by Grants-in-aid for Scientifi c Research K39T ULK2, ULK2 , Atg5, and FAK, and rat LC3 were N-terminally fused to the from the Ministry of Education, Culture, Sports, Science and Technology of K46N GFP fragment. A cDNA encoding mouse ULK1 was N-terminally tagged Japan. The authors also thank the Kato Memorial Bioscience Foundation and with the HA epitope. These cDNAs were subcloned into pMXs-puro or the Toray Science Foundation for fi nancial support. pMXs-IP (provided by T. Kitamura, University of Tokyo, Tokyo, Japan). The resulting vectors were used to transfect Plat E cells and thereby generate Submitted: 12 December 2007 recombinant retroviruses. MEFs and NIH 3T3 cells were infected with the Accepted: 2 April 2008 recombinant retroviruses and selected in medium containing 1 μ g/ml puromycin. Cells stably expressing the recombinant proteins were pooled for experiments ( Kamura et al., 2004 ). References Immunoprecipitation and immunoblotting Abbi , S. , H. Ueda , C. Zheng , L.A. Cooper , J. Zhao , R. Christopher , and J.L. Cell lysates were prepared in a lysis buffer (50 mM Tris-HCl, pH 7.5, 150 Guan . 2002 . Regulation of focal adhesion kinase by a novel protein in- mM NaCl, 1 mM EDTA, 0.5% Triton X-100, 1 mM PMSF, 1 mM Na VO , 3 4 hibitor FIP200. Mol. Biol. Cell . 13 : 3178 – 3191 . and protease inhibitor cocktail [Complete EDTA-free protease inhibitor; Abeliovich , H. , C. Zhang , W.A. Dunn Jr ., K.M. Shokat , and D.J. Klionsky . 2003 . Roche]). The lysates were clarifi ed by centrifugation at 15,000 rpm for 15 min Chemical genetic analysis of Apg1 reveals a non-kinase role in the induc- and were subjected to immunoprecipitation using specifi c antibodies in tion of autophagy. Mol. Biol. Cell . 14 : 477 – 490 . combination with protein G – Sepharose (GE Healthcare). Precipitated immuno- Bamba , N. , T. Chano , T. Taga , S. Ohta , Y. Takeuchi , and H. Okabe . 2004 . complexes were washed fi ve times in lysis buffer and boiled in sample buffer. Expression and regulation of RB1CC1 in developing murine and human Samples were subsequently separated by SDS-PAGE and transferred to tissues. Int. J. Mol. Med. 14 : 583 – 587 . Immobilon-P polyvinylidene difl uoride membranes (Millipore). Immunoblot Bj ø rk ø y , G. , T. Lamark , A. Brech , H. Outzen , M. Perander , A. Ø vervatn , H. analysis was performed with the indicated antibodies and visualized Stenmark , and T. Johansen . 2005 . p62/SQSTM1 forms protein aggregates with SuperSignal West Pico Chemiluminescent substrate (Thermo Fisher Sci- degraded by autophagy and has a protective effect on huntingtin-induced entifi c). The signal intensities were analyzed using an imaging analyzer cell death. J. Cell Biol. 171 : 603 – 614 . (LAS-3000mini; Fujifi lm) and Multi Gauge software (version 3.0; Fujifi lm). Carragher , N.O. , and M.C. Frame . 2004 . Focal adhesion and actin dynamics: a Contrast and brightness adjustment was applied to the whole images using place where kinases and proteases meet to promote invasion. T rends Cell Photoshop 7.0.1 (Adobe). Biol. 14 : 241 – 249 . Chan , E.Y. , S. Kir , and S.A. Tooze . 2007 . siRNA screening of the kinome iden- Fluorescence microscopy tifi es ULK1 as a multidomain modulator of autophagy. J. Biol. Chem. MEF or NIH3T3 cells expressing protein fused to GFP were directly ob- 282 : 25464 – 25474 . served with a fl uorescence microscope (IX81; Olympus) equipped with a Chano , T. , S. Ikegawa , K. Kontani , H. Okabe , N. Baldini , and Y. Saeki . 2002a . charge-coupled device camera (ORCA ER; Hamamatsu Photonics). A 60 × Identifi cation of RB1CC1, a novel human gene that can induce RB1 in PlanAPO oil immersion lens (1.42 NA; Olympus) was used. Images were various human cells. Oncogene . 21 : 1295 – 1298 . acquired using MetaMorph image analysis software version. For examina- Chano , T. , K. Kontani , K. Teramoto , H. Okabe , and S. Ikegawa . 2002b . Truncating tion by immunofl uorescence microscopy, cells grown on gelatinized cover- mutations of RB1CC1 in human breast cancer. Nat. Genet. 31 : 285 – 288 . slips were fi xed and stained with an anti-Atg16L1, anti-FIP200, or anti-HA Chano , T. , M. Saji , H. Inoue , K. Minami , T. Kobayashi , O. Hino , and H. Okabe . antibody as previously described ( Mizushima et al., 2001 ). 2006 . Neuromuscular abundance of RB1CC1 contributes to the non-pro- liferating enlarged cell phenotype through both RB1 maintenance and Kinase assay TSC1 degradation. Int. J. Mol. Med. 18 : 425 – 432 . Cells were washed with PBS and then lysed in an extraction buffer (20 mM Chen , G.C. , J.Y. Lee , H.W. Tang , J. Debnath , S.M. Thomas , and J. Settleman . Tris-HCl, pH7.5, 150 mM NaCl, 10 mM  -glycerophosphate, 5 mM 2007 . Genetic interactions between Drosophila melanogaster Atg1 and EGTA, 1 mM sodium pyrophosphate, 5 mM NaF, 1 mM Na VO , and 3 4 paxillin reveal a role for paxillin in autophagosome formation. A utophagy . 0.5% Triton X-100) supplemented with protease inhibitors (10 μ g/ml each 4 : 37 – 45 . of pepstatin A, chymostatin, leupeptin, and E64 [Peptide Institute, Inc.]). Cheong , H. , T. Yorimitsu , F. Reggiori , J.E. Legakis , C.W. W ang , and D.J. ULK1 was immunoprecipitated with anti-ULK1 antibody, and an in vitro Klionsky . 2005 . Atg17 regulates the magnitude of the autophagic re- protein kinase assay was performed for 30 min at 30 ° C in the presence of sponse. Mol. Biol. Cell . 16 : 3438 – 3453 . -[ P]ATP (GE Healthcare) and myelin basic protein (Millipore). The reac- Cheong , H. , U. Nair, J. Geng , and D.J. Klionsky . 2008 . The Atg1 kinase complex tion products were separated by SDS-PAGE and the intensities of the P- is involved in the regulation of protein recruitment to initiate sequestering labeled myelin basic protein bands were visualized with a BAS image vesicle formation for nonspecifi c autophagy in Saccharomyces cerevi- siae. Mol. Biol. Cell . 19 : 668 – 681 . analyzer (Fujifi lm). The signal intensities were quantifi ed using Multi Gauge software. The amount of immunoprecipitated ULK1 was monitored by im- Cuervo , A.M. 2004 . Autophagy: in sickness and in health. Trends Cell Biol. munoblot analysis using ULK1 antibody (Santa Cruz Biotechnology, Inc.). 14 : 70 – 77 . Deminoff , S.J. , and P .K. Herman . 2007 . Identifying atg1 substrates: four means Real-time PCR to an end. Autophagy . 3 : 667 – 673 . Real-time PCR was performed on a Thermal Cycler Dice (Takara) using Gan , B. , Z.K. Melkoumian , X. Wu , K.L. Guan , and J.L. Guan . 2005 . Identifi cation SYBR premix EX Taq (Takara). The primer sets used were as follows: of FIP200 interaction with the TSC1 – TSC2 complex and its role in regu- mouse ULK1 forward, 5  -TTACCAGCGCATCGAGCA-3  ; and reverse, lation of cell size control. J. Cell Biol. 170 : 379 – 389 . 508 JCB • VOLUME 181 • NUMBER 3 • 2008 Gan , B. , X. Peng , T. Nagy , A. Alcaraz , H. Gu , and J.L. Guan . 2006 . Role of Levine , B. , and D.J. Klionsky . 2004 . Development by self-digestion: mo- FIP200 in cardiac and liver development and its regulation of TNF  and lecular mechanisms and biological functions of autophagy. De v. Cell . TSC – mTOR signaling pathways. J. Cell Biol. 175 : 121 – 133 . 6 : 463 – 477 . Gavin , A.C. , P. Aloy , P. Grandi , R. Krause , M. Boesche , M. Marzioch , C. Rau , Matsui , Y. , H. Takagi , X. Qu , M. Abdellatif , H. Sakoda , T. Asano , B. Levine , and L.J. Jensen , S. Bastuck , B. Dumpelfeld , et al . 2006 . Proteome survey re- J. Sadoshima . 2007 . Distinct roles of autophagy in the heart during ische- veals modularity of the yeast cell machinery. Natur e . 440 : 631 – 636 . mia and reperfusion: roles of AMP-activated protein kinase and Beclin 1 in mediating autophagy. Circ. Res. 100 : 914 – 922 . Guertin , D.A. , and D.M. Sabatini . 2007 . Defi ning the role of mTOR in cancer. Meijer , A.J. , and P. Codogno . 2004 . Regulation and role of autophagy in mam- Cancer Cell . 12 : 9 – 22 . malian cells. Int. J. Biochem. Cell Biol. 36 : 2445 – 2462 . Hanada , T. , N.N. Noda , Y. Satomi , Y. Ichimura , Y. Fujioka , T. Takao , F. Melendez , A. , Z. Tall ó czy , M. Seaman , E.-L. Eskelinen , D.H. Hall , and B. Inagaki , and Y. Ohusmi . 2007 . The ATG12-ATG5 conjugate has a Levine . 2003 . Autophagy genes are essential for dauer development and novel e3-like activity for protein lipidation in autophagy. J. Biol. Chem. life-span extension in C. elegans. Science . 301 : 1387 – 1391 . 282 : 37298 – 37302 . Melkoumian , Z.K. , X. Peng , B. Gan , X. Wu , and J.L. Guan . 2005 . Mechanism Hanaoka , H. , T. Noda , Y. Shirano , T. Kato , H. Hayashi , D. Shibata , S. Tabata , of cell cycle regulation by FIP200 in human breast cancer cells. Cancer and Y. Ohsumi . 2002 . Leaf senescence and starvation-induced chlorosis Res. 65 : 6676 – 6684 . are accelerated by the disruption of an Arabidopsis autophagy gene. Plant Physiol. 129 : 1181 – 1193 . Mizushima , N. 2007 . Autophagy: process and function. Genes Dev. 21 : 2861 – 2873 . Hara , T. , K. Nakamura , M. Matsui , A. Yamamoto , Y. Nakahara , R. Suzuki- Mizushima , N. , and D.J. Klionsky . 2007 . Protein turnover via autophagy: impli- Migishima , M. Yokoyama , K. Mishima , I. Saito , H. Okano , and N. cations for metabolism. Annu. Rev. Nutr. 27 : 19 – 40 . Mizushima . 2006 . Suppression of basal autophagy in neural cells causes Mizushima , N. , and T . Yoshimori . 2007 . How to interpret LC3 immunoblotting. neurodegenerative disease in mice. Nature . 441 : 885 – 889 . Autophagy . 3 : 542 – 545 . Ho , Y. , A. Gruhler , A. Heilbut , G.D. Bader, L. Moore , S.L. Adams , A. Millar, P. Mizushima , N. , A. Yamamoto , M. Hatano , Y. Kobayashi , Y. Kabeya , K. Suzuki , Taylor , K. Bennett , K. Boutilier, et al . 2002 . Systematic identifi cation of T. Tokuhisa , Y. Ohsumi , and T. Yoshimori . 2001 . Dissection of autopha- protein complexes in Saccharomyces cerevisiae by mass spectrometry. gosome formation using Apg5-defi cient mouse embryonic stem cells. Nature . 415 : 180 – 183 . J. Cell Biol. 152 : 657 – 667 . Hosokawa , N. , Y. Hara , and N. Mizushima . 2006 . Generation of cell lines with Mizushima , N. , A. Kuma , Y. Kobayashi , A. Yamamoto , M. Matsubae , T. Takao , tetracycline-regulated autophagy and a role for autophagy in controlling T. Natsume , Y. Ohsumi , and T. Yoshimori . 2003 . Mouse Apg16L, a novel cell size. FEBS Lett. 580 : 2623 – 2629 . WD-repeat protein, targets to the autophagic isolation membrane with the Ilic , D. , Y. Furuta , S. Kanazawa , N. Takeda , K. Sobue , N. Nakatsuji , S. Nomura , Apg12-Apg5 conjugate. J . Cell Sci. 116 : 1679 – 1688 . J. Fujimoto , M. Okada , T. Yamamoto , and S. Aizawa . 1995 . Reduced cell Mizushima , N. , B. Levine , A.M. Cuervo , and D.J. Klionsky . 2008 . Autophagy motility and enhanced focal adhesion contact formation in cells from fi ghts disease through cellular self-digestion. Natur e . 451 : 1069 – 1075 . FAK-defi cient mice. Natur e . 377 : 539 – 544 . Mukaiyama , H. , M. Oku , M. Baba , T. Samizo , A.T. Hammond , B.S. Glick , N. Inoki , K. , and K.L. Guan . 2006 . Complexity of the TOR signaling network. Kato , and Y. Sakai . 2002 . Paz2 and 13 other PAZ gene products regu- Trends Cell Biol. 16 : 206 – 212 . late vacuolar engulfment of peroxisomes during micropexophagy. Genes Kabeya , Y. , N. Mizushima , T. Ueno , A. Yamamoto , T. Kirisako , T. Noda , E. Cells . 7 : 75 – 90 . Kominami , Y. Ohsumi , and T. Yoshimori . 2000 . LC3, a mammalian ho- Natsume , T. , Y. Yamauchi , H. Nakayama , T. Shinkawa , M. Yanagida , N. mologue of yeast Apg8p, is localized in autophagosome membranes after Takahashi , and T. Isobe . 2002 . A direct nanofl ow liquid chromatogra- processing. EMBO J . 19 : 5720 – 5728 . phy-tandem mass spectrometry system for interaction proteomics. Anal. Kabeya , Y. , Y. Kamada , M. Baba , H. Takikawa , M. Sasaki , and Y. Ohsumi . 2005 . Chem. 74 : 4725 – 4733 . Atg17 functions in cooperation with Atg1 and Atg13 in yeast autophagy. Nice , D.C. , T.K. Sato , P.E. Stromhaug , S.D. Emr , and D.J. Klionsky . 2002 . Mol. Biol. Cell . 16 : 2544 – 2553 . Cooperative binding of the cytoplasm to vacuole targeting pathway Kabeya , Y. , T. Kawamata , K. Suzuki , and Y. Ohsumi . 2007 . Cis1/Atg31 is proteins, Cvt13 and Cvt20, to phosphatidylinositol 3-phosphate at the required for autophagosome formation in Saccharomyces cerevisiae. pre-autophagosomal structure is required for selective autophagy. J . Biol. Biochem. Biophys. Res. Commun. 356 : 405 – 410 . Chem. 277 : 30198 – 30207 . Kamada , Y. , T. Funakoshi , T. Shintani , K. Nagano , M. Ohsumi , and Y. Ohsumi . Ogura , K. , C. Wicky , L. Magnenat , H. Tobler, I. Mori , F. Muller , and Y. 2000 . Tor-mediated induction of autophagy via an Apg1 protein kinase Ohshima . 1994 . Caenorhabditis elegans unc-51 gene required for complex. J . Cell Biol. 150 : 1507 – 1513 . axonal elongation encodes a novel serine/threonine kinase. Genes Dev. 8 : 2389 – 2400 . Kamura , T. , T. Hara , M. Matsumoto , N. Ishida , F. Okumura , S. Hatakeyama , M. Yoshida , K. Nakayama , and K.I. Nakayama . 2004 . Cytoplasmic ubiqui- Ogura , K. , M. Shirakawa , T.M. Barnes , S. Hekimi , and Y. Ohshima . 1997 . tin ligase KPC regulates proteolysis of p27(Kip1) at G1 phase. Nat. Cell The UNC-14 protein required for axonal elongation and guidance in Biol. 6 : 1229 – 1235 . Caenorhabditis elegans interacts with the serine/threonine kinase UNC-51. Genes Dev. 11 : 1801 – 1811 . Kawamata , T. , Y. Kamada , K. Suzuki , N. Kuboshima , H. Akimatsu , S. Ota , M. Ohsumi , and Y. Ohsumi . 2005 . Characterization of a novel auto phagy- Okazaki , N. , J. Yan , S. Yuasa , T. Ueno , E. Kominami , Y. Masuho , H. Koga , and specifi c gene, ATG29. Bioc hem. Biophys. Res. Commun. 338 : 1884 – 1889 . M. Muramatsu . 2000 . Interaction of the Unc-51-like kinase and micro- tubule-associated protein light chain 3 related proteins in the brain: pos- Kawamata , T. , Y. Kamada , Y. Kabeya , T. Sekito , and Y. Ohsumi . 2008 . Organization sible role of vesicular transport in axonal elongation. Brain Res. Mol. of the pre-autophagosomal structure responsible for autophagosome for- Brain Res. 85 : 1 – 12 . mation. Mol. Biol. Cell . DOI:10.1091/mbc.E07-10-1048. Otto , G.P. , M.Y. Wu , N. Kazgan , O.R. Anderson , and R.H. Kessin . 2004 . Kim , J. , W.-P. Huang , and D.J. Klionsky . 2001a . Membrane recruitment of Aut7p Dictyostelium macroautophagy mutants vary in the severity of their de- in the autophagy and cytoplasm to vacuole targeting pathways requires velopmental defects. J . Biol. Chem. 279 : 15621 – 15629 . Aut1p, Aut2p, and the autophagy conjugation complex. J . Cell Biol. 152 : 51 – 64 . Reggiori , F. , K.A. Tucker , P.E. Stromhaug , and D.J. Klionsky . 2004 . The Atg1- Atg13 complex regulates Atg9 and Atg23 retrieval transport from the pre- Kim , J. , Y. Kamada , P.E. Stromhaug , J. Guan , A. Hefner-Gravink , M. Baba , S.V. autophagosomal structure. Dev. Cell . 6 : 79 – 90 . Scott , Y. Ohsumi , W.A. Dunn Jr ., and D.J. Klionsky . 2001b . Cvt9/Gsa9 functions in sequestering selective cytosolic cargo destined for the vacuole. Rubinsztein , D.C. 2006 . The roles of intracellular protein-degradation pathways J. Cell Biol. 153 : 381 – 396 . in neurodegeneration. Nature . 443 : 780 – 786 . Klionsky , D.J. 2005 . The molecular machinery of autophagy: unanswered ques- Sarkar , S. , R.A. Floto , Z. Berger , S. Imarisio , A. Cordenier , M. Pasco , L.J. Cook , tions. J. Cell Sci. 118 : 7 – 18 . and D.C. Rubinsztein . 2005 . Lithium induces autophagy by inhibiting inositol monophosphatase. J. Cell Biol. 170 : 1101 – 1111 . Komatsu , M. , S. Waguri , T. Chiba , S. Murata , J.I. Iwata , I. Tanida , T. Ueno , M. Koike , Y. Uchiyama , E. Kominami , and K. Tanaka . 2006 . Loss of auto phagy Scarlatti , F. , C. Bauvy, A. Ventruti , G. Sala , F. Cluzeaud , A. Vandewalle , R. in the central nervous system causes neurodegeneration in mice. Nature . Ghidoni , and P . Codogno . 2004 . Ceramide-mediated macroautophagy 441 : 880 – 884 . involves inhibition of protein kinase B and up-regulation of beclin 1. J. Biol. Chem. 279 : 18384 – 18391 . Krogan , N.J. , G. Cagney , H. Yu , G. Zhong , X. Guo , A. Ignatchenko , J. Li , S. Pu , N. Datta , A.P. Tikuisis , et al . 2006 . Global landscape of Scott , R.C. , O. Schuldiner , and T.P. Neufeld . 2004 . Role and regulation of protein complexes in the yeast Saccharomyces cerevisiae . Nature . starvation-induced autophagy in the Drosophila fat body. Dev. Cell . 440 : 637 – 643 . 7 : 167 – 178 . Kuma , A. , M. Hatano , M. Matsui , A. Yamamoto , H. Nakaya , T. Yoshimori , Y. Scott , R.C. , G. Juhasz , and T.P. Neufeld . 2007 . Direct induction of autophagy Ohsumi , T. Tokuhisa , and N. Mizushima . 2004 . The role of autophagy by Atg1 inhibits cell growth and induces apoptotic cell death. Curr. Biol. during the early neonatal starvation period. Nature . 432 : 1032 – 1036 . 17 : 1 – 11 . ULK – FIP200 COMPLEX IN AUTOPHAGY • Hara et al. 509 Scott , S.V. , D.C. Nice III , J.J. Nau , L.S. Weisman , Y. Kamada , I. Keizer-Gunnink , T. Funakoshi , M. Veenhuis , Y. Ohsumi , and D.J. Klionsky . 2000 . Apg13p and Vac8p are part of a complex of phosphoproteins that are required for cytoplasm to vacuole targeting. J. Biol. Chem. 275 : 25840 – 25849 . Suzuki , K. , and Y. Ohsumi . 2007 . Molecular machinery of autophagosome for- mation in yeast, Saccharomyces cerevisiae. FEBS Lett. 581 : 2156 – 2161 . Suzuki , K. , T. Kirisako , Y. Kamada , N. Mizushima , T. Noda , and Y. Ohsumi . 2001 . The pre-autophagosomal structure organized by concerted func- tions of APG genes is essential for autophagosome formation. EMBO J. 20 : 5971 – 5981 . Suzuki , K. , Y. Kubota , T. Sekito , and Y. Ohsumi . 2007 . Hierarchy of Atg proteins in pre-autophagosomal structure organization. Genes Cells . 12 : 209 – 218 . Tanida , I. , N. Minematsu-Ikeguchi , T. Ueno , and E. Kominami . 2005 . Lysosomal turnover, but not a cellular level, of endogenous LC3 is a marker for autophagy. Autophagy . 1 : 84 – 91 . Tekinay , T. , M.Y. Wu , G.P. Otto , O.R. Anderson , and R.H. Kessin . 2006 . Function of the Dictyostelium discoideum Atg1 kinase during autophagy and development. Eukaryot. Cell . 5 : 1797 – 1806 . Tomoda , T. , R.S. Bhatt , H. Kuroyanagi , T. Shirasawa, and M.E. Hatten . 1999 . A mouse serine/threonine kinase homologous to C. elegans UNC51 func- tions in parallel fi ber formation of cerebellar granule neurons. Neur on . 24 : 833 – 846 . Tomoda , T. , J.H. Kim , C. Zhan , and M.E. Hatten . 2004 . Role of Unc51.1 and its binding partners in CNS axon outgrowth. Genes De v. 18 : 541 – 558 . Ueda , H. , S. Abbi , C. Zheng , and J.L. Guan . 2000 . Suppression of Pyk2 kinase and cellular activities by FIP200. J . Cell Biol. 149 : 423 – 430 . Wullschleger , S. , R. Loewith , and M.N. Hall . 2006 . TOR signaling in growth and metabolism. Cell . 124 : 471 – 484 . Yamamoto , A. , Y. Tagawa , T. Yoshimori , Y. Moriyama , R. Masaki , and Y. Tashiro . 1998 . Bafi lomycin A prevents maturation of autophagic vacuoles by in- hibiting fusion between autophagosomes and lysosomes in rat hepatoma cell line, H-4-II-E cells. Cell Struct. Funct. 23 : 33 – 42 . Yan , J. , H. Kuroyanagi , A. Kuroiwa , Y. Matsuda , H. Tokumitsu , T. Tomoda , T. Shirasawa , and M. Muramatsu . 1998 . Identifi cation of mouse ULK1, a novel protein kinase structurally related to C. elegans UNC-51. Biochem. Biophys. Res. Commun. 246 : 222 – 227 . Yan , J. , H. Kuroyanagi , T. Tomemori , N. Okazaki , K. Asato , Y. Matsuda , Y. Suzuki , Y. Ohshima , S. Mitani , Y. Masuho , et al . 1999 . Mouse ULK2, a novel member of the UNC-51-like protein kinases: unique features of functional domains. Oncogene . 18 : 5850 – 5859 . Young , A.R. , E.Y. Chan , X.W. Hu , R. Kochl , S.G. Crawshaw , S. High , D.W. Hailey , J. Lippincott-Schwartz , and S.A. Tooze . 2006 . Starvation and ULK1-dependent cycling of mammalian Atg9 between the TGN and endosomes. J . Cell Sci. 119 : 3888 – 3900 . Zeng , X. , J.H. Overmeyer , and W.A. Maltese . 2006 . Functional specifi city of the mammalian Beclin-Vps34 PI 3-kinase complex in macroautophagy versus endocytosis and lysosomal enzyme traffi cking. J. Cell Sci. 119 : 259 – 270 . Zhou , X. , J.R. Babu , S. da Silva , Q. Shu , I.A. Graef , T. Oliver , T. T omoda , T. Tani , M.W. Wooten , and F. Wang . 2007 . Unc-51-like kinase 1/2-medi- ated endocytic processes regulate fi lopodia extension and branching of sensory axons. Proc. Natl. Acad. Sci. USA . 104 : 5842 – 5847 . 510 JCB • VOLUME 181 • NUMBER 3 • 2008

Journal

The Journal of Cell BiologyPubmed Central

Published: May 5, 2008

There are no references for this article.