Cell Science at a Glance 1707

Mammalian been implicated in several human diseases, pathways, and we will address the ever- such as cancer, certain neurodegenerative growing roles of autophagy in human macroautophagy at disorders and infectious diseases. physiology and pathology. a glance Although autophagy is thought to be predominantly a cell-survival mechanism, Autophagy machinery Brinda Ravikumar, Marie Futter, some evidence points towards a role in cell The foundation for understanding the Luca Jahreiss, Viktor I. death. Our understanding of mammalian mammalian autophagy machinery was Korolchuk, Maike Lichtenberg, autophagy, in terms of the molecular provided by a series of genetic screens in Shouqing Luo, Dunecan C. O. machineries and signalling cascades that the yeast Saccharomyces cerevisiae; these Massey, Fiona M. Menzies, Usha are involved in its regulation, has grown screens identified around 30 so-called Narayanan, Maurizio Renna, considerably over the last few years. In autophagy-related (ATG) genes that are Maria Jimenez-Sanchez, Sovan particular, there has been an explosion of required for autophagy (Xie and Klionsky, Sarkar, Benjamin Underwood, data in the last 3 years trying to address the 2007). About half of these genes have Ashley Winslow and David C. importance of mammalian autophagy in obvious mammalian counterparts, and Rubinsztein* physiology and pathophysiology. Here, we many of the core aspects of the process are Department of Medical Genetics, Cambridge aim to summarise the recent advances in conserved. It is possible that some genes Institute for Medical Research, Addenbrooke’s mammalian macroautophagy in terms of that do not have obvious orthologues in Hospital, Hills Road, Cambridge CB2 0XY, UK *Author for correspondence (e-mail: its regulation, which will include newly mammals still exist but have been missed, [email protected]) identified molecules and signalling as there might be structural and functional

Journal of Cell Science 122, 1707-1711 Published by The Company of Biologists 2009 doi:10.1242/jcs.031773

Autophagy refers to a set of non-specific bulk degradation processes in which cells deliver cytoplasmic substrates for lysosomal degradation. Types of autophagy include macroautophagy, chaperone-mediated autophagy and microautophagy. Chaperone-mediated autophagy is selective for specific cytosolic proteins that contain a pentapeptide motif. This motif is recognised by the chaperone heat shock

Journal of Cell Science cognate 70 (Hsc70), which transfers protein substrates to the lysosomal membrane where, through binding to the receptor lysosome-associated membrane protein 2A (LAMP2A), they are translocated into the lysosomal lumen and degraded. In microautophagy, lysosomes can also directly engulf cytoplasm by invagination, protrusion and/or septation of the lysosomal limiting membrane. The focus of this poster article, however, is mammalian macroautophagy.

Macroautophagy (referred to here as autophagy) is a process in which cells form double-membrane vesicles, called autophagosomes, around a portion of cytoplasm. These autophagosomes ultimately fuse with lysosomes, resulting in degradation of their contents. Autophagy is upregulated under physiological stress conditions such as starvation. However, mammalian cells undergo autophagy at a basal level that might be important for the clearance of normally occurring, misfolded, ubiquitylated proteins. Autophagy has also (See poster insert) 1708 Journal of Cell Science 122 (11)

orthology without obvious sequence conjugated to PE to form membrane- manner to lysosomes, which are clustered similarity. associated LC3-II, a process that requires around the microtubule-organising centre the activities of Atg7 (E1-like) and Atg3 (MTOC; located near the nucleus). There, Initiation of autophagosome formation (E2-like) (Ohsumi and Mizushima, 2004). autophagosomes tether, dock and fuse with Autophagosome formation appears to start The Atg5-Atg12 conjugate seems to lysosomes, and the contents of the two at phagophore (autophagosome precursor; modulate LC3-I conjugation to PE by vesicles are mixed (Jahreiss et al., 2008). also known as pre-autophagosomal acting in an E3-like fashion (Hanada et al., The details of this aspect of mammalian structures)-assembly sites (PAS). The 2007) and the Atg5-Atg12-Atg16L autophagy are still unclear, although the source of the membrane is unclear, complex also determines the sites of LC3 SNARE proteins that are involved in yeast although recent data support a contribution lipidation (Fujita et al., 2008). In this way, autophagosome-vacuole fusion have been from the endoplasmic reticulum (ER) (Axe LC3 is specifically targeted to Atg5- characterised (Ishihara et al., 2001). et al., 2008). The formation of the Atg12-associated membranes, which are En route to fusion with the lysosomes, phagophore requires the activity of the expanded phagophores. autophagosomes can fuse with endosomes class-III phosphoinositide 3-kinase (PI3K) to form amphisomes. It is currently not Vps34, which forms phosphatidylinositol Crosstalk between the two ubiquitylation- clear whether amphisome formation is a 3-phosphate [PtdIns(3)P]. Chemical like systems has also been suggested. prerequisite for autophagosome-lysosome inhibition of Vps34 by 3-methyladenine or Atg10 can interact with LC3-I and fusion. Reduced activity of some ESCRT wortmannin blocks the formation of new facilitate LC3-I conjugation to PE (endosomal sorting complex required autophagosomes. Vps34 is part of a large (Nemoto et al., 2003). Similarly, Atg3 for transport) proteins disrupts macromolecular complex specific for co-immunoprecipitates with Atg12, and autophagosome-lysosome fusion, resulting autophagy that contains the proteins Atg6 overexpression of Atg3 increases Atg5- in the accumulation of autophagosomes (also called beclin 1), Atg14 and Vps15 Atg12 conjugation (Tanida et al., 2002). (Skibinski et al., 2005). Similarly, LAMP2 (p150) (Itakura et al., 2008). Other proteins Although Atg5-Atg12 is lost upon deficiency has been associated with the that are involved in the initiation stage of completion of autophagosome formation, accumulation of autophagosomes, which is autophagosome formation include Atg5, LC3-II remains associated with consistent with a defect in fusion Atg12, Atg16, the newly identified autophagosomes even after fusion (Eskelinen et al., 2002). autophagy-related protein focal adhesion with lysosomes, after which LC3-II on the kinase (FAK)-family interacting protein of cytosolic face of autolysosomes can be Signals for autophagosome 200 kD (FIP200), which interacts with delipidated and recycled (to LC3-I). formation Atg1 (also called ULK1) (Hara et al., Conjugated LC3 is a substrate for Atg4, mTOR-dependent pathway 2008), and the mammalian orthologue of and Atg4 delipidates LC3-II and removes One of the classical pathways that regulate Atg13 (Chan et al., 2009; Hosokawa et al., it from the membrane. Furthermore, the autophagy is controlled by the mammalian 2009; Jung et al., 2009). production of reactive oxygen species target of rapamycin (mTOR). mTOR (ROS; specifically H2O2) during starvation activity inhibits mammalian autophagy,

Journal of Cell Science Autophagosome elongation results in oxidation and inactivation of but its activity is inhibited under starvation Atg5 and Atg12 are involved in the first of Atg4. This inhibits LC3-II delipidation and conditions, which contributes to two ubiquitylation-like reactions that might promote autophagosome formation starvation-induced autophagy. Autophagy control autophagy. Atg12 is conjugated to (Scherz-Shouval et al., 2007). is also induced by inhibiting mTOR with Atg5 in a reaction that requires Atg7 drugs such as rapamycin (Rubinsztein et [ubiquitin-activating-enzyme (E1)-like] LC3-II is the only known protein that al., 2007). Mammalian Atg13, ULK1 and and Atg10 [ubiquitin-conjugating-enzyme specifically associates with autophago - ULK2 have recently been identified as (E2)-like]. Atg5-Atg12 conjugates are somes and not with other vesicular direct targets of mTOR (Chan et al., 2009; localised onto the PAS and dissociate upon structures. Thus, LC3-II levels correlate Hosokawa et al., 2009; Jung et al., 2009). completion of autophagosome formation. with autophagic vacuole numbers, which Atg13 binds to ULK1 and ULK2 The process of Atg5-Atg12 conjugation can also be assessed by scoring LC3- (ULK1/2) and mediates their interaction depends on Vps34 function, and Vps34 positive vesicle numbers (Kabeya et al., with FIP200. Under nutrient-rich activity, along with autophagy, is positively 2000). LC3-II can mediate membrane conditions, mTOR is associated with this regulated by the small GTPase Rab5 tethering and hemifusion, and these complex. Inhibition of mTOR leads to its (Ravikumar et al., 2008). Atg5-Atg12 functions might be crucial for the dissociation from the complex and results interacts non-covalently with Atg16L expansion of autophagosome membranes. in the partial dephosphorylation of Atg13 (Atg16-like) to form a complex of These data also raise the possibility that and ULK1/2; this activates ULK1/2 to approximately 800 kDa (Ohsumi and LC3 assists the final fusion of the pre- phosphorylate FIP200 and thereby induce Mizushima, 2004). autophagosomal double-membrane ‘cups’ autophagy (Chan et al., 2009; Hosokawa into fused vesicles (Nakatogawa et al., et al., 2009; Jung et al., 2009). The second ubiquitylation-like reaction 2007). involves the conjugation of microtubule- Several signalling molecules regulate associated protein 1 light chain 3 (MAP1- Autophagosome maturation and autophagy via mTOR. Insulin or insulin- LC3; also known as Atg8 and LC3) to the fusion like growth factor (IGF) signalling lipid phosphatidylethanolamine (PE). LC3 Autophagosomes form randomly in the activates mTOR via PI3K and Akt. is cleaved at its C-terminus by Atg4 to cytoplasm. They are then trafficked along Activation of adenosine-monophosphate- form cytosolic LC3-I, which is covalently microtubules in a dynein-dependent activated protein kinase (AMPK) inhibits Journal of Cell Science 122 (11) 1709

mTOR activity via tuberous sclerosis cAMP levels) (Williams et al., 2008). In organelles, which cannot enter the complex 1 (Tsc1), Tsc2 and Ras homology this pathway, autophagy is inhibited when proteasome, are accessible to autophagy. enriched in brain (Rheb) (Hall et al., 2008). intracellular cAMP levels are increased by Indeed, autophagy appears to be a crucial p53, a commonly mutated gene in human adenylyl cyclase (AC), which influences route for the degradation of aggregation- cancers, can positively and negatively autophagy by activating the guanine prone proteins. These include neuro- regulate autophagy via the mTOR nucleotide exchange factor Epac. Epac degenerative-disease-associated proteins pathway. Oncogenic or genotoxic stress then activates Rap2B, which inhibits such as mutant huntingtin (which causes stabilises and activates p53. This can autophagy by activating phospholipase Cε Huntington’s disease), and mutant forms stimulate autophagy by activating AMPK (PLCε), resulting in the production of IP3, of α-synuclein (which causes forms of or by upregulating phosphatase and tensin which mediates the release of Ca2+ from familial Parkinson’s disease). The homologue (PTEN) and Tsc1. Genetic or ER stores. Increased intracytosolic Ca2+ clearance of such proteins is impaired chemical inhibition of p53, however, also blocks autophagy by activating calpains (a when autophagy is compromised. activates autophagy (Levine and Abrams, family of Ca2+-dependent cysteine However, autophagy upregulation is a 2008). proteases), which mediate their effects on possible therapeutic strategy for such autophagy through Gsα, which is activated diseases, as drugs that induce autophagy by Recently, further insights have been after calpain cleavage. This, in turn, mTOR-dependent or mTOR-independent provided into the mechanisms behind increases AC activity to increase cAMP routes enhance the clearance of such starvation-induced autophagy. Autophagy levels, thus forming a loop. Other mutant proteins and alleviate their toxicity can be inhibited by the binding of the compounds that induce autophagy include in a range of animal models (Sarkar et al., apoptosis-related proteins B-cell ceramide, sphingosine, trehalose, 2008). lymphoma 2 (Bcl2) or basal-cell fluspirilene, trifluoperazine, pimozide, lymphoma-extra large (Bcl-XL) to beclin 1 nicardipine, penitrem A, niguldipine and This function of autophagy might also be (Atg6). Starvation induces Jun N-terminal amiodarone (Zhang et al., 2007), but their relevant physiologically, because protein kinase 1 (Jnk1) activity, which mechanisms of action are not well aggregates form in the brain and some phosphorylates Bcl2, thereby disrupting understood. other tissues (from endogenous ‘normal’ the interaction between beclin 1 and Bcl-2 proteins) in Atg5- or Atg7-knockout mice, and inducing autophagy (Wei et al., 2008). Physiology and pathology which have compromised autophagy (Hara This mechanism might also account for the Starvation et al., 2006; Komatsu et al., 2006). Such a upregulation of autophagy after One of the ancestral purposes of autophagy mechanism might also contribute to other proteasome inhibition or ER stress, as one has been as a means of recycling neurodegenerative diseases. For instance, study showed that ER-stress-induced macromolecules to provide new nutrients recent studies suggest that autophagosome- autophagy is Jnk1-dependent and that at times of starvation. This is a key role for lysosome fusion is impaired in a form of proteasome inhibition can induce ER stress autophagy in single-cell organisms such as frontotemporal dementia that is caused by (Ding et al., 2007). Several other beclin-1 yeast, and is a crucial function in mammals mutations in a gene in the ESCRT

Journal of Cell Science binding partners such as activating as well. For instance, in the immediate complex, and by mutations in the molecule in beclin-1-regulated autophagy newborn period there is relative starvation dynein-complex component dynactin that (Ambra), Rab5, ultraviolet-radiation before breastfeeding is established. cause a form of motor neuron disease resistance-associated gene (UVRAG) and Autophagy-deficient mice are apparently (Munch et al., 2004; Skibinski et al., 2005). beclin-1-associated autophagy-related key normal at birth but die soon thereafter, This will impair the clearance of regulator (Barkor) can activate beclin 1. owing to an inability to recycle nutrients autophagic substrates and predispose cells (Kuma et al., 2004). to aggregate formation. mTOR-independent pathway An mTOR-independent pathway for the Autophagy appears to be important for Infectious agents and immunity induction of autophagy has recently been mammalian development as well. Autophagy is also a crucial clearance route discovered (Sarkar et al., 2005). In this Fertilisation induces autophagy, and for a range of infectious agents, including pathway, the inhibition of inositol autophagy-defective oocytes derived from Mycobacterium tuberculosis (the causative monophosphatase (IMPase) reduces free oocyte-specific Atg5-knockout mice failed agent of tuberculosis), the group A inositol and myoinositol-1,4,5- to develop beyond the four- and eight-cell streptococcal bacterium Streptococcus triphosphate (IP3) levels, which leads to an stages if they were fertilised by Atg5-null pyogenes (the causative agent of upregulation of autophagy. Lithium, sperm (Tsukamoto et al., 2008). streptococcal pharyngitis, toxic shock carbemazepine and valproate – drugs that Autophagy also appears to regulate the syndrome and necrotising fasciitis) and are used to treat a range of neurological and clearance of apoptotic corpses during viruses such as herpes simplex virus type I. psychiatric conditions – induce autophagy development [for instance, during Conversely, some bacteria and viruses via this pathway (Sarkar et al., 2005). embryonic cavitation (Qu et al., 2007)]. have also evolved to subvert the Further studies have shown that this autophagic system and use autophagy for pathway is regulated by intracellular Ca2+ Aggregation-prone proteins replication (Levine and Deretic, 2007). levels and cyclic AMP (cAMP), and have The key proteolytic systems in mammalian revealed additional drugs that might induce cells are autophagy and the ubiquitin- Autophagy might have implications in autophagy, such as verapamil (an L-type proteasome system. The proteasome can diseases that are linked to infection, as it is Ca2+-channel antagonist) and clonidine (an only process unfolded proteins, as it has a a route that enables the presentation imidazoline-receptor agonist that reduces narrow opening; however, oligomers and of cytosolic antigens by major 1710 Journal of Cell Science 122 (11)

early Sec proteins for its formation and NSF/SNARE for histocompatibility complex (MHC) class II improved tools for its detection. Perhaps vacuolar fusion. Mol. Biol. Cell 12, 3690-3702. molecules. Recent studies suggest a wider the most exciting areas of development Itakura, E., Kishi, C., Inoue, K. and Mizushima, N. role in immunity, as autophagy in thymic have come from the realisation that (2008). Beclin 1 forms two distinct phosphatidylinositol 3-kinase complexes with mammalian Atg14 and UVRAG. epithelial cells regulates the T-cell repertoire autophagy might be a crucial process Mol. Biol. Cell 19, 5360-5372. and is crucial for the development of that governs a wide range of physiological Jahreiss, L., Menzies, F. M. and Rubinsztein, D. C. immunological tolerance (Levine and (2008). The itinerary of autophagosomes: from peripheral processes and diseases in humans. Besides formation to kiss-and-run fusion with lysosomes. Traffic Deretic, 2007). The immunological roles of the neurodegenerative diseases, infectious 9, 574-587. autophagy might also account for the robust agents, immunological disorders and Jung, C. H., Jun, C. B., Ro, S. H., Kim, Y. M., Otto, N. M., Cao, J., Kundu, M. and Kim, D. H. (2009). ULK- associations of variants in two autophagy cancer scenarios that have been discussed, Atg13-FIP200 complexes mediate mTOR signaling to the genes, Atg16L and immunity-related recent data suggest that autophagy might autophagy machinery. Mol. Biol. Cell 20, 1992-2003. GTPase family-M (IRGM), with the be important in other conditions ranging Kabeya, Y., Mizushima, N., Ueno, T., Yamamoto, A., Kirisako, T., Noda, T., Kominami, E., Ohsumi, Y. and autoimmune condition Crohn’s disease from cardiomyopathies to pancreatitis. Yoshimori, T. (2000). LC3, a mammalian homologue of (Massey and Parkes, 2007). Further understanding of the physiological yeast Apg8p, is localized in autophagosome membranes after processing. EMBO J. 19, 5720-5728. and pathological roles of this process is Komatsu, M., Waguri, S., Chiba, T., Murata, S., Iwata, Autophagy and cell death crucial, but will require more knowledge of J., Tanida, I., Ueno, T., Koike, M., Uchiyama, Y., Although increased numbers of the basic cell biology and signalling Kominami, E. et al. (2006). Loss of autophagy in the autophagosomes sometimes occur in dying central nervous system causes neurodegeneration in mice. pathways that regulate autophagy. Nature 441, 880-884. cells, this increase is often not the result of Kuma, A., Hatano, M., Matsui, M., Yamamoto, A., autophagy-mediated cell death. Indeed, Work in the laboratory of D.C.R. on autophagy and Nakaya, H., Yoshimori, T., Ohsumi, Y., Tokuhisa, T. disease is funded by the Wellcome Trust (Senior and Mizushima, N. (2004). The role of autophagy during autophagy has cytoprotective roles. Fellowship to D.C.R.), MRC, Action Medical the early neonatal starvation period. Nature 432, 1032- Blocking autophagy increases the Research, The Sackler Trust and EU. Deposited in 1036. susceptibility of cells to pro-apoptotic PMC for release after 6 months. Levine, B. and Deretic, V. (2007). Unveiling the roles of autophagy in innate and adaptive immunity. Nat. Rev. insults, whereas enhancing autophagy is Immunol. 7, 767-777. anti-apoptotic. This might be because References Levine, B. and Abrams, J. (2008). p53: the Janus of autophagy enhances the clearance of Axe, E. L., Walker, S. A., Manifava, M., Chandra, P., autophagy? Nat. Cell Biol. 10, 637-639. Roderick, H. L., Habermann, A., Griffiths, G. and Levine, B., Sinha, S. and Kroemer, G. (2008). Bcl-2 mitochondria and reduces mitochondrial Ktistakis, N. T. (2008). Autophagosome formation from family members: dual regulators of apoptosis and load, thereby diminishing the amount of membrane compartments enriched in phosphatidylinositol autophagy. Autophagy 4, 600-606. cytochrome c release and subsequent 3-phosphate and dynamically connected to the Maiuri, M. C., Zalckvar, E., Kimchi, A. and Kroemer, endoplasmic reticulum. J. Cell Biol. 182, 685-701. G. (2007). Self-eating and self-killing: crosstalk between caspase-9 activation that occur after an Chan, E. Y., Longatti, A., McKnight, N. C. and Tooze, autophagy and apoptosis. Nat. Rev. Mol. Cell. Biol. 8, 741- apoptotic insult (Ravikumar et al., 2006). S. A. (2009). Kinase-inactivated ULK proteins inhibit 752. autophagy via their conserved C-terminal domains using Massey, D. C. and Parkes, M. (2007). Genome-wide an Atg13-independent mechanism. Mol. Cell. Biol. 29, association scanning highlights two autophagy genes, Because of its anti-apoptotic effects, it 157-171. ATG16L1 and IRGM, as being significantly associated might seem that the upregulation of Ding, W. X., Ni, H. M., Gao, W., Yoshimori, T., Stolz, with Crohn’s disease. Autophagy 3, 649-651. Munch, C., Sedlmeier, R., Meyer, T., Homberg, V., autophagy predisposes cells to cancer. D. B., Ron, D. and Yin, X. M. (2007). Linking of autophagy to ubiquitin-proteasome system is important for Sperfeld, A. D., Kurt, A., Prudlo, J., Peraus, G., Hanemann, C. O., Stumm, G. et al. (2004). Point Journal of Cell Science Although the situation is likely to be the regulation of endoplasmic reticulum stress and cell viability. Am. J. Pathol. 171, 513-524. mutations of the p150 subunit of dynactin (DCTN1) gene complex, the existing view is that in ALS. Neurology 63, 724-726. autophagy downregulation predisposes Eskelinen, E. L., Illert, A. L., Tanaka, Y., Schwarzmann, G., Blanz, J., Von Figura, K. and Saftig, Nakatogawa, H., Ichimura, Y. and Ohsumi, Y. (2007). Atg8, a ubiquitin-like protein required for autophagosome cells to carcinogenesis, which is consistent P. (2002). Role of LAMP-2 in lysosome biogenesis and formation, mediates membrane tethering and hemifusion. autophagy. Mol. Biol. Cell 13, 3355-3368. with observations that hemizygous loss of Cell 130, 165-178. Fujita, N., Itoh, T., Omori, H., Fukuda, M., Noda, T. beclin 1 is associated with increased Nemoto, T., Tanida, I., Tanida-Miyake, E., Minematsu- and Yoshimori, T. (2008). The Atg16L complex specifies Ikeguchi, N., Yokota, M., Ohsumi, M., Ueno, T. and tumorigenicity (Levine et al., 2008). the site of LC3 lipidation for membrane biogenesis in Kominami, E. (2003). The mouse APG10 homologue, an autophagy. Mol. Biol. Cell 19, 2092-2100. However, blocking autophagy might aid E2-like enzyme for Apg12p conjugation, facilitates MAP- Hall, M. N. (2008). mTOR – what does it do? Transplant LC3 modification. J. Biol. Chem. 278, 39517-39526. certain chemotherapeutic regimes for Proc. 40, S5-S8. established cancers by enhancing their Ohsumi, Y. and Mizushima, N. (2004). Two ubiquitin- Hanada, T., Noda, N. N., Satomi, Y., Ichimura, Y., like conjugation systems essential for autophagy. Semin. killing effects. Fujioka, Y., Takao, T., Inagaki, F. and Ohsumi, Y. Cell Dev. Biol. 15, 231-236. (2007). The Atg12-Atg5 conjugate has a novel E3-like Qu, X., Zou, Z., Sun, Q., Luby-Phelps, K., Cheng, P., activity for protein lipidation in autophagy. J. Biol. Chem. Hogan, R. N., Gilpin, C. and Levine, B. (2007). Although the relationship between 282, 37298-37302. Autophagy gene-dependent clearance of apoptotic cells apoptosis and autophagy is still unclear, Hara, T., Nakamura, K., Matsui, M., Yamamoto, A., during embryonic development. Cell 128, 931-946. there are crucial proteins that are relevant Nakahara, Y., Suzuki-Migishima, R., Yokoyama, M., Ravikumar, B., Berger, Z., Vacher, C., O’Kane, C. J. Mishima, K., Saito, I., Okano, H. et al. (2006). and Rubinsztein, D. C. (2006). Rapamycin pre-treatment to both processes, implying some degree of Suppression of basal autophagy in neural cells causes protects against apoptosis. Hum. Mol. Genet. 15, 1209- crosstalk: Bcl2 and Bcl-XL are anti- neurodegenerative disease in mice. Nature 441, 885-889. 1216. apoptotic as well as being blockers of Hara, T., Takamura, A., Kishi, C., Iemura, S., Ravikumar, B., Imarisio, S., Sarkar, S., O’Kane, C. J. Natsume, T., Guan, J. L. and Mizushima, N. (2008). and Rubinsztein, D. C. (2008). Rab5 modulates autophagy (as discussed above), and Atg5 FIP200, a ULK-interacting protein, is required for aggregation and toxicity of mutant huntingtin through has been proposed to be a pro-apoptotic autophagosome formation in mammalian cells. J. Cell macroautophagy in cell and fly models of Huntington Biol. 181, 497-510. disease. J. Cell Sci. 121, 1649-1660. protein (Maiuri et al., 2007). Hosokawa, N., Hara, T., Kaizuka, T., Kishi, C., Rubinsztein, D. C., Gestwicki, J. E., Murphy, L. O. and Takamura, A., Miura, Y., Iemura, S. I., Natsume, T., Klionsky, D. J. (2007). Potential therapeutic applications Conclusions and perspectives Takehana, K., Yamada, N. et al. (2009). Nutrient- of autophagy. Nat. Rev. Drug Discov. 6, 304-312. dependent mTORC1 association with the ULK1-Atg13- Sarkar, S., Floto, R. A., Berger, Z., Imarisio, S., Over the last 5 years there has been a FIP200 complex required for autophagy. Mol. Biol. Cell Cordenier, A., Pasco, M., Cook, L. J. and Rubinsztein, dramatic increase in interest in mammalian 20, 1981-1991. D. C. (2005). Lithium induces autophagy by inhibiting autophagy. This is partly due to a growing Ishihara, N., Hamasaki, M., Yokota, S., Suzuki, K., inositol monophosphatase. J. Cell Biol. 170, 1101-1111. Kamada, Y., Kihara, A., Yoshimori, T., Noda, T. and Sarkar, S., Ravikumar, B., Floto, R. A. and understanding of the process, coupled with Ohsumi, Y. (2001). Autophagosome requires specific Rubinsztein, D. C. (2008). Rapamycin and mTOR- Journal of Cell Science 122 (11) 1711

independent autophagy inducers ameliorate toxicity of substrates, GATE-16, GABARAP, and MAP-LC3, and Xie, Z. and Klionsky, D. J. (2007). Autophagosome polyglutamine-expanded huntingtin and related facilitates the conjugation of hApg12p to hApg5p. J. Biol. formation: core machinery and adaptations. Nat. Cell Biol. proteinopathies. Cell Death Differ. 16, 46-56. Chem. 277, 13739-13744. 9, 1102-1109. Scherz-Shouval, R., Shvets, E., Fass, E., Shorer, H., Gil, Tsukamoto, S., Kuma, A., Murakami, M., Kishi, C., Zhang, L., Yu, J., Pan, H., Hu, P., Hao, Y., Cai, W., Zhu, L. and Elazar, Z. (2007). Reactive oxygen species are Yamamoto, A. and Mizushima, N. (2008). Autophagy is H., Yu, A. D., Xie, X., Ma, D. et al. (2007). Small essential for autophagy and specifically regulate the essential for preimplantation development of mouse molecule regulators of autophagy identified by an image- activity of Atg4. EMBO J. 26, 1749-1760. embryos. Science 321, 117-120. based high-throughput screen. Proc. Natl. Acad. Sci. USA Skibinski, G., Parkinson, N. J., Brown, J. M., Wei, Y., Pattingre, S., Sinha, S., Bassik, M. and Levine, 104, 19023-19028. Chakrabarti, L., Lloyd, S. L., Hummerich, H., Nielsen, B. (2008). JNK1-mediated phosphorylation of Bcl-2 J. E., Hodges, J. R., Spillantini, M. G., Thusgaard, T. regulates starvation-induced autophagy. Mol. Cell 30, 678- Cell Science at a Glance on the Web et al. (2005). Mutations in the endosomal ESCRTIII- 688. Electronic copies of the poster insert are complex subunit CHMP2B in frontotemporal dementia. Williams, A., Sarkar, S., Cuddon, P., Ttofi, E. K., Saiki, available in the online version of this article Nat. Genet. 37, 806-808. S., Siddiqi, F. H., Jahreiss, L., Fleming, A., Pask, D., at jcs.biologists.org. The JPEG images can Tanida, I., Tanida-Miyake, E., Komatsu, M., Ueno, T. Goldsmith, P. et al. (2008). Novel targets for be downloaded for printing or used as and Kominami, E. (2002). Human Apg3p/Aut1p Huntington’s disease in an mTOR-independent autophagy slides. homologue is an authentic E2 enzyme for multiple pathway. Nat. Chem. Biol. 4, 295-305. Journal of Cell Science