201
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Döring T, Prange R. Rab33B and its autophagic Atg5/12/16L1 effector assist in hepatitis B virus naked capsid formation and release. Cell Microbiol 2015; 17:747-64. [PMID: 25439980 DOI: 10.1111/cmi.12398] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 11/21/2014] [Accepted: 11/26/2014] [Indexed: 12/22/2022]
Abstract
Hepatitis B virus morphogenesis is accompanied by the production and release of non-enveloped capsids/nucleocapsids. Capsid particles are formed inside the cell cytosol by multimerization of core protein subunits and ultimately exported in an uncommon coatless state. Here, we investigated potential roles of Rab GTPases in capsid formation and trafficking by using RNA interference and overexpression studies. Naked capsid release does not require functions of the endosome-associated Rab5, Rab7 and Rab27 proteins, but depends on functional Rab33B, a GTPase participating in autophagosome formation via interaction with the Atg5-Atg12/Atg16L1 complex. During capsid formation, Rab33B acts in conjunction with its effector, as silencing of Atg5, Atg12 and Atg16L1 also impaired capsid egress. Analysis of capsid maturation steps revealed that Rab33B and Atg5/12/16L1 are required for proper particle assembly and/or stability. In support, the capsid protein was found to interact with Atg5 and colocalize with Atg5/12/16L1, implicating that autophagy pathway functions are involved in capsid biogenesis. However, a complete and functional autophagy pathway is dispensable for capsid release, as judged by knockdown analysis of Atg8/LC3 family members and pharmaceutical ablation of canonical autophagy. Experiments aimed at analysing the capsid release-stimulating activity of the Alix protein provide further evidence for a link between capsid formation and autophagy.
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Affiliation(s)
- Tatjana Döring
- Department of Medical Microbiology and Hygiene, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, D-55101, Germany
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202
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Fatty acid synthase is preferentially degraded by autophagy upon nitrogen starvation in yeast. Proc Natl Acad Sci U S A 2015; 112:1434-9. [PMID: 25605918 DOI: 10.1073/pnas.1409476112] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Autophagy, an evolutionarily conserved intracellular catabolic process, leads to the degradation of cytosolic proteins and organelles in the vacuole/lysosome. Different forms of selective autophagy have recently been described. Starvation-induced protein degradation, however, is considered to be nonselective. Here we describe a novel interaction between autophagy-related protein 8 (Atg8) and fatty acid synthase (FAS), a pivotal enzymatic complex responsible for the entire synthesis of C16- and C18-fatty acids in yeast. We show that although FAS possesses housekeeping functions, under starvation conditions it is delivered to the vacuole for degradation by autophagy in a Vac8- and Atg24-dependent manner. We also provide evidence that FAS degradation is essential for survival under nitrogen deprivation. Our results imply that during nitrogen starvation specific proteins are preferentially recruited into autophagosomes.
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203
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Niso-Santano M, Malik SA, Pietrocola F, Bravo-San Pedro JM, Mariño G, Cianfanelli V, Ben-Younès A, Troncoso R, Markaki M, Sica V, Izzo V, Chaba K, Bauvy C, Dupont N, Kepp O, Rockenfeller P, Wolinski H, Madeo F, Lavandero S, Codogno P, Harper F, Pierron G, Tavernarakis N, Cecconi F, Maiuri MC, Galluzzi L, Kroemer G. Unsaturated fatty acids induce non-canonical autophagy. EMBO J 2015; 34:1025-41. [PMID: 25586377 DOI: 10.15252/embj.201489363] [Citation(s) in RCA: 132] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 12/19/2014] [Indexed: 12/21/2022] Open
Abstract
To obtain mechanistic insights into the cross talk between lipolysis and autophagy, two key metabolic responses to starvation, we screened the autophagy-inducing potential of a panel of fatty acids in human cancer cells. Both saturated and unsaturated fatty acids such as palmitate and oleate, respectively, triggered autophagy, but the underlying molecular mechanisms differed. Oleate, but not palmitate, stimulated an autophagic response that required an intact Golgi apparatus. Conversely, autophagy triggered by palmitate, but not oleate, required AMPK, PKR and JNK1 and involved the activation of the BECN1/PIK3C3 lipid kinase complex. Accordingly, the downregulation of BECN1 and PIK3C3 abolished palmitate-induced, but not oleate-induced, autophagy in human cancer cells. Moreover, Becn1(+/-) mice as well as yeast cells and nematodes lacking the ortholog of human BECN1 mounted an autophagic response to oleate, but not palmitate. Thus, unsaturated fatty acids induce a non-canonical, phylogenetically conserved, autophagic response that in mammalian cells relies on the Golgi apparatus.
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Affiliation(s)
- Mireia Niso-Santano
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Shoaib Ahmad Malik
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Government College University, Faisalabad, Pakistan
| | - Federico Pietrocola
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Université Paris Sud/Paris 11, Le Kremlin Bicêtre, France
| | - José Manuel Bravo-San Pedro
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Guillermo Mariño
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Valentina Cianfanelli
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy Unit of Cell Stress and Survival, Danish Cancer Society Research Center, Copenhagen, Denmark
| | - Amena Ben-Younès
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Rodrigo Troncoso
- Advanced Center for Chronic Disease (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences/Faculty of Medicine, University of Chile, Santiago, Chile Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile Faculty of Medicine, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile
| | - Maria Markaki
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Valentina Sica
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Université Paris Sud/Paris 11, Le Kremlin Bicêtre, France
| | - Valentina Izzo
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Kariman Chaba
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Chantal Bauvy
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France INSERM, U1151, Paris, France Institut Necker Enfants-Malades, Paris, France
| | - Nicolas Dupont
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France INSERM, U1151, Paris, France Institut Necker Enfants-Malades, Paris, France
| | - Oliver Kepp
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France INSERM, U1138, Paris, France Cell Biology & Metabolomics Platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France
| | - Patrick Rockenfeller
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria BioTechMed Graz, Graz, Austria
| | - Heimo Wolinski
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria BioTechMed Graz, Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria BioTechMed Graz, Graz, Austria
| | - Sergio Lavandero
- Advanced Center for Chronic Disease (ACCDiS), Faculty of Chemical & Pharmaceutical Sciences/Faculty of Medicine, University of Chile, Santiago, Chile Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile Faculty of Medicine, Institute of Nutrition and Food Technology, University of Chile, Santiago, Chile Department of Internal Medicine (Cardiology Division), University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Patrice Codogno
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France INSERM, U1151, Paris, France Institut Necker Enfants-Malades, Paris, France
| | - Francis Harper
- Gustave Roussy Comprehensive Cancer Center, Villejuif, France CNRS, UMR8122, Villejuif, France
| | - Gérard Pierron
- Gustave Roussy Comprehensive Cancer Center, Villejuif, France CNRS, UMR8122, Villejuif, France
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece Department of Basic Sciences, Faculty of Medicine, University of Crete, Heraklion, Greece
| | - Francesco Cecconi
- Department of Biology, University of Rome 'Tor Vergata', Rome, Italy Unit of Cell Stress and Survival, Danish Cancer Society Research Center, Copenhagen, Denmark Laboratory of Molecular Neuroembryology, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Maria Chiara Maiuri
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France
| | - Lorenzo Galluzzi
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France Gustave Roussy Comprehensive Cancer Center, Villejuif, France INSERM, U1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Guido Kroemer
- Equipe 11 labellisée par la Ligue contre le Cancer, Centre de Recherche des Cordeliers, Paris, France INSERM, U1138, Paris, France Université Paris Descartes, Sorbonne Paris Cité, Paris, France Cell Biology & Metabolomics Platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France Pôle de Biologie, Hôpital Européen Georges Pompidou, AP-HP, Paris, France
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204
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Randow F, Youle RJ. Self and nonself: how autophagy targets mitochondria and bacteria. Cell Host Microbe 2015; 15:403-11. [PMID: 24721569 DOI: 10.1016/j.chom.2014.03.012] [Citation(s) in RCA: 212] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Autophagy is an evolutionarily conserved pathway that transports cytoplasmic components for degradation into lysosomes. Selective autophagy can capture physically large objects, including cell-invading pathogens and damaged or superfluous organelles. Selectivity is achieved by cargo receptors that detect substrate-associated "eat-me" signals. In this Review, we discuss basic principles of selective autophagy and compare the "eat-me" signals and cargo receptors that mediate autophagy of bacteria and bacteria-derived endosymbionts-i.e., mitochondria.
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Affiliation(s)
- Felix Randow
- MRC Laboratory of Molecular Biology, Division of Protein and Nucleic Acid Chemistry, Francis Crick Avenue, Cambridge CB2 0QH, UK; University of Cambridge, Department of Medicine, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
| | - Richard J Youle
- Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health Bethesda, MD 20892, USA.
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205
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Poillet-Perez L, Despouy G, Delage-Mourroux R, Boyer-Guittaut M. Interplay between ROS and autophagy in cancer cells, from tumor initiation to cancer therapy. Redox Biol 2014; 4:184-92. [PMID: 25590798 PMCID: PMC4803791 DOI: 10.1016/j.redox.2014.12.003] [Citation(s) in RCA: 335] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Revised: 12/08/2014] [Accepted: 12/09/2014] [Indexed: 12/20/2022] Open
Abstract
Cancer formation is a complex and highly regulated multi-step process which is highly dependent of its environment, from the tissue to the patient. This complexity implies the development of specific treatments adapted to each type of tumor. The initial step of cancer formation requires the transformation of a healthy cell to a cancer cell, a process regulated by multiple intracellular and extracellular stimuli. The further steps, from the anarchic proliferation of cancer cells to form a primary tumor to the migration of cancer cells to distant organs to form metastasis, are also highly dependent of the tumor environment but of intracellular molecules and pathways as well. In this review, we will focus on the regulatory role of reactive oxygen species (ROS) and autophagy levels during the course of cancer development, from cellular transformation to the formation of metastasis. These data will allow us to discuss the potential of this molecule or pathway as putative future therapeutic targets. In cancer cells, ROS are able to regulate the different steps of autophagy pathway. During cancer initiation, anti-tumoral autophagy is going through ROS elimination. During cancer development, pro-tumoral autophagy is linked to decreased ROS levels. Autophagy inhibitor or antioxidant with anti-cancer drug: a new therapeutic approach?
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Affiliation(s)
- Laura Poillet-Perez
- Université de Franche-Comté, Laboratoire de Biochimie, EA3922 «Estrogènes, Expression Génique et Pathologies du Système Nerveux Central», SFR IBCT FED4234, UFR Sciences et Techniques, 16 Route de Gray, 25030 Besançon Cedex, France
| | - Gilles Despouy
- Université de Franche-Comté, Laboratoire de Biochimie, EA3922 «Estrogènes, Expression Génique et Pathologies du Système Nerveux Central», SFR IBCT FED4234, UFR Sciences et Techniques, 16 Route de Gray, 25030 Besançon Cedex, France
| | - Régis Delage-Mourroux
- Université de Franche-Comté, Laboratoire de Biochimie, EA3922 «Estrogènes, Expression Génique et Pathologies du Système Nerveux Central», SFR IBCT FED4234, UFR Sciences et Techniques, 16 Route de Gray, 25030 Besançon Cedex, France
| | - Michaël Boyer-Guittaut
- Université de Franche-Comté, Laboratoire de Biochimie, EA3922 «Estrogènes, Expression Génique et Pathologies du Système Nerveux Central», SFR IBCT FED4234, UFR Sciences et Techniques, 16 Route de Gray, 25030 Besançon Cedex, France.
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206
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Deegan S, Koryga I, Glynn SA, Gupta S, Gorman AM, Samali A. A close connection between the PERK and IRE arms of the UPR and the transcriptional regulation of autophagy. Biochem Biophys Res Commun 2014; 456:305-11. [PMID: 25475719 DOI: 10.1016/j.bbrc.2014.11.076] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 11/20/2014] [Indexed: 02/04/2023]
Abstract
Endoplasmic reticulum (ER) stress is known to lead to activation of both the unfolded protein response (UPR) and autophagy. Although regulatory connections have been identified between the UPR and autophagy, it is still unclear to what extent the UPR regulates the genes involved at the different stages of the autophagy pathway. Here, we carried out a microarray analysis of HCT116 cells subjected to ER stress and observed the transcriptional upregulation of a large cohort of autophagy-related genes. Of particular interest, we identified the transcriptional upregulation of the autophagy receptor genes SQSTM1/p62, NBR1 and BNIP3L/NIX in response to ER stress and show that the inhibition of the UPR transmembrane receptors, PERK and IRE1, abrogates this upregulation.
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Affiliation(s)
- Shane Deegan
- Apoptosis Research Centre, National University of Ireland Galway, Ireland; School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Izabela Koryga
- Apoptosis Research Centre, National University of Ireland Galway, Ireland; School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Sharon A Glynn
- Apoptosis Research Centre, National University of Ireland Galway, Ireland; Prostate Cancer Institute, National University of Ireland Galway, Ireland
| | - Sanjeev Gupta
- Apoptosis Research Centre, National University of Ireland Galway, Ireland; School of Medicine, National University of Ireland Galway, Ireland
| | - Adrienne M Gorman
- Apoptosis Research Centre, National University of Ireland Galway, Ireland; School of Natural Sciences, National University of Ireland Galway, Ireland
| | - Afshin Samali
- Apoptosis Research Centre, National University of Ireland Galway, Ireland; School of Natural Sciences, National University of Ireland Galway, Ireland.
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207
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Ge L, Zhang M, Schekman R. Phosphatidylinositol 3-kinase and COPII generate LC3 lipidation vesicles from the ER-Golgi intermediate compartment. eLife 2014; 3:e04135. [PMID: 25432021 PMCID: PMC4270069 DOI: 10.7554/elife.04135] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 11/14/2014] [Indexed: 01/01/2023] Open
Abstract
Formation of the autophagosome requires significant membrane input from cellular organelles. However, no direct evidence has been developed to link autophagic factors and the mobilization of membranes to generate the phagophore. Previously, we established a cell-free LC3 lipidation reaction to identify the ER-Golgi intermediate compartment (ERGIC) as a membrane source for LC3 lipidation, a key step of autophagosome biogenesis (Ge et al., eLife 2013; 2:e00947). We now report that starvation activation of autophagic phosphotidylinositol-3 kinase (PI3K) induces the generation of small vesicles active in LC3 lipidation. Subcellular fractionation studies identified the ERGIC as the donor membrane in the generation of small lipidation-active vesicles. COPII proteins are recruited to the ERGIC membrane in starved cells, dependent on active PI3K. We conclude that starvation activates the autophagic PI3K, which in turn induces the recruitment of COPII to the ERGIC to bud LC3 lipidation-active vesicles as one potential membrane source of the autophagosome.
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Affiliation(s)
- Liang Ge
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Min Zhang
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
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208
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Pérez-Pérez ME, Zaffagnini M, Marchand CH, Crespo JL, Lemaire SD. The yeast autophagy protease Atg4 is regulated by thioredoxin. Autophagy 2014; 10:1953-64. [PMID: 25483965 DOI: 10.4161/auto.34396] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Autophagy is a membrane-trafficking process whereby double-membrane vesicles called autophagosomes engulf and deliver intracellular material to the vacuole for degradation. Atg4 is a cysteine protease with an essential function in autophagosome formation. Mounting evidence suggests that reactive oxygen species may play a role in the control of autophagy and could regulate Atg4 activity but the precise mechanisms remain unclear. In this study, we showed that reactive oxygen species activate autophagy in the model yeast Saccharomyces cerevisiae and unraveled the molecular mechanism by which redox balance controls Atg4 activity. A combination of biochemical assays, redox titrations, and site-directed mutagenesis revealed that Atg4 is regulated by oxidoreduction of a single disulfide bond between Cys338 and Cys394. This disulfide has a low redox potential and is very efficiently reduced by thioredoxin, suggesting that this oxidoreductase plays an important role in Atg4 regulation. Accordingly, we found that autophagy activation by rapamycin was more pronounced in a thioredoxin mutant compared with wild-type cells. Moreover, in vivo studies indicated that Cys338 and Cys394 are required for the proper regulation of autophagosome biogenesis, since mutation of these cysteines resulted in increased recruitment of Atg8 to the phagophore assembly site. Thus, we propose that the fine-tuning of Atg4 activity depending on the intracellular redox state may regulate autophagosome formation.
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Key Words
- ATG, autophagy-related
- Ape1, aminopeptidase I
- Asc, ascorbate
- Atg4
- Cvt, cytoplasm-to-vacuole targeting
- DTNB, 5, 5′-dithiobis (2-nitro-benzoic acid)
- DTT, dithiothreitol
- DTTox, oxidized DTT
- DTTred, reduced DTT
- Eh, redox potential
- Em, midpoint redox potential
- GSH, reduced glutathione
- GSNO, S-nitrosoglutathione
- GSSG, oxidized glutathione
- Gsr, glutathione reductase
- IAM, iodoacetamide
- NEM, N-ethylmaleimide
- PAS, phagophore assembly site
- PE, phosphatidylethanolamine
- PTM, post-translational modification
- ROS, reactive oxygen species
- SD, synthetic minimal medium
- Trr1, thioredoxin reductase 1
- Trx1, thioredoxin 1
- YPD, yeast peptone dextrose
- autophagy
- phagophore assembly site
- rap, rapamycin
- redox regulation
- thioredoxin
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Affiliation(s)
- María Esther Pérez-Pérez
- a Centre National de la Recherche Scientifique; UMR8226; Laboratoire de Biologie Moléculaire et Cellulaire des Eucaryotes; Institut de Biologie Physico-Chimique ; Paris , France
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209
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Chen Y, He J, Tian M, Zhang SY, Guo MR, Kasimu R, Wang JH, Ouyang L. UNC51-like kinase 1, autophagic regulator and cancer therapeutic target. Cell Prolif 2014; 47:494-505. [PMID: 25327638 DOI: 10.1111/cpr.12145] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/12/2014] [Indexed: 02/05/2023] Open
Abstract
Autophagy, the cell process of self-digestion, plays a pivotal role in maintaining energy homoeostasis and protein synthesis. When required, it causes degradation of long-lived proteins and damaged organelles, indicating that it may play a dual role in cancer, by both protecting against and promoting cell death. The autophagy-related gene (Atg) family, with more than 35 members, regulates multiple stages of the process. Serine/threonine protein kinase Atg1 in yeast, for example, can interact with other ATG gene products, functioning in autophagosome formation. One mammalian homologue of Atg1, UNC-51-like kinase 1 (ULK1) and its related complex ULK1-mAtg13-FIP200 can mediate autophagy under nutrient-deprived conditions, by protein-protein interactions and post-translational modifications. Although specific mechanisms of how ULK1 and its complex transduces upstream signals to the downstream central autophagy pathways is not fully understood, past studies have indicated that ULK1 can both suppress and promote tumour growth under different conditions. Here, we summarize some properties of ULK1 which can regulate autophagy in cancer, which may shed new light on future cancer therapy strategies, utilizing ULK1 as a potential new target.
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Affiliation(s)
- Y Chen
- State Key Laboratory of Biotherapy & Collaborative Innovation Center of Biotherapy, Department of Gastrointestinal Surgery, West China Hospital, Sichuan University, Chengdu, 610041, China
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210
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Coronavirus membrane-associated papain-like proteases induce autophagy through interacting with Beclin1 to negatively regulate antiviral innate immunity. Protein Cell 2014; 5:912-27. [PMID: 25311841 PMCID: PMC4259884 DOI: 10.1007/s13238-014-0104-6] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 08/01/2014] [Indexed: 12/21/2022] Open
Abstract
Autophagy plays important roles in modulating viral replication and antiviral immune response. Coronavirus infection is associated with the autophagic process, however, little is known about the mechanisms of autophagy induction and its contribution to coronavirus regulation of host innate responses. Here, we show that the membrane-associated papain-like protease PLP2 (PLP2-TM) of coronaviruses acts as a novel autophagy-inducing protein. Intriguingly, PLP2-TM induces incomplete autophagy process by increasing the accumulation of autophagosomes but blocking the fusion of autophagosomes with lysosomes. Furthermore, PLP2-TM interacts with the key autophagy regulators, LC3 and Beclin1, and promotes Beclin1 interaction with STING, the key regulator for antiviral IFN signaling. Finally, knockdown of Beclin1 partially reverses PLP2-TM's inhibitory effect on innate immunity which resulting in decreased coronavirus replication. These results suggested that coronavirus papain-like protease induces incomplete autophagy by interacting with Beclin1, which in turn modulates coronavirus replication and antiviral innate immunity.
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211
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Tanaka C, Tan LJ, Mochida K, Kirisako H, Koizumi M, Asai E, Sakoh-Nakatogawa M, Ohsumi Y, Nakatogawa H. Hrr25 triggers selective autophagy-related pathways by phosphorylating receptor proteins. ACTA ACUST UNITED AC 2014; 207:91-105. [PMID: 25287303 PMCID: PMC4195827 DOI: 10.1083/jcb.201402128] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The budding yeast kinase Hrr25 regulates two selective autophagy–related pathways by phosphorylating degradation target receptors and thereby promoting their interaction with Atg11 and the formation of autophagosomal membrane. In selective autophagy, degradation targets are specifically recognized, sequestered by the autophagosome, and transported into the lysosome or vacuole. Previous studies delineated the molecular basis by which the autophagy machinery recognizes those targets, but the regulation of this process is still poorly understood. In this paper, we find that the highly conserved multifunctional kinase Hrr25 regulates two distinct selective autophagy–related pathways in Saccharomyces cerevisiae. Hrr25 is responsible for the phosphorylation of two receptor proteins: Atg19, which recognizes the assembly of vacuolar enzymes in the cytoplasm-to-vacuole targeting pathway, and Atg36, which recognizes superfluous peroxisomes in pexophagy. Hrr25-mediated phosphorylation enhances the interactions of these receptors with the common adaptor Atg11, which recruits the core autophagy-related proteins that mediate the formation of the autophagosomal membrane. Thus, this study introduces regulation of selective autophagy as a new role of Hrr25 and, together with other recent studies, reveals that different selective autophagy–related pathways are regulated by a uniform mechanism: phosphoregulation of the receptor–adaptor interaction.
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Affiliation(s)
- Chikara Tanaka
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Li-Jing Tan
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Keisuke Mochida
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Hiromi Kirisako
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Michiko Koizumi
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Eri Asai
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Machiko Sakoh-Nakatogawa
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Yoshinori Ohsumi
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
| | - Hitoshi Nakatogawa
- Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan Frontier Research Center and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8503, Japan
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212
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Abstract
DAP-kinase (DAPK) is a Ca(2+)-calmodulin regulated kinase with various, diverse cellular activities, including regulation of apoptosis and caspase-independent death programs, cytoskeletal dynamics, and immune functions. Recently, DAPK has also been shown to be a critical regulator of autophagy, a catabolic process whereby the cell consumes cytoplasmic contents and organelles within specialized vesicles, called autophagosomes. Here we present the latest findings demonstrating how DAPK modulates autophagy. DAPK positively contributes to the induction stage of autophagosome nucleation by modulating the Vps34 class III phosphatidyl inositol 3-kinase complex by two independent mechanisms. The first involves a kinase cascade in which DAPK phosphorylates protein kinase D, which then phosphorylates and activates Vps34. In the second mechanism, DAPK directly phosphorylates Beclin 1, a necessary component of the Vps34 complex, thereby releasing it from its inhibitor, Bcl-2. In addition to these established pathways, we will discuss additional connections between DAPK and autophagy and potential mechanisms that still remain to be fully validated. These include myosin-dependent trafficking of Atg9-containing vesicles to the sites of autophagosome formation, membrane fusion events that contribute to expansion of the autophagosome membrane and maturation through the endocytic pathway, and trafficking to the lysosome on microtubules. Finally, we discuss how DAPK's participation in the autophagic process may be related to its function as a tumor suppressor protein, and its role in neurodegenerative diseases.
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213
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Caza TN, Fernandez DR, Talaber G, Oaks Z, Haas M, Madaio MP, Lai ZW, Miklossy G, Singh RR, Chudakov DM, Malorni W, Middleton F, Banki K, Perl A. HRES-1/Rab4-mediated depletion of Drp1 impairs mitochondrial homeostasis and represents a target for treatment in SLE. Ann Rheum Dis 2014; 73:1888-97. [PMID: 23897774 PMCID: PMC4047212 DOI: 10.1136/annrheumdis-2013-203794] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 06/13/2013] [Accepted: 07/09/2013] [Indexed: 01/27/2023]
Abstract
OBJECTIVE Accumulation of mitochondria underlies T-cell dysfunction in systemic lupus erythematosus (SLE). Mitochondrial turnover involves endosomal traffic regulated by HRES-1/Rab4, a small GTPase that is overexpressed in lupus T cells. Therefore, we investigated whether (1) HRES-1/Rab4 impacts mitochondrial homeostasis and (2) Rab geranylgeranyl transferase inhibitor 3-PEHPC blocks mitochondrial accumulation in T cells, autoimmunity and disease development in lupus-prone mice. METHODS Mitochondria were evaluated in peripheral blood lymphocytes (PBL) of 38 SLE patients and 21 healthy controls and mouse models by flow cytometry, microscopy and western blot. MRL/lpr mice were treated with 125 μg/kg 3-PEHPC or 1 mg/kg rapamycin for 10 weeks, from 4 weeks of age. Disease was monitored by antinuclear antibody (ANA) production, proteinuria, and renal histology. RESULTS Overexpression of HRES-1/Rab4 increased the mitochondrial mass of PBL (1.4-fold; p=0.019) and Jurkat cells (2-fold; p=0.000016) and depleted the mitophagy initiator protein Drp1 both in human (-49%; p=0.01) and mouse lymphocytes (-41%; p=0.03). Drp1 protein levels were profoundly diminished in PBL of SLE patients (-86±3%; p=0.012). T cells of 4-week-old MRL/lpr mice exhibited 4.7-fold over-expression of Rab4A (p=0.0002), the murine homologue of HRES-1/Rab4, and depletion of Drp1 that preceded the accumulation of mitochondria, ANA production and nephritis. 3-PEHPC increased Drp1 (p=0.03) and reduced mitochondrial mass in T cells (p=0.02) and diminished ANA production (p=0.021), proteinuria (p=0.00004), and nephritis scores of lupus-prone mice (p<0.001). CONCLUSIONS These data reveal a pathogenic role for HRES-1/Rab4-mediated Drp1 depletion and identify endocytic control of mitophagy as a treatment target in SLE.
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Affiliation(s)
- Tiffany N Caza
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - David R Fernandez
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Gergely Talaber
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Zachary Oaks
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Mark Haas
- Department of Pathology, Cedars-Sinai Medical Center, Los Angeles, California, USA
| | - Michael P Madaio
- Department of Medicine, Medical College of Georgia, Augusta, Georgia, USA
| | - Zhi-wei Lai
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Gabriella Miklossy
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Ram R Singh
- Department of Medicine, UCLA, Los Angeles, California, USA
| | - Dmitriy M Chudakov
- Shemiakin-Ovchinnikov Institute of Bioorganic Chemistry, RAS, Moscow, Russia
| | - Walter Malorni
- Department of Experimental Medicine, University of Rome, Rome, Italy
| | - Frank Middleton
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Katalin Banki
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Andras Perl
- Departments of Medicine, Microbiology, and Immunology, Biochemistry and Molecular Biology, Neuroscience and Physiology, and Pathology, SUNY Upstate Medical University, Syracuse, New York, USA
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214
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Okamoto K. Organellophagy: eliminating cellular building blocks via selective autophagy. ACTA ACUST UNITED AC 2014; 205:435-45. [PMID: 24862571 PMCID: PMC4033777 DOI: 10.1083/jcb.201402054] [Citation(s) in RCA: 153] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Maintenance of organellar quality and quantity is critical for cellular homeostasis and adaptation to variable environments. Emerging evidence demonstrates that this kind of control is achieved by selective elimination of organelles via autophagy, termed organellophagy. Organellophagy consists of three key steps: induction, cargo tagging, and sequestration, which involve signaling pathways, organellar landmark molecules, and core autophagy-related proteins, respectively. In addition, posttranslational modifications such as phosphorylation and ubiquitination play important roles in recruiting and tailoring the autophagy machinery to each organelle. The basic principles underlying organellophagy are conserved from yeast to mammals, highlighting its biological relevance in eukaryotic cells.
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Affiliation(s)
- Koji Okamoto
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
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215
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Maday S, Holzbaur ELF. Autophagosome biogenesis in primary neurons follows an ordered and spatially regulated pathway. Dev Cell 2014; 30:71-85. [PMID: 25026034 DOI: 10.1016/j.devcel.2014.06.001] [Citation(s) in RCA: 261] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 04/08/2014] [Accepted: 05/30/2014] [Indexed: 02/03/2023]
Abstract
Autophagy is an essential degradative pathway in neurons, yet little is known about mechanisms driving autophagy in highly polarized cells. Here, we use dual-color live-cell imaging to investigate the neuron-specific mechanisms of constitutive autophagosome biogenesis in primary dorsal root ganglion (DRG) and hippocampal cultures. Under basal conditions, autophagosomes are continuously generated in the axon tip. There is an ordered assembly of proteins recruited with stereotypical kinetics onto the developing autophagosome. Plasma- or mitochondrial-derived membranes were not incorporated into nascent autophagosomes in the distal axon. Rather, autophagosomes are generated at double FYVE-containing protein 1 (DFCP1)-positive subdomains of the endoplasmic reticulum (ER), distinct from ER exit sites. Biogenesis events are enriched distally; autophagosomes form infrequently in dendrites, the soma, or midaxon, consistent with a compartmentalized pathway for constitutive autophagy in primary neurons. Distal biogenesis may facilitate degradation of damaged mitochondria and long-lived cytoplasmic proteins reaching the axon tip via slow axonal transport.
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Affiliation(s)
- Sandra Maday
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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216
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Yuan HX, Russell RC, Guan KL. Regulation of PIK3C3/VPS34 complexes by MTOR in nutrient stress-induced autophagy. Autophagy 2014; 9:1983-95. [PMID: 24013218 DOI: 10.4161/auto.26058] [Citation(s) in RCA: 209] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Autophagy is a cellular defense response to stress conditions, such as nutrient starvation. The type III phosphatidylinositol (PtdIns) 3-kinase, whose catalytic subunit is PIK3C3/VPS34, plays a critical role in intracellular membrane trafficking and autophagy induction. PIK3C3 forms multiple complexes and the ATG14-containing PIK3C3 is specifically involved in autophagy induction. Mechanistic target of rapamycin (MTOR) complex 1, MTORC1, is a key cellular nutrient sensor and integrator to stimulate anabolism and inhibit catabolism. Inactivation of TORC1 by nutrient starvation plays a critical role in autophagy induction. In this report we demonstrated that MTORC1 inactivation is critical for the activation of the autophagy-specific (ATG14-containing) PIK3C3 kinase, whereas it has no effect on ATG14-free PIK3C3 complexes. MTORC1 inhibits the PtdIns 3-kinase activity of ATG14-containing PIK3C3 by phosphorylating ATG14, which is required for PIK3C3 inhibition by MTORC1 both in vitro and in vivo. Our data suggest a mechanistic link between amino acid starvation and autophagy induction via the direct activation of the autophagy-specific PIK3C3 kinase.
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217
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Abstract
Autophagy is the main cellular catabolic process responsible for degrading organelles and large protein aggregates. It is initiated by the formation of a unique membrane structure, the phagophore, which engulfs part of the cytoplasm and forms a double-membrane vesicle termed the autophagosome. Fusion of the outer autophagosomal membrane with the lysosome and degradation of the inner membrane contents complete the process. The extent of autophagy must be tightly regulated to avoid destruction of proteins and organelles essential for cell survival. Autophagic activity is thus regulated by external and internal cues, which initiate the formation of well-defined autophagy-related protein complexes that mediate autophagosome formation and selective cargo recruitment into these organelles. Autophagosome formation and the signaling pathways that regulate it have recently attracted substantial attention. In this review, we analyze the different signaling pathways that regulate autophagy and discuss recent progress in our understanding of autophagosome biogenesis.
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Affiliation(s)
- Adi Abada
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
| | - Zvulun Elazar
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot, Israel
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218
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Clinical significance of autophagic protein LC3 levels and its correlation with XIAP expression in hepatocellular carcinoma. Med Oncol 2014; 31:108. [DOI: 10.1007/s12032-014-0108-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 06/30/2014] [Indexed: 12/11/2022]
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219
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Politi Y, Gal L, Kalifa Y, Ravid L, Elazar Z, Arama E. Paternal mitochondrial destruction after fertilization is mediated by a common endocytic and autophagic pathway in Drosophila. Dev Cell 2014; 29:305-20. [PMID: 24823375 DOI: 10.1016/j.devcel.2014.04.005] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 01/16/2014] [Accepted: 04/02/2014] [Indexed: 12/12/2022]
Abstract
Almost all animals contain mitochondria of maternal origin only, but the exact mechanisms underlying this phenomenon are still vague. We investigated the fate of Drosophila paternal mitochondria after fertilization. We demonstrate that the sperm mitochondrial derivative (MD) is rapidly eliminated in a stereotypical process dubbed paternal mitochondrial destruction (PMD). PMD is initiated by a network of vesicles resembling multivesicular bodies and displaying common features of the endocytic and autophagic pathways. These vesicles associate with the sperm tail and mediate the disintegration of its plasma membrane. Subsequently, the MD separates from the axoneme and breaks into smaller fragments, which are then sequestered by autophagosomes for degradation in lysosomes. We further provide evidence for the involvement of the ubiquitin pathway and the autophagy receptor p62 in this process. Finally, we show that the ubiquitin ligase Parkin is not involved in PMD, implying a divergence from the autophagic pathway of damaged mitochondria.
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Affiliation(s)
- Yoav Politi
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Liron Gal
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yossi Kalifa
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Liat Ravid
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Zvulun Elazar
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eli Arama
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
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220
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Targeting SQSTM1/p62 induces cargo loading failure and converts autophagy to apoptosis via NBK/Bik. Mol Cell Biol 2014; 34:3435-49. [PMID: 25002530 DOI: 10.1128/mcb.01383-13] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In selective autophagy, the adaptor protein SQSTM1/p62 plays a critical role in recognizing/loading cargo (e.g., malfolded proteins) into autophagosomes for lysosomal degradation. Here we report that whereas SQSTM1/p62 levels fluctuated in a time-dependent manner during autophagy, inhibition or knockdown of Cdk9/cyclin T1 transcriptionally downregulated SQSTM1/p62 but did not affect autophagic flux. These interventions, or short hairpin RNA (shRNA) directly targeting SQSTM1/p62, resulted in cargo loading failure and inefficient autophagy, phenomena recently described for Huntington's disease neurons. These events led to the accumulation of the BH3-only protein NBK/Bik on endoplasmic reticulum (ER) membranes, most likely by blocking loading and autophagic degradation of NBK/Bik, culminating in apoptosis. Whereas NBK/Bik upregulation was further enhanced by disruption of distal autophagic events (e.g., autophagosome maturation) by chloroquine (CQ) or Lamp2 shRNA, it was substantially diminished by inhibition of autophagy initiation (e.g., genetically by shRNA targeting Ulk1, beclin-1, or Atg5 or pharmacologically by 3-methyladenine [3-MA] or spautin-1), arguing that NBK/Bik accumulation stems from inefficient autophagy. Finally, NBK/Bik knockdown markedly attenuated apoptosis in vitro and in vivo. Together, these findings identify novel cross talk between autophagy and apoptosis, wherein targeting SQSTM1/p62 converts cytoprotective autophagy to an inefficient form due to cargo loading failure, leading to NBK/Bik accumulation, which triggers apoptosis.
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221
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Xia P, Wang S, Huang G, Du Y, Zhu P, Li M, Fan Z. RNF2 is recruited by WASH to ubiquitinate AMBRA1 leading to downregulation of autophagy. Cell Res 2014; 24:943-58. [PMID: 24980959 PMCID: PMC4123297 DOI: 10.1038/cr.2014.85] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 05/01/2014] [Accepted: 05/26/2014] [Indexed: 12/17/2022] Open
Abstract
WASH (Wiskott-Aldrich syndrome protein (WASP) and SCAR homolog) was identified to function in endosomal sorting via Arp2/3 activation. We previously demonstrated that WASH is a new interactor of BECN1 and present in the BECN1-PIK3C3 complex with AMBRA1. The AMBRA1-DDB1-CUL4A complex is an E3 ligase for K63-linked ubiquitination of BECN1, which is required for starvation-induced autophagy. WASH suppresses autophagy by inhibition of BECN1 ubiquitination. However, how AMBRA1 is regulated during autophagy remains elusive. Here, we found that RNF2 associates with AMBRA1 to act as an E3 ligase to ubiquitinate AMBRA1 via K48 linkage. RNF2 mediates ubiquitination of AMBRA1 at lysine 45. Notably, RNF2 deficiency enhances autophagy induction. Upon autophagy induction, RNF2 potentiates AMBRA1 degradation with the help of WASH. WASH deficiency impairs the association of RNF2 with AMBRA1 to impede AMBRA1 degradation. Our findings reveal another novel layer of regulation of autophagy through WASH recruitment of RNF2 for AMBRA1 degradation leading to downregulation of autophagy.
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Affiliation(s)
- Pengyan Xia
- 1] Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China [2] University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuo Wang
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Guanling Huang
- 1] Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China [2] University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ying Du
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Pingping Zhu
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Man Li
- 1] Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China [2] University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zusen Fan
- Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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222
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Wang S, Xia P, Ye B, Huang G, Liu J, Fan Z. Transient activation of autophagy via Sox2-mediated suppression of mTOR is an important early step in reprogramming to pluripotency. Cell Stem Cell 2014; 13:617-25. [PMID: 24209762 DOI: 10.1016/j.stem.2013.10.005] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Revised: 08/09/2013] [Accepted: 10/07/2013] [Indexed: 12/13/2022]
Abstract
Autophagy is an essential cellular mechanism that degrades cytoplasmic proteins and organelles to recycle their components. Here we show that autophagy is required for reprogramming of somatic cells to form induced pluripotent stem cells (iPSCs). Our data indicate that mammalian target of rapamycin (mTOR) is downregulated by Sox2 at an early stage of iPSC generation and that this transient downregulation of mTOR is required for reprogramming to take place. In the absence of Sox2, mTOR remains at a high level and inhibits autophagy. Mechanistically, Sox2 binds to a repressive region on the mTOR promoter and recruits the NuRD complex to mediate transcriptional repression. We also detected enhanced autophagy at the four- to eight-cell stage of embryonic development, and a similar Sox2 and mTOR-mediated regulatory pathway seems to operate in this context as well. Thus, our findings reveal Sox2-dependent temporal regulation of autophagy as a key step in cellular reprogramming processes.
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Affiliation(s)
- Shuo Wang
- CAS Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
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223
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Le Bars R, Marion J, Le Borgne R, Satiat-Jeunemaitre B, Bianchi MW. ATG5 defines a phagophore domain connected to the endoplasmic reticulum during autophagosome formation in plants. Nat Commun 2014; 5:4121. [PMID: 24947672 DOI: 10.1038/ncomms5121] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 05/14/2014] [Indexed: 02/03/2023] Open
Abstract
Autophagosomes are the organelles responsible for macroautophagy and arise, in yeast and animals, from the sealing of a cup-shaped double-membrane precursor, the phagophore. How the phagophore is generated and grows into a sealed autophagosome is still not clear in detail, and unknown in plants. This is due, in part, to the scarcity of structurally informative, real-time imaging data of the required protein machinery at the phagophore formation site. Here we find that in intact living Arabidopsis tissue, autophagy-related protein ATG5, which is essential for autophagosome formation, is present at the phagophore site from early, sub-resolution stages and later defines a torus-shaped structure on a flat cisternal early phagophore. Movement and expansion of this structure are accompanied by the underlying endoplasmic reticulum, suggesting tight connections between the two compartments. Detailed real-time and 3D imaging of the growing phagophore are leveraged to propose a model for autophagosome formation in plants.
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Affiliation(s)
- Romain Le Bars
- Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France
| | - Jessica Marion
- Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France
| | - Rémi Le Borgne
- 1] Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France [2] Pôle de Biologie Cellulaire, Imagif, Centre de Recherche de Gif, (FRC3115), Saclay Plant Sciences, CNRS, 91198 Gif-sur-Yvette, France
| | - Béatrice Satiat-Jeunemaitre
- 1] Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France [2] Pôle de Biologie Cellulaire, Imagif, Centre de Recherche de Gif, (FRC3115), Saclay Plant Sciences, CNRS, 91198 Gif-sur-Yvette, France
| | - Michele Wolfe Bianchi
- 1] Laboratoire Dynamique de la Compartimentation Cellulaire, CNRS UPR2355, Institut des Sciences du Végétal, Centre de Recherche de Gif (FRC3115), Saclay Plant Sciences, 91198 Gif-sur-Yvette, France [2] UFR Sciences et Technologie, Université Paris-Est Créteil Val de Marne (UPEC), 61 av. Général de Gaulle, 94010 Créteil, France
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224
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Jo C, Kim S, Cho SJ, Choi KJ, Yun SM, Koh YH, Johnson GVW, Park SI. Sulforaphane induces autophagy through ERK activation in neuronal cells. FEBS Lett 2014; 588:3081-8. [PMID: 24952354 DOI: 10.1016/j.febslet.2014.06.036] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 05/30/2014] [Accepted: 06/08/2014] [Indexed: 01/07/2023]
Abstract
Sulforaphane (SFN), an activator of nuclear factor E2-related factor 2 (Nrf2), has been reported to induce autophagy in several cells. However, little is known about its signaling mechanism of autophagic induction. Here, we provide evidence that SFN induces autophagy with increased levels of LC3-II through extracellular signal-regulated kinase (ERK) activation in neuronal cells. Pretreatment with NAC (N-acetyl-l-cysteine), a well-known antioxidant, completely blocked the SFN-induced increase in LC3-II levels and activation of ERK. Knockdown or overexpression of Nrf2 did not affect autophagy. Together, the results suggest that SFN-mediated generation of reactive oxygen species (ROS) induces autophagy via ERK activation, independent of Nrf2 activity in neuronal cells.
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Affiliation(s)
- Chulman Jo
- Division of Brain Diseases, Center for Biomedical Sciences, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea.
| | - Sunhyo Kim
- Division of Brain Diseases, Center for Biomedical Sciences, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea
| | - Sun-Jung Cho
- Division of Brain Diseases, Center for Biomedical Sciences, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea
| | - Ki Ju Choi
- Division of Respiratory Viruses, Center for Infectious Diseases, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea
| | - Sang-Moon Yun
- Division of Brain Diseases, Center for Biomedical Sciences, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea
| | - Young Ho Koh
- Division of Brain Diseases, Center for Biomedical Sciences, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea
| | - Gail V W Johnson
- Department of Anesthesiology, University of Rochester Medical Center, University of Rochester, 601 Elmwood Ave., Rochester, NY, USA
| | - Sang Ick Park
- Division of Brain Diseases, Center for Biomedical Sciences, Korea National Institute of Health, 187 Osongsaengmyeong2(i)-ro, Osong-eup, Cheongwon-gun, Chungcheongbuk-do 363-951, Republic of Korea.
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225
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Hosogi S, Kusuzaki K, Inui T, Wang X, Marunaka Y. Cytosolic chloride ion is a key factor in lysosomal acidification and function of autophagy in human gastric cancer cell. J Cell Mol Med 2014; 18:1124-33. [PMID: 24725767 PMCID: PMC4508152 DOI: 10.1111/jcmm.12257] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 01/22/2014] [Indexed: 12/21/2022] Open
Abstract
The purpose of the present study was to clarify roles of cytosolic chloride ion (Cl(-) ) in regulation of lysosomal acidification [intra-lysosomal pH (pHlys )] and autophagy function in human gastric cancer cell line (MKN28). The MKN28 cells cultured under a low Cl(-) condition elevated pHlys and reduced the intra-lysosomal Cl(-) concentration ([Cl(-) ]lys ) via reduction of cytosolic Cl(-) concentration ([Cl(-) ]c ), showing abnormal accumulation of LC3II and p62 participating in autophagy function (dysfunction of autophagy) accompanied by inhibition of cell proliferation via G0 /G1 arrest without induction of apoptosis. We also studied effects of direct modification of H(+) transport on lysosomal acidification and autophagy. Application of bafilomycin A1 (an inhibitor of V-type H(+) -ATPase) or ethyl isopropyl amiloride [EIPA; an inhibitor of Na(+) /H(+) exchanger (NHE)] elevated pHlys and decreased [Cl(-) ]lys associated with inhibition of cell proliferation via induction of G0 /G1 arrest similar to the culture under a low Cl(-) condition. However, unlike low Cl(-) condition, application of the compound, bafilomycin A1 or EIPA, induced apoptosis associated with increases in caspase 3 and 9 without large reduction in [Cl(-) ]c compared with low Cl(-) condition. These observations suggest that the lowered [Cl(-) ]c primarily causes dysfunction of autophagy without apoptosis via dysfunction of lysosome induced by disturbance of intra-lysosomal acidification. This is the first study showing that cytosolic Cl(-) is a key factor of lysosome acidification and autophagy.
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Affiliation(s)
- Shigekuni Hosogi
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of MedicineKyoto, Japan
- Japan Institute for Food Education and Health, Heian Jogakuin (St. Agnes') UniversityKyoto, Japan
- * Correspondence to: Dr. Shigekuni HOSOGI, M.D., Ph.D. and Prof. Yoshinori MARUNAKA, M.D., Ph.D., Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan., Tel.: +81-75-251-5311, Fax: +81-75-251-0295, E-mails: for Shigekuni Hosogi; for Yoshinori Marunaka
| | - Katsuyuki Kusuzaki
- Japan Institute for Food Education and Health, Heian Jogakuin (St. Agnes') UniversityKyoto, Japan
- Department of Orthopaedic Surgery, Kyoto Kujo HospitalKyoto, Japan
| | - Toshio Inui
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of MedicineKyoto, Japan
- Department of Bio-Ionomics, Graduate School of Medical Science, Kyoto Prefectural University of MedicineKyoto, Japan
- Saisei Mirai ClinicsMoriguchi, Japan
| | - Xiangdong Wang
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of MedicineKyoto, Japan
- Department of Respiratory Medicine, Shanghai Respiratory Research Institute, Fudan University Zhongshan HospitalShanghai, China
| | - Yoshinori Marunaka
- Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of MedicineKyoto, Japan
- Japan Institute for Food Education and Health, Heian Jogakuin (St. Agnes') UniversityKyoto, Japan
- Department of Bio-Ionomics, Graduate School of Medical Science, Kyoto Prefectural University of MedicineKyoto, Japan
- Department of Respiratory Medicine, Shanghai Respiratory Research Institute, Fudan University Zhongshan HospitalShanghai, China
- * Correspondence to: Dr. Shigekuni HOSOGI, M.D., Ph.D. and Prof. Yoshinori MARUNAKA, M.D., Ph.D., Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan., Tel.: +81-75-251-5311, Fax: +81-75-251-0295, E-mails: for Shigekuni Hosogi; for Yoshinori Marunaka
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Birgisdottir ÅB, Lamark T, Johansen T. The LIR motif - crucial for selective autophagy. J Cell Sci 2014; 126:3237-47. [PMID: 23908376 DOI: 10.1242/jcs.126128] [Citation(s) in RCA: 622] [Impact Index Per Article: 62.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
(Macro)autophagy is a fundamental degradation process for macromolecules and organelles of vital importance for cell and tissue homeostasis. Autophagy research has gained a strong momentum in recent years because of its relevance to cancer, neurodegenerative diseases, muscular dystrophy, lipid storage disorders, development, ageing and innate immunity. Autophagy has traditionally been thought of as a bulk degradation process that is mobilized upon nutritional starvation to replenish the cell with building blocks and keep up with the energy demand. This view has recently changed dramatically following an array of papers describing various forms of selective autophagy. A main driving force has been the discovery of specific autophagy receptors that sequester cargo into forming autophagosomes (phagophores). At the heart of this selectivity lies the LC3-interacting region (LIR) motif, which ensures the targeting of autophagy receptors to LC3 (or other ATG8 family proteins) anchored in the phagophore membrane. LIR-containing proteins include cargo receptors, members of the basal autophagy apparatus, proteins associated with vesicles and of their transport, Rab GTPase-activating proteins (GAPs) and specific signaling proteins that are degraded by selective autophagy. Here, we comment on these new insights and focus on the interactions of LIR-containing proteins with members of the ATG8 protein family.
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Affiliation(s)
- Åsa Birna Birgisdottir
- Molecular Cancer Research Group, Institute of Medical Biology, University of Tromsø, 9037 Tromsø, Norway
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227
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Abstract
Autophagy is a lysosome-mediated degradative system that is a highly conserved pathway present in all eukaryotes. In all cells, double-membrane autophagosomes form and engulf cytoplasmic components, delivering them to the lysosome for degradation. Autophagy is essential for cell health and can be activated to function as a recycling pathway in the absence of nutrients or as a quality-control pathway to eliminate damaged organelles or even to eliminate invading pathogens. Autophagy was first identified as a pathway in mammalian cells using morphological techniques, but the Atg (autophagy-related) genes required for autophagy were identified in yeast genetic screens. Despite tremendous advances in elucidating the function of individual Atg proteins, our knowledge of how autophagosomes form and subsequently interact with the endosomal pathway has lagged behind. Recent progress toward understanding where and how both the endocytotic and autophagic pathways overlap is reviewed here.
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Affiliation(s)
- Sharon A Tooze
- London Research Institute, Cancer Research UK, Secretory Pathways Laboratory, London WC2A 3LY, United Kingdom
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228
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Two ubiquitin-like conjugation systems that mediate membrane formation during autophagy. Essays Biochem 2014; 55:39-50. [PMID: 24070470 DOI: 10.1042/bse0550039] [Citation(s) in RCA: 203] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In autophagy, the autophagosome, a transient organelle specialized for the sequestration and lysosomal or vacuolar transport of cellular constituents, is formed via unique membrane dynamics. This process requires concerted actions of a distinctive set of proteins named Atg (autophagy-related). Atg proteins include two ubiquitin-like proteins, Atg12 and Atg8 [LC3 (light-chain 3) and GABARAP (γ-aminobutyric acid receptor-associated protein) in mammals]. Sequential reactions by the E1 enzyme Atg7 and the E2 enzyme Atg10 conjugate Atg12 to the lysine residue in Atg5, and the resulting Atg12-Atg5 conjugate forms a complex with Atg16. On the other hand, Atg8 is first processed at the C-terminus by Atg4, which is related to ubiquitin-processing/deconjugating enzymes. Atg8 is then activated by Atg7 (shared with Atg12) and, via the E2 enzyme Atg3, finally conjugated to the amino group of the lipid PE (phosphatidylethanolamine). The Atg12-Atg5-Atg16 complex acts as an E3 enzyme for the conjugation reaction of Atg8; it enhances the E2 activity of Atg3 and specifies the site of Atg8-PE production to be autophagy-related membranes. Atg8-PE is suggested to be involved in autophagosome formation at multiple steps, including membrane expansion and closure. Moreover, Atg4 cleaves Atg8-PE to liberate Atg8 from membranes for reuse, and this reaction can also regulate autophagosome formation. Thus these two ubiquitin-like systems are intimately involved in driving the biogenesis of the autophagosomal membrane.
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229
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Arnoldi F, De Lorenzo G, Mano M, Schraner EM, Wild P, Eichwald C, Burrone OR. Rotavirus increases levels of lipidated LC3 supporting accumulation of infectious progeny virus without inducing autophagosome formation. PLoS One 2014; 9:e95197. [PMID: 24736649 PMCID: PMC3988245 DOI: 10.1371/journal.pone.0095197] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 03/24/2014] [Indexed: 01/09/2023] Open
Abstract
Replication of many RNA viruses benefits from subversion of the autophagic pathway through many different mechanisms. Rotavirus, the main etiologic agent of pediatric gastroenteritis worldwide, has been recently described to induce accumulation of autophagosomes as a mean for targeting viral proteins to the sites of viral replication. Here we show that the viral-induced increase of the lipidated form of LC3 does not correlate with an augmented formation of autophagosomes, as detected by immunofluorescence and electron microscopy. The LC3-II accumulation was found to be dependent on active rotavirus replication through the use of antigenically intact inactivated viral particles and of siRNAs targeting viral genes that are essential for viral replication. Silencing expression of LC3 or of Atg7, a protein involved in LC3 lipidation, resulted in a significant impairment of viral titers, indicating that these elements of the autophagic pathway are required at late stages of the viral cycle.
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Affiliation(s)
- Francesca Arnoldi
- Department of Medicine, Surgery and Health Sciences, University of Trieste, Trieste, Italy
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano (Trieste), Italy
| | - Giuditta De Lorenzo
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano (Trieste), Italy
| | - Miguel Mano
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano (Trieste), Italy
| | - Elisabeth M. Schraner
- Institute of Veterinary Anatomy, University of Zürich, Zürich, Switzerland
- Institute of Virology, University of Zürich, Zürich, Switzerland
| | - Peter Wild
- Institute of Veterinary Anatomy, University of Zürich, Zürich, Switzerland
- Institute of Virology, University of Zürich, Zürich, Switzerland
| | | | - Oscar R. Burrone
- International Centre for Genetic Engineering and Biotechnology (ICGEB), Padriciano (Trieste), Italy
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230
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Betulinic acid-induced mitochondria-dependent cell death is counterbalanced by an autophagic salvage response. Cell Death Dis 2014; 5:e1169. [PMID: 24722294 PMCID: PMC5424116 DOI: 10.1038/cddis.2014.139] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 02/17/2014] [Accepted: 02/26/2014] [Indexed: 12/12/2022]
Abstract
Betulinic acid (BetA) is a plant-derived pentacyclic triterpenoid that exerts potent anti-cancer effects in vitro and in vivo. It was shown to induce apoptosis via a direct effect on mitochondria. This is largely independent of proapoptotic BAK and BAX, but can be inhibited by cyclosporin A (CsA), an inhibitor of the permeability transition (PT) pore. Here we show that blocking apoptosis with general caspase inhibitors did not prevent cell death, indicating that alternative, caspase-independent cell death pathways were activated. BetA did not induce necroptosis, but we observed a strong induction of autophagy in several cancer cell lines. Autophagy was functional as shown by enhanced flux and degradation of long-lived proteins. BetA-induced autophagy could be blocked, just like apoptosis, with CsA, suggesting that autophagy is activated as a response to the mitochondrial damage inflicted by BetA. As both a survival and cell death role have been attributed to autophagy, autophagy-deficient tumor cells and mouse embryo fibroblasts were analyzed to determine the role of autophagy in BetA-induced cell death. This clearly established BetA-induced autophagy as a survival mechanism and indicates that BetA utilizes an as yet-undefined mechanism to kill cancer cells.
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231
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Sawa-Makarska J, Abert C, Romanov J, Zens B, Ibiricu I, Martens S. Cargo binding to Atg19 unmasks additional Atg8 binding sites to mediate membrane-cargo apposition during selective autophagy. Nat Cell Biol 2014; 16:425-433. [PMID: 24705553 PMCID: PMC4009068 DOI: 10.1038/ncb2935] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 02/14/2014] [Indexed: 01/01/2023]
Abstract
Autophagy protects cells from harmful substances such as protein aggregates, damaged mitochondria and intracellular pathogens and has been implicated in a variety of diseases. Selectivity of autophagic processes is mediated by cargo receptors that link cargo to Atg8 family proteins on the developing autophagosomal membrane. To avoid collateral degradation during constitutive autophagic pathways the autophagic machinery must not only select cargo but also exclude non-cargo material. Here we show that cargo directly activates the cargo receptor Atg19 by exposing multiple Atg8 binding sites. Furthermore, Atg19 mediates tight apposition of the cargo and Atg8-coated membranes in a fully reconstituted system. These properties are essential for the function of Atg19 during selective autophagy in vivo. Our results suggest that cargo receptors contribute to tight membrane bending of the isolation membrane around the cargo.
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Affiliation(s)
- Justyna Sawa-Makarska
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Christine Abert
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Julia Romanov
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Bettina Zens
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Iosune Ibiricu
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
| | - Sascha Martens
- Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, Dr. Bohr-Gasse 9/3, 1030 Vienna, Austria
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232
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Gao D, Zhang J, Zhao J, Wen H, Pan J, Zhang S, Fang Y, Li X, Cai Y, Wang X, Wang S. Autophagy activated by Toxoplasma gondii infection in turn facilitates Toxoplasma gondii proliferation. Parasitol Res 2014; 113:2053-8. [PMID: 24696274 DOI: 10.1007/s00436-014-3853-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 03/05/2014] [Indexed: 11/28/2022]
Abstract
Autophagy was found to play an antimicrobial or antiparasitic role in the activation of host cells to defend against intracellular pathogens, at the same time, pathogens could compete with host cell and take advantage of autophagy to provide access for its proliferation, but there are few articles for studying the outcome of this competition between host cell and pathogens. Therefore, the aim of our study was to investigate the relationship between autophagy activated by Toxoplasma gondii (T. gondii) and proliferation of T. gondii affected by autophagy in vitro. Firstly, human embryonic fibroblasts (HEF) cells were infected with T. gondii for different times. The monodansylcadaverine (MDC) staining, acridine orange (AO) staining, punctuate GFP-LC3 distribution, and transmission electron microscopy (TEM) assays were conducted, and the results were consistent in showing that gondii infection could induce autophagy. Secondly, HEF cells were infected with T. gondii and treated with autophagy inhibitor bafilomycin A1 or inducer lithium chloride for different times. Giemsa staining was conducted, and the results exhibited that T. gondii infection-induced autophagy could in turn promote T. gondii proliferation. Simultaneously, the results of Giemsa staining also revealed that autophagy inhibitor could reduce the number of each cell infected with T. gondii and inhibit T. gondii proliferation. In contrast, autophagy inducer could increase the number of each cell infected with T. gondii and encourage T. gondii proliferation. Therefore, our study suggests that T. gondii infection could activate autophagy, and this autophagy could in turn facilitate T. gondii proliferation in HEF cells for limiting nutrients.
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Affiliation(s)
- Dongmei Gao
- Department of Clinical Laboratory, Third Affiliated Hospital of Anhui Medical University, Hefei, 230032, China
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233
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Romao S, Gasser N, Becker AC, Guhl B, Bajagic M, Vanoaica D, Ziegler U, Roesler J, Dengjel J, Reichenbach J, Münz C. Autophagy proteins stabilize pathogen-containing phagosomes for prolonged MHC II antigen processing. ACTA ACUST UNITED AC 2014; 203:757-66. [PMID: 24322427 PMCID: PMC3857489 DOI: 10.1083/jcb.201308173] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
A subset of phagosomes in human macrophages and dendritic cells that is marked by a coat of autophagy-related proteins maintains phagocytosed antigens for prolonged presentation on MHC class II molecules. Antigen preservation for presentation is a hallmark of potent antigen-presenting cells. In this paper, we report that in human macrophages and dendritic cells, a subset of phagosomes gets coated with Atg8/LC3, a component of the molecular machinery of macroautophagy, and maintains phagocytosed antigens for prolonged presentation on major histocompatibility complex class II molecules. These Atg8/LC3-positive phagosomes are formed around the antigen with TLR2 agonists and require reactive oxygen species production by NOX2 for their generation. A deficiency in the NOX2-dependent formation of these antigen storage phagosomes could contribute to compromise antifungal immune control in chronic granulomatous disease patients.
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Affiliation(s)
- Susana Romao
- Viral Immunobiology, Institute of Experimental Immunology, and 2 Center for Microscopy and Image Analysis, University of Zürich, 8006 Zürich, Switzerland
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234
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Keipert S, Ost M, Johann K, Imber F, Jastroch M, van Schothorst EM, Keijer J, Klaus S. Skeletal muscle mitochondrial uncoupling drives endocrine cross-talk through the induction of FGF21 as a myokine. Am J Physiol Endocrinol Metab 2014; 306:E469-82. [PMID: 24347058 DOI: 10.1152/ajpendo.00330.2013] [Citation(s) in RCA: 166] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
UCP1-Tg mice with ectopic expression of uncoupling protein 1 (UCP1) in skeletal muscle (SM) are a model of improved substrate metabolism and increased longevity. Analysis of myokine expression showed an induction of fibroblast growth factor 21 (FGF21) in SM, resulting in approximately fivefold elevated circulating FGF21 in UCP1-Tg mice. Despite a reduced muscle mass, UCP1-Tg mice showed no evidence for a myopathy or muscle autophagy deficiency but an activation of integrated stress response (ISR; eIF2α/ATF4) in SM. Targeting mitochondrial function in vitro by treating C2C12 myoblasts with the uncoupler FCCP resulted in a dose-dependent activation of ISR, which was associated with increased expression of FGF21, which was also observed by treatment with respiratory chain inhibitors antimycin A and myxothiazol. The cofactor required for FGF21 action, β-klotho, was expressed in white adipose tissue (WAT) of UCP1-Tg mice, which showed an increased browning of WAT similar to what occurred in altered adipocyte morphology, increased brown adipocyte markers (UCP1, CIDEA), lipolysis (HSL phosphorylation), and respiratory capacity. Importantly, treatment of primary white adipocytes with serum of transgenic mice resulted in increased UCP1 expression. Additionally, UCP1-Tg mice showed reduced body length through the suppressed IGF-I-GH axis and decreased bone mass. We conclude that the induction of FGF21 as a myokine is coupled to disturbance of mitochondrial function and ISR activation in SM. FGF21 released from SM has endocrine effects leading to increased browning of WAT and can explain the healthy metabolic phenotype of UCP1-Tg mice. These results confirm muscle as an important endocrine regulator of whole body metabolism.
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Affiliation(s)
- Susanne Keipert
- German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany
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235
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Kalvari I, Tsompanis S, Mulakkal NC, Osgood R, Johansen T, Nezis IP, Promponas VJ. iLIR: A web resource for prediction of Atg8-family interacting proteins. Autophagy 2014; 10:913-25. [PMID: 24589857 PMCID: PMC5119064 DOI: 10.4161/auto.28260] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Macroautophagy was initially considered to be a nonselective process for bulk breakdown of cytosolic material. However, recent evidence points toward a selective mode of autophagy mediated by the so-called selective autophagy receptors (SARs). SARs act by recognizing and sorting diverse cargo substrates (e.g., proteins, organelles, pathogens) to the autophagic machinery. Known SARs are characterized by a short linear sequence motif (LIR-, LRS-, or AIM-motif) responsible for the interaction between SARs and proteins of the Atg8 family. Interestingly, many LIR-containing proteins (LIRCPs) are also involved in autophagosome formation and maturation and a few of them in regulating signaling pathways. Despite recent research efforts to experimentally identify LIRCPs, only a few dozen of this class of—often unrelated—proteins have been characterized so far using tedious cell biological, biochemical, and crystallographic approaches. The availability of an ever-increasing number of complete eukaryotic genomes provides a grand challenge for characterizing novel LIRCPs throughout the eukaryotes. Along these lines, we developed iLIR, a freely available web resource, which provides in silico tools for assisting the identification of novel LIRCPs. Given an amino acid sequence as input, iLIR searches for instances of short sequences compliant with a refined sensitive regular expression pattern of the extended LIR motif (xLIR-motif) and retrieves characterized protein domains from the SMART database for the query. Additionally, iLIR scores xLIRs against a custom position-specific scoring matrix (PSSM) and identifies potentially disordered subsequences with protein interaction potential overlapping with detected xLIR-motifs. Here we demonstrate that proteins satisfying these criteria make good LIRCP candidates for further experimental verification. Domain architecture is displayed in an informative graphic, and detailed results are also available in tabular form. We anticipate that iLIR will assist with elucidating the full complement of LIRCPs in eukaryotes.
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Affiliation(s)
- Ioanna Kalvari
- Bioinformatics Research Laboratory; Department of Biological Sciences; University of Cyprus; Nicosia, Cyprus
| | - Stelios Tsompanis
- Bioinformatics Research Laboratory; Department of Biological Sciences; University of Cyprus; Nicosia, Cyprus; Student in International Erasmus Exchange Programme (2012-2013)
| | | | - Richard Osgood
- School of Life Sciences; University of Warwick; Coventry, UK
| | - Terje Johansen
- Molecular Cancer Research Group; Institute of Medical Biology; University of Tromsø; Tromsø, Norway
| | - Ioannis P Nezis
- School of Life Sciences; University of Warwick; Coventry, UK
| | - Vasilis J Promponas
- Bioinformatics Research Laboratory; Department of Biological Sciences; University of Cyprus; Nicosia, Cyprus
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236
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Oxidative stress, hypoxia, and autophagy in the neovascular processes of age-related macular degeneration. BIOMED RESEARCH INTERNATIONAL 2014; 2014:768026. [PMID: 24707498 PMCID: PMC3950832 DOI: 10.1155/2014/768026] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Revised: 10/13/2013] [Accepted: 10/13/2013] [Indexed: 11/25/2022]
Abstract
Age-related macular degeneration (AMD) is the leading cause of severe and irreversible loss of vision in the elderly in developed countries. AMD is a complex chronic neurodegenerative disease associated with many environmental, lifestyle, and genetic factors. Oxidative stress and the production of reactive oxygen species (ROS) seem to play a pivotal role in AMD pathogenesis. It is known that the macula receives the highest blood flow of any tissue in the body when related to size, and anything that can reduce the rich blood supply can cause hypoxia, malfunction, or disease. Oxidative stress can affect both the lipid rich retinal outer segment structure and the light processing in the macula. The response to oxidative stress involves several cellular defense reactions, for example, increases in antioxidant production and proteolysis of damaged proteins. The imbalance between production of damaged cellular components and degradation leads to the accumulation of detrimental products, for example, intracellular lipofuscin and extracellular drusen. Autophagy is a central lysosomal clearance system that may play an important role in AMD development. There are many anatomical changes in retinal pigment epithelium (RPE), Bruch's membrane, and choriocapillaris in response to chronic oxidative stress, hypoxia, and disturbed autophagy and these are estimated to be crucial components in the pathology of neovascular processes in AMD.
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237
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Abstract
SIGNIFICANCE Autophagy is a highly conserved eukaryotic cellular recycling process. Through the degradation of cytoplasmic organelles, proteins, and macromolecules, and the recycling of the breakdown products, autophagy plays important roles in cell survival and maintenance. Accordingly, dysfunction of this process contributes to the pathologies of many human diseases. RECENT ADVANCES Extensive research is currently being done to better understand the process of autophagy. In this review, we describe current knowledge of the morphology, molecular mechanism, and regulation of mammalian autophagy. CRITICAL ISSUES At the mechanistic and regulatory levels, there are still many unanswered questions and points of confusion that have yet to be resolved. FUTURE DIRECTIONS Through further research, a more complete and accurate picture of the molecular mechanism and regulation of autophagy will not only strengthen our understanding of this significant cellular process, but will aid in the development of new treatments for human diseases in which autophagy is not functioning properly.
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Affiliation(s)
- Katherine R Parzych
- Department of Molecular, Cellular and Developmental Biology, Life Sciences Institute, University of Michigan , Ann Arbor, Michigan
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238
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Regulation of autophagy by the Rab GTPase network. Cell Death Differ 2014; 21:348-58. [PMID: 24440914 DOI: 10.1038/cdd.2013.187] [Citation(s) in RCA: 298] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/22/2013] [Accepted: 11/21/2013] [Indexed: 01/14/2023] Open
Abstract
Autophagy (macroautophagy) is a highly conserved intracellular and lysosome-dependent degradation process in which autophagic substrates are enclosed and degraded by a double-membrane vesicular structure in a continuous and dynamic vesicle transport process. The Rab protein is a small GTPase that belongs to the Ras-like GTPase superfamily and regulates the vesicle traffic process. Numerous Rab proteins have been shown to be involved in various stages of autophagy. Rab1, Rab5, Rab7, Rab9A, Rab11, Rab23, Rab32, and Rab33B participate in autophagosome formation, whereas Rab9 is required in non-canonical autophagy. Rab7, Rab8B, and Rab24 have a key role in autophagosome maturation. Rab8A and Rab25 are also involved in autophagy, but their role is unknown. Here, we summarize new findings regarding the involvement of Rabs in autophagy and provide insights regarding future research on the mechanisms of autophagy regulation.
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239
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Abstract
Macroautophagy is a conserved degradative process mediated through formation of a unique double-membrane structure, the autophagosome. The discovery of autophagy-related (Atg) genes required for autophagosome formation has led to the characterization of approximately 20 genes mediating this process. Recent structural studies of the Atg proteins have provided the molecular basis for their function. Here we summarize the recent progress in elucidating the structural basis for autophagosome formation.
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240
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Abstract
Autophagy and apoptosis control the turnover of organelles and proteins within cells, and of cells within organisms, respectively, and many stress pathways sequentially elicit autophagy, and apoptosis within the same cell. Generally autophagy blocks the induction of apoptosis, and apoptosis-associated caspase activation shuts off the autophagic process. However, in special cases, autophagy or autophagy-relevant proteins may help to induce apoptosis or necrosis, and autophagy has been shown to degrade the cytoplasm excessively, leading to 'autophagic cell death'. The dialogue between autophagy and cell death pathways influences the normal clearance of dying cells, as well as immune recognition of dead cell antigens. Therefore, the disruption of the relationship between autophagy and apoptosis has important pathophysiological consequences.
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241
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Talaber G, Miklossy G, Oaks Z, Liu Y, Tooze SA, Chudakov DM, Banki K, Perl A. HRES-1/Rab4 promotes the formation of LC3(+) autophagosomes and the accumulation of mitochondria during autophagy. PLoS One 2014; 9:e84392. [PMID: 24404161 PMCID: PMC3880286 DOI: 10.1371/journal.pone.0084392] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Accepted: 11/22/2013] [Indexed: 02/07/2023] Open
Abstract
HRES-1/Rab4 is a small GTPase that regulates endocytic recycling. It has been colocalized to mitochondria and the mechanistic target of rapamycin (mTOR), a suppressor of autophagy. Since the autophagosomal membrane component microtubule-associated protein light chain 3 (LC3) is derived from mitochondria, we investigated the impact of HRES-1/Rab4 on the formation of LC3(+) autophagosomes, their colocalization with HRES-1/Rab4 and mitochondria, and the retention of mitochondria during autophagy induced by starvation and rapamycin. HRES-1/Rab4 exhibited minimal baseline colocalization with LC3, which was enhanced 22-fold upon starvation or 6-fold upon rapamycin treatment. Colocalization of HRES-1/Rab4 with mitochondria was increased >2-fold by starvation or rapamycin. HRES-1/Rab4 overexpression promoted the colocalization of mitochondria with LC3 upon starvation or rapamycin treatment. A dominant-negative mutant, HRES-1/Rab4(S27N) had reduced colocalization with LC3 and mitochondria upon starvation but not rapamycin treatment. A constitutively active mutant, HRES-1/Rab4(Q72L) showed diminished colocalization with LC3 but promoted the partitioning of mitochondria with LC3 upon starvation or rapamycin treatment. Phosphorylation-resistant mutant HRES-1/Rab4(S204Q) showed diminished colocalization with LC3 but increased partitioning to mitochondria. A newly discovered C-terminally truncated native isoform, HRES-1/Rab4(1-121), showed enhanced localization to LC3 and mitochondria without starvation or rapamycin treatment. HRES-1/Rab4(1-121) increased the formation of LC3(+) autophagosomes in resting cells, while other isoforms promoted autophagosome formation upon starvation. HRES-1/Rab4, HRES-1/Rab4(1-121), HRES-1/Rab4(Q72L) and HRES-1/Rab4(S204Q) promoted the accumulation of mitochondria during starvation. The specificity of HRES-1/Rab4-mediated mitochondrial accumulation is indicated by its abrogation by dominant-negative HRES-1/Rab4(S27N) mutation. The formation of interconnected mitochondrial tubular networks was markedly enhanced by HRES-1/Rab4(Q72L) upon starvation, which may contribute to the retention of mitochondria during autophagy. The present study thus indicates that HRES-1/Rab4 regulates autophagy through promoting the formation of LC3(+) autophagosomes and the preservation of mitochondria.
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Affiliation(s)
- Gergely Talaber
- Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
| | - Gabriella Miklossy
- Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
| | - Zachary Oaks
- Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
- Biochemistry and Molecular Biology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
| | - Yuxin Liu
- Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
| | - Sharon A. Tooze
- Cancer Research UK London Research Institute, London, England, United Kingdom
| | - Dmitriy M. Chudakov
- Shemiakin-Ovchinnikov Institute of Bioorganic Chemistry, RAS, Moscow, Russia
| | - Katalin Banki
- Department of Pathology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
| | - Andras Perl
- Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
- Biochemistry and Molecular Biology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
- Microbiology and Immunology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America
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242
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Sahani MH, Itakura E, Mizushima N. Expression of the autophagy substrate SQSTM1/p62 is restored during prolonged starvation depending on transcriptional upregulation and autophagy-derived amino acids. Autophagy 2014; 10:431-41. [PMID: 24394643 PMCID: PMC4077882 DOI: 10.4161/auto.27344] [Citation(s) in RCA: 285] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
SQSTM1/p62 (sequestosome 1) is a multifunctional signaling molecule, involved in a variety of cellular pathways. SQSTM1 is one of the best-known autophagic substrates, and is therefore widely used as an indicator of autophagic degradation. Here we report that the expression level of SQSTM1 can be restored during prolonged starvation. Upon starvation, SQSTM1 is initially degraded by autophagy. However, SQSTM1 is restored back to basal levels during prolonged starvation in mouse embryonic fibroblasts and HepG2 cells, but not in HeLa and HEK293 cells. Restoration of SQSTM1 depends on its transcriptional upregulation, which is triggered by amino acid starvation. Furthermore, amino acids derived from the autophagy–lysosome pathway are used for de novo synthesis of SQSTM1 under starvation conditions. The restoration of SQSTM1 is independent of reactivation of MTORC1 (mechanistic target of rapamycin complex 1). These results suggest that the expression level of SQSTM1 in starved cells is determined by at least 3 factors: autophagic degradation, transcriptional upregulation, and availability of lysosomal-derived amino acids. The results of this study also indicate that the expression level of SQSTM1 does not always inversely correlate with autophagic activity.
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Affiliation(s)
- Mayurbhai Himatbhai Sahani
- Department of Physiology and Cell Biology; Tokyo Medical and Dental University; Tokyo, Japan; Department of Biochemistry and Molecular Biology; Graduate School and Faculty of Medicine; University of Tokyo; Tokyo, Japan
| | - Eisuke Itakura
- Department of Physiology and Cell Biology; Tokyo Medical and Dental University; Tokyo, Japan
| | - Noboru Mizushima
- Department of Physiology and Cell Biology; Tokyo Medical and Dental University; Tokyo, Japan; Department of Biochemistry and Molecular Biology; Graduate School and Faculty of Medicine; University of Tokyo; Tokyo, Japan
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243
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Zientara-Rytter K, Sirko A. Significant role of PB1 and UBA domains in multimerization of Joka2, a selective autophagy cargo receptor from tobacco. FRONTIERS IN PLANT SCIENCE 2014; 5:13. [PMID: 24550923 PMCID: PMC3907767 DOI: 10.3389/fpls.2014.00013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Accepted: 01/12/2014] [Indexed: 05/20/2023]
Abstract
Tobacco Joka2 protein is a hybrid homolog of two mammalian selective autophagy cargo receptors, p62 and NBR1. These proteins can directly interact with the members of ATG8 family and the polyubiquitinated cargoes designed for degradation. Function of the selective autophagy cargo receptors relies on their ability to form protein aggregates. It has been shown that the N-terminal PB1 domain of p62 is involved in formation of aggregates, while the UBA domains of p62 and NBR1 have been associated mainly with cargo binding. Here we focus on roles of PB1 and UBA domains in localization and aggregation of Joka2 in plant cells. We show that Joka2 can homodimerize not only through its N-terminal PB1-PB1 interactions but also via interaction between N-terminal PB1 and C-terminal UBA domains. We also demonstrate that Joka2 co-localizes with recombinant ubiquitin and sequestrates it into aggregates and that C-terminal part (containing UBA domains) is sufficient for this effect. Our results indicate that Joka2 accumulates in cytoplasmic aggregates and suggest that in addition to these multimeric forms it also exists in the nucleus and cytoplasm in a monomeric form.
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Affiliation(s)
| | - Agnieszka Sirko
- *Correspondence: Agnieszka Sirko, Department of Plant Biochemistry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul. Pawinskiego 5A, 02-106 Warsaw, Poland e-mail:
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244
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The Ca2+ channel TRPML3 specifically interacts with the mammalian ATG8 homologue GATE16 to regulate autophagy. Biochem Biophys Res Commun 2014; 443:56-61. [DOI: 10.1016/j.bbrc.2013.11.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 11/11/2013] [Indexed: 11/24/2022]
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245
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Kishi-Itakura C, Koyama-Honda I, Itakura E, Mizushima N. Ultrastructural analysis of autophagosome organization using mammalian autophagy-deficient cells. J Cell Sci 2014; 127:4089-102. [DOI: 10.1242/jcs.156034] [Citation(s) in RCA: 152] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Autophagy is mediated by a unique organelle, the autophagosome. Autophagosome formation involves a number of autophagy-related (ATG) proteins and complicated membrane dynamics. Although the hierarchical relationships of ATG proteins have been investigated, how individual ATG proteins or their complexes contribute to the organization of the autophagic membrane remains largely unknown. Here, systematic ultrastructural analysis of mouse embryonic fibroblasts and HeLa cells deficient in various ATG proteins revealed that the emergence of the isolation membrane (phagophore) requires FIP200/RB1CC1, ATG9A, and PtdIns 3-kinase activity. By contrast, small premature isolation membrane- and autophagosome-like structures were generated in cells lacking VMP1 and ATG2A/B, respectively. The isolation membranes could elongate in cells lacking ATG5, but these did not mature into autophagosomes. We also found that ferritin clusters accumulated at the autophagosome formation site together with p62/SQSTM1 in autophagy-deficient cells. These results reveal the specific functions of these representative ATG proteins in autophagic membrane organization and ATG-independent recruitment of ferritin to the autophagosome formation site.
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246
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Conway KL, Kuballa P, Song JH, Patel KK, Castoreno AB, Yilmaz OH, Jijon HB, Zhang M, Aldrich LN, Villablanca EJ, Peloquin JM, Goel G, Lee IA, Mizoguchi E, Shi HN, Bhan AK, Shaw SY, Schreiber SL, Virgin HW, Shamji AF, Stappenbeck TS, Reinecker HC, Xavier RJ. Atg16l1 is required for autophagy in intestinal epithelial cells and protection of mice from Salmonella infection. Gastroenterology 2013; 145:1347-57. [PMID: 23973919 PMCID: PMC3840157 DOI: 10.1053/j.gastro.2013.08.035] [Citation(s) in RCA: 185] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 07/18/2013] [Accepted: 08/15/2013] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Intestinal epithelial cells aid in mucosal defense by providing a physical barrier against entry of pathogenic bacteria and secreting antimicrobial peptides (AMPs). Autophagy is an important component of immune homeostasis. However, little is known about its role in specific cell types during bacterial infection in vivo. We investigated the role of autophagy in the response of intestinal epithelial and antigen-presenting cells to Salmonella infection in mice. METHODS We generated mice deficient in Atg16l1 in epithelial cells (Atg16l1(f/f) × Villin-cre) or CD11c(+) cells (Atg16l1(f/f) × CD11c-cre); these mice were used to assess cell type-specific antibacterial autophagy. All responses were compared with Atg16l1(f/f) mice (controls). Mice were infected with Salmonella enterica serovar typhimurium; cecum and small-intestine tissues were collected for immunofluorescence, histology, and quantitative reverse-transcription polymerase chain reaction analyses of cytokines and AMPs. Modulators of autophagy were screened to evaluate their effects on antibacterial responses in human epithelial cells. RESULTS Autophagy was induced in small intestine and cecum after infection with S typhimurium, and required Atg16l1. S typhimurium colocalized with microtubule-associated protein 1 light chain 3β (Map1lc3b or LC3) in the intestinal epithelium of control mice but not in Atg16l1(f/f) × Villin-cre mice. Atg16l1(f/f) × Villin-cre mice also had fewer Paneth cells and abnormal granule morphology, leading to reduced expression of AMPs. Consistent with these defective immune responses, Atg16l1(f/f) × Villin-cre mice had increased inflammation and systemic translocation of bacteria compared with control mice. In contrast, we observed few differences between Atg16l1(f/f) × CD11c-cre and control mice. Trifluoperazine promoted autophagy and bacterial clearance in HeLa cells; these effects were reduced upon knockdown of ATG16L1. CONCLUSIONS Atg16l1 regulates autophagy in intestinal epithelial cells and is required for bacterial clearance. It also is required to prevent systemic infection of mice with enteric bacteria.
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Affiliation(s)
- Kara L. Conway
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA,Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Center for Computational and Integrative Biology; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Petric Kuballa
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA,Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Center for Computational and Integrative Biology; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Joo-Hye Song
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Khushbu K. Patel
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO USA
| | - Adam B. Castoreno
- Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA
| | - Omer H. Yilmaz
- Pathology Department; Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Humberto B. Jijon
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA,Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Center for Computational and Integrative Biology; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Mei Zhang
- Mucosal Immunology Laboratory; Massachusetts General Hospital and Harvard Medical School; Charlestown, MA USA
| | - Leslie N. Aldrich
- Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Department of Chemistry and Chemical Biology; Harvard University; Cambridge, MA USA
| | - Eduardo J. Villablanca
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA,Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Center for Computational and Integrative Biology; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Joanna M. Peloquin
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Gautam Goel
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA,Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Center for Computational and Integrative Biology; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - In-Ah Lee
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Emiko Mizoguchi
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Hai Ning Shi
- Mucosal Immunology Laboratory; Massachusetts General Hospital and Harvard Medical School; Charlestown, MA USA
| | - Atul K. Bhan
- Pathology Department; Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
| | - Stanley Y. Shaw
- Center for Systems Biology, Simches Research Center, Massachusetts General Hospital; Harvard Medical School; Boston, MA, USA
| | - Stuart L. Schreiber
- Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Department of Chemistry and Chemical Biology; Harvard University; Cambridge, MA USA
| | - Herbert W. Virgin
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO USA
| | - Alykhan F. Shamji
- Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA
| | - Thaddeus S. Stappenbeck
- Department of Pathology and Immunology; Washington University School of Medicine; St. Louis, MO USA
| | - Hans C. Reinecker
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
| | - Ramnik J. Xavier
- Gastrointestinal Unit and Center for the Study of Inflammatory Bowel Disease; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA,Broad Institute of Massachusetts Institute of Technology and Harvard University; Cambridge, MA USA,Center for Computational and Integrative Biology; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
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Abstract
Autophagy is a highly conserved cytoplasmic degradation pathway that has an impact on many physiological and disease states, including immunity, tumorigenesis and neurodegeneration. Recent studies suggest that autophagy may also have important functions in embryogenesis and development. Many autophagy gene-knockout mice have embryonic lethality at different stages of development. Furthermore, interactions of autophagy with crucial developmental pathways such as Wnt, Shh (Sonic Hedgehog), TGFβ (transforming growth factor β) and FGF (fibroblast growth factor) have been reported. This suggests that autophagy may regulate cell fate decisions, such as differentiation and proliferation. In the present article, we discuss how mammalian autophagy may affect phenotypes associated with development.
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248
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Autophagy in inflammation, infection, neurodegeneration and cancer. Int Immunopharmacol 2013; 18:55-65. [PMID: 24262302 DOI: 10.1016/j.intimp.2013.11.001] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 10/31/2013] [Accepted: 11/05/2013] [Indexed: 02/02/2023]
Abstract
In its classical form, autophagy is an essential, homeostatic process by which cytoplasmic components are degraded in a double-membrane-bound autophagosome in response to starvation. Paradoxically, although autophagy is primarily a protective process for the cell, it can also play a role in cell death. The roles of autophagy bridge both the innate and adaptive immune systems and autophagic dysfunction is associated with inflammation, infection, neurodegeneration and cancer. In this review, we discuss the contribution of autophagy to inflammatory, infectious and neurodegenerative diseases, as well as cancer.
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249
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Yuk JM, Jo EK. Crosstalk between autophagy and inflammasomes. Mol Cells 2013; 36:393-9. [PMID: 24213677 PMCID: PMC3887939 DOI: 10.1007/s10059-013-0298-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 09/11/2013] [Indexed: 12/20/2022] Open
Abstract
A variety of cellular stresses activate the autophagy pathway, which is fundamentally important in protection against injurious stimuli. Defects in the autophagy process are associated with a variety of human diseases, including inflammatory and metabolic diseases. The inflammasomes are emerging as key signaling platforms directing the maturation and secretion of interleukin-1 family cytokines in response to pathogenic and sterile stimuli. Recent studies have identified the critical role of inflammasome activation in host defense and inflammation. Delineation of the relationship between autophagy and inflammasome activation is now being greatly facilitated by the use of mice models of autophagy gene deficiency and clinical studies. We surveyed the recent research regarding the contribution of autophagy to the control of inflammation, in particular the association between autophagy and inflammasomes. Understanding the mechanisms by which autophagy balances inflammation might facilitate the development of autophagy-based therapeutic modalities for infectious and inflammatory diseases.
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Affiliation(s)
- Jae-Min Yuk
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon 301-747, Korea
- Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon 301-747, Korea
| | - Eun-Kyeong Jo
- Department of Microbiology, Chungnam National University School of Medicine, Daejeon 301-747, Korea
- Infection Signaling Network Research Center, Chungnam National University School of Medicine, Daejeon 301-747, Korea
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250
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Structural basis for recognition of autophagic receptor NDP52 by the sugar receptor galectin-8. Nat Commun 2013; 4:1613. [PMID: 23511477 DOI: 10.1038/ncomms2606] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 02/14/2013] [Indexed: 02/06/2023] Open
Abstract
Infectious bacteria are cleared from mammalian cells by host autophagy in combination with other upstream cellular components, such as the autophagic receptor NDP52 and sugar receptor galectin-8. However, the detailed molecular basis of the interaction between these two receptors remains to be elucidated. Here, we report the biochemical characterization of both NDP52 and galectin-8 as well as the crystal structure of galectin-8 complexed with an NDP52 peptide. The unexpected observation of nicotinamide adenine dinucleotide located at the carbohydrate-binding site expands our knowledge of the sugar-binding specificity of galectin-8. The NDP52-galectin-8 complex structure explains the key determinants for recognition on both receptors and defines a special orientation of N- and C-terminal carbohydrate recognition domains of galectin-8. Dimeric NDP52 forms a ternary complex with two monomeric galectin-8 molecules as well as two LC3C molecules. These results lay the groundwork for understanding how host cells target bacterial pathogens for autophagy.
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