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Abstract
Autophagy constitutes a prominent mechanism through which eukaryotic cells preserve homeostasis in baseline conditions and in response to perturbations of the intracellular or extracellular microenvironment. Autophagic responses can be relatively non-selective or target a specific subcellular compartment. At least in part, this depends on the balance between the availability of autophagic substrates ("offer") and the cellular need of autophagic products or functions for adaptation ("demand"). Irrespective of cargo specificity, adaptive autophagy relies on a panel of sensors that detect potentially dangerous cues and convert them into signals that are ultimately relayed to the autophagic machinery. Here, we summarize the molecular systems through which specific subcellular compartments-including the nucleus, mitochondria, plasma membrane, reticular apparatus, and cytosol-convert homeostatic perturbations into an increased offer of autophagic substrates or an accrued cellular demand for autophagic products or functions.
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402
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Ward C, Martinez-Lopez N, Otten EG, Carroll B, Maetzel D, Singh R, Sarkar S, Korolchuk VI. Autophagy, lipophagy and lysosomal lipid storage disorders. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:269-84. [DOI: 10.1016/j.bbalip.2016.01.006] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 01/07/2016] [Accepted: 01/12/2016] [Indexed: 12/30/2022]
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403
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Bernard A, Klionsky DJ. Toward an understanding of autophagosome-lysosome fusion: The unsuspected role of ATG14. Autophagy 2016; 11:583-4. [PMID: 25920502 DOI: 10.1080/15548627.2015.1029220] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Although largely overlooked relative to the process of phagophore formation, the mechanism through which autophagosomes fuse with lysosomes is a critical aspect of macroautophagy that is not fully understood. In particular, this step must be carefully regulated to prevent premature fusion of an incomplete autophagosome (that is, a phagophore) with a lysosome, because such an event would not allow access of the partially sequestered cargo to the lysosome lumen. The identification of the autophagosome-associated SNARE protein STX17 (syntaxin 17) provided some clue in the understanding of this process. STX17 is recruited specifically to mature autophagosomes, and functions in mediating autophagosome-lysosome fusion by forming a complex with the Qbc SNARE SNAP29 and the lysosomal R-SNARE VAMP8. Additionally, STX17 plays a role in the early events of autophagy by interacting with the phosphatidylinositol 3-kinase complex component ATG14. Upon autophagy induction STX17 is strictly required for ATG14 recruitment to the ER-mitochondria contact sites, a critical step for the assembly of the phagophore and therefore for autophagosome formation. In their recent paper, Diao and collaborators now show that the ATG14-STX17-SNAP29 interaction mediates autophagosome-lysosome tethering and fusion events, thus revealing a novel function of ATG14 in the later steps of the autophagy pathway.
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Affiliation(s)
- Amélie Bernard
- a Life Sciences Institute; University of Michigan ; Ann Arbor , MI USA
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404
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Paul P, Münz C. Autophagy and Mammalian Viruses: Roles in Immune Response, Viral Replication, and Beyond. Adv Virus Res 2016; 95:149-95. [PMID: 27112282 DOI: 10.1016/bs.aivir.2016.02.002] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autophagy is an important cellular catabolic process conserved from yeast to man. Double-membrane vesicles deliver their cargo to the lysosome for degradation. Hence, autophagy is one of the key mechanisms mammalian cells deploy to rid themselves of intracellular pathogens including viruses. However, autophagy serves many more functions during viral infection. First, it regulates the immune response through selective degradation of immune components, thus preventing possibly harmful overactivation and inflammation. Additionally, it delivers virus-derived antigens to antigen-loading compartments for presentation to T lymphocytes. Second, it might take an active part in the viral life cycle by, eg, facilitating its release from cells. Lastly, in the constant arms race between host and virus, autophagy is often hijacked by viruses and manipulated to their own advantage. In this review, we will highlight key steps during viral infection in which autophagy plays a role. We have selected some exemplary viruses and will describe the molecular mechanisms behind their intricate relationship with the autophagic machinery, a result of host-pathogen coevolution.
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Affiliation(s)
- P Paul
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - C Münz
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland.
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405
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Mechanistically Dissecting Autophagy: Insights from In Vitro Reconstitution. J Mol Biol 2016; 428:1700-13. [PMID: 26946034 DOI: 10.1016/j.jmb.2016.02.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 02/19/2016] [Accepted: 02/19/2016] [Indexed: 12/13/2022]
Abstract
Autophagy is a fundamental cellular mechanism responsible for bulk turnover of cytoplasmic components. It is broadly related to many cellular activities, physiological processes, and pathological conditions. Autophagy entails a spatiotemporal interaction between cytosolic factors and membranes that are remodeled to encapsulate autophagic cargo within an autophagosome. Although majority of the factors [autophagy-related gene (Atg) proteins] involved in autophagy have been identified by genetic studies, the mechanism accounting for how these factors act upon the membrane to remodel it and efficiently recruit cargo for degradation is unclear. In vitro reconstitution of several different aspects of autophagy has provided important insights into the understanding of the mechanistic details underlying autophagic membrane remodeling and cargo recruitment. Here, we highlight these efforts toward studying autophagy through in vitro approaches.
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406
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Bento CF, Renna M, Ghislat G, Puri C, Ashkenazi A, Vicinanza M, Menzies FM, Rubinsztein DC. Mammalian Autophagy: How Does It Work? Annu Rev Biochem 2016; 85:685-713. [PMID: 26865532 DOI: 10.1146/annurev-biochem-060815-014556] [Citation(s) in RCA: 495] [Impact Index Per Article: 61.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Autophagy is a conserved intracellular pathway that delivers cytoplasmic contents to lysosomes for degradation via double-membrane autophagosomes. Autophagy substrates include organelles such as mitochondria, aggregate-prone proteins that cause neurodegeneration and various pathogens. Thus, this pathway appears to be relevant to the pathogenesis of diverse diseases, and its modulation may have therapeutic value. Here, we focus on the cell and molecular biology of mammalian autophagy and review the key proteins that regulate the process by discussing their roles and how these may be modulated by posttranslational modifications. We consider the membrane-trafficking events that impact autophagy and the questions relating to the sources of autophagosome membrane(s). Finally, we discuss data from structural studies and some of the insights these have provided.
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Affiliation(s)
- Carla F Bento
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - Maurizio Renna
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - Ghita Ghislat
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - Claudia Puri
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - Avraham Ashkenazi
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - Mariella Vicinanza
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - Fiona M Menzies
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
| | - David C Rubinsztein
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Cambridge CB2 0XY, United Kingdom;
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407
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Rao Y, Matscheko N, Wollert T. Autophagy in the test tube: In vitro reconstitution of aspects of autophagosome biogenesis. FEBS J 2016; 283:2034-43. [PMID: 26797728 DOI: 10.1111/febs.13661] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 12/30/2015] [Accepted: 01/14/2016] [Indexed: 01/02/2023]
Abstract
Autophagy is a versatile recycling pathway that delivers cytoplasmic contents to lysosomal compartments for degradation. It involves the formation of a cup-shaped membrane that expands to capture cargo. After the cargo has been entirely enclosed, the membrane is sealed to generate a double-membrane-enclosed compartment, termed the autophagosome. Depending on the physiological state of the cell, the cargo is selected either specifically or non-specifically. The process involves a highly conserved set of autophagy-related proteins. Reconstitution of their action on model membranes in vitro has contributed tremendously to our understanding of autophagosome biogenesis. This review will focus on various in vitro techniques that have been employed to decipher the function of the autophagic core machinery.
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Affiliation(s)
- Yijian Rao
- Molecular Membrane and Organelle Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Nena Matscheko
- Molecular Membrane and Organelle Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Thomas Wollert
- Molecular Membrane and Organelle Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
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408
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Kaushal GP, Shah SV. Autophagy in acute kidney injury. Kidney Int 2016; 89:779-91. [PMID: 26924060 DOI: 10.1016/j.kint.2015.11.021] [Citation(s) in RCA: 273] [Impact Index Per Article: 34.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 11/12/2015] [Accepted: 11/19/2015] [Indexed: 02/09/2023]
Abstract
Autophagy is a conserved multistep pathway that degrades and recycles damaged organelles and macromolecules to maintain intracellular homeostasis. The autophagy pathway is upregulated under stress conditions including cell starvation, hypoxia, nutrient and growth-factor deprivation, endoplasmic reticulum stress, and oxidant injury, most of which are involved in the pathogenesis of acute kidney injury (AKI). Recent studies demonstrate that basal autophagy in the kidney is vital for the normal homeostasis of the proximal tubules. Deletion of key autophagy proteins impaired renal function and increased p62 levels and oxidative stress. In models of AKI, autophagy deletion in proximal tubules worsened tubular injury and renal function, highlighting that autophagy is renoprotective in models of AKI. In addition to nonselective sequestration of autophagic cargo, autophagy can facilitate selective degradation of damaged organelles, particularly mitochondrial degradation through the process of mitophagy. Damaged mitochondria accumulate in autophagy-deficient kidneys of mice subjected to ischemia-reperfusion injury, but the precise mechanisms of regulation of mitophagy in AKI are not yet elucidated. Recent progress in identifying the interplay of autophagy, apoptosis, and regulated necrosis has revived interest in examining shared pathways/molecules in this crosstalk during the pathogenesis of AKI. Autophagy and its associated pathways pose potentially unique targets for therapeutic interventions in AKI.
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Affiliation(s)
- Gur P Kaushal
- Renal Section, Medicine Service, Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, USA; Division of Nephrology, Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
| | - Sudhir V Shah
- Renal Section, Medicine Service, Central Arkansas Veterans Healthcare System, Little Rock, Arkansas, USA; Division of Nephrology, Department of Internal Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
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409
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Lu Q, Yokoyama CC, Williams JW, Baldridge MT, Jin X, DesRochers B, Bricker T, Wilen CB, Bagaitkar J, Loginicheva E, Sergushichev A, Kreamalmeyer D, Keller BC, Zhao Y, Kambal A, Green DR, Martinez J, Dinauer MC, Holtzman MJ, Crouch EC, Beatty W, Boon ACM, Zhang H, Randolph GJ, Artyomov MN, Virgin HW. Homeostatic Control of Innate Lung Inflammation by Vici Syndrome Gene Epg5 and Additional Autophagy Genes Promotes Influenza Pathogenesis. Cell Host Microbe 2016; 19:102-13. [PMID: 26764600 PMCID: PMC4714358 DOI: 10.1016/j.chom.2015.12.011] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 11/11/2015] [Accepted: 12/18/2015] [Indexed: 12/21/2022]
Abstract
Mutations in the autophagy gene EPG5 are linked to the multisystem human disease Vici syndrome, which is characterized in part by pulmonary abnormalities, including recurrent infections. We found that Epg5-deficient mice exhibited elevated baseline innate immune cellular and cytokine-based lung inflammation and were resistant to lethal influenza virus infection. Lung transcriptomics, bone marrow transplantation experiments, and analysis of cellular cytokine expression indicated that Epg5 plays a role in lung physiology through its function in macrophages. Deletion of other autophagy genes including Atg14, Fip200, Atg5, and Atg7 in myeloid cells also led to elevated basal lung inflammation and influenza resistance. This suggests that Epg5 and other Atg genes function in macrophages to limit innate immune inflammation in the lung. Disruption of this normal homeostatic dampening of lung inflammation results in increased resistance to influenza, suggesting that normal homeostatic mechanisms that limit basal tissue inflammation support some infectious diseases.
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Affiliation(s)
- Qun Lu
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Christine C Yokoyama
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jesse W Williams
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Megan T Baldridge
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Xiaohua Jin
- Department of Internal Medicine (Pulmonary and Critical Care Medicine), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Brittany DesRochers
- Department of Internal Medicine (Pulmonary and Critical Care Medicine), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Traci Bricker
- Department of Internal Medicine (Pulmonary and Critical Care Medicine), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Craig B Wilen
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Juhi Bagaitkar
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Pediatrics (Hematology/Oncology), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ekaterina Loginicheva
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alexey Sergushichev
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA; Computer Technologies Department, ITMO University, St. Petersburg 197101, Russia
| | - Darren Kreamalmeyer
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Brian C Keller
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Internal Medicine (Pulmonary and Critical Care Medicine), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Yan Zhao
- State Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Amal Kambal
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Douglas R Green
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Jennifer Martinez
- Immunity, Inflammation, and Disease Laboratory, NIEHS, National Institutes of Health, Research Triangle Park, NC 27703, USA
| | - Mary C Dinauer
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Pediatrics (Hematology/Oncology), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael J Holtzman
- Department of Internal Medicine (Pulmonary and Critical Care Medicine), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Erika C Crouch
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Wandy Beatty
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Adrianus C M Boon
- Department of Internal Medicine (Pulmonary and Critical Care Medicine), Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Hong Zhang
- State Key Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Gwendalyn J Randolph
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Maxim N Artyomov
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Herbert W Virgin
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
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410
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Liu X, Mao K, Yu AYH, Omairi-Nasser A, Austin J, Glick BS, Yip CK, Klionsky DJ. The Atg17-Atg31-Atg29 Complex Coordinates with Atg11 to Recruit the Vam7 SNARE and Mediate Autophagosome-Vacuole Fusion. Curr Biol 2016; 26:150-160. [PMID: 26774783 DOI: 10.1016/j.cub.2015.11.054] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 11/05/2015] [Accepted: 11/19/2015] [Indexed: 12/29/2022]
Abstract
Macroautophagy (hereafter autophagy) is an evolutionarily conserved process in which portions of the cytoplasm are engulfed, degraded, and subsequently recycled. The Atg17-Atg31-Atg29 complex translocates to the phagophore assembly site (PAS), where an autophagosome forms, at a very early stage of autophagy, playing a vital role in autophagy induction. Here, we identified a novel role of this complex in a late stage of autophagy where it coordinates with Atg11 to regulate autophagy-specific fusion with the vacuole. Atg17 and Atg11 interact with the vacuolar SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) Vam7 independently of each other. Several hydrophobic residues in helix 1 and helix 4 of Atg17 and the SNARE domain of Vam7 mediate the Atg17-Vam7 interaction. An F317D mutation of Atg17, which diminishes its interaction with Vam7 without affecting its interaction with Atg13 or Atg31, leads to a defect in the fusion of autophagosomes with the vacuole and decreased autophagy activity. These results provide the first demonstration that the Atg17-Atg31-Atg29 complex functions in both early and late stages of autophagy and also provide a mechanistic explanation for the coordination of autophagosome completion and fusion with the vacuole.
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Affiliation(s)
- Xu Liu
- Life Sciences Institute and the Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Kai Mao
- Life Sciences Institute and the Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Angela Y H Yu
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC V6T1Z3, Canada
| | - Amin Omairi-Nasser
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Jotham Austin
- Electron Microscopy Core Facility, University of Chicago, Chicago, IL 60637, USA
| | - Benjamin S Glick
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Calvin K Yip
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, BC V6T1Z3, Canada
| | - Daniel J Klionsky
- Life Sciences Institute and the Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
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411
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Xia Q, Wang H, Hao Z, Fu C, Hu Q, Gao F, Ren H, Chen D, Han J, Ying Z, Wang G. TDP-43 loss of function increases TFEB activity and blocks autophagosome-lysosome fusion. EMBO J 2015; 35:121-42. [PMID: 26702100 DOI: 10.15252/embj.201591998] [Citation(s) in RCA: 134] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2015] [Accepted: 11/16/2015] [Indexed: 11/09/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that is characterized by selective loss of motor neurons in brain and spinal cord. TAR DNA-binding protein 43 (TDP-43) was identified as a major component of disease pathogenesis in ALS, frontotemporal lobar degeneration (FTLD), and other neurodegenerative disease. Despite the fact that TDP-43 is a multi-functional protein involved in RNA processing and a large number of TDP-43 RNA targets have been discovered, the initial toxic effect and the pathogenic mechanism underlying TDP-43-linked neurodegeneration remain elusive. In this study, we found that loss of TDP-43 strongly induced a nuclear translocation of TFEB, the master regulator of lysosomal biogenesis and autophagy, through targeting the mTORC1 key component raptor. This regulation in turn enhanced global gene expressions in the autophagy-lysosome pathway (ALP) and increased autophagosomal and lysosomal biogenesis. However, loss of TDP-43 also impaired the fusion of autophagosomes with lysosomes through dynactin 1 downregulation, leading to accumulation of immature autophagic vesicles and overwhelmed ALP function. Importantly, inhibition of mTORC1 signaling by rapamycin treatment aggravated the neurodegenerative phenotype in a TDP-43-depleted Drosophila model, whereas activation of mTORC1 signaling by PA treatment ameliorated the neurodegenerative phenotype. Taken together, our data indicate that impaired mTORC1 signaling and influenced ALP may contribute to TDP-43-mediated neurodegeneration.
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Affiliation(s)
- Qin Xia
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Hongfeng Wang
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Zongbing Hao
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Cheng Fu
- Key Laboratory of Brain Function and Disease, School of Life Sciences University of Science & Technology of China Chinese Academy of Sciences, Hefei, Anhui, China
| | - Qingsong Hu
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Feng Gao
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Haigang Ren
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Dong Chen
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China
| | - Junhai Han
- Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences Southeast University, Nanjing, Jiangsu, China
| | - Zheng Ying
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, College of Pharmaceutical Sciences Soochow University, Suzhou, Jiangsu, China
| | - Guanghui Wang
- Laboratory of Molecular Neuropathology, Jiangsu Key Laboratory of Translational Research and Therapy for Neuro-Psycho-Diseases and College of Pharmaceutical Sciences, Soochow University, Suzhou, Jiangsu, China Key Laboratory of Brain Function and Disease, School of Life Sciences University of Science & Technology of China Chinese Academy of Sciences, Hefei, Anhui, China
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412
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He J, Johnson JL, Monfregola J, Ramadass M, Pestonjamasp K, Napolitano G, Zhang J, Catz SD. Munc13-4 interacts with syntaxin 7 and regulates late endosomal maturation, endosomal signaling, and TLR9-initiated cellular responses. Mol Biol Cell 2015; 27:572-87. [PMID: 26680738 PMCID: PMC4751605 DOI: 10.1091/mbc.e15-05-0283] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 12/08/2015] [Indexed: 12/23/2022] Open
Abstract
The molecular mechanisms that regulate late endosomal maturation and function are not completely elucidated, and direct evidence of a calcium sensor is lacking. Here we identify a novel mechanism of late endosomal maturation that involves a new molecular interaction between the tethering factor Munc13-4, syntaxin 7, and VAMP8. Munc13-4 binding to syntaxin 7 was significantly increased by calcium. Colocalization of Munc13-4 and syntaxin 7 at late endosomes was demonstrated by high-resolution and live-cell microscopy. Munc13-4-deficient cells show increased numbers of significantly enlarged late endosomes, a phenotype that was mimicked by the fusion inhibitor chloroquine in wild-type cells and rescued by expression of Munc13-4 but not by a syntaxin 7-binding-deficient mutant. Late endosomes from Munc13-4-KO neutrophils show decreased degradative capacity. Munc13-4-knockout neutrophils show impaired endosomal-initiated, TLR9-dependent signaling and deficient TLR9-specific CD11b up-regulation. Thus we present a novel mechanism of late endosomal maturation and propose that Munc13-4 regulates the late endocytic machinery and late endosomal-associated innate immune cellular functions.
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Affiliation(s)
- Jing He
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Jennifer L Johnson
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Jlenia Monfregola
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Mahalakshmi Ramadass
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Kersi Pestonjamasp
- Cancer Center Microscopy Shared Resource, University of California, San Diego, La Jolla, CA 92093
| | - Gennaro Napolitano
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Jinzhong Zhang
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
| | - Sergio D Catz
- Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037
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413
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Wesselborg S, Stork B. Autophagy signal transduction by ATG proteins: from hierarchies to networks. Cell Mol Life Sci 2015; 72:4721-57. [PMID: 26390974 PMCID: PMC4648967 DOI: 10.1007/s00018-015-2034-8] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 08/13/2015] [Accepted: 08/31/2015] [Indexed: 02/07/2023]
Abstract
Autophagy represents an intracellular degradation process which is involved in both cellular homeostasis and disease settings. In the last two decades, the molecular machinery governing this process has been characterized in detail. To date, several key factors regulating this intracellular degradation process have been identified. The so-called autophagy-related (ATG) genes and proteins are central to this process. However, several additional molecules contribute to the outcome of an autophagic response. Several review articles describing the molecular process of autophagy have been published in the recent past. In this review article we would like to add the most recent findings to this knowledge, and to give an overview of the network character of the autophagy signaling machinery.
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Affiliation(s)
- Sebastian Wesselborg
- Institute of Molecular Medicine I, Heinrich-Heine-University, Universitätsstr. 1, Building 23.12, 40225, Düsseldorf, Germany
| | - Björn Stork
- Institute of Molecular Medicine I, Heinrich-Heine-University, Universitätsstr. 1, Building 23.12, 40225, Düsseldorf, Germany.
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414
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Heijnen H, van der Sluijs P. Platelet secretory behaviour: as diverse as the granules … or not? J Thromb Haemost 2015; 13:2141-51. [PMID: 26391322 DOI: 10.1111/jth.13147] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 09/05/2015] [Indexed: 12/19/2022]
Abstract
Platelets play a central role in the arrest of bleeding after damage to a blood vessel and in the development of thrombosis. Platelets rapidly respond after interaction with sub-endothelial components and release cargo from their storage granules. The three principal granule types of platelets are α-granules, dense granules and lysosomes. Timed release of granule contents and regulated expression of critical receptors are essential for maintenance of the platelet thrombus, yet also have important functions beyond hemostasis (i.e. inflammatory reactions and immune responses). α-granules store adhesive molecules such as von Willebrand factor and fibrinogen, growth factors and inflammatory and angiogenic mediators, which play crucial roles in inflammatory responses and tumor genesis. The α-granules comprise a group of subcellular compartments with a unique composition and ultrastructure. Recent studies have suggested that differential secretory kinetics of α-granule subtypes is responsible for a thematic release of adhesive and inflammatory mediators. In addition, new results indicate that activation-dependent synthesis and release of cytokines also contribute to the inflammatory role of platelets. We will discuss the various methods that platelets use to regulate secretory processes and how these relate to potential differential secretion patterns, thereby promoting adhesiveness and/or inflammatory functions. We will focus on the heterogenic granule population, open canalicular system (OCS) plasticity, the role of contractile and mechanobiological forces, and the fusogenic machinery.
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Affiliation(s)
- H Heijnen
- Department of Clinical Chemistry and Hematology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - P van der Sluijs
- Department of Cell Biology, University Medical Center Utrecht, Utrecht, the Netherlands
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415
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Tan X, Thapa N, Choi S, Anderson RA. Emerging roles of PtdIns(4,5)P2--beyond the plasma membrane. J Cell Sci 2015; 128:4047-56. [PMID: 26574506 PMCID: PMC4712784 DOI: 10.1242/jcs.175208] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Phosphoinositides are a collection of lipid messengers that regulate most subcellular processes. Amongst the seven phosphoinositide species, the roles for phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] at the plasma membrane, such as in endocytosis, exocytosis, actin polymerization and focal adhesion assembly, have been extensively studied. Recent studies have argued for the existence of PtdIns(4,5)P2 at multiple intracellular compartments, including the nucleus, endosomes, lysosomes, autolysosomes, autophagic precursor membranes, ER, mitochondria and the Golgi complex. Although the generation, regulation and functions of PtdIns(4,5)P2 are less well-defined in most other intracellular compartments, accumulating evidence demonstrates crucial roles for PtdIns(4,5)P2 in endolysosomal trafficking, endosomal recycling, as well as autophagosomal pathways, which are the focus of this Commentary. We summarize and discuss how phosphatidylinositol phosphate kinases, PtdIns(4,5)P2 and PtdIns(4,5)P2-effectors regulate these intracellular protein and membrane trafficking events.
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Affiliation(s)
- Xiaojun Tan
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Narendra Thapa
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Suyong Choi
- Program in Cellular and Molecular Biology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
| | - Richard A Anderson
- Program in Molecular and Cellular Pharmacology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA Program in Cellular and Molecular Biology, University of Wisconsin-Madison School of Medicine and Public Health, 1300 University Avenue, Madison, WI 53706, USA
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416
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Morris DH, Yip CK, Shi Y, Chait BT, Wang QJ. BECLIN 1-VPS34 COMPLEX ARCHITECTURE: UNDERSTANDING THE NUTS AND BOLTS OF THERAPEUTIC TARGETS. ACTA ACUST UNITED AC 2015; 10:398-426. [PMID: 26692106 DOI: 10.1007/s11515-015-1374-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Autophagy is an important lysosomal degradation pathway that aids in the maintenance of cellular homeostasis by breaking down and recycling intracellular contents. Dysregulation of autophagy is linked to a growing number of human diseases. The Beclin 1-Vps34 protein-protein interaction network is critical for autophagy regulation and is therefore essential to cellular integrity. Manipulation of autophagy, in particular via modulation of the action of the Beclin 1-Vps34 complexes, is considered a promising route to combat autophagy-related diseases. Here we summarize recent findings on the core components and structural architecture of the Beclin 1-Vps34 complexes, and how these findings provide valuable insights into the molecular mechanisms that underlie the multiple functions of these complexes and for devising therapeutic strategies.
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Affiliation(s)
- Deanna H Morris
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536
| | - Calvin K Yip
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada V6T1Z3
| | - Yi Shi
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY 10065
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY 10065
| | - Qing Jun Wang
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40536 ; Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, KY 40536, USA ; Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
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417
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Recent Advances in Deciphering the Structure and Molecular Mechanism of the AAA+ ATPase N-Ethylmaleimide-Sensitive Factor (NSF). J Mol Biol 2015; 428:1912-26. [PMID: 26546278 DOI: 10.1016/j.jmb.2015.10.026] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 10/24/2015] [Accepted: 10/27/2015] [Indexed: 12/16/2022]
Abstract
N-ethylmaleimide-sensitive factor (NSF), first discovered in 1988, is a key factor for eukaryotic trafficking, including protein and hormone secretion and neurotransmitter release. It is a member of the AAA+ family (ATPases associated with diverse cellular activities). NSF disassembles soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes in conjunction with soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP). Structural studies of NSF and its complex with SNAREs and SNAPs (known as 20S supercomplex) started about 20years ago. Crystal structures of individual N and D2 domains of NSF and low-resolution electron microscopy structures of full-length NSF and 20S supercomplex have been reported over the years. Nevertheless, the molecular architecture of the 20S supercomplex and the molecular mechanism of NSF-mediated SNARE complex disassembly remained unclear until recently. Here we review recent atomic-resolution or near-atomic resolution structures of NSF and of the 20S supercomplex, as well as recent insights into the molecular mechanism and energy requirements of NSF. We also compare NSF with other known AAA+ family members.
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418
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Zhu Q, Yamakuchi M, Lowenstein CJ. SNAP23 Regulates Endothelial Exocytosis of von Willebrand Factor. PLoS One 2015; 10:e0118737. [PMID: 26266817 PMCID: PMC4534191 DOI: 10.1371/journal.pone.0118737] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 07/22/2015] [Indexed: 11/18/2022] Open
Abstract
Endothelial exocytosis regulates vascular thrombosis and inflammation. The trafficking and release of endothelial vesicles is mediated by SNARE (Soluble NSF Attachment protein REceptors) molecules, but the exact identity of endothelial SNAREs has been unclear. Three SNARE molecules form a ternary complex, including isoforms of the syntaxin (STX), vesicle-associated membrane protein (VAMP), and synaptosomal-associated protein (SNAP) families. We now identify SNAP23 as the predominant endothelial SNAP isoform that mediates endothelial exocytosis of von Willebrand Factor (VWF). SNAP23 was localized to the plasma membrane. Knockdown of SNAP23 decreased endothelial exocytosis, suggesting it is important for endothelial exocytosis. SNAP23 interacted with the endothelial exocytic machinery, and formed complexes with other known endothelial SNARE molecules. Taken together, these data suggest that SNAP23 is a key component of the endothelial SNARE machinery that mediates endothelial exocytosis.
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Affiliation(s)
- Qiuyu Zhu
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Munekazu Yamakuchi
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Charles J. Lowenstein
- Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail:
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419
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Irannejad R, Tsvetanova NG, Lobingier BT, von Zastrow M. Effects of endocytosis on receptor-mediated signaling. Curr Opin Cell Biol 2015; 35:137-43. [PMID: 26057614 PMCID: PMC4529812 DOI: 10.1016/j.ceb.2015.05.005] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 05/18/2015] [Accepted: 05/20/2015] [Indexed: 01/31/2023]
Abstract
Cellular mechanisms of membrane traffic and signal transduction are deeply interconnected. The present review discusses how membrane trafficking in the endocytic pathway impacts receptor-mediated signaling. Examples of recent progress are highlighted, focusing on the endocytosis-signaling nexus in mammals.
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Affiliation(s)
- Roshanak Irannejad
- Departments of Psychiatry and of Cellular & Molecular Pharmacology, University of California, San Francisco School of Medicine, 600 16th Street, San Francisco CA 94158-2140 USA
| | - Nikoleta G. Tsvetanova
- Departments of Psychiatry and of Cellular & Molecular Pharmacology, University of California, San Francisco School of Medicine, 600 16th Street, San Francisco CA 94158-2140 USA
| | - Braden T. Lobingier
- Departments of Psychiatry and of Cellular & Molecular Pharmacology, University of California, San Francisco School of Medicine, 600 16th Street, San Francisco CA 94158-2140 USA
| | - Mark von Zastrow
- Departments of Psychiatry and of Cellular & Molecular Pharmacology, University of California, San Francisco School of Medicine, 600 16th Street, San Francisco CA 94158-2140 USA
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420
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Abstract
Autophagy is important for maintaining cellular homeostasis, and thus its deficiency is implicated in a broad spectrum of human diseases. Its role in platelet function has only recently been examined. Our biochemical and imaging studies demonstrate that the core autophagy machinery exists in platelets, and that autophagy is constitutively active in resting platelets. Moreover, autophagy is induced upon platelet activation, as indicated by agonist-induced loss of the autophagy marker LC3II. Additional experiments, using inhibitors of platelet activation, proteases, and lysosomal acidification, as well as platelets from knockout mouse strains, show that agonist-induced LC3II loss is a consequence of platelet signaling cascades and requires proteases, acidic compartments, and membrane fusion. To assess the physiological role of platelet autophagy, we generated a mouse strain with a megakaryocyte- and platelet-specific deletion of Atg7, an enzyme required for LC3II production. Ex vivo analysis of platelets from these mice shows modest defects in aggregation and granule cargo packaging. Although these mice have normal platelet numbers and size distributions, they exhibit a robust bleeding diathesis in the tail-bleeding assay and a prolonged occlusion time in the FeCl3-induced carotid injury model. Our results demonstrate that autophagy occurs in platelets and is important for hemostasis and thrombosis.
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421
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Abstract
Autophagy is a conserved catabolic process that degrades cytoplasmic constituents and organelles in the lysosome. Starvation-induced protein degradation is a salient feature of autophagy but recent progress has illuminated how autophagy, during both starvation and nutrient-replete conditions, can mobilize diverse cellular energy and nutrient stores such as lipids, carbohydrates and iron. Processes such as lipophagy, glycophagy and ferritinophagy enable cells to salvage key metabolites to sustain and facilitate core anabolic functions. Here, we discuss the established and emerging roles of autophagy in fuelling biosynthetic capacity and in promoting metabolic and nutrient homeostasis.
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422
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Levine B, Liu R, Dong X, Zhong Q. Beclin orthologs: integrative hubs of cell signaling, membrane trafficking, and physiology. Trends Cell Biol 2015; 25:533-44. [PMID: 26071895 PMCID: PMC4554927 DOI: 10.1016/j.tcb.2015.05.004] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 05/04/2015] [Accepted: 05/07/2015] [Indexed: 12/25/2022]
Abstract
Beclin orthologs are crucial regulators of autophagy and related membrane-trafficking pathways. Multiple signaling pathways converge on Beclin 1 to regulate cellular stress responses, membrane trafficking, and physiology.
The Beclin family, including yeast Atg6 (autophagy related gene 6), its orthologs in higher eukaryotic species, and the more recently characterized mammalian-specific Beclin 2, are essential molecules in autophagy and other membrane-trafficking events. Extensive studies of Beclin orthologs have provided considerable insights into the regulation of autophagy, the diverse roles of autophagy in physiology and disease, and potential new strategies to modulate autophagy in a variety of clinical diseases. In this review we discuss the functions of Beclin orthologs, the regulation of such functions by diverse cellular signaling pathways, and the effects of such regulation on downstream cellular processes including tumor suppression and metabolism. These findings suggest that Beclin orthologs serve as crucial molecules that integrate diverse environmental signals with membrane trafficking events to ensure optimal responses of the cell to stressful stimuli.
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Affiliation(s)
- Beth Levine
- Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Rong Liu
- Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xiaonan Dong
- Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Qing Zhong
- Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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