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Sakai Y, Oku M. ATG and ESCRT control multiple modes of microautophagy. FEBS Lett 2024; 598:48-58. [PMID: 37857501 DOI: 10.1002/1873-3468.14760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/30/2023] [Accepted: 09/01/2023] [Indexed: 10/21/2023]
Abstract
The discovery of microautophagy, the direct engulfment of cytoplasmic material by the lysosome, dates back to 1966 in a morphological study of mammalian cells by Christian de Duve. Since then, studies on microautophagy have shifted toward the elucidation of the physiological significance of the process. However, in contrast to macroautophagy, studies on the molecular mechanisms of microautophagy have been limited. Only recent studies revealed that ATG proteins involved in macroautophagy are also operative in several types of microautophagy and that ESCRT proteins, responsible for the multivesicular body pathway, play a central role in most microautophagy processes. In this review, we summarize our current knowledge on the function of ATG and ESCRT proteins in microautophagy.
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Affiliation(s)
- Yasuyoshi Sakai
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Japan
| | - Masahide Oku
- Department of Bioscience and Biotechnology, Faculty of Bioenvironmental Sciences, Kyoto University of Advanced Science, Kameoka, Japan
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2
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Nitrogen Starvation and Stationary Phase Lipophagy Have Distinct Molecular Mechanisms. Int J Mol Sci 2020; 21:ijms21239094. [PMID: 33260464 PMCID: PMC7730393 DOI: 10.3390/ijms21239094] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 11/24/2020] [Accepted: 11/26/2020] [Indexed: 01/06/2023] Open
Abstract
In yeast, the selective autophagy of intracellular lipid droplets (LDs) or lipophagy can be induced by either nitrogen (N) starvation or carbon limitation (e.g., in the stationary (S) phase). We developed the yeast, Komagataella phaffii (formerly Pichia pastoris), as a new lipophagy model and compared the N-starvation and S-phase lipophagy in over 30 autophagy-related mutants using the Erg6-GFP processing assay. Surprisingly, two lipophagy pathways had hardly overlapping stringent molecular requirements. While the N-starvation lipophagy strictly depended on the core autophagic machinery (Atg1-Atg9, Atg18, and Vps15), vacuole fusion machinery (Vam7 and Ypt7), and vacuolar proteolysis (proteinases A and B), only Atg6 and proteinases A and B were essential for the S-phase lipophagy. The rest of the proteins were only partially required in the S-phase. Moreover, we isolated the prl1 (for the positive regulator of lipophagy 1) mutant affected in the S-phase lipophagy, but not N-starvation lipophagy. The prl1 defect was at a stage of delivery of the LDs from the cytoplasm to the vacuole, further supporting the mechanistically different nature of the two lipophagy pathways. Taken together, our results suggest that N-starvation and S-phase lipophagy have distinct molecular mechanisms.
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3
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Lee HN, Zarza X, Kim JH, Yoon MJ, Kim SH, Lee JH, Paris N, Munnik T, Otegui MS, Chung T. Vacuolar Trafficking Protein VPS38 Is Dispensable for Autophagy. PLANT PHYSIOLOGY 2018; 176:1559-1572. [PMID: 29184027 PMCID: PMC5813560 DOI: 10.1104/pp.17.01297] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 11/27/2017] [Indexed: 05/18/2023]
Abstract
Phosphatidylinositol 3-P (PI3P) is a signaling molecule that controls a variety of processes in endosomal, autophagic, and vacuolar/lysosomal trafficking in yeasts and mammals. Vacuolar protein sorting 34 (Vps34) is a conserved PI3K present in multiple complexes with specific functions and regulation. In yeast, the PI3K complex II consists of Vps34p, Vps15p, Vps30p/Atg6p, and Vps38p, and is essential for vacuolar protein sorting. Here, we describe the Arabidopsis (Arabidopsis thaliana) homolog of yeast Vps38p and human UV radiation resistance-associated gene protein. Arabidopsis VPS38 interacts with VPS30/ATG6 both in yeast and in planta. Although the level of PI3P in Arabidopsis vps38 mutants is similar to that in wild type, vps38 cells contain enlarged multivesicular endosomes and fewer organelles enriched in PI3P than the wild type. The vps38 mutants are defective in the trafficking of vacuolar cargo and its receptor VACUOLAR SORTING RECEPTOR2;1. The mutants also exhibit abnormal cytoplasmic distributions of endocytic cargo, such as auxin efflux carriers PINFORMED1 (PIN1) and PIN2. Constitutive autophagy is normal in the mutants but starvation-induced autophagy was slightly inhibited. We conclude that Arabidopsis VPS38 is dispensable for autophagy but essential for efficient targeting of biosynthetic and endocytic cargo to the vacuole.
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Affiliation(s)
- Han Nim Lee
- Department of Biological Sciences, Pusan National University, Busan 46241, Korea
| | - Xavier Zarza
- Swammerdam Institute for Life Sciences, Section Plant Cell Biology, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Jeong Hun Kim
- Department of Biological Sciences, Pusan National University, Busan 46241, Korea
| | - Min Ji Yoon
- Department of Biological Sciences, Pusan National University, Busan 46241, Korea
| | - Sang-Hoon Kim
- Department of Biology Education, Pusan National University, Busan 46241, Korea
| | - Jae-Hoon Lee
- Department of Biology Education, Pusan National University, Busan 46241, Korea
| | - Nadine Paris
- Biochimie et Physiologie Moléculaire des Plantes, Institute Biologie Intégrative des Plantes, UMR 5004 CNRS/UMR 0386 INRA/Montpellier SupAgro/Université Montpellier 2, F-34060 Montpellier Cedex 1, France
| | - Teun Munnik
- Swammerdam Institute for Life Sciences, Section Plant Cell Biology, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Marisa S Otegui
- Laboratory of Cell and Molecular Biology and Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Taijoon Chung
- Department of Biological Sciences, Pusan National University, Busan 46241, Korea
- Institute of Systems Biology, Pusan National University, Busan 46241, Korea
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Reidick C, Boutouja F, Platta HW. The class III phosphatidylinositol 3-kinase Vps34 in Saccharomyces cerevisiae. Biol Chem 2017; 398:677-685. [PMID: 27935849 DOI: 10.1515/hsz-2016-0288] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/14/2016] [Indexed: 12/23/2022]
Abstract
The class III phosphatidylinositol 3-kinase Vps34 (vacuolar protein sorting 34) catalyzes for the formation of the signaling lipid phosphatidylinositol-3-phopsphate, which is a central factor in the regulation of autophagy, endocytic trafficking and vesicular transport. In this article, we discuss the functional role of the lipid kinase Vps34 in Saccharomyces cerevisiae.
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Affiliation(s)
- Christina Reidick
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, D-44801 Bochum
| | - Fahd Boutouja
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, D-44801 Bochum
| | - Harald W Platta
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, D-44801 Bochum
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Cheng X, Ma X, Ding X, Li L, Jiang X, Shen Z, Chen S, Liu W, Gong W, Sun Q. Pacer Mediates the Function of Class III PI3K and HOPS Complexes in Autophagosome Maturation by Engaging Stx17. Mol Cell 2017; 65:1029-1043.e5. [DOI: 10.1016/j.molcel.2017.02.010] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 01/06/2017] [Accepted: 02/10/2017] [Indexed: 11/25/2022]
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Xie F, Liu W, Feng F, Li X, He L, Lv D, Qin X, Li L, Li L, Chen L. Apelin-13 promotes cardiomyocyte hypertrophy via PI3K-Akt-ERK1/2-p70S6K and PI3K-induced autophagy. Acta Biochim Biophys Sin (Shanghai) 2015; 47:969-80. [PMID: 26607438 DOI: 10.1093/abbs/gmv111] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Apelin is highly expressed in rat left ventricular hypertrophy Sprague Dawley rat models, and it plays a crucial role in the cardiovascular system. The aim this study was to clarify whether apelin-13 promotes hypertrophy in H9c2 rat cardiomyocytes and to investigate its underlying mechanism. The cardiomyocyte hypertrophy was observed by measuring the diameter, volume, and protein content of H9c2 cells. The activation of autophagy was evaluated by observing the morphology of autophagosomes by transmission electron microscopy, observing the subcellular localization of LC3 by light microscopy, and detecting the membrane-associated form of LC3 by western blot analysis. The phosphatidylinositol 3-kinase (PI3K) signaling pathway was identified and the proteins expression was detected using western blot analysis. The results revealed that apelin-13 increased the diameter, volume, and protein content of H9c2 cells and promoted the phosphorylation of PI3K, Akt, ERK1/2, and p70S6K. Apelin-13 activated the PI3K-Akt-ERK1/2-p70S6K pathway. PI3K inhibitor LY294002, Akt inhibitor 1701-1, ERK1/2 inhibitor PD98059 attenuated the increase of the cell diameter, volume, protein content induced by apelin-13. Apelin-13 increased the autophagosomes and up-regulated the expressions of beclin 1 and LC3-II/I both transiently and stably. The autophagy inhibitor 3MA ameliorated the increase of cell diameter, volume, and protein content that were induced by apelin-13. These results suggested that apelin-13 promotes H9c2 rat cardiomyocyte hypertrophy via PI3K-Akt-ERK1/2-p70S6K and PI3K-induced autophagy.
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Affiliation(s)
- Feng Xie
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Wei Liu
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China Department of Pharmacy, The Third Xiangya Hospital of Central South University, Changsha 410013, China
| | - Fen Feng
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Xin Li
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Lu He
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Deguan Lv
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Xuping Qin
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Lifang Li
- Departments of Microbiology and Immunology, University of South China, Hengyang 421001, China
| | - Lanfang Li
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
| | - Linxi Chen
- Institute of Pharmacy and Pharmacology, Learning Key Laboratory for Pharmacoproteomics, University of South China, Hengyang 421001, China
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Reidick C, El Magraoui F, Meyer HE, Stenmark H, Platta HW. Regulation of the Tumor-Suppressor Function of the Class III Phosphatidylinositol 3-Kinase Complex by Ubiquitin and SUMO. Cancers (Basel) 2014; 7:1-29. [PMID: 25545884 PMCID: PMC4381249 DOI: 10.3390/cancers7010001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 12/08/2014] [Indexed: 12/19/2022] Open
Abstract
The occurrence of cancer is often associated with a dysfunction in one of the three central membrane-involution processes—autophagy, endocytosis or cytokinesis. Interestingly, all three pathways are controlled by the same central signaling module: the class III phosphatidylinositol 3-kinase (PI3K-III) complex and its catalytic product, the phosphorylated lipid phosphatidylinositol 3-phosphate (PtdIns3P). The activity of the catalytic subunit of the PI3K-III complex, the lipid-kinase VPS34, requires the presence of the membrane-targeting factor VPS15 as well as the adaptor protein Beclin 1. Furthermore, a growing list of regulatory proteins associates with VPS34 via Beclin 1. These accessory factors define distinct subunit compositions and thereby guide the PI3K-III complex to its different cellular and physiological roles. Here we discuss the regulation of the PI3K-III complex components by ubiquitination and SUMOylation. Especially Beclin 1 has emerged as a highly regulated protein, which can be modified with Lys11-, Lys48- or Lys63-linked polyubiquitin chains catalyzed by distinct E3 ligases from the RING-, HECT-, RBR- or Cullin-type. We also point out other cross-links of these ligases with autophagy in order to discuss how these data might be merged into a general concept.
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Affiliation(s)
- Christina Reidick
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Bochum 44801, Germany.
| | - Fouzi El Magraoui
- Biomedical Research, Human Brain Proteomics II, Leibniz-Institut für Analytische Wissenschaften-ISAS, Dortmund 44139, Germany.
| | - Helmut E Meyer
- Biomedical Research, Human Brain Proteomics II, Leibniz-Institut für Analytische Wissenschaften-ISAS, Dortmund 44139, Germany.
| | - Harald Stenmark
- Department of Biochemistry, Institute for Cancer Research, Oslo University Hospital, Montebello, Oslo 0310, Norway.
| | - Harald W Platta
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Bochum 44801, Germany.
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Kim YM, Jung CH, Seo M, Kim EK, Park JM, Bae SS, Kim DH. mTORC1 phosphorylates UVRAG to negatively regulate autophagosome and endosome maturation. Mol Cell 2014; 57:207-18. [PMID: 25533187 DOI: 10.1016/j.molcel.2014.11.013] [Citation(s) in RCA: 205] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 09/22/2014] [Accepted: 11/14/2014] [Indexed: 02/07/2023]
Abstract
mTORC1 plays a key role in autophagy as a negative regulator. The currently known targets of mTORC1 in the autophagy pathway mainly function at early stages of autophagosome formation. Here, we identify that mTORC1 inhibits later stages of autophagy by phosphorylating UVRAG. Under nutrient-enriched conditions, mTORC1 binds and phosphorylates UVRAG. The phosphorylation positively regulates the association of UVRAG with RUBICON, thereby enhancing the antagonizing effect of RUBICON on UVRAG-mediated autophagosome maturation. Upon dephosphorylation, UVRAG is released from RUBICON to interact with the HOPS complex, a component for the late endosome and lysosome fusion machinery, and enhances autophagosome and endosome maturation. Consequently, the dephosphorylation of UVRAG facilitates the lysosomal degradation of epidermal growth factor receptor (EGFR), reduces EGFR signaling, and suppresses cancer cell proliferation and tumor growth. These results demonstrate that mTORC1 engages in late stages of autophagy and endosome maturation, defining a broader range of mTORC1 functions in the membrane-associated processes.
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Affiliation(s)
- Young-Mi Kim
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Chang Hwa Jung
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Division of Metabolism and Functionality Research, Korea Food Research Institute, 463-746, Republic of Korea
| | - Minchul Seo
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Eun Kyoung Kim
- Department of Pharmacology, Pusan National University, Pusan, 626-870, Republic of Korea
| | - Ji-Man Park
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Sun Sik Bae
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Department of Pharmacology, Pusan National University, Pusan, 626-870, Republic of Korea
| | - Do-Hyung Kim
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA; Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA.
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Hagstrom D, Ma C, Guha-Polley S, Subramani S. The unique degradation pathway of the PTS2 receptor, Pex7, is dependent on the PTS receptor/coreceptor, Pex5 and Pex20. Mol Biol Cell 2014; 25:2634-43. [PMID: 25009284 PMCID: PMC4148252 DOI: 10.1091/mbc.e13-12-0716] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In Pichia pastoris, the PTS2 receptor, Pex7, is selectively degraded in a regulated manner. The shuttling of Pex7, and consequently its degradation, depends on the receptor recycling pathways used by Pex5 and Pex20 and relies on an interaction between Pex7 and Pex20. The shuttling and stability of Pex7 are divergent from those of Pex5 and Pex20. Peroxisomal matrix protein import uses two peroxisomal targeting signals (PTSs). Most matrix proteins use the PTS1 pathway and its cargo receptor, Pex5. The PTS2 pathway is dependent on another receptor, Pex7, and its coreceptor, Pex20. We found that during the matrix protein import cycle, the stability and dynamics of Pex7 differ from those of Pex5 and Pex20. In Pichia pastoris, unlike Pex5 and Pex20, Pex7 is constitutively degraded in wild-type cells but is stabilized in pex mutants affecting matrix protein import. Degradation of Pex7 is more prevalent in cells grown in methanol, in which the PTS2 pathway is nonessential, in comparison with oleate, suggesting regulation of Pex7 turnover. Pex7 must shuttle into and out of peroxisomes before it is polyubiquitinated and degraded by the proteasome. The shuttling of Pex7, and consequently its degradation, is dependent on the receptor recycling pathways of Pex5 and Pex20 and relies on an interaction between Pex7 and Pex20. We also found that blocking the export of Pex20 from peroxisomes inhibits PTS1-mediated import, suggesting sharing of limited components in the export of PTS receptors/coreceptors. The shuttling and stability of Pex7 are divergent from those of Pex5 and Pex20, exemplifying a novel interdependence of the PTS1 and PTS2 pathways.
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Affiliation(s)
- Danielle Hagstrom
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0322
| | - Changle Ma
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0322 College of Life Sciences, Shandong Normal University, Jinan, Shandong 250014, China
| | - Soumi Guha-Polley
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0322
| | - Suresh Subramani
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0322
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Nazarko TY, Ozeki K, Till A, Ramakrishnan G, Lotfi P, Yan M, Subramani S. Peroxisomal Atg37 binds Atg30 or palmitoyl-CoA to regulate phagophore formation during pexophagy. ACTA ACUST UNITED AC 2014; 204:541-57. [PMID: 24535825 PMCID: PMC3926955 DOI: 10.1083/jcb.201307050] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
The acyl-CoA–binding protein Atg37 is a new component of the pexophagic receptor protein complex that regulates the recruitment of Atg11 by Atg30 in the peroxisomal membrane during pexophagy Autophagy is a membrane trafficking pathway that sequesters proteins and organelles into autophagosomes. The selectivity of this pathway is determined by autophagy receptors, such as the Pichia pastoris autophagy-related protein 30 (Atg30), which controls the selective autophagy of peroxisomes (pexophagy) through the assembly of a receptor protein complex (RPC). However, how the pexophagic RPC is regulated for efficient formation of the phagophore, an isolation membrane that sequesters the peroxisome from the cytosol, is unknown. Here we describe a new, conserved acyl-CoA–binding protein, Atg37, that is an integral peroxisomal membrane protein required specifically for pexophagy at the stage of phagophore formation. Atg30 recruits Atg37 to the pexophagic RPC, where Atg37 regulates the recruitment of the scaffold protein, Atg11. Palmitoyl-CoA competes with Atg30 for Atg37 binding. The human orthologue of Atg37, acyl-CoA–binding domain containing protein 5 (ACBD5), is also peroxisomal and is required specifically for pexophagy. We suggest that Atg37/ACBD5 is a new component and positive regulator of the pexophagic RPC.
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Affiliation(s)
- Taras Y Nazarko
- Section of Molecular Biology, Division of Biological Sciences, and 2 San Diego Center for Systems Biology, University of California, San Diego, La Jolla, CA 92093
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Takáts S, Pircs K, Nagy P, Varga Á, Kárpáti M, Hegedűs K, Kramer H, Kovács AL, Sass M, Juhász G. Interaction of the HOPS complex with Syntaxin 17 mediates autophagosome clearance in Drosophila. Mol Biol Cell 2014; 25:1338-54. [PMID: 24554766 PMCID: PMC3982998 DOI: 10.1091/mbc.e13-08-0449] [Citation(s) in RCA: 196] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Interaction of the autophagosomal SNARE Syntaxin 17 (Syx17) with the homotypic fusion and vacuole protein–sorting (HOPS) tethering complex is necessary for the fusion of autophagosomes with lysosomes. HOPS, but not Syx17, is also required for endocytic degradation and biosynthetic transport to lysosomes and eye pigment granules. Homotypic fusion and vacuole protein sorting (HOPS) is a tethering complex required for trafficking to the vacuole/lysosome in yeast. Specific interaction of HOPS with certain SNARE (soluble NSF attachment protein receptor) proteins ensures the fusion of appropriate vesicles. HOPS function is less well characterized in metazoans. We show that all six HOPS subunits (Vps11 [vacuolar protein sorting 11]/CG32350, Vps18/Dor, Vps16A, Vps33A/Car, Vps39/CG7146, and Vps41/Lt) are required for fusion of autophagosomes with lysosomes in Drosophila. Loss of these genes results in large-scale accumulation of autophagosomes and blocks autophagic degradation under basal, starvation-induced, and developmental conditions. We find that HOPS colocalizes and interacts with Syntaxin 17 (Syx17), the recently identified autophagosomal SNARE required for fusion in Drosophila and mammals, suggesting their association is critical during tethering and fusion of autophagosomes with lysosomes. HOPS, but not Syx17, is also required for endocytic down-regulation of Notch and Boss in developing eyes and for proper trafficking to lysosomes and eye pigment granules. We also show that the formation of autophagosomes and their fusion with lysosomes is largely unaffected in null mutants of Vps38/UVRAG (UV radiation resistance associated), a suggested binding partner of HOPS in mammals, while endocytic breakdown and lysosome biogenesis is perturbed. Our results establish the role of HOPS and its likely mechanism of action during autophagy in metazoans.
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Affiliation(s)
- Szabolcs Takáts
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pazmany s. 1/C, H-1117 Budapest, Hungary Department of Neuroscience, Department of Cell Biology, University of Texas Southwestern Medical School, Dallas, TX 75390-9111
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Jiang P, Nishimura T, Sakamaki Y, Itakura E, Hatta T, Natsume T, Mizushima N. The HOPS complex mediates autophagosome-lysosome fusion through interaction with syntaxin 17. Mol Biol Cell 2014; 25:1327-37. [PMID: 24554770 PMCID: PMC3982997 DOI: 10.1091/mbc.e13-08-0447] [Citation(s) in RCA: 350] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Membrane fusion is generally controlled by Rabs, soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), and tethering complexes. Syntaxin 17 (STX17) was recently identified as the autophagosomal SNARE required for autophagosome-lysosome fusion in mammals and Drosophila. In this study, to better understand the mechanism of autophagosome-lysosome fusion, we searched for STX17-interacting proteins. Immunoprecipitation and mass spectrometry analysis identified vacuolar protein sorting 33A (VPS33A) and VPS16, which are components of the homotypic fusion and protein sorting (HOPS)-tethering complex. We further confirmed that all HOPS components were coprecipitated with STX17. Knockdown of VPS33A, VPS16, or VPS39 blocked autophagic flux and caused accumulation of STX17- and microtubule-associated protein light chain (LC3)-positive autophagosomes. The endocytic pathway was also affected by knockdown of VPS33A, as previously reported, but not by knockdown of STX17. By contrast, ultraviolet irradiation resistance-associated gene (UVRAG), a known HOPS-interacting protein, did not interact with the STX17-HOPS complex and may not be directly involved in autophagosome-lysosome fusion. Collectively these results suggest that, in addition to its well-established function in the endocytic pathway, HOPS promotes autophagosome-lysosome fusion through interaction with STX17.
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Affiliation(s)
- Peidu Jiang
- Department of Biochemistry and Molecular Biology, Graduate School, and Faculty of Medicine, University of Tokyo, Tokyo 113-0033, Japan Department of Physiology and Cell Biology, Tokyo Medical and Dental University, Tokyo 113-8519, Japan Research Center for Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8519, Japan Molecular Profiling Research Center for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tokyo 135-0064, Japan
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Platta HW, Hagen S, Reidick C, Erdmann R. The peroxisomal receptor dislocation pathway: to the exportomer and beyond. Biochimie 2013; 98:16-28. [PMID: 24345375 DOI: 10.1016/j.biochi.2013.12.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 12/05/2013] [Indexed: 12/29/2022]
Abstract
The biogenesis of peroxisomes is an ubiquitin-dependent process. In particular, the import of matrix proteins into the peroxisomal lumen requires the modification of import receptors with ubiquitin. The matrix proteins are synthesized on free polyribosomes in the cytosol and are recognized by import receptors via a peroxisomal targeting sequence (PTS). Subsequent to the transport of the receptor/cargo-complex to the peroxisomal membrane and the release of the cargo into the peroxisomal lumen, the PTS-receptors are exported back to the cytosol for further rounds of matrix protein import. The exportomer represents the molecular machinery required for the retrotranslocation of the PTS-receptors. It comprises enzymes for the ubiquitination as well as for the ATP-dependent extraction of the PTS-receptors from the peroxisomal membrane. Furthermore, recent evidence indicates a mechanistic interconnection of the ATP-dependent removal of the PTS-receptors with the translocation of the matrix protein into the organellar lumen. Interestingly, the components of the peroxisomal exportomer seem also to be involved in cellular tasks that are distinct from the ubiquitination and dislocation of the peroxisomal PTS-receptors. This includes work that indicates a central function of this machinery in the export of peroxisomal matrix proteins in plants, while a subset of exportomer components is involved in the meiocyte formation in some fungi, the peroxisome-chloroplast contact during photorespiration in plants and possibly even the selective degradation of peroxisomes via pexophagy. In this review, we want to discuss the central role of the exportomer during matrix protein import, but also highlight distinct roles of exportomer constituents in additional cellular processes. This article is part of a Special Issue entitled: Peroxisomes: biogenesis, functions and diseases.
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Affiliation(s)
- Harald W Platta
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
| | - Stefanie Hagen
- Systembiochemie, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Christina Reidick
- Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany
| | - Ralf Erdmann
- Systembiochemie, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
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Phosphorylation of mitophagy and pexophagy receptors coordinates their interaction with Atg8 and Atg11. EMBO Rep 2013; 14:441-9. [PMID: 23559066 DOI: 10.1038/embor.2013.40] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 03/08/2013] [Accepted: 03/12/2013] [Indexed: 12/31/2022] Open
Abstract
The selective autophagy receptors Atg19 and Atg32 interact with two proteins of the core autophagic machinery: the scaffold protein Atg11 and the ubiquitin-like protein Atg8. We found that the Pichia pastoris pexophagy receptor, Atg30, also interacts with Atg8. Both Atg30 and Atg32 interactions are regulated by phosphorylation close to Atg8-interaction motifs. Extending this finding to Saccharomyces cerevisiae, we confirmed phosphoregulation for the mitophagy and pexophagy receptors, Atg32 and Atg36. Each Atg30 molecule must interact with both Atg8 and Atg11 for full functionality, and these interactions occur independently and not simultaneously, but rather in random order. We present a common model for the phosphoregulation of selective autophagy receptors.
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15
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WU P, XU CM. Advances in Relationship Between Class Ⅲ PI3K Complex and Autophagy*. PROG BIOCHEM BIOPHYS 2012. [DOI: 10.3724/sp.j.1206.2011.00387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Pexophagy: the selective degradation of peroxisomes. Int J Cell Biol 2012; 2012:512721. [PMID: 22536249 PMCID: PMC3320016 DOI: 10.1155/2012/512721] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 11/23/2011] [Indexed: 12/18/2022] Open
Abstract
Peroxisomes are single-membrane-bounded organelles present in the majority of eukaryotic cells. Despite the existence of great diversity among different species, cell types, and under different environmental conditions, peroxisomes contain enzymes involved in β-oxidation of fatty acids and the generation, as well as detoxification, of hydrogen peroxide. The exigency of all eukaryotic cells to quickly adapt to different environmental factors requires the ability to precisely and efficiently control peroxisome number and functionality. Peroxisome homeostasis is achieved by the counterbalance between organelle biogenesis and degradation. The selective degradation of superfluous or damaged peroxisomes is facilitated by several tightly regulated pathways. The most prominent peroxisome degradation system uses components of the general autophagy core machinery and is therefore referred to as “pexophagy.” In this paper we focus on recent developments in pexophagy and provide an overview of current knowledge and future challenges in the field. We compare different modes of pexophagy and mention shared and distinct features of pexophagy in yeast model systems, mammalian cells, and other organisms.
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17
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Sibirny AA. Mechanisms of autophagy and pexophagy in yeasts. BIOCHEMISTRY (MOSCOW) 2011; 76:1279-90. [DOI: 10.1134/s0006297911120017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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18
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The phosphoinositide 3-kinase Vps34p is required for pexophagy in Saccharomyces cerevisiae. Biochem J 2011; 434:161-70. [PMID: 21121900 DOI: 10.1042/bj20101115] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
PIds (phosphoinositides) are phosphorylated derivatives of the membrane phospholipid PtdIns that have emerged as key regulators of many aspects of cellular physiology. We have discovered a PtdIns3P-synthesizing activity in peroxisomes of Saccharomyces cerevisiae and have demonstrated that the lipid kinase Vps34p is already associated with peroxisomes during biogenesis. However, although Vps34 is required, it is not essential for optimal peroxisome biogenesis. The function of Vps34p-containing complex I as well as a subset of PtdIns3P-binding proteins proved to be mandatory for the regulated degradation of peroxisomes. This demonstrates that PtdIns3P-mediated signalling is required for pexophagy.
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19
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Hayward AP, Dinesh-Kumar SP. What can plant autophagy do for an innate immune response? ANNUAL REVIEW OF PHYTOPATHOLOGY 2011; 49:557-76. [PMID: 21370973 DOI: 10.1146/annurev-phyto-072910-095333] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Autophagy plays an established role in the execution of senescence, starvation, and stress responses in plants. More recently, an emerging role for autophagy has been discovered during the plant innate immune response. Recent papers have shown autophagy to restrict, and conversely, to also promote programmed cell death (PCD) at the site of pathogen infection. These initial studies have piqued our excitement, but they have also revealed gaps in our understanding of plant autophagy regulation, in our ability to monitor autophagy in plant cells, and in our ability to manipulate autophagic activity. In this review, we present the most pressing questions now facing the field of plant autophagy in general, with specific focus on autophagy as it occurs during a plant-pathogen interaction. To begin to answer these questions, we place recent findings in the context of studies of autophagy and immunity in other systems, and in the context of the mammalian immune response in particular.
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Affiliation(s)
- Andrew P Hayward
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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20
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Regulation of membrane biogenesis in autophagy via PI3P dynamics. Semin Cell Dev Biol 2010; 21:671-6. [DOI: 10.1016/j.semcdb.2010.04.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Revised: 04/07/2010] [Accepted: 04/08/2010] [Indexed: 12/20/2022]
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21
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Manjithaya R, Nazarko TY, Farré JC, Subramani S. Molecular mechanism and physiological role of pexophagy. FEBS Lett 2010; 584:1367-73. [PMID: 20083110 DOI: 10.1016/j.febslet.2010.01.019] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 01/12/2010] [Accepted: 01/12/2010] [Indexed: 12/26/2022]
Abstract
Pexophagy is a selective autophagy process wherein damaged and/or superfluous peroxisomes undergo vacuolar degradation. In methylotropic yeasts, where pexophagy has been studied most extensively, this process occurs by either micro- or macropexophagy: processes analogous to micro- and macroautophagy. Recent studies have identified specific factors and illustrated mechanisms involved in pexophagy. Although mechanistically pexophagy relies heavily on the core autophagic machinery, the latest findings about the role of auxiliary pexophagy factors have highlighted specialized membrane structures required for micropexophagy, and shown how cargo selectivity is achieved and how cargo size dictates the requirement for these factors during pexophagy. These insights and additional observations in the literature provide a framework for an understanding of the physiological role(s) of pexophagy.
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Affiliation(s)
- Ravi Manjithaya
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093-0322, USA
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