1
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Holzer E, Martens S, Tulli S. The Role of ATG9 Vesicles in Autophagosome Biogenesis. J Mol Biol 2024; 436:168489. [PMID: 38342428 DOI: 10.1016/j.jmb.2024.168489] [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: 12/19/2023] [Revised: 02/02/2024] [Accepted: 02/07/2024] [Indexed: 02/13/2024]
Abstract
Autophagy mediates the degradation and recycling of cellular material in the lysosomal system. Dysfunctional autophagy is associated with a plethora of diseases including uncontrolled infections, cancer and neurodegeneration. In macroautophagy (hereafter autophagy) this material is encapsulated in double membrane vesicles, the autophagosomes, which form upon induction of autophagy. The precursors to autophagosomes, referred to as phagophores, first appear as small flattened membrane cisternae, which gradually enclose the cargo material as they grow. The assembly of phagophores during autophagy initiation has been a major subject of investigation over the past decades. A special focus has been ATG9, the only conserved transmembrane protein among the core machinery. The majority of ATG9 localizes to small Golgi-derived vesicles. Here we review the recent advances and breakthroughs regarding our understanding of how ATG9 and the vesicles it resides in serve to assemble the autophagy machinery and to establish membrane contact sites for autophagosome biogenesis. We also highlight open questions in the field that need to be addressed in the years to come.
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Affiliation(s)
- Elisabeth Holzer
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria; Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Campus-Vienna-Biocenter 1, Vienna, Austria.
| | - Sascha Martens
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria.
| | - Susanna Tulli
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria; University of Vienna, Max Perutz Labs, Department of Biochemistry and Cell Biology, Vienna, Austria.
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2
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Isola D, Elazar Z. Phospholipid Supply for Autophagosome Biogenesis. J Mol Biol 2024; 436:168691. [PMID: 38944336 DOI: 10.1016/j.jmb.2024.168691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 06/10/2024] [Accepted: 06/24/2024] [Indexed: 07/01/2024]
Abstract
Autophagy is a cellular degradation pathway where double-membrane autophagosomes form de novo to engulf cytoplasmic material destined for lysosomal degradation. This process requires regulated membrane remodeling, beginning with the initial autophagosomal precursor and progressing to its elongation and maturation into a fully enclosed, fusion-capable vesicle. While the core protein machinery involved in autophagosome formation has been extensively studied over the past two decades, the role of phospholipids in this process has only recently been studied. This review focuses on the phospholipid composition of the phagophore membrane and the mechanisms that supply lipids to expand this unique organelle.
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Affiliation(s)
- Damilola Isola
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Zvulun Elazar
- Departments of Biomolecular Sciences, The Weizmann Institute of Science, 76100 Rehovot, Israel.
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3
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Paddar MA, Wang F, Trosdal ES, Hendrix E, He Y, Salemi M, Mudd M, Jia J, Duque TLA, Javed R, Phinney B, Deretic V. Noncanonical roles of ATG5 and membrane atg8ylation in retromer assembly and function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.10.602886. [PMID: 39026874 PMCID: PMC11257513 DOI: 10.1101/2024.07.10.602886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
ATG5 is one of the core autophagy proteins with additional functions such as noncanonical membrane atg8ylation, which among a growing number of biological outputs includes control of tuberculosis in animal models. Here we show that ATG5 associates with retromer's core components VPS26, VPS29 and VPS35 and modulates retromer function. Knockout of ATG5 blocked trafficking of a key glucose transporter sorted by the retromer, GLUT1, to the plasma membrane. Knockouts of other genes essential for membrane atg8ylation, of which ATG5 is a component, affected GLUT1 sorting, indicating that membrane atg8ylation as a process affects retromer function and endosomal sorting. The contribution of membrane atg8ylation to retromer function in GLUT1 sorting was independent of canonical autophagy. These findings expand the scope of membrane atg8ylation to specific sorting processes in the cell dependent on the retromer and its known interactors.
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Affiliation(s)
- Masroor Ahmad Paddar
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Fulong Wang
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Einar S Trosdal
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Emily Hendrix
- Department of Chemistry & Chemical Biology, The University of New Mexico, Albuquerque, NM, USA
| | - Yi He
- Department of Chemistry & Chemical Biology, The University of New Mexico, Albuquerque, NM, USA
| | - Michelle Salemi
- Proteomics Core Facility, UC Davis Genome Center, University of California, Davis, CA 95616, USA
| | - Michal Mudd
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Jingyue Jia
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Thabata L A Duque
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Ruheena Javed
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
| | - Brett Phinney
- Proteomics Core Facility, UC Davis Genome Center, University of California, Davis, CA 95616, USA
| | - Vojo Deretic
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
- Lead Contact
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4
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Shi Y, Suzuki K. Quantitative analysis of the spatial distance between autophagy-related membrane structures and the endoplasmic reticulum in Saccharomyces cerevisiae. Autophagy 2024; 20:1673-1680. [PMID: 38478967 PMCID: PMC11210900 DOI: 10.1080/15548627.2024.2330033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 03/08/2024] [Indexed: 03/25/2024] Open
Abstract
Macroautophagy/autophagy is the process by which cells degrade their cytoplasmic proteins or organelles in vacuoles to maintain cellular homeostasis under severe environmental conditions. In the yeast Saccharomyces cerevisiae, autophagy-related (Atg) proteins essential for autophagosome formation accumulate near the vacuole to form the dot-shaped phagophore assembly site/pre-autophagosomal structure (PAS). The PAS then generates the phagophore/isolation membrane (PG), which expands to become a closed double-membrane autophagosome. Hereinafter, we refer to the PAS, PG, and autophagosome as autophagy-related structures (ARSs). During autophagosome formation, Atg2 is responsible for tethering the ARS to the endoplasmic reticulum (ER) via ER exit sites (ERESs), and for transferring phospholipids from the ER to ARSs. Therefore, ARS and the ER are spatially close in the presence of Atg2 but are separated in its absence. Because the contact of an ARS with the ER must be established at the earliest stage of autophagosome formation, it is important to know whether the ARS is tethered to the ER. In this study, we developed a rapid and objective method to estimate tethering of the ARS to the ER by measuring the distance between the ARS and ERES under fluorescence microscopy, and found that tethering of the ARS to the ER was lost without Atg1. This method might be useful to predict the tethering activity of Atg2.Abbreviation: ARS, autophagy-related structure; Dautas, automated measurement of the distance between autophagy-related structures and ER exit sites analysis system; ERES, endoplasmic reticulum exit site; PAS, phagophore assembly site/pre-autophagosomal structure; PCR, polymerase chain reaction; PG, phagophore/isolation membrane; prApe1, precursor of vacuolar aminopeptidase I; Qautas, quantitative autophagy-related structure analysis system; SD/CA; synthetic dextrose plus casamino acid medium; WT, wild-type.
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Affiliation(s)
- Yang Shi
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa, Chiba, Japan
| | - Kuninori Suzuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa, Chiba, Japan
- Life Science Data Research Center, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba, Japan
- Collaborative Research Institute for Innovative Microbiology, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
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5
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Baumann V, Achleitner S, Tulli S, Schuschnig M, Klune L, Martens S. Faa1 membrane binding drives positive feedback in autophagosome biogenesis via fatty acid activation. J Cell Biol 2024; 223:e202309057. [PMID: 38573225 PMCID: PMC10993510 DOI: 10.1083/jcb.202309057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Revised: 02/14/2024] [Accepted: 03/22/2024] [Indexed: 04/05/2024] Open
Abstract
Autophagy serves as a stress response pathway by mediating the degradation of cellular material within lysosomes. In autophagy, this material is encapsulated in double-membrane vesicles termed autophagosomes, which form from precursors referred to as phagophores. Phagophores grow by lipid influx from the endoplasmic reticulum into Atg9-positive compartments and local lipid synthesis provides lipids for their expansion. How phagophore nucleation and expansion are coordinated with lipid synthesis is unclear. Here, we show that Faa1, an enzyme activating fatty acids, is recruited to Atg9 vesicles by directly binding to negatively charged membranes with a preference for phosphoinositides such as PI3P and PI4P. We define the membrane-binding surface of Faa1 and show that its direct interaction with the membrane is required for its recruitment to phagophores. Furthermore, the physiological localization of Faa1 is key for its efficient catalysis and promotes phagophore expansion. Our results suggest a positive feedback loop coupling phagophore nucleation and expansion to lipid synthesis.
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Affiliation(s)
- Verena Baumann
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Sonja Achleitner
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
- Vienna BioCenter PhD Program, A Doctoral School of the University of Vienna, Medical University of Vienna, Vienna, Austria
| | - Susanna Tulli
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Martina Schuschnig
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Lara Klune
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
| | - Sascha Martens
- Max Perutz Labs, Vienna BioCenter Campus (VBC), Vienna, Austria
- Max Perutz Labs, Department of Biochemistry and Cell Biology, University of Vienna, Vienna, Austria
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6
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Suzuki SW, West M, Zhang Y, Fan JS, Roberts RT, Odorizzi G, Emr SD. A role for Vps13-mediated lipid transfer at the ER-endosome contact site in ESCRT-mediated sorting. J Cell Biol 2024; 223:e202307094. [PMID: 38319250 PMCID: PMC10847051 DOI: 10.1083/jcb.202307094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 12/27/2023] [Accepted: 01/22/2024] [Indexed: 02/07/2024] Open
Abstract
Endosomes are specialized organelles that function in the secretory and endocytic protein sorting pathways. Endocytosed cell surface receptors and transporters destined for lysosomal degradation are sorted into intraluminal vesicles (ILVs) at endosomes by endosomal sorting complexes required for transport (ESCRT) proteins. The endosomes (multivesicular bodies, MVBs) then fuse with the lysosome. During endosomal maturation, the number of ILVs increases, but the size of endosomes does not decrease despite the consumption of the limiting membrane during ILV formation. Vesicle-mediated trafficking is thought to provide lipids to support MVB biogenesis. However, we have uncovered an unexpected contribution of a large bridge-like lipid transfer protein, Vps13, in this process. Here, we reveal that Vps13-mediated lipid transfer at ER-endosome contact sites is required for the ESCRT pathway. We propose that Vps13 may play a critical role in supplying lipids to the endosome, ensuring continuous ESCRT-mediated sorting during MVB biogenesis.
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Affiliation(s)
- Sho W. Suzuki
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Matthew West
- Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Yichen Zhang
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Jenny S. Fan
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Rachel T. Roberts
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Greg Odorizzi
- Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, USA
| | - Scott D. Emr
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
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7
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Ke PY. Molecular Mechanism of Autophagosome-Lysosome Fusion in Mammalian Cells. Cells 2024; 13:500. [PMID: 38534345 DOI: 10.3390/cells13060500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/11/2024] [Accepted: 03/12/2024] [Indexed: 03/28/2024] Open
Abstract
In eukaryotes, targeting intracellular components for lysosomal degradation by autophagy represents a catabolic process that evolutionarily regulates cellular homeostasis. The successful completion of autophagy initiates the engulfment of cytoplasmic materials within double-membrane autophagosomes and subsequent delivery to autolysosomes for degradation by acidic proteases. The formation of autolysosomes relies on the precise fusion of autophagosomes with lysosomes. In recent decades, numerous studies have provided insights into the molecular regulation of autophagosome-lysosome fusion. In this review, an overview of the molecules that function in the fusion of autophagosomes with lysosomes is provided. Moreover, the molecular mechanism underlying how these functional molecules regulate autophagosome-lysosome fusion is summarized.
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Affiliation(s)
- Po-Yuan Ke
- Department of Biochemistry & Molecular Biology, Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
- Liver Research Center, Chang Gung Memorial Hospital, Taoyuan 33305, Taiwan
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8
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Kotani T, Yasuda Y, Nakatogawa H. Molecular Mechanism of Autophagy, Cytoplasmic Zoning by Lipid Membranes. J Biochem 2024; 175:155-165. [PMID: 37983716 DOI: 10.1093/jb/mvad099] [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: 08/31/2023] [Revised: 11/02/2023] [Accepted: 11/06/2023] [Indexed: 11/22/2023] Open
Abstract
Autophagy is a highly conserved intracellular degradation mechanism. The most distinctive feature of autophagy is the formation of double-membrane structures called autophagosomes, which compartmentalize portions of the cytoplasm. The outer membrane of the autophagosome fuses with the vacuolar/lysosomal membrane, leading to the degradation of the contents of the autophagosome. Approximately 30 years have passed since the identification of autophagy-related (ATG) genes and Atg proteins essential for autophagosome formation, and the primary functions of these Atg proteins have been elucidated. These achievements have significantly advanced our understanding of the mechanism of autophagosome formation. This article summarizes our current knowledge on how the autophagosome precursor is generated, and how the membrane expands and seals to complete the autophagosome.
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Affiliation(s)
- Tetsuya Kotani
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, S2-14 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan
| | - Yuri Yasuda
- School of Life Science and Technology, Tokyo Institute of Technology, S2-14 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan
| | - Hitoshi Nakatogawa
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, S2-14 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan
- School of Life Science and Technology, Tokyo Institute of Technology, S2-14 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501, Japan
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9
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van Vliet AR, Jefferies HBJ, Faull PA, Chadwick J, Ibrahim F, Skehel MJ, Tooze SA. Exploring the ATG9A interactome uncovers interaction with VPS13A. J Cell Sci 2024; 137:jcs261081. [PMID: 38294121 PMCID: PMC10911177 DOI: 10.1242/jcs.261081] [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: 02/16/2023] [Accepted: 01/17/2024] [Indexed: 02/01/2024] Open
Abstract
ATG9A, a transmembrane protein of the core autophagy pathway, cycles between the Golgi, endosomes and a vesicular compartment. ATG9A was recently shown to act as a lipid scramblase, and this function is thought to require its interaction with another core autophagy protein, ATG2A, which acts as a lipid transfer protein. Together, ATG9A and ATG2A are proposed to function to expand the growing autophagosome. However, ATG9A is implicated in other pathways including membrane repair and lipid droplet homeostasis. To elucidate other ATG9A interactors within the autophagy pathway, or interactors beyond autophagy, we performed an interactome analysis through mass spectrometry. This analysis revealed a host of proteins involved in lipid synthesis and trafficking, including ACSL3, VPS13A and VPS13C. Furthermore, we show that ATG9A directly interacts with VPS13A and forms a complex that is distinct from the ATG9A-ATG2A complex.
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Affiliation(s)
| | | | - Peter A. Faull
- Proteomics Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | | | - Fairouz Ibrahim
- Proteomics Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Mark J. Skehel
- Proteomics Science Technology Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Sharon A. Tooze
- Molecular Cell Biology of Autophagy, The Francis Crick Institute, London NW1 1AT, UK
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10
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Voeltz GK, Sawyer EM, Hajnóczky G, Prinz WA. Making the connection: How membrane contact sites have changed our view of organelle biology. Cell 2024; 187:257-270. [PMID: 38242082 DOI: 10.1016/j.cell.2023.11.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 11/13/2023] [Accepted: 11/29/2023] [Indexed: 01/21/2024]
Abstract
The view of organelles and how they operate together has changed dramatically over the last two decades. The textbook view of organelles was that they operated largely independently and were connected by vesicular trafficking and the diffusion of signals through the cytoplasm. We now know that all organelles make functional close contacts with one another, often called membrane contact sites. The study of these sites has moved to center stage in cell biology as it has become clear that they play critical roles in healthy and developing cells and during cell stress and disease states. Contact sites have important roles in intracellular signaling, lipid metabolism, motor-protein-mediated membrane dynamics, organelle division, and organelle biogenesis. Here, we summarize the major conceptual changes that have occurred in cell biology as we have come to appreciate how contact sites integrate the activities of organelles.
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Affiliation(s)
- G K Voeltz
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
| | - E M Sawyer
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Boulder, CO 80309, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - G Hajnóczky
- MitoCare Center, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - W A Prinz
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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11
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Eskelinen EL. Novel insights into autophagosome biogenesis revealed by cryo-electron tomography. FEBS Lett 2024; 598:9-16. [PMID: 37625816 DOI: 10.1002/1873-3468.14726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 08/11/2023] [Accepted: 08/14/2023] [Indexed: 08/27/2023]
Abstract
Autophagosome biogenesis, from the appearance of the phagophore to elongation and closure into an autophagosome, is one of the long-lasting open questions in the autophagy field. Recent studies utilising cryo-electron tomography and detailed analysis of the image data have revealed new information on the membrane dynamics of these events, including the shape and dimensions of omegasomes, phagophores and autophagosomes, and their relationships with the organelles around them. One of the important predictions from the new results is that 60-80% of the autophagosome membrane area is delivered by direct lipid transfer or lipid synthesis. Cryo-electron tomography can be expected to provide new directions for autophagy research in the near future.
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12
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Deretic V. Atg8ylation as a host-protective mechanism against Mycobacterium tuberculosis. FRONTIERS IN TUBERCULOSIS 2023; 1:1275882. [PMID: 37901138 PMCID: PMC10612523 DOI: 10.3389/ftubr.2023.1275882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/31/2023]
Abstract
Nearly two decades have passed since the first report on autophagy acting as a cell-autonomous defense against Mycobacterium tuberculosis. This helped usher a new area of research within the field of host-pathogen interactions and led to the recognition of autophagy as an immunological mechanism. Interest grew in the fundamental mechanisms of antimicrobial autophagy and in the prophylactic and therapeutic potential for tuberculosis. However, puzzling in vivo data have begun to emerge in murine models of M. tuberculosis infection. The control of infection in mice affirmed the effects of certain autophagy genes, specifically ATG5, but not of other ATGs. Recent studies with a more complete inactivation of ATG genes now show that multiple ATG genes are indeed necessary for protection against M. tuberculosis. These particular ATG genes are involved in the process of membrane atg8ylation. Atg8ylation in mammalian cells is a broad response to membrane stress, damage and remodeling of which canonical autophagy is one of the multiple downstream outputs. The current developments clarify the controversies and open new avenues for both fundamental and translational studies.
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Affiliation(s)
- Vojo Deretic
- Autophagy, Inflammation and Metabolism Center of Biochemical Research Excellence
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, 915 Camino de Salud, NE, Albuquerque, NM 87131, USA
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13
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Korfhage JL, Wan N, Elhan H, Kauffman L, Pineda M, Fuller DM, Thiam AR, Reinisch KM, Melia TJ. ATG2A-mediated bridge-like lipid transport regulates lipid droplet accumulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.14.553257. [PMID: 37645754 PMCID: PMC10461963 DOI: 10.1101/2023.08.14.553257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
ATG2 proteins facilitate bulk lipid transport between membranes. ATG2 is an essential autophagy protein, but ATG2 also localizes to lipid droplets (LDs), and genetic depletion of ATG2 increases LD numbers while impairing fatty acid transport from LDs to mitochondria. How ATG2 supports LD homeostasis and whether lipid transport regulates this homeostasis remains unknown. Here we demonstrate that ATG2 is preferentially recruited to phospholipid monolayers such as those surrounding LDs rather than to phospholipid bilayers. In vitro, ATG2 can drive phospholipid transport from artificial LDs with rates that correlate with the binding affinities, such that phospholipids are moved much more efficiently when one of the ATG2-interacting structures is an artificial LD. ATG2 is thought to exhibit 'bridge-like" lipid transport, with lipids flowing across the protein between membranes. We mutated key amino acids within the bridge to form a transport-dead ATG2 mutant (TD-ATG2A) which we show specifically blocks bridge-like, but not shuttle-like, lipid transport in vitro. TD-ATG2A still localizes to LDs, but is unable to rescue LD accumulation in ATG2 knockout cells. Thus, ATG2 has a natural affinity for, and an enhanced activity upon LD surfaces and uses bridge-like lipid transport to support LD dynamics in cells.
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Affiliation(s)
- Justin L. Korfhage
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
| | - Neng Wan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
| | - Helin Elhan
- Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 75005 Paris, France
| | - Lisa Kauffman
- Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 75005 Paris, France
| | - Mia Pineda
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
| | - Devin M. Fuller
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 75005 Paris, France
| | - Karin M. Reinisch
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
| | - Thomas J. Melia
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510
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Melia TJ. Growing thin - How bulk lipid transport drives expansion of the autophagosome membrane but not of its lumen. Curr Opin Cell Biol 2023; 83:102190. [PMID: 37385155 PMCID: PMC10528516 DOI: 10.1016/j.ceb.2023.102190] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 05/30/2023] [Accepted: 05/30/2023] [Indexed: 07/01/2023]
Abstract
The key event in macroautophagy is the de novo formation of a new organelle called the autophagosome which when complete, will have captured bits of cytoplasm within its double-membrane structure. Eventual fusion with the lysosome allows this captured material to be degraded back to simple molecules which can be recycled to support cell function during starvation. How autophagosomes form has been a challenging question for over 60 years. This review highlights work that forms the basis for an autophagosome membrane expansion model grounded in protein-mediated lipid transport.
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15
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Nguyen A, Lugarini F, David C, Hosnani P, Alagöz Ç, Friedrich A, Schlütermann D, Knotkova B, Patel A, Parfentev I, Urlaub H, Meinecke M, Stork B, Faesen AC. Metamorphic proteins at the basis of human autophagy initiation and lipid transfer. Mol Cell 2023:S1097-2765(23)00321-0. [PMID: 37209685 DOI: 10.1016/j.molcel.2023.04.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 02/23/2023] [Accepted: 04/27/2023] [Indexed: 05/22/2023]
Abstract
Autophagy is a conserved intracellular degradation pathway that generates de novo double-membrane autophagosomes to target a wide range of material for lysosomal degradation. In multicellular organisms, autophagy initiation requires the timely assembly of a contact site between the ER and the nascent autophagosome. Here, we report the in vitro reconstitution of a full-length seven-subunit human autophagy initiation supercomplex built on a core complex of ATG13-101 and ATG9. Assembly of this core complex requires the rare ability of ATG13 and ATG101 to switch between distinct folds. The slow spontaneous metamorphic conversion is rate limiting for the self-assembly of the supercomplex. The interaction of the core complex with ATG2-WIPI4 enhances tethering of membrane vesicles and accelerates lipid transfer of ATG2 by both ATG9 and ATG13-101. Our work uncovers the molecular basis of the contact site and its assembly mechanisms imposed by the metamorphosis of ATG13-101 to regulate autophagosome biogenesis in space and time.
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Affiliation(s)
- Anh Nguyen
- Max-Planck Institute for Multidisciplinary Sciences, Laboratory of Biochemistry of Signal Dynamics, Göttingen, Germany
| | - Francesca Lugarini
- Max-Planck Institute for Multidisciplinary Sciences, Laboratory of Biochemistry of Signal Dynamics, Göttingen, Germany
| | - Céline David
- Institute of Molecular Medicine I, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Pouya Hosnani
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany; University Medical Centre Göttingen, Department of Cellular Biochemistry, Göttingen, Germany
| | - Çağla Alagöz
- Max-Planck Institute for Multidisciplinary Sciences, Laboratory of Biochemistry of Signal Dynamics, Göttingen, Germany
| | - Annabelle Friedrich
- Institute of Molecular Medicine I, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - David Schlütermann
- Institute of Molecular Medicine I, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Barbora Knotkova
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany; University Medical Centre Göttingen, Department of Cellular Biochemistry, Göttingen, Germany
| | - Anoshi Patel
- Max-Planck Institute for Multidisciplinary Sciences, Laboratory of Biochemistry of Signal Dynamics, Göttingen, Germany
| | - Iwan Parfentev
- Max-Planck Institute for Multidisciplinary Sciences, Bioanalytical Mass Spectrometry, Göttingen, Germany
| | - Henning Urlaub
- Max-Planck Institute for Multidisciplinary Sciences, Bioanalytical Mass Spectrometry, Göttingen, Germany; University Medical Centre Göttingen, Institute of Clinical Chemistry, Bioanalytics Group, Göttingen, Germany
| | - Michael Meinecke
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany; University Medical Centre Göttingen, Department of Cellular Biochemistry, Göttingen, Germany
| | - Björn Stork
- Institute of Molecular Medicine I, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
| | - Alex C Faesen
- Max-Planck Institute for Multidisciplinary Sciences, Laboratory of Biochemistry of Signal Dynamics, Göttingen, Germany.
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Leterme S, Bastien O, Aiese Cigliano R, Amato A, Michaud M. Phylogenetic and Structural Analyses of VPS13 Proteins in Archaeplastida Reveal Their Complex Evolutionary History in Viridiplantae. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231211976. [PMID: 38033810 PMCID: PMC10683392 DOI: 10.1177/25152564231211976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 10/09/2023] [Accepted: 10/18/2023] [Indexed: 12/02/2023]
Abstract
VPS13 is a lipid transfer protein family conserved among Eukaryotes and playing roles in fundamental processes involving vesicular transport and membrane expansion including autophagy and organelle biogenesis. VPS13 folds into a long hydrophobic tunnel, allowing lipid transport, decorated by distinct domains involved in protein localization and regulation. Whereas VPS13 organization and function have been extensively studied in yeast and mammals, information in organisms originating from primary endosymbiosis is scarce. In the higher plant Arabidopsis thaliana, four paralogs, AtVPS13S, X, M1, and M2, were identified, AtVPS13S playing a role in the regulation of root growth, cell patterning, and reproduction. In this work, we performed phylogenetic, as well as domain and structural modeling of VPS13 proteins in Archaeplastida in order to understand their general organization and evolutionary history. We confirmed the presence of human VPS13B orthologues in some phyla and described two new VPS13 families presenting a particular domain arrangement: VPS13R in Rhodophytes and VPS13Y in Chlorophytes and Streptophytes. By focusing on Viridiplantae, we were able to draw the evolutionary history of these proteins made by multiple gene gains and duplications as well as domain rearrangements. We showed that some Chlorophytes have only three (AtVPS13M, S, Y) whereas some Charophytes have up to six VPS13 paralogs (AtVPS13M1, M2, S, Y, X, B). We also highlighted specific structural features of VPS13M and X paralogs. This study reveals the complex evolution of VPS13 family and opens important perspectives for their functional characterization in photosynthetic organisms.
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Affiliation(s)
- Sébastien Leterme
- Université Grenoble Alpes, CNRS, CEA, INRAE, IRIG, LPCV, Grenoble, France
| | - Olivier Bastien
- Université Grenoble Alpes, CNRS, CEA, INRAE, IRIG, LPCV, Grenoble, France
| | | | - Alberto Amato
- Université Grenoble Alpes, CNRS, CEA, INRAE, IRIG, LPCV, Grenoble, France
| | - Morgane Michaud
- Université Grenoble Alpes, CNRS, CEA, INRAE, IRIG, LPCV, Grenoble, France
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