1
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Álvarez-Guerra I, Block E, Broeskamp F, Gabrijelčič S, Infant T, de Ory A, Habernig L, Andréasson C, Levine TP, Höög JL, Büttner S. LDO proteins and Vac8 form a vacuole-lipid droplet contact site to enable starvation-induced lipophagy in yeast. Dev Cell 2024; 59:759-775.e5. [PMID: 38354739 DOI: 10.1016/j.devcel.2024.01.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 11/15/2023] [Accepted: 01/18/2024] [Indexed: 02/16/2024]
Abstract
Lipid droplets (LDs) are fat storage organelles critical for energy and lipid metabolism. Upon nutrient exhaustion, cells consume LDs via gradual lipolysis or via lipophagy, the en bloc uptake of LDs into the vacuole. Here, we show that LDs dock to the vacuolar membrane via a contact site that is required for lipophagy in yeast. The LD-localized LDO proteins carry an intrinsically disordered region that directly binds vacuolar Vac8 to form vCLIP, the vacuolar-LD contact site. Nutrient limitation drives vCLIP formation, and its inactivation blocks lipophagy, resulting in impaired caloric restriction-induced longevity. We establish a functional link between lipophagy and microautophagy of the nucleus, both requiring Vac8 to form respective contact sites upon metabolic stress. In sum, we identify the tethering machinery of vCLIP and find that Vac8 provides a platform for multiple and competing contact sites associated with autophagy.
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Affiliation(s)
- Irene Álvarez-Guerra
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Emma Block
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Filomena Broeskamp
- Department of Chemistry and Molecular Biology, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Sonja Gabrijelčič
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Terence Infant
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Ana de Ory
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Lukas Habernig
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Claes Andréasson
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden
| | - Tim P Levine
- UCL Institute of Ophthalmology, Bath Street, London EC1V 9EL, UK
| | - Johanna L Höög
- Department of Chemistry and Molecular Biology, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Sabrina Büttner
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 10691 Stockholm, Sweden.
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2
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Kim H, Park J, Kim H, Ko N, Park J, Jang E, Yoon S, Diaz J, Lee C, Jun Y. Structures of Vac8-containing protein complexes reveal the underlying mechanism by which Vac8 regulates multiple cellular processes. Proc Natl Acad Sci U S A 2023; 120:e2211501120. [PMID: 37094131 PMCID: PMC10161063 DOI: 10.1073/pnas.2211501120] [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: 07/06/2022] [Accepted: 03/30/2023] [Indexed: 04/26/2023] Open
Abstract
Vac8, a yeast vacuolar protein with armadillo repeats, mediates various cellular processes by changing its binding partners; however, the mechanism by which Vac8 differentially regulates these processes remains poorly understood. Vac8 interacts with Nvj1 to form the nuclear-vacuole junction (NVJ) and with Atg13 to mediate cytoplasm-to-vacuole targeting (Cvt), a selective autophagy-like pathway that delivers cytoplasmic aminopeptidase I directly to the vacuole. In addition, Vac8 associates with Myo2, a yeast class V myosin, through its interaction with Vac17 for vacuolar inheritance from the mother cell to the emerging daughter cell during cell divisions. Here, we determined the X-ray crystal structure of the Vac8-Vac17 complex and found that its interaction interfaces are bipartite, unlike those of the Vac8-Nvj1 and Vac8-Atg13 complexes. When the key amino acids present in the interface between Vac8 and Vac17 were mutated, vacuole inheritance was severely impaired in vivo. Furthermore, binding of Vac17 to Vac8 prevented dimerization of Vac8, which is required for its interactions with Nvj1 and Atg13, by clamping the H1 helix to the ARM1 domain of Vac8 and thereby preventing exposure of the binding interface for Vac8 dimerization. Consistently, the binding affinity of Vac17-bound Vac8 for Nvj1 or Atg13 was markedly lower than that of free Vac8. Likewise, free Vac17 had no affinity for the Vac8-Nvj1 and Vac8-Atg13 complexes. These results provide insights into how vacuole inheritance and other Vac8-mediated processes, such as NVJ formation and Cvt, occur independently of one another.
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Affiliation(s)
- Hyejin Kim
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan44919, South Korea
| | - Jihyeon Park
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
| | - Hyunwoo Kim
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan44919, South Korea
| | - Naho Ko
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
| | - Jumi Park
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan44919, South Korea
| | - Eunhong Jang
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
| | - So Young Yoon
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
| | - Joyce Anne R. Diaz
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
| | - Changwook Lee
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan44919, South Korea
| | - Youngsoo Jun
- Cell Logistics Research Center, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju61005, South Korea
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3
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Capitanio C, Bieber A, Wilfling F. How Membrane Contact Sites Shape the Phagophore. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231162495. [PMID: 37366413 PMCID: PMC10243513 DOI: 10.1177/25152564231162495] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 02/15/2023] [Accepted: 02/18/2023] [Indexed: 06/28/2023]
Abstract
During macroautophagy, phagophores establish multiple membrane contact sites (MCSs) with other organelles that are pivotal for proper phagophore assembly and growth. In S. cerevisiae, phagophore contacts have been observed with the vacuole, the ER, and lipid droplets. In situ imaging studies have greatly advanced our understanding of the structure and function of these sites. Here, we discuss how in situ structural methods like cryo-CLEM can give unprecedented insights into MCSs, and how they help to elucidate the structural arrangements of MCSs within cells. We further summarize the current knowledge of the contact sites in autophagy, focusing on autophagosome biogenesis in the model organism S. cerevisiae.
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Affiliation(s)
- Cristina Capitanio
- Department of Molecular Machines and
Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
- Aligning Science Across Parkinson's (ASAP)
Collaborative Research Network, Chevy Chase, MD, USA
| | - Anna Bieber
- Department of Molecular Machines and
Signaling, Max Planck Institute of Biochemistry, Martinsried, Germany
- Aligning Science Across Parkinson's (ASAP)
Collaborative Research Network, Chevy Chase, MD, USA
| | - Florian Wilfling
- Mechanisms of Cellular Quality Control, Max Planck Institute of Biophysics, Frankfurt a. M., Germany
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4
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Zwilling E, Reggiori F. Membrane Contact Sites in Autophagy. Cells 2022; 11:cells11233813. [PMID: 36497073 PMCID: PMC9735501 DOI: 10.3390/cells11233813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Revised: 11/24/2022] [Accepted: 11/25/2022] [Indexed: 11/29/2022] Open
Abstract
Eukaryotes utilize different communication strategies to coordinate processes between different cellular compartments either indirectly, through vesicular transport, or directly, via membrane contact sites (MCSs). MCSs have been implicated in lipid metabolism, calcium signaling and the regulation of organelle biogenesis in various cell types. Several studies have shown that MCSs play a crucial role in the regulation of macroautophagy, an intracellular catabolic transport route that is characterized by the delivery of cargoes (proteins, protein complexes or aggregates, organelles and pathogens) to yeast and plant vacuoles or mammalian lysosomes, for their degradation and recycling into basic metabolites. Macroautophagy is characterized by the de novo formation of double-membrane vesicles called autophagosomes, and their biogenesis requires an enormous amount of lipids. MCSs appear to have a central role in this supply, as well as in the organization of the autophagy-related (ATG) machinery. In this review, we will summarize the evidence for the participation of specific MCSs in autophagosome formation, with a focus on the budding yeast and mammalian systems.
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Affiliation(s)
- Emma Zwilling
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000C Aarhus, Denmark
| | - Fulvio Reggiori
- Department of Biomedicine, Aarhus University, Ole Worms Allé 4, 8000C Aarhus, Denmark
- Aarhus Institute of Advanced Studies (AIAS), Aarhus University, Høegh-Guldbergs Gade 6B, 8000C Aarhus, Denmark
- Correspondence:
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5
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Troutman KK, Varlakhanova NV, Tornabene BA, Ramachandran R, Ford MGJ. Conserved Pib2 regions have distinct roles in TORC1 regulation at the vacuole. J Cell Sci 2022; 135:276418. [PMID: 36000409 PMCID: PMC9584352 DOI: 10.1242/jcs.259994] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 08/15/2022] [Indexed: 12/27/2022] Open
Abstract
TORC1 is a critical controller of cell growth in eukaryotes. In yeast (Saccharomyces cerevisiae), the presence of nutrients is signaled to TORC1 by several upstream regulatory sensors that together coordinate TORC1 activity. TORC1 localizes to both vacuolar and endosomal membranes, where differential signaling occurs. This localization is mimicked by Pib2, a key upstream TORC1 regulator that is essential for TORC1 reactivation after nutrient starvation or pharmacological inhibition. Pib2 has both positive and negative effects on TORC1 activity, but the mechanisms remain poorly understood. Here, we pinpoint the Pib2 inhibitory function on TORC1 to residues within short, conserved N-terminal regions. We also show that the Pib2 C-terminal regions, helical region E and tail, are essential for TORC1 reactivation. Furthermore, the Pib2 FYVE domain plays a role in vacuolar localization, but it is surprisingly unnecessary for recovery from rapamycin exposure. Using chimeric Pib2 targeting constructs, we show that endosomal localization is not necessary for TORC1 reactivation and cell growth after rapamycin treatment. Thus, a comprehensive molecular dissection of Pib2 demonstrates that each of its conserved regions differentially contribute to Pib2-mediated regulation of TORC1 activity.
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Affiliation(s)
- Kayla K. Troutman
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Natalia V. Varlakhanova
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Bryan A. Tornabene
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Rajesh Ramachandran
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
| | - Marijn G. J. Ford
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA,Author for correspondence ()
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6
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Tang L, Chu T, Shang J, Yang R, Song C, Bao D, Tan Q, Jian H. Oxidative Stress and Autophagy Are Important Processes in Post Ripeness and Brown Film Formation in Mycelium of Lentinula edodes. Front Microbiol 2022; 13:811673. [PMID: 35283832 PMCID: PMC8908433 DOI: 10.3389/fmicb.2022.811673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/18/2022] [Indexed: 11/17/2022] Open
Abstract
Lentinula edodes (Berk.) Pegler, the shiitake mushroom, is one of the most important mushrooms in the global mushroom industry. Although mycelium post ripeness and brown film (BF) formation are crucial for fruiting body initiation, the underlying molecular mechanisms of BF formation are largely unknown. In this study, proteomic quantification (relative and absolute) and metabolomic profiling of L. edodes were performed using isobaric tags and gas chromatography-mass spectroscopy, respectively. A total of 2,474 proteins were identified, which included 239 differentially expressed proteins. Notably, several proteins associated with autophagy were upregulated, including RPD3, TOR1, VAC8, VPS1, and VPS27. Transmission electron microscopy also indicated that autophagy occurred in post ripeness and BF formation. In time-dependent analysis of the metabolome, metabolites associated with oxidative stress and autophagy changed significantly, including mannitol, trehalose, myo-inositol, glucose, leucine, valine, glutamine, and 4-aminobutyric acid. Thus, oxidative stress and autophagy were important processes in post ripeness and BF formation in L. edodes, and new insights were gained into molecular mechanisms at proteome and metabolome levels.
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Affiliation(s)
- Lihua Tang
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China
| | - Ting Chu
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China.,School of Food Sciences and Technology, Shanghai Ocean University, Shanghai, China
| | - Junjun Shang
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China
| | - Ruiheng Yang
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China
| | - Chunyan Song
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China
| | - Dapeng Bao
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China
| | - Qi Tan
- Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences, Key Laboratory of Edible Fungi Resources and Utilization (South), Ministry of Agriculture and Rural Affairs (China), National Engineering Research Center of Edible Fungi, Shanghai, China
| | - Huahua Jian
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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7
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Degradation of nuclear components via different autophagy pathways. Trends Cell Biol 2022; 32:574-584. [DOI: 10.1016/j.tcb.2021.12.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/21/2021] [Accepted: 12/23/2021] [Indexed: 12/21/2022]
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8
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Spatial control of avidity regulates initiation and progression of selective autophagy. Nat Commun 2021; 12:7194. [PMID: 34893607 PMCID: PMC8664900 DOI: 10.1038/s41467-021-27420-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 11/17/2021] [Indexed: 11/11/2022] Open
Abstract
Autophagosomes form at the endoplasmic reticulum in mammals, and between the vacuole and the endoplasmic reticulum in yeast. However, the roles of these sites and the mechanisms regulating autophagosome formation are incompletely understood. Vac8 is required for autophagy and recruits the Atg1 kinase complex to the vacuole. Here we show that Vac8 acts as a central hub to nucleate the phagophore assembly site at the vacuolar membrane during selective autophagy. Vac8 directly recruits the cargo complex via the Atg11 scaffold. In addition, Vac8 recruits the phosphatidylinositol 3-kinase complex independently of autophagy. Cargo-dependent clustering and Vac8-dependent sequestering of these early autophagy factors, along with local Atg1 activation, promote phagophore assembly site assembly at the vacuole. Importantly, ectopic Vac8 redirects autophagosome formation to the nuclear membrane, indicating that the vacuolar membrane is not specifically required. We propose that multiple avidity-driven interactions drive the initiation and progression of selective autophagy. The molecular principles governing the initiation of autophagosome formation are not clearly understood. Here we show that the vacuolar protein Vac8 coordinates this process by promoting an avidity-driven assembly of several autophagy factors.
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9
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Gu W, Luo Z, Vonrhein C, Jia X, Ve T, Nanson JD, Kobe B. Crystal structure determination of the armadillo repeat domain of Drosophila SARM1 using MIRAS phasing. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2021; 77:364-373. [PMID: 34605441 DOI: 10.1107/s2053230x21006786] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 06/29/2021] [Indexed: 11/11/2022]
Abstract
The crystal structure determination of the armadillo repeat motif (ARM) domain of Drosophila SARM1 (dSARM1ARM) is described, which required the combination of a number of sources of phase information in order to obtain interpretable electron-density maps. SARM1 is a central executioner of programmed axon degeneration, a common feature of the early phase of many neurodegenerative diseases. SARM1 is held in the inactive state in healthy axons by its N-terminal auto-inhibitory ARM domain, and is activated to cleave NAD upon injury, triggering subsequent axon degeneration. To characterize the molecular mechanism of SARM1 activation, it was sought to determine the crystal structure of the SARM1 ARM domain. Here, the recombinant production and crystallization of dSARM1ARM is described, as well as the unconventional process used for structure determination. Crystals were obtained in the presence of NMN, a precursor of NAD and a potential activator of SARM1, only after in situ proteolysis of the N-terminal 63 residues. After molecular-replacement attempts failed, the crystal structure of dSARM1ARM was determined at 1.65 Å resolution using the MIRAS phasing technique with autoSHARP, combining data from native, selenomethionine-labelled and bromide-soaked crystals. The structure will further the understanding of SARM1 regulation.
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Affiliation(s)
- Weixi Gu
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
| | - Zhenyao Luo
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
| | | | - Xinying Jia
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
| | - Thomas Ve
- Institute for Glycomics, Griffith University, Southport, Queensland 4222, Australia
| | - Jeffrey D Nanson
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
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10
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Lei Y, Zhang X, Xu Q, Liu S, Li C, Jiang H, Lin H, Kong E, Liu J, Qi S, Li H, Xu W, Lu K. Autophagic elimination of ribosomes during spermiogenesis provides energy for flagellar motility. Dev Cell 2021; 56:2313-2328.e7. [PMID: 34428398 DOI: 10.1016/j.devcel.2021.07.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 05/17/2021] [Accepted: 07/23/2021] [Indexed: 02/05/2023]
Abstract
How autophagy initiation is regulated and what the functional significance of this regulation is are unknown. Here, we characterized the role of yeast Vac8 in autophagy initiation through recruitment of PIK3C3-C1 to the phagophore assembly site (PAS). This recruitment is dependent on the palmitoylation of Vac8 and on its middle ARM domains for binding PIK3C3-C1. Vac8-mediated anchoring of PIK3C3-C1 promotes PtdIns3P generation at the PAS and recruitment of the PtdIns3P binding protein Atg18-Atg2. The mouse homolog of Vac8, ARMC3, is conserved and functions in autophagy in mouse testes. Mice lacking ARMC3 have normal viability but show complete male infertility. Proteomic analysis indicated that the autophagic degradation of cytosolic ribosomes was blocked in ARMC3-deficient spermatids, which caused low energy levels of mitochondria and motionless flagella. These studies uncovered a function of Vac8/ARMC3 in PtdIns3-kinase anchoring at the PAS and its physical significance in mammalian spermatogenesis with a germ tissue-specific autophagic function.
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Affiliation(s)
- Yuqing Lei
- Department of Pathology, West China Second University Hospital, State Key Laboratory of Biotherapy, and Key Laboratory of Birth Defects and Related Diseases of Women and Children of Ministry of Education, Sichuan University, Chengdu 610041, China
| | - Xueguang Zhang
- Department of Obstetrics/Gynecology, Joint Laboratory of Reproductive Medicine (SCU-CUHK), Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, China
| | - Qingjia Xu
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Shiyan Liu
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Chunxia Li
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Hui Jiang
- Department of Urology, Peking University Third Hospital, Beijing 100191, China; Department of Reproductive Medicine Center, Peking University Third Hospital, Beijing 100191, China
| | - Haocheng Lin
- Department of Urology, Peking University Third Hospital, Beijing 100191, China; Department of Reproductive Medicine Center, Peking University Third Hospital, Beijing 100191, China
| | - Eryan Kong
- Institute of Psychiatry and Neuroscience, Xinxiang Medical University, Xinxiang 453003, China
| | - Jiaming Liu
- Department of Urology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Shiqian Qi
- Department of Urology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China
| | - Huihui Li
- Department of Pathology, West China Second University Hospital, State Key Laboratory of Biotherapy, and Key Laboratory of Birth Defects and Related Diseases of Women and Children of Ministry of Education, Sichuan University, Chengdu 610041, China.
| | - Wenming Xu
- Department of Obstetrics/Gynecology, Joint Laboratory of Reproductive Medicine (SCU-CUHK), Key Laboratory of Obstetric, Gynecologic and Pediatric Diseases and Birth Defects of Ministry of Education, West China Second University Hospital, Sichuan University, Chengdu 610041, China.
| | - Kefeng Lu
- Department of Neurology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu 610041, China.
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11
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Feng Z, Jia B, Zhang M. Liquid-Liquid Phase Separation in Biology: Specific Stoichiometric Molecular Interactions vs Promiscuous Interactions Mediated by Disordered Sequences. Biochemistry 2021; 60:2397-2406. [PMID: 34291921 DOI: 10.1021/acs.biochem.1c00376] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Extensive studies in the past few years have shown that nonmembrane bound organelles are likely assembled via liquid-liquid phase separation (LLPS), a process that is driven by multivalent protein-protein and/or protein-nucleic acid interactions. Both stoichiometric molecular interactions and intrinsically disordered region (IDR)-driven interactions can promote the assembly of membraneless organelles, and the field is currently dominated by IDR-driven biological condensate formation. Here we discuss recent studies that demonstrate the importance of specific biomolecular interactions for functions of diverse physiological condensates. We suggest that phase separation based on combinations of specific interactions and promiscuous IDR-driven interactions is likely a general feature of biological condensation under physiological conditions.
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Affiliation(s)
- Zhe Feng
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong China.,School of Life Sciences, Fudan University, Shanghai 200433, China
| | - Bowen Jia
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong China
| | - Mingjie Zhang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
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12
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GRAMD1-mediated accessible cholesterol sensing and transport. Biochim Biophys Acta Mol Cell Biol Lipids 2021; 1866:158957. [PMID: 33932585 DOI: 10.1016/j.bbalip.2021.158957] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/09/2021] [Accepted: 04/19/2021] [Indexed: 01/19/2023]
Abstract
Cholesterol, an essential lipid for cell signaling and structural integrity of cellular membranes, is highly enriched in the plasma membrane (PM). However, the regulatory mechanisms that control its biosynthesis and uptake both reside in the endoplasmic reticulum (ER). Thus, the ER needs to constantly monitor the levels of PM cholesterol. This is in part mediated by regulated transport of a biochemically defined pool of cholesterol, termed "accessible" cholesterol, from the PM to the ER via evolutionarily conserved ER-anchored lipid transfer proteins, the GRAMD1s/Asters (GRAMD1a/1b/1c) (Lam/Ltc proteins in yeast). GRAMD1s possess cytosolically exposed GRAM domain and StART-like domain followed by a transmembrane ER anchor. They form homo- and hetero-meric complexes and move to the contacts formed between the ER and the PM by sensing a transient expansion of the accessible pool of cholesterol in the PM via the GRAM domain and facilitate its extraction and transport to the ER via the StART-like domain. The GRAMD1b GRAM domain possesses distinct, but synergistic sites, for recognizing accessible cholesterol and anionic lipids, including phosphatidylserine, within the PM. This property of the GRAM domain contributes to regulated tethering of the PM to ER membrane where GRAMD1s are anchored and fine-tunes StART-like domain-dependent accessible cholesterol transport. Thus, cells use GRAMD1s to sense the levels of cholesterol in the PM and regulate transport of accessible PM cholesterol to the ER in order to maintain cholesterol homeostasis.
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13
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Tosal-Castano S, Peselj C, Kohler V, Habernig L, Berglund LL, Ebrahimi M, Vögtle FN, Höög J, Andréasson C, Büttner S. Snd3 controls nucleus-vacuole junctions in response to glucose signaling. Cell Rep 2021; 34:108637. [PMID: 33472077 DOI: 10.1016/j.celrep.2020.108637] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 12/08/2020] [Accepted: 12/21/2020] [Indexed: 12/29/2022] Open
Abstract
Membrane contact sites facilitate the exchange of metabolites between organelles to support interorganellar communication. The nucleus-vacuole junctions (NVJs) establish physical contact between the perinuclear endoplasmic reticulum (ER) and the vacuole. Although the NVJ tethers are known, how NVJ abundance and composition are controlled in response to metabolic cues remains elusive. Here, we identify the ER protein Snd3 as central factor for NVJ formation. Snd3 interacts with NVJ tethers, supports their targeting to the contacts, and is essential for NVJ formation. Upon glucose exhaustion, Snd3 relocalizes from the ER to NVJs and promotes contact expansion regulated by central glucose signaling pathways. Glucose replenishment induces the rapid dissociation of Snd3 from the NVJs, preceding the slow disassembly of the junctions. In sum, this study identifies a key factor required for formation and regulation of NVJs and provides a paradigm for metabolic control of membrane contact sites.
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Affiliation(s)
- Sergi Tosal-Castano
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden
| | - Carlotta Peselj
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden
| | - Verena Kohler
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden
| | - Lukas Habernig
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden
| | - Lisa Larsson Berglund
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan 9C, 41390 Gothenburg, Sweden
| | - Mahsa Ebrahimi
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden
| | - F-Nora Vögtle
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Stefan-Meier-Straße 17, 79104 Freiburg, Germany; Centre for Integrative Biological Signalling Studies, University of Freiburg, 79104 Freiburg, Germany
| | - Johanna Höög
- Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan 9C, 41390 Gothenburg, Sweden
| | - Claes Andréasson
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden
| | - Sabrina Büttner
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 10691 Stockholm, Sweden; Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria.
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14
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Kohler V, Büttner S. Remodelling of Nucleus-Vacuole Junctions During Metabolic and Proteostatic Stress. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211016608. [PMID: 34124572 PMCID: PMC7610967 DOI: 10.1177/25152564211016608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/21/2021] [Accepted: 04/21/2021] [Indexed: 12/18/2022]
Abstract
Cellular adaptation to stress and metabolic cues requires a coordinated response of different intracellular compartments, separated by semipermeable membranes. One way to facilitate interorganellar communication is via membrane contact sites, physical bridges between opposing organellar membranes formed by an array of tethering machineries. These contact sites are highly dynamic and establish an interconnected organellar network able to quickly respond to external and internal stress by changing size, abundance and molecular architecture. Here, we discuss recent work on nucleus-vacuole junctions, connecting yeast vacuoles with the nucleus. Appearing as small, single foci in mitotic cells, these contacts expand into one enlarged patch upon nutrient exhaustion and entry into quiescence or can be shaped into multiple large foci essential to sustain viability upon proteostatic stress at the nuclear envelope. We highlight the remarkable plasticity and rapid remodelling of these contact sites upon metabolic or proteostatic stress and their emerging importance for cellular fitness.
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Affiliation(s)
- Verena Kohler
- Department of Molecular Biosciences, The Wenner‐Gren Institute, Stockholm University, Stockholm, Sweden
| | - Sabrina Büttner
- Department of Molecular Biosciences, The Wenner‐Gren Institute, Stockholm University, Stockholm, Sweden
- Institute of Molecular Biosciences, University of Graz, Graz, Austria
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15
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Zheng Koh DH, Saheki Y. Regulation of Plasma Membrane Sterol Homeostasis by Nonvesicular Lipid Transport. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211042451. [PMID: 37366378 PMCID: PMC10259818 DOI: 10.1177/25152564211042451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Sterol contributes to the structural integrity of cellular membranes and plays an important role in the regulation of cell signaling in eukaryotes. It is either produced in the endoplasmic reticulum or taken up from the extracellular environment. In most eukaryotic cells, however, the majority of sterol is enriched in the plasma membrane. Thus, the transport of sterol between the plasma membrane and other organelles, including the endoplasmic reticulum, is crucial for maintaining sterol homeostasis. While vesicular transport that relies on membrane budding and fusion reactions plays an important role in bulk sterol transport, this mode of transport is slow and non-selective. Growing evidence suggests a critical role of nonvesicular transport mediated by evolutionarily conserved families of lipid transfer proteins in more rapid and selective delivery of sterol. Some lipid transfer proteins act primarily at the sites of contacts formed between the endoplasmic reticulum and other organelles or the plasma membrane without membrane fusion. In this review, we describe the similarities and differences of sterol biosynthesis and uptake in mammals and yeast and discuss the role of their lipid transfer proteins in maintaining plasma membrane sterol homeostasis.
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Affiliation(s)
- Dylan Hong Zheng Koh
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
| | - Yasunori Saheki
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
- Institute of Resource Development and
Analysis, Kumamoto University, Kumamoto 860-0811, Japan
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16
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In vitro reconstitution of autophagic processes. Biochem Soc Trans 2020; 48:2003-2014. [PMID: 32897375 DOI: 10.1042/bst20200130] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 08/12/2020] [Accepted: 08/13/2020] [Indexed: 11/17/2022]
Abstract
Autophagy is a lysosomal degradation system that involves de novo autophagosome formation. A lot of factors are involved in autophagosome formation, including dozens of Atg proteins that form supramolecular complexes, membrane structures including vesicles and organelles, and even membraneless organelles. Because these diverse higher-order structural components cooperate to mediate de novo formation of autophagosomes, it is too complicated to be elaborated only by cell biological approaches. Recent trials to regenerate each step of this phenomenon in vitro have started to elaborate on the molecular mechanisms of such a complicated process by simplification. In this review article, we outline the in vitro reconstitution trials in autophagosome formation, mainly focusing on the reports in the past few years and discussing the molecular mechanisms of autophagosome formation by comparing in vitro and in vivo observations.
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17
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Lord CL, Wente SR. Nuclear envelope-vacuole contacts mitigate nuclear pore complex assembly stress. J Cell Biol 2020; 219:211463. [PMID: 33053148 PMCID: PMC7563749 DOI: 10.1083/jcb.202001165] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 08/10/2020] [Accepted: 09/23/2020] [Indexed: 01/04/2023] Open
Abstract
The intricacy of nuclear pore complex (NPC) biogenesis imposes risks of failure that can cause defects in nuclear transport and nuclear envelope (NE) morphology; however, cellular mechanisms used to alleviate NPC assembly stress are not well defined. In the budding yeast Saccharomyces cerevisiae, we demonstrate that NVJ1- and MDM1-enriched NE-vacuole contacts increase when NPC assembly is compromised in several nup mutants, including nup116ΔGLFG cells. These interorganelle nucleus-vacuole junctions (NVJs) cooperate with lipid droplets to maintain viability and enhance NPC formation in assembly mutants. Additionally, NVJs function with ATG1 to remodel the NE and promote vacuole-dependent degradation of specific nucleoporins in nup116ΔGLFG cells. Importantly, NVJs significantly improve the physiology of NPC assembly mutants, despite having only negligible effects when NPC biogenesis is unperturbed. These results therefore define how NE-vacuole interorganelle contacts coordinate responses to mitigate deleterious cellular effects caused by disrupted NPC assembly.
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18
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Chang L, Yang J, Jo CH, Boland A, Zhang Z, McLaughlin SH, Abu-Thuraia A, Killoran RC, Smith MJ, Côté JF, Barford D. Structure of the DOCK2-ELMO1 complex provides insights into regulation of the auto-inhibited state. Nat Commun 2020; 11:3464. [PMID: 32651375 PMCID: PMC7351999 DOI: 10.1038/s41467-020-17271-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 06/17/2020] [Indexed: 12/29/2022] Open
Abstract
DOCK (dedicator of cytokinesis) proteins are multidomain guanine nucleotide exchange factors (GEFs) for RHO GTPases that regulate intracellular actin dynamics. DOCK proteins share catalytic (DOCKDHR2) and membrane-associated (DOCKDHR1) domains. The structurally-related DOCK1 and DOCK2 GEFs are specific for RAC, and require ELMO (engulfment and cell motility) proteins for function. The N-terminal RAS-binding domain (RBD) of ELMO (ELMORBD) interacts with RHOG to modulate DOCK1/2 activity. Here, we determine the cryo-EM structures of DOCK2-ELMO1 alone, and as a ternary complex with RAC1, together with the crystal structure of a RHOG-ELMO2RBD complex. The binary DOCK2-ELMO1 complex adopts a closed, auto-inhibited conformation. Relief of auto-inhibition to an active, open state, due to a conformational change of the ELMO1 subunit, exposes binding sites for RAC1 on DOCK2DHR2, and RHOG and BAI GPCRs on ELMO1. Our structure explains how up-stream effectors, including DOCK2 and ELMO1 phosphorylation, destabilise the auto-inhibited state to promote an active GEF.
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Affiliation(s)
- Leifu Chang
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
- Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907, USA
| | - Jing Yang
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | - Chang Hwa Jo
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec, H3T 1J4, Canada
| | - Andreas Boland
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
- Department of Molecular Biology, Science III, University of Geneva, Geneva, Switzerland
| | - Ziguo Zhang
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK
| | | | - Afnan Abu-Thuraia
- Montreal Institute of Clinical Research (IRCM), Montréal, QC, H2W 1R7, Canada
| | - Ryan C Killoran
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec, H3T 1J4, Canada
| | - Matthew J Smith
- Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Québec, H3T 1J4, Canada
- Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, QC, H3T 1J4, Canada
| | - Jean-Francois Côté
- Montreal Institute of Clinical Research (IRCM), Montréal, QC, H2W 1R7, Canada
- Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Montréal, QC, H3C 3J7, Canada
- Department of Anatomy and Cell Biology, McGill University, Montréal, QC, H3A 0C7, Canada
| | - David Barford
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK.
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19
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Bo Otto F, Thumm M. Nucleophagy-Implications for Microautophagy and Health. Int J Mol Sci 2020; 21:ijms21124506. [PMID: 32599961 PMCID: PMC7352367 DOI: 10.3390/ijms21124506] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 06/18/2020] [Accepted: 06/22/2020] [Indexed: 12/12/2022] Open
Abstract
Nucleophagy, the selective subtype of autophagy that targets nuclear material for autophagic degradation, was not only shown to be a model system for the study of selective macroautophagy, but also for elucidating the role of the core autophagic machinery within microautophagy. Nucleophagy also emerged as a system associated with a variety of disease conditions including cancer, neurodegeneration and ageing. Nucleophagic processes are part of natural cell development, but also act as a response to various stress conditions. Upon releasing small portions of nuclear material, micronuclei, the autophagic machinery transfers these micronuclei to the vacuole for subsequent degradation. Despite sharing many cargos and requiring the core autophagic machinery, recent investigations revealed the aspects that set macro- and micronucleophagy apart. Central to the discrepancies found between macro- and micronucleophagy is the nucleus vacuole junction, a large membrane contact site formed between nucleus and vacuole. Exclusion of nuclear pore complexes from the junction and its exclusive degradation by micronucleophagy reveal compositional differences in cargo. Regarding their shared reliance on the core autophagic machinery, micronucleophagy does not involve normal autophagosome biogenesis observed for macronucleophagy, but instead maintains a unique role in overall microautophagy, with the autophagic machinery accumulating at the neck of budding vesicles.
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20
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Gatica D, Wen X, Cheong H, Klionsky DJ. Vac8 determines phagophore assembly site vacuolar localization during nitrogen starvation-induced autophagy. Autophagy 2020; 17:1636-1648. [PMID: 32508216 DOI: 10.1080/15548627.2020.1776474] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Macroautophagy/autophagy is a key catabolic process in which different cellular components are sequestered inside double-membrane vesicles called autophagosomes for subsequent degradation. In yeast, autophagosome formation occurs at the phagophore assembly site (PAS), a specific perivacuolar location that works as an organizing center for the recruitment of different autophagy-related (Atg) proteins. How the PAS is localized to the vacuolar periphery is not well understood. Here we show that the vacuolar membrane protein Vac8 is required for correct vacuolar localization of the PAS. We provide evidence that Vac8 anchors the PAS to the vacuolar membrane by binding Atg13 and recruiting the Atg1 initiation complex. VAC8 deletion or mislocalization of the protein reduce autophagy activity, highlighting the importance of both the PAS and the correct vacuolar localization of the Atg1 initiation complex for efficient and robust autophagy.Abbreviations: AID: auxin-inducible degradation; Atg: autophagy-related; Cvt: cytoplasm-to-vacuole targeting; DMSO: dimethyl sulfoxide; ER: endoplasmic reticulum; GFP: green fluorescent protein; IAA: 3-indole acetic acid; PAS: phagophore assembly site; RFP: red fluorescent protein.
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Affiliation(s)
- Damian Gatica
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.,Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Xin Wen
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.,Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Heesun Cheong
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Daniel J Klionsky
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.,Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
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21
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Munzel L, Neumann P, Otto FB, Krick R, Metje-Sprink J, Kroppen B, Karedla N, Enderlein J, Meinecke M, Ficner R, Thumm M. Atg21 organizes Atg8 lipidation at the contact of the vacuole with the phagophore. Autophagy 2020; 17:1458-1478. [PMID: 32515645 DOI: 10.1080/15548627.2020.1766332] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Coupling of Atg8 to phosphatidylethanolamine is crucial for the expansion of the crescent-shaped phagophore during cargo engulfment. Atg21, a PtdIns3P-binding beta-propeller protein, scaffolds Atg8 and its E3-like complex Atg12-Atg5-Atg16 during lipidation. The crystal structure of Atg21, in complex with the Atg16 coiled-coil domain, showed its binding at the bottom side of the Atg21 beta-propeller. Our structure allowed detailed analyses of the complex formation of Atg21 with Atg16 and uncovered the orientation of the Atg16 coiled-coil domain with respect to the membrane. We further found that Atg21 was restricted to the phagophore edge, near the vacuole, known as the vacuole isolation membrane contact site (VICS). We identified a specialized vacuolar subdomain at the VICS, typical of organellar contact sites, where the membrane protein Vph1 was excluded, while Vac8 was concentrated. Furthermore, Vac8 was required for VICS formation. Our results support a specialized organellar contact involved in controlling phagophore elongation. Abbreviations: FCCS: fluorescence cross correlation spectroscopy; NVJ: nucleus-vacuole junction; PAS: phagophore assembly site; PE: phosphatidylethanolamine; PROPPIN: beta-propeller that binds phosphoinositides; PtdIns3P: phosphatidylinositol- 3-phosphate; VICS: vacuole isolation membrane contact site.
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Affiliation(s)
- Lena Munzel
- Department of Cellular Biochemistry, University Medicine, Goettingen, Germany
| | - Piotr Neumann
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, University of Goettingen, Goettingen, Germany
| | - Florian B Otto
- Department of Cellular Biochemistry, University Medicine, Goettingen, Germany
| | - Roswitha Krick
- Department of Cellular Biochemistry, University Medicine, Goettingen, Germany
| | - Janina Metje-Sprink
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Goettingen, Germany
| | - Benjamin Kroppen
- Department of Cellular Biochemistry, University Medicine, Goettingen, Germany
| | - Narain Karedla
- Physics Department III, University of Goettingen, Goettingen, Germany
| | - Jörg Enderlein
- Physics Department III, University of Goettingen, Goettingen, Germany
| | - Michael Meinecke
- Department of Cellular Biochemistry, University Medicine, Goettingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, University of Goettingen, Goettingen, Germany
| | - Michael Thumm
- Department of Cellular Biochemistry, University Medicine, Goettingen, Germany
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22
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Gatica D, Damasio A, Pascual C, Klionsky DJ, Ragusa MJ, Popelka H. The carboxy terminus of yeast Atg13 binds phospholipid membrane via motifs that overlap with the Vac8-interacting domain. Autophagy 2020; 16:1007-1020. [PMID: 31352862 PMCID: PMC7469566 DOI: 10.1080/15548627.2019.1648117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 07/15/2019] [Accepted: 07/22/2019] [Indexed: 10/26/2022] Open
Abstract
Macroautophagy/autophagy is a conserved catabolic recycling pathway involving the sequestration of cytoplasmic components within double-membrane vesicles termed autophagosomes. The autophagy-related (Atg) protein Atg13 is a key member of the autophagy initiation complex. The Atg13 C terminus is an intrinsically disordered region (IDR) harboring a binding site for the vacuolar membrane protein Vac8. Recent reports suggest Atg13 acts as a hub to assemble the initiation complex, and also participates in membrane recognition. Here we show that the Atg13 C terminus directly binds to lipid membranes via electrostatic interactions between positively charged residues in Atg13 and negatively charged phospholipids as well as a hydrophobic insertion of a Phe residue. We identified 2 sets of residues in the Atg13 IDR that affect its phospholipid-binding properties; these residues overlap with the Vac8-binding domain of Atg13. Our data indicate that Atg13 binding to phospholipids and Vac8 is mutually exclusive, and both are required for efficient autophagy. ABBREVIATIONS Atg: autophagy-related; CD: circular dichroism; Cvt: cytoplasm-to-vacuole targeting; IDR: intrinsically disordered region; ITC: isothermal calorimetry; MIM: MIT-interacting motif; MKO: multiple-knockout; PAS: phagophore assembly site; PC: phosphatidylcholine; PS: phosphatidylserine; PtdIns: phosphatidylinositol; PtdIns3P: phosphatidylinositol-3-phosphate.
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Affiliation(s)
- Damián Gatica
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | | | - Clarence Pascual
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Daniel J. Klionsky
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | | | - Hana Popelka
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
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23
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Kohler V, Aufschnaiter A, Büttner S. Closing the Gap: Membrane Contact Sites in the Regulation of Autophagy. Cells 2020; 9:E1184. [PMID: 32397538 PMCID: PMC7290522 DOI: 10.3390/cells9051184] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 04/29/2020] [Accepted: 05/07/2020] [Indexed: 12/14/2022] Open
Abstract
In all eukaryotic cells, intracellular organization and spatial separation of incompatible biochemical processes is established by individual cellular subcompartments in form of membrane-bound organelles. Virtually all of these organelles are physically connected via membrane contact sites (MCS), allowing interorganellar communication and a functional integration of cellular processes. These MCS coordinate the exchange of diverse metabolites and serve as hubs for lipid synthesis and trafficking. While this of course indirectly impacts on a plethora of biological functions, including autophagy, accumulating evidence shows that MCS can also directly regulate autophagic processes. Here, we focus on the nexus between interorganellar contacts and autophagy in yeast and mammalian cells, highlighting similarities and differences. We discuss MCS connecting the ER to mitochondria or the plasma membrane, crucial for early steps of both selective and non-selective autophagy, the yeast-specific nuclear-vacuolar tethering system and its role in microautophagy, the emerging function of distinct autophagy-related proteins in organellar tethering as well as novel MCS transiently emanating from the growing phagophore and mature autophagosome.
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Affiliation(s)
- Verena Kohler
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden;
| | - Andreas Aufschnaiter
- Department of Biochemistry and Biophysics, Stockholm University, 106 91 Stockholm, Sweden;
| | - Sabrina Büttner
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91 Stockholm, Sweden;
- Institute of Molecular Biosciences, University of Graz, 8010 Graz, Austria
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24
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Abstract
Mutations in human PAX6 gene are associated with various congenital eye malformations including aniridia, foveal hypoplasia, and congenital nystagmus. These various phenotypes may depend on the mutation spectrums that can affect DNA-binding affinity, although this hypothesis is debatable. We screened PAX6 mutations in two unrelated patients with congenital nystagmus, and measured DNA-binding affinity through isothermal titration calorimetry (ITC). To elucidate phenotypic differences according to DNA-binding affinity, we also compared DNA-binding affinity among the previously reported PAX6 missense mutations within the linker region between two subdomains of the paired domain (PD). We identified two novel mutations of PAX6 gene: c.214 G > T (p.Gly72Cys) and c.249_250delinsCGC (p.Val84Alafs*8). Both were located within the linker region between the two subdomains of the PD. ITC measurement revealed that the mutation p.Val84Alafs*8 had no DNA-binding affinity, while the p.Gly72Cys mutation showed a decreased binding affinity (Kd = 0.58 μM) by approximately 1.4 times compared to the wild type-PAX6 (Kd = 0.41 μM). We also found that there was no close relationship between DNA-binding affinity and phenotypic differences. Our results suggest that the DNA-binding affinity alone might be insufficient to determine PAX6-related phenotypes, and that other modifier genes or environmental factors might affect phenotypes of the PAX6 gene.
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25
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Fujioka Y, Alam JM, Noshiro D, Mouri K, Ando T, Okada Y, May AI, Knorr RL, Suzuki K, Ohsumi Y, Noda NN. Phase separation organizes the site of autophagosome formation. Nature 2020; 578:301-305. [PMID: 32025038 DOI: 10.1038/s41586-020-1977-6] [Citation(s) in RCA: 236] [Impact Index Per Article: 59.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 12/02/2019] [Indexed: 11/09/2022]
Abstract
Many biomolecules undergo liquid-liquid phase separation to form liquid-like condensates that mediate diverse cellular functions1,2. Autophagy is able to degrade such condensates using autophagosomes-double-membrane structures that are synthesized de novo at the pre-autophagosomal structure (PAS) in yeast3-5. Whereas Atg proteins that associate with the PAS have been characterized, the physicochemical and functional properties of the PAS remain unclear owing to its small size and fragility. Here we show that the PAS is in fact a liquid-like condensate of Atg proteins. The autophagy-initiating Atg1 complex undergoes phase separation to form liquid droplets in vitro, and point mutations or phosphorylation that inhibit phase separation impair PAS formation in vivo. In vitro experiments show that Atg1-complex droplets can be tethered to membranes via specific protein-protein interactions, explaining the vacuolar membrane localization of the PAS in vivo. We propose that phase separation has a critical, active role in autophagy, whereby it organizes the autophagy machinery at the PAS.
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Affiliation(s)
- Yuko Fujioka
- Institute of Microbial Chemistry (BIKAKEN), Tokyo, Japan
| | | | - Daisuke Noshiro
- Institute of Microbial Chemistry (BIKAKEN), Tokyo, Japan.,Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Kazunari Mouri
- Center for Biosystems Dynamics Research (BDR), RIKEN, Osaka, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kanazawa, Japan
| | - Yasushi Okada
- Center for Biosystems Dynamics Research (BDR), RIKEN, Osaka, Japan.,Department of Physics, Universal Biology Institute (UBI) and International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo, Japan
| | - Alexander I May
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan.,Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Roland L Knorr
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany.,Graduate School and Faculty of Medicine, The University of Tokyo, Tokyo, Japan.,Max Planck Institute of Molecular Plant Physiology, Potsdam, Germany
| | - Kuninori Suzuki
- Life Science Data Research Center, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Tokyo, Japan
| | - Yoshinori Ohsumi
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan
| | - Nobuo N Noda
- Institute of Microbial Chemistry (BIKAKEN), Tokyo, Japan.
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26
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Hollenstein DM, Gómez-Sánchez R, Ciftci A, Kriegenburg F, Mari M, Torggler R, Licheva M, Reggiori F, Kraft C. Vac8 spatially confines autophagosome formation at the vacuole in S. cerevisiae. J Cell Sci 2019; 132:jcs.235002. [PMID: 31649143 PMCID: PMC6899017 DOI: 10.1242/jcs.235002] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 10/01/2019] [Indexed: 01/02/2023] Open
Abstract
Autophagy is initiated by the formation of a phagophore assembly site (PAS), the precursor of autophagosomes. In mammals, autophagosome formation sites form throughout the cytosol in specialized subdomains of the endoplasmic reticulum (ER). In yeast, the PAS is also generated close to the ER, but always in the vicinity of the vacuole. How the PAS is anchored to the vacuole and the functional significance of this localization are unknown. Here, we investigated the role of the PAS–vacuole connection for bulk autophagy in the yeast Saccharomyces cerevisiae. We show that Vac8 constitutes a vacuolar tether that stably anchors the PAS to the vacuole throughout autophagosome biogenesis via the PAS component Atg13. S. cerevisiae lacking Vac8 show inefficient autophagosome–vacuole fusion, and form fewer and smaller autophagosomes that often localize away from the vacuole. Thus, the stable PAS–vacuole connection established by Vac8 creates a confined space for autophagosome biogenesis between the ER and the vacuole, and allows spatial coordination of autophagosome formation and autophagosome–vacuole fusion. These findings reveal that the spatial regulation of autophagosome formation at the vacuole is required for efficient bulk autophagy. Highlighted Article: Vac8 tethers the phagophore assembly site to the vacuole, which creates a confined space for autophagosome biogenesis and coordinates autophagosome formation with vacuolar fusion.
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Affiliation(s)
- David M Hollenstein
- Department of Biochemistry and Cell Biology, Max Perutz Labs, University of Vienna, Vienna BioCenter, Dr. Bohr-Gasse 9, 1030 Vienna, Austria
| | - Rubén Gómez-Sánchez
- Department of Biomedical Sciences of Cells & Systems, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands
| | - Akif Ciftci
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Franziska Kriegenburg
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany
| | - Muriel Mari
- Department of Biomedical Sciences of Cells & Systems, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands
| | - Raffaela Torggler
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Mariya Licheva
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany
| | - Fulvio Reggiori
- Department of Biomedical Sciences of Cells & Systems, University of Groningen, University Medical Center Groningen, 9713 AV Groningen, The Netherlands
| | - Claudine Kraft
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, 79104 Freiburg, Germany .,CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg
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Park J, Kim HI, Jeong H, Lee M, Jang SH, Yoon SY, Kim H, Park ZY, Jun Y, Lee C. Quaternary structures of Vac8 differentially regulate the Cvt and PMN pathways. Autophagy 2019; 16:991-1006. [PMID: 31512555 PMCID: PMC7469494 DOI: 10.1080/15548627.2019.1659615] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Armadillo (ARM) repeat proteins constitute a large protein family with diverse and fundamental functions in all organisms, and armadillo repeat domains share high structural similarity. However, exactly how these structurally similar proteins can mediate diverse functions remains a long-standing question. Vac8 (vacuole related 8) is a multifunctional protein that plays pivotal roles in various autophagic pathways, including piecemeal microautophagy of the nucleus (PMN) and cytoplasm-to-vacuole targeting (Cvt) pathways in the budding yeast Saccharomyces cerevisiae. Vac8 comprises an H1 helix at the N terminus, followed by 12 armadillo repeats. Herein, we report the crystal structure of Vac8 bound to Atg13, a key component of autophagic machinery. The 70-Å extended loop of Atg13 binds to the ARM domain of Vac8 in an antiparallel manner. Structural, biochemical, and in vivo experiments demonstrated that the H1 helix of Vac8 intramolecularly associates with the first ARM and regulates its self-association, which is crucial for Cvt and PMN pathways. The structure of H1 helix-deleted Vac8 complexed with Atg13 reveals that Vac8[Δ19–33]-Atg13 forms a heterotetramer and adopts an extended superhelical structure exclusively employed in the Cvt pathway. Most importantly, comparison of Vac8-Nvj1 and Vac8-Atg13 provides a molecular understanding of how a single ARM domain protein adopts different quaternary structures depending on its associated proteins to differentially regulate 2 closely related but distinct cellular pathways. Abbreviations Ape1: aminopeptidase I; ARM: armadillo repeat; Atg: autophagy-related; AUC: analytical ultracentrifugation; Cvt: cytoplasm-to-vacuole targeting; DIC: differential interference contrast; GFP: green fluorescent protein; GST: glutathione-S-transferase; ITC: isothermal titration calorimetry; NVJ: nucleus-vacuole junction; PDB: protein data bank; PMN: piecemeal microautophagy of the nucleus; prApe1: precursor Ape1; RMSD: root-mean-square deviation; SAXS: small-angle X-ray scattering; SD-N: nitrogen starvation medium; SEC: size-exclusion chromatography; tAtg13: Atg13 construct comprising residues 567–695; tNvj1: Nvj1 construct comprising residues 229–321; tVac8: Vac8 construct comprising residues 10–515; Vac8: vacuole related 8
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Affiliation(s)
- Jumi Park
- Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Hye-In Kim
- Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea.,School of Life Sciences, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Hanbin Jeong
- Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Miriam Lee
- Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea.,School of Life Sciences, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Se Hwan Jang
- School of Life Sciences, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - So Young Yoon
- Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea.,School of Life Sciences, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Hyejin Kim
- Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Zee-Yong Park
- School of Life Sciences, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Youngsoo Jun
- Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea.,School of Life Sciences, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
| | - Changwook Lee
- Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology , Ulsan, Republic of Korea.,Cell Logistics Research Center, Gwangju Institute of Science and Technology , Gwangju, Republic of Korea
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28
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Vac8 Controls Vacuolar Membrane Dynamics during Different Autophagy Pathways in Saccharomyces cerevisiae. Cells 2019; 8:cells8070661. [PMID: 31262095 PMCID: PMC6678646 DOI: 10.3390/cells8070661] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 06/21/2019] [Accepted: 06/28/2019] [Indexed: 01/08/2023] Open
Abstract
The yeast vacuole is a vital organelle, which is required for the degradation of aberrant intracellular or extracellular substrates and the recycling of the resulting nutrients as newly available building blocks for the cellular metabolism. Like the plant vacuole or the mammalian lysosome, the yeast vacuole is the destination of biosynthetic trafficking pathways that transport the vacuolar enzymes required for its functions. Moreover, substrates destined for degradation, like extracellular endocytosed cargoes that are transported by endosomes/multivesicular bodies as well as intracellular substrates that are transported via different forms of autophagosomes, have the vacuole as destination. We found that non-selective bulk autophagy of cytosolic proteins as well as the selective autophagic degradation of peroxisomes (pexophagy) and ribosomes (ribophagy) was dependent on the armadillo repeat protein Vac8 in Saccharomyces cerevisiae. Moreover, we showed that pexophagy and ribophagy depended on the palmitoylation of Vac8. In contrast, we described that Vac8 was not involved in the acidification of the vacuole nor in the targeting and maturation of certain biosynthetic cargoes, like the aspartyl-protease Pep4 (PrA) and the carboxy-peptidase Y (CPY), indicating a role of Vac8 in the uptake of selected cargoes. In addition, we found that the hallmark phenotype of the vac8Δ strain, namely the characteristic appearance of fragmented and clustered vacuoles, depended on the growth conditions. This fusion defect observed in standard glucose medium can be complemented by the replacement with oleic acid or glycerol medium. This complementation of vacuolar morphology also partially restores the degradation of peroxisomes. In summary, we found that Vac8 controlled vacuolar morphology and activity in a context- and cargo-dependent manner.
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Bingol B. Autophagy and lysosomal pathways in nervous system disorders. Mol Cell Neurosci 2018; 91:167-208. [PMID: 29729319 DOI: 10.1016/j.mcn.2018.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Revised: 04/26/2018] [Accepted: 04/28/2018] [Indexed: 12/12/2022] Open
Abstract
Autophagy is an evolutionarily conserved pathway for delivering cytoplasmic cargo to lysosomes for degradation. In its classically studied form, autophagy is a stress response induced by starvation to recycle building blocks for essential cellular processes. In addition, autophagy maintains basal cellular homeostasis by degrading endogenous substrates such as cytoplasmic proteins, protein aggregates, damaged organelles, as well as exogenous substrates such as bacteria and viruses. Given their important role in homeostasis, autophagy and lysosomal machinery are genetically linked to multiple human disorders such as chronic inflammatory diseases, cardiomyopathies, cancer, and neurodegenerative diseases. Multiple targets within the autophagy and lysosomal pathways offer therapeutic opportunities to benefit patients with these disorders. Here, I will summarize the mechanisms of autophagy pathways, the evidence supporting a pathogenic role for disturbed autophagy and lysosomal degradation in nervous system disorders, and the therapeutic potential of autophagy modulators in the clinic.
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Affiliation(s)
- Baris Bingol
- Genentech, Inc., Department of Neuroscience, 1 DNA Way, South San Francisco 94080, United States.
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