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Lee C, Lepore D, Lee SH, Kim TG, Buwa N, Lee J, Munson M, Yoon TY. Exocyst stimulates multiple steps of exocytic SNARE complex assembly and vesicle fusion. Nat Struct Mol Biol 2024:10.1038/s41594-024-01388-2. [PMID: 39242980 DOI: 10.1038/s41594-024-01388-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 08/13/2024] [Indexed: 09/09/2024]
Abstract
Exocyst is a large multisubunit tethering complex essential for targeting and fusion of secretory vesicles in eukaryotic cells. Although the assembled exocyst complex has been proposed to tether vesicles to the plasma membrane and activate soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) for membrane fusion, the key biochemical steps that exocyst stimulates in SNARE-mediated fusion are undetermined. Here we use a combination of single-molecule and bulk fluorescence assays to investigate the roles of purified octameric yeast exocyst complexes in a reconstituted yeast exocytic SNARE assembly and vesicle fusion system. Exocyst had stimulatory roles in multiple distinct steps ranging from SNARE protein activation to binary and ternary complex assembly. Importantly, exocyst had a downstream role in driving membrane fusion and full content mixing of vesicle lumens. Our data suggest that exocyst provides extensive chaperoning functions across the entire process of SNARE complex assembly and fusion, thereby governing exocytosis at multiple steps.
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Affiliation(s)
- Chanwoo Lee
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul, South Korea
| | - Dante Lepore
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Seung-Hak Lee
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul, South Korea
| | - Tae Gyun Kim
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul, South Korea
| | - Natasha Buwa
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Jongchan Lee
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul, South Korea
| | - Mary Munson
- Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Medical School, Worcester, MA, USA.
| | - Tae-Young Yoon
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul, South Korea.
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DAmico KA, Stanton AE, Shirkey JD, Travis SM, Jeffrey PD, Hughson FM. Structure of a membrane tethering complex incorporating multiple SNAREs. Nat Struct Mol Biol 2024; 31:246-254. [PMID: 38196032 PMCID: PMC10923073 DOI: 10.1038/s41594-023-01164-8] [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: 01/14/2023] [Accepted: 10/26/2023] [Indexed: 01/11/2024]
Abstract
Most membrane fusion reactions in eukaryotic cells are mediated by multisubunit tethering complexes (MTCs) and SNARE proteins. MTCs are much larger than SNAREs and are thought to mediate the initial attachment of two membranes. Complementary SNAREs then form membrane-bridging complexes whose assembly draws the membranes together for fusion. Here we present a cryo-electron microscopy structure of the simplest known MTC, the 255-kDa Dsl1 complex of Saccharomyces cerevisiae, bound to the two SNAREs that anchor it to the endoplasmic reticulum. N-terminal domains of the SNAREs form an integral part of the structure, stabilizing a Dsl1 complex configuration with unexpected similarities to the 850-kDa exocyst MTC. The structure of the SNARE-anchored Dsl1 complex and its comparison with exocyst reveal what are likely to be common principles underlying MTC function. Our structure also implies that tethers and SNAREs can work together as a single integrated machine.
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Affiliation(s)
- Kevin A DAmico
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Abigail E Stanton
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Jaden D Shirkey
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Sophie M Travis
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Philip D Jeffrey
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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Stanton AE, Hughson FM. The machinery of vesicle fusion. Curr Opin Cell Biol 2023; 83:102191. [PMID: 37421936 PMCID: PMC10529041 DOI: 10.1016/j.ceb.2023.102191] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 06/01/2023] [Accepted: 06/07/2023] [Indexed: 07/10/2023]
Abstract
The compartmentalization of eukaryotic cells is reliant on the fidelity of vesicle-mediated intracellular transport. Vesicles deliver their cargo via membrane fusion, a process requiring membrane tethers, Sec1/Munc18 (SM) proteins, and SNAREs. These components function in concert to ensure that membrane fusion is efficient and accurate, but the mechanisms underlying their cooperative action are still in many respects mysterious. In this brief review, we highlight recent progress toward a more integrative understanding of the vesicle fusion machinery. We focus particular attention on cryo-electron microscopy structures of intact multisubunit tethers in complex with SNAREs or SM proteins, as well as a structure of an SM protein bound to multiple SNAREs. The insights gained from this work emphasize the advantages of studying the fusion machinery intact and in context.
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Affiliation(s)
- Abigail E Stanton
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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Foltman M, Mendez I, Bech-Serra JJ, de la Torre C, Brace JL, Weiss EL, Lucas M, Queralt E, Sanchez-Diaz A. TOR complex 1 negatively regulates NDR kinase Cbk1 to control cell separation in budding yeast. PLoS Biol 2023; 21:e3002263. [PMID: 37647291 PMCID: PMC10468069 DOI: 10.1371/journal.pbio.3002263] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 07/19/2023] [Indexed: 09/01/2023] Open
Abstract
The target of rapamycin (TOR) signalling pathway plays a key role in the coordination between cellular growth and the cell cycle machinery in eukaryotes. The underlying molecular mechanisms by which TOR might regulate events after anaphase remain unknown. We show for the first time that one of the 2 TOR complexes in budding yeast, TORC1, blocks the separation of cells following cytokinesis by phosphorylation of a member of the NDR (nuclear Dbf2-related) protein-kinase family, the protein Cbk1. We observe that TORC1 alters the phosphorylation pattern of Cbk1 and we identify a residue within Cbk1 activation loop, T574, for which a phosphomimetic substitution makes Cbk1 catalytically inactive and, indeed, reproduces TORC1 control over cell separation. In addition, we identify the exocyst component Sec3 as a key substrate of Cbk1, since Sec3 activates the SNARE complex to promote membrane fusion. TORC1 activity ultimately compromises the interaction between Sec3 and a t-SNARE component. Our data indicate that TORC1 negatively regulates cell separation in budding yeast by participating in Cbk1 phosphorylation, which in turn controls the fusion of secretory vesicles transporting hydrolase at the site of division.
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Affiliation(s)
- Magdalena Foltman
- Mechanisms and Regulation of Cell Division Research Unit, Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, Santander, Spain
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain
| | - Iván Mendez
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain
- Structural Biology of Macromolecular Complexes Research Unit, Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, Santander, Spain
| | - Joan J. Bech-Serra
- Josep Carreras Leukaemia Research Institute, IJC Building, Campus ICO-Germans Trias i Pujol, Barcelona, Spain
| | - Carolina de la Torre
- Josep Carreras Leukaemia Research Institute, IJC Building, Campus ICO-Germans Trias i Pujol, Barcelona, Spain
| | - Jennifer L. Brace
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois, United States of America
| | - Eric L. Weiss
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois, United States of America
| | - María Lucas
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain
- Structural Biology of Macromolecular Complexes Research Unit, Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, Santander, Spain
| | - Ethel Queralt
- Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain
| | - Alberto Sanchez-Diaz
- Mechanisms and Regulation of Cell Division Research Unit, Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC, Santander, Spain
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain
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Khakurel A, Lupashin VV. Role of GARP Vesicle Tethering Complex in Golgi Physiology. Int J Mol Sci 2023; 24:6069. [PMID: 37047041 PMCID: PMC10094427 DOI: 10.3390/ijms24076069] [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: 02/22/2023] [Revised: 03/17/2023] [Accepted: 03/19/2023] [Indexed: 04/14/2023] Open
Abstract
The Golgi associated retrograde protein complex (GARP) is an evolutionarily conserved component of Golgi membrane trafficking machinery that belongs to the Complexes Associated with Tethering Containing Helical Rods (CATCHR) family. Like other multisubunit tethering complexes such as COG, Dsl1, and Exocyst, the GARP is believed to function by tethering and promoting fusion of the endosome-derived small trafficking intermediate. However, even twenty years after its discovery, the exact structure and the functions of GARP are still an enigma. Recent studies revealed novel roles for GARP in Golgi physiology and identified human patients with mutations in GARP subunits. In this review, we summarized our knowledge of the structure of the GARP complex, its protein partners, GARP functions related to Golgi physiology, as well as cellular defects associated with the dysfunction of GARP subunits.
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Affiliation(s)
| | - Vladimir V. Lupashin
- Department of Physiology and Cell Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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DAmico KA, Stanton AE, Shirkey JD, Travis SM, Jeffrey PD, Hughson FM. Structure of a Membrane Tethering Complex Incorporating Multiple SNAREs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.30.526244. [PMID: 36778436 PMCID: PMC9915479 DOI: 10.1101/2023.01.30.526244] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Most membrane fusion reactions in eukaryotic cells are mediated by membrane tethering complexes (MTCs) and SNARE proteins. MTCs are much larger than SNAREs and are thought to mediate the initial attachment of two membranes. Complementary SNAREs then form membrane-bridging complexes whose assembly draws the membranes together for fusion. Here, we present a cryo-EM structure of the simplest known MTC, the 255-kDa Dsl1 complex, bound to the two SNAREs that anchor it to the endoplasmic reticulum. N-terminal domains of the SNAREs form an integral part of the structure, stabilizing a Dsl1 complex configuration with remarkable and unexpected similarities to the 850-kDa exocyst MTC. The structure of the SNARE-anchored Dsl1 complex and its comparison with exocyst reveal what are likely to be common principles underlying MTC function. Our structure also implies that tethers and SNAREs can work together as a single integrated machine.
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Affiliation(s)
- Kevin A DAmico
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Abigail E Stanton
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Jaden D Shirkey
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Sophie M Travis
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Philip D Jeffrey
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
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