1
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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 2025; 32:150-160. [PMID: 39242980 DOI: 10.1038/s41594-024-01388-2] [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: 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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2
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Meek S, Hernandez AC, Oliva B, Gallego O. The exocyst in context. Biochem Soc Trans 2024; 52:2113-2122. [PMID: 39377315 PMCID: PMC11555703 DOI: 10.1042/bst20231401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2024] [Revised: 09/06/2024] [Accepted: 09/09/2024] [Indexed: 10/09/2024]
Abstract
The exocyst is a hetero-octameric complex involved in the exocytosis arm of cellular trafficking. Specifically, it tethers secretory vesicles to the plasma membrane, but it is also a main convergence point for many players of exocytosis: regulatory proteins, motor proteins, lipids and Soluble N-ethylmaleimide-sensitive factor Attachment Protein Receptor (SNARE) proteins are all connected physically by the exocyst. Despite extensive knowledge about its structure and interactions, the exocyst remains an enigma precisely because of its increasingly broad and flexible role across the exocytosis process. To solve the molecular mechanism of such a multi-tasking complex, dynamical structures with self, other proteins, and environment should be described. And to do this, interrogation within contexts increasingly close to native conditions is needed. Here we provide a perspective on how different experimental contexts have been used to study the exocyst, and those that could be used in the future. This review describes the structural breakthroughs on the isolated in vitro exocyst, followed by the use of membrane reconstitution assays for revealing in vitro exocyst functionality. Next, it moves to in situ cell contexts, reviewing imaging techniques that have been, and that ideally could be, used to look for near-native structure and organization dynamics. Finally, it looks at the exocyst structure in situ within evolutionary contexts, and the potential of structure prediction therein. From in vitro, to in situ, cross-context investigation of exocyst structure has begun, and will be critical for functional mechanism elucidation.
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Affiliation(s)
- Sasha Meek
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Altair C. Hernandez
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Baldomero Oliva
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
| | - Oriol Gallego
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona 08003, Spain
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3
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Zuriegat Q, Abubakar YS, Wang Z, Chen M, Zhang J. Emerging Roles of Exocyst Complex in Fungi: A Review. J Fungi (Basel) 2024; 10:614. [PMID: 39330374 PMCID: PMC11433146 DOI: 10.3390/jof10090614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2024] [Revised: 08/19/2024] [Accepted: 08/21/2024] [Indexed: 09/28/2024] Open
Abstract
The exocyst complex, an evolutionarily conserved octameric protein assembly, plays a central role in the targeted binding and fusion of vesicles at the plasma membrane. In fungal cells, this transport system is essential for polarized growth, morphogenesis, cell wall maintenance and virulence. Recent advances have greatly improved our understanding of the role and regulation of the exocyst complex in fungi. This review synthesizes these developments and focuses on the intricate interplay between the exocyst complex, specific fungal cargos and regulatory proteins. Insights into thestructure of the exocyst and its functional dynamics have revealed new dimensions of its architecture and its interactions with the cellular environment. Furthermore, the regulation of exocyst activity involves complex signaling pathways and interactions with cytoskeletal elements that are crucial for its role in vesicle trafficking. By exploring these emerging themes, this review provides a comprehensive overview of the multifaceted functions of the exocyst complex in fungal biology. Understanding these mechanisms offers potential avenues for novel therapeutic strategies against fungal pathogens and insights into the general principles of vesicle trafficking in eukaryotic cells. The review therefore highlights the importance of the exocyst complex in maintaining cellular functions and its broader implications in fungal pathogenicity and cell biology.
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Affiliation(s)
- Qussai Zuriegat
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
| | - Yakubu Saddeeq Abubakar
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
| | - Zonghua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, College of Materials and Chemical Engineering, Minjiang University, Fuzhou 350108, China
| | - Meilian Chen
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, College of Materials and Chemical Engineering, Minjiang University, Fuzhou 350108, China
| | - Jun Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
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4
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Duan M, Plemel RL, Takenaka T, Lin A, Delgado BM, Nattermann U, Nickerson DP, Mima J, Miller EA, Merz AJ. SNARE chaperone Sly1 directly mediates close-range vesicle tethering. J Cell Biol 2024; 223:e202001032. [PMID: 38478018 PMCID: PMC10943277 DOI: 10.1083/jcb.202001032] [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: 01/16/2020] [Revised: 12/20/2023] [Accepted: 02/22/2024] [Indexed: 03/17/2024] Open
Abstract
The essential Golgi protein Sly1 is a member of the Sec1/mammalian Unc-18 (SM) family of SNARE chaperones. Sly1 was originally identified through remarkable gain-of-function alleles that bypass requirements for diverse vesicle tethering factors. Employing genetic analyses and chemically defined reconstitutions of ER-Golgi fusion, we discovered that a loop conserved among Sly1 family members is not only autoinhibitory but also acts as a positive effector. An amphipathic lipid packing sensor (ALPS)-like helix within the loop directly binds high-curvature membranes. Membrane binding is required for relief of Sly1 autoinhibition and also allows Sly1 to directly tether incoming vesicles to the Qa-SNARE on the target organelle. The SLY1-20 mutation bypasses requirements for diverse tethering factors but loses this ability if the tethering activity is impaired. We propose that long-range tethers, including Golgins and multisubunit tethering complexes, hand off vesicles to Sly1, which then tethers at close range to initiate trans-SNARE complex assembly and fusion in the early secretory pathway.
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Affiliation(s)
- Mengtong Duan
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Rachael L. Plemel
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | | | - Ariel Lin
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Department of Biology, California State University, San Bernardino, CA, USA
| | | | - Una Nattermann
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Biophysics, Structure, and Design Graduate Program, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | | | - Joji Mima
- Institute for Protein Research, Osaka University, Osaka, Japan
| | | | - Alexey J. Merz
- Department of Biochemistry, University of Washington, Seattle, WA, USA
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5
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More KJ, Kaur H, Simpson AGB, Spiegel FW, Dacks JB. Contractile vacuoles: a rapidly expanding (and occasionally diminishing?) understanding. Eur J Protistol 2024; 94:126078. [PMID: 38688044 DOI: 10.1016/j.ejop.2024.126078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 03/18/2024] [Accepted: 03/20/2024] [Indexed: 05/02/2024]
Abstract
Osmoregulation is the homeostatic mechanism essential for the survival of organisms in hypoosmotic and hyperosmotic conditions. In freshwater or soil dwelling protists this is frequently achieved through the action of an osmoregulatory organelle, the contractile vacuole. This endomembrane organelle responds to the osmotic challenges and compensates by collecting and expelling the excess water to maintain the cellular osmolarity. As compared with other endomembrane organelles, this organelle is underappreciated and under-studied. Here we review the reported presence or absence of contractile vacuoles across eukaryotic diversity, as well as the observed variability in the structure, function, and molecular machinery of this organelle. Our findings highlight the challenges and opportunities for constructing cellular and evolutionary models for this intriguing organelle.
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Affiliation(s)
- Kiran J More
- Division of Infectious Diseases, Department of Medicine, and Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Harpreet Kaur
- Division of Infectious Diseases, Department of Medicine, and Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Alastair G B Simpson
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada; Department of Biology, Dalhousie University, Halifax, NS, Canada
| | - Frederick W Spiegel
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Joel B Dacks
- Division of Infectious Diseases, Department of Medicine, and Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada; Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic; Centre for Life's Origins and Evolution, Department of Genetics, Evolution, & Environment, University College, London, United Kingdom.
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6
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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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7
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Georgiou X, Dimou S, Diallinas G, Samiotaki M. The interactome of the UapA transporter reveals putative new players in anterograde membrane cargo trafficking. Fungal Genet Biol 2023; 169:103840. [PMID: 37730157 DOI: 10.1016/j.fgb.2023.103840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 09/01/2023] [Accepted: 09/15/2023] [Indexed: 09/22/2023]
Abstract
Neosynthesized plasma membrane (PM) proteins co-translationally translocate to the ER, concentrate at regions called ER-exit sites (ERes) and pack into COPII secretory vesicles which are sorted to the early-Golgi through membrane fusion. Following Golgi maturation, membrane cargoes reach the late-Golgi, from where they exit in clathrin-coated vesicles destined to the PM, directly or through endosomes. Post-Golgi membrane cargo trafficking also involves the cytoskeleton and the exocyst. The Golgi-dependent secretory pathway is thought to be responsible for the trafficking of all major membrane proteins. However, our recent findings in Aspergillus nidulans showed that several plasma membrane cargoes, such as transporters and receptors, follow a sorting route that seems to bypass Golgi functioning. To gain insight on membrane trafficking and specifically Golgi-bypass, here we used proximity dependent biotinylation (PDB) coupled with data-independent acquisition mass spectrometry (DIA-MS) for identifying transient interactors of the UapA transporter. Our assays, which included proteomes of wild-type and mutant strains affecting ER-exit or endocytosis, identified both expected and novel interactions that might be physiologically relevant to UapA trafficking. Among those, we validated, using reverse genetics and fluorescence microscopy, that COPI coatomer is essential for ER-exit and anterograde trafficking of UapA and other membrane cargoes. We also showed that ArfAArf1 GTPase activating protein (GAP) Glo3 contributes to UapA trafficking at increased temperature. This is the first report addressing the identification of transient interactions during membrane cargo biogenesis using PDB and proteomics coupled with fungal genetics. Our work provides a basis for dissecting dynamic membrane cargo trafficking via PDB assays.
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Affiliation(s)
- Xenia Georgiou
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece
| | - Sofia Dimou
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece; Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion 70013, Greece.
| | - Martina Samiotaki
- Biomedical Sciences Research Center "Alexander Fleming", Institute for Bioinnovation, Vari 16672, Greece.
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8
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Fan T, Fan Y, Yang Y, Qian D, Niu Y, An L, Xiang Y. SEC1A and SEC6 synergistically regulate pollen tube polar growth. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2023. [PMID: 36951316 DOI: 10.1111/jipb.13486] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 03/21/2023] [Indexed: 06/18/2023]
Abstract
Pollen tube polar growth is a key physiological activity for angiosperms to complete double fertilization, which is highly dependent on the transport of polar substances mediated by secretory vesicles. The exocyst and Sec1/Munc18 (SM) proteins are involved in the regulation of the tethering and fusion of vesicles and plasma membranes, but the molecular mechanism by which they regulate pollen tube polar growth is still unclear. In this study, we found that loss of function of SEC1A, a member of the SM protein family in Arabidopsis thaliana, resulted in reducing pollen tube growth and a significant increase in pollen tube width. SEC1A was diffusely distributed in the pollen tube cytoplasm, and was more concentrated at the tip of the pollen tube. Through co-immunoprecipitation-mass spectrometry screening, protein interaction analysis and in vivo microscopy, we found that SEC1A interacted with the exocyst subunit SEC6, and they mutually affected the distribution and secretion rate at the tip of the pollen tube. Meanwhile, the functional loss of SEC1A and SEC6 significantly affected the distribution of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex member SYP125 at the tip of the pollen tube, and led to the disorder of pollen tube cell wall components. Genetic analysis revealed that the pollen tube-related phenotype of the sec1a sec6 double mutant was significantly enhanced compared with their respective single mutants. Therefore, we speculated that SEC1A and SEC6 cooperatively regulate the fusion of secretory vesicles and plasma membranes in pollen tubes, thereby affecting the length and the width of pollen tubes.
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Affiliation(s)
- Tingting Fan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yuemin Fan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yang Yang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Dong Qian
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yue Niu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Lizhe An
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
| | - Yun Xiang
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China
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9
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Miller BK, Rossi G, Hudson S, Cully D, Baker RW, Brennwald P. Allosteric regulation of exocyst: Discrete activation of tethering by two spatial signals. J Cell Biol 2023; 222:213852. [PMID: 36729146 PMCID: PMC9929655 DOI: 10.1083/jcb.202206108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 11/17/2022] [Accepted: 01/05/2023] [Indexed: 02/03/2023] Open
Abstract
The exocyst imparts spatial control during exocytic vesicle tethering through its interactions with proteins and lipids on the vesicle and the plasma membrane. One such interaction is with the vesicle tether Sro7, although the outcome of this interaction is poorly understood. Here, we describe how Sro7 binding to the Exo84 subunit results in activation of the exocyst complex which leads to an increase in avidity for the Rab GTPase Sec4 and an increase in exocyst-mediated vesicle tethering. Gain-of-function (GOF) mutations in Exo84 that mimic Sro7 activation replicate these biochemical changes and result in allosteric changes within the complex. Direct comparison of GOF mutants which mimic Sro7- and Rho/Cdc42-activation of the exocyst reveals distinct mechanisms and outcomes. We propose a model by which these two activation pathways reside within the same tethering complex but remain insulated from one another. Structural modeling suggests a related mechanism for Sro7 activation of the exocyst in yeast and Ral GTPase activation of the exocyst in animal cells.
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Affiliation(s)
- Brittany K. Miller
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Guendalina Rossi
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Sara Hudson
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - David Cully
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Richard W. Baker
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Patrick Brennwald
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA,Correspondence to Patrick Brennwald:
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10
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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: 1.0] [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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11
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Gingras RM, Sulpizio AM, Park J, Bretscher A. High-resolution secretory timeline from vesicle formation at the Golgi to fusion at the plasma membrane in S. cerevisiae. eLife 2022; 11:e78750. [PMID: 36331188 PMCID: PMC9671497 DOI: 10.7554/elife.78750] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 11/03/2022] [Indexed: 11/06/2022] Open
Abstract
Most of the components in the yeast secretory pathway have been studied, yet a high-resolution temporal timeline of their participation is lacking. Here, we define the order of acquisition, lifetime, and release of critical components involved in late secretion from the Golgi to the plasma membrane. Of particular interest is the timing of the many reported effectors of the secretory vesicle Rab protein Sec4, including the myosin-V Myo2, the exocyst complex, the lgl homolog Sro7, and the small yeast-specific protein Mso1. At the trans-Golgi network (TGN) Sec4's GEF, Sec2, is recruited to Ypt31-positive compartments, quickly followed by Sec4 and Myo2 and vesicle formation. While transported to the bud tip, the entire exocyst complex, including Sec3, is assembled on to the vesicle. Before fusion, vesicles tether for 5 s, during which the vesicle retains the exocyst complex and stimulates lateral recruitment of Rho3 on the plasma membrane. Sec2 and Myo2 are rapidly lost, followed by recruitment of cytosolic Sro7, and finally the SM protein Sec1, which appears for just 2 s prior to fusion. Perturbation experiments reveal an ordered and robust series of events during tethering that provide insights into the function of Sec4 and effector exchange.
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Affiliation(s)
- Robert M Gingras
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
| | - Abigail M Sulpizio
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
| | - Joelle Park
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
| | - Anthony Bretscher
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell UniversityIthacaUnited States
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12
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Li PH, He JY, Cai YJ, Wei YS, Zhu XL, Yang JDH, Yang SQ, Zhou S, Qin QW, Sun HY. Molecular cloning, inducible expression and function analysis of Epinephelus coioides Sec6 response to SGIV infection. FISH & SHELLFISH IMMUNOLOGY 2022; 124:462-471. [PMID: 35483595 DOI: 10.1016/j.fsi.2022.04.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Revised: 03/19/2022] [Accepted: 04/21/2022] [Indexed: 06/14/2023]
Abstract
Exocyst complex component 3 Sec6 of mammals, one of the components of the exocyst complex, participates in numerous cellular functions, such as promoting cell migration and inhibiting apoptosis. In this study, the Sec6 was obtained from Epinephelus coioides, an economically important cultured fish. The full length of E. coioides Sec6 was 2655 bp including a 245 bp 5' UTR, a 154 bp 3' UTR, and a 2256 bp open reading frame (ORF) encoding 751 amino acids, with a molecular mass of 86.76 kDa and a theoretical pI of 5.57. Sec6 mRNA was detected in all the tissues examined, but the expression level is different in these tissues. Using fluorescence microscopy, Sec6 were distributed in both the nucleus and the cytoplasm. After SGIV infection, the expression of E. coioides Sec6 was significantly up-regulated in both trunk kidney and spleen response to Singapore grouper iridovirus (SGIV), an important pathogens of E. coioides. Sec6 could increase the SGIV-induced cytopathic effects (CPE), the expression of the SGIV genes VP19, LITAF, MCP, ICP18 and MCP, and the viral titers. Besides, E. coioides Sec6 significantly downregulated the promoter of NF-κB and AP-1, and inhibited the SGIV-induced apoptosis. The results demonstrated that E. coioides Sec6 might play important roles in SGIV infection.
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Affiliation(s)
- Pin-Hong Li
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China; Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, PR China
| | - Jia-Yang He
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China
| | - Yi-Jie Cai
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China
| | - Yu-Si Wei
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China
| | - Xiang-Long Zhu
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China
| | - Jia-Deng-Hui Yang
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China
| | - Shi-Qi Yang
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China
| | - Sheng Zhou
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China; Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, PR China
| | - Qi-Wei Qin
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China; Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, PR China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266000, PR China; Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, PR China.
| | - Hong-Yan Sun
- University Joint Laboratory of Guangdong Province, Hong Kong and Macao Region on Marine Bioresource Conservation and Exploitation, College of Marine Sciences, South China Agricultural University, Guangzhou, 510642, PR China; Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510642, PR China.
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13
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Wang S, Ma C. Neuronal SNARE complex assembly guided by Munc18-1 and Munc13-1. FEBS Open Bio 2022; 12:1939-1957. [PMID: 35278279 PMCID: PMC9623535 DOI: 10.1002/2211-5463.13394] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Revised: 02/28/2022] [Accepted: 03/10/2022] [Indexed: 01/25/2023] Open
Abstract
Neurotransmitter release by Ca2+ -triggered synaptic vesicle exocytosis is essential for information transmission in the nervous system. The soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) syntaxin-1, SNAP-25, and synaptobrevin-2 form the SNARE complex to bring synaptic vesicles and the plasma membranes together and to catalyze membrane fusion. Munc18-1 and Munc13-1 regulate synaptic vesicle priming via orchestrating neuronal SNARE complex assembly. In this review, we summarize recent advances toward the functions and molecular mechanisms of Munc18-1 and Munc13-1 in guiding neuronal SNARE complex assembly, and discuss the functional similarities and differences between Munc18-1 and Munc13-1 in neurons and their homologs in other intracellular membrane trafficking systems.
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Affiliation(s)
- Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
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14
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Pang L, Ma Z, Zhang X, Huang Y, Li R, Miao Y, Li R. The small GTPase RABA2a recruits SNARE proteins to regulate the secretory pathway in parallel with the exocyst complex in Arabidopsis. MOLECULAR PLANT 2022; 15:398-418. [PMID: 34798312 DOI: 10.1016/j.molp.2021.11.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 10/24/2021] [Accepted: 11/12/2021] [Indexed: 05/22/2023]
Abstract
Delivery of proteins to the plasma membrane occurs via secretion, which requires tethering, docking, priming, and fusion of vesicles. In yeast and mammalian cells, an evolutionarily conserved RAB GTPase activation cascade functions together with the exocyst and SNARE proteins to coordinate vesicle transport with fusion at the plasma membrane. However, it is unclear whether this is the case in plants. In this study, we show that the small GTPase RABA2a recruits and interacts with the VAMP721/722-SYP121-SNAP33 SNARE ternary complex for membrane fusion. Through immunoprecipitation coupled with mass spectrometry analysis followed by the validatation with a series of biochemical assays, we identified the SNARE proteins VAMP721 and SYP121 as the interactors and downstream effectors of RABA2a. Further expreiments showed that RABA2a interacts with all members of the SNARE complex in its GTP-bound form and modulates the assembly of the VAMP721/722-SYP121-SNAP33 SNARE ternary complex. Intriguingly, we did not observe the interaction of the exocyst subunits with either RABA2a or theSNARE proteins in several different experiments. Neither RABA2a inactivation affects the subcellular localization or assembly of the exocystnor the exocyst subunit mutant exo84b shows the disrupted RABA2a-SNARE association or SNARE assembly, suggesting that the RABA2a-SNARE- and exocyst-mediated secretory pathways are largely independent. Consistently, our live imaging experiments reveal that the two sets of proteins follow non-overlapping trafficking routes, and genetic and cell biologyanalyses indicate that the two pathways select different cargos. Finally, we demonstrate that the plant-specific RABA2a-SNARE pathway is essential for the maintenance of potassium homeostasis in Arabisopsis seedlings. Collectively, our findings imply that higher plants might have generated different endomembrane sorting pathways during evolution and may enable the highly conserved endomembrane proteins to participate in plant-specific trafficking mechanisms for adaptation to the changing environment.
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Affiliation(s)
- Lei Pang
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Zhiming Ma
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Xi Zhang
- College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China
| | - Yuanzhi Huang
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Ruili Li
- College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China
| | - Yansong Miao
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Ruixi Li
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China.
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15
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Mielnicka A, Michaluk P. Exocytosis in Astrocytes. Biomolecules 2021; 11:1367. [PMID: 34572580 PMCID: PMC8471187 DOI: 10.3390/biom11091367] [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: 08/16/2021] [Revised: 09/10/2021] [Accepted: 09/14/2021] [Indexed: 12/17/2022] Open
Abstract
Until recently, astrocytes were thought to be a part of a simple "brain glue" providing only a supporting role for neurons. However, the discoveries of the last two decades have proven astrocytes to be dynamic partners participating in brain metabolism and actively influencing communication between neurons. The means of astrocyte-neuron communication are diverse, although regulated exocytosis has received the most attention but also caused the most debate. Similar to most of eukaryotic cells, astrocytes have a complex range of vesicular organelles which can undergo exocytosis as well as intricate molecular mechanisms that regulate this process. In this review, we focus on the components needed for regulated exocytosis to occur and summarise the knowledge about experimental evidence showing its presence in astrocytes.
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Affiliation(s)
| | - Piotr Michaluk
- BRAINCITY, Laboratory of Neurobiology, The Nencki Institute of Experimental Biology, PAS, 02-093 Warsaw, Poland;
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16
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Plasma membrane phospholipid signature recruits the plant exocyst complex via the EXO70A1 subunit. Proc Natl Acad Sci U S A 2021; 118:2105287118. [PMID: 34470819 DOI: 10.1073/pnas.2105287118] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polarized exocytosis is essential for many vital processes in eukaryotic cells, where secretory vesicles are targeted to distinct plasma membrane domains characterized by their specific lipid-protein composition. Heterooctameric protein complex exocyst facilitates the vesicle tethering to a target membrane and is a principal cell polarity regulator in eukaryotes. The architecture and molecular details of plant exocyst and its membrane recruitment have remained elusive. Here, we show that the plant exocyst consists of two modules formed by SEC3-SEC5-SEC6-SEC8 and SEC10-SEC15-EXO70-EXO84 subunits, respectively, documenting the evolutionarily conserved architecture within eukaryotes. In contrast to yeast and mammals, the two modules are linked by a plant-specific SEC3-EXO70 interaction, and plant EXO70 functionally dominates over SEC3 in the exocyst recruitment to the plasma membrane. Using an interdisciplinary approach, we found that the C-terminal part of EXO70A1, the canonical EXO70 isoform in Arabidopsis, is critical for this process. In contrast to yeast and animal cells, the EXO70A1 interaction with the plasma membrane is mediated by multiple anionic phospholipids uniquely contributing to the plant plasma membrane identity. We identified several evolutionary conserved EXO70 lysine residues and experimentally proved their importance for the EXO70A1-phospholipid interactions. Collectively, our work has uncovered plant-specific features of the exocyst complex and emphasized the importance of the specific protein-lipid code for the recruitment of peripheral membrane proteins.
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17
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Abstract
SNARE proteins and Sec1/Munc18 (SM) proteins constitute the core molecular engine that drives nearly all intracellular membrane fusion and exocytosis. While SNAREs are known to couple their folding and assembly to membrane fusion, the physiological pathways of SNARE assembly and the mechanistic roles of SM proteins have long been enigmatic. Here, we review recent advances in understanding the SNARE-SM fusion machinery with an emphasis on biochemical and biophysical studies of proteins that mediate synaptic vesicle fusion. We begin by discussing the energetics, pathways, and kinetics of SNARE folding and assembly in vitro. Then, we describe diverse interactions between SM and SNARE proteins and their potential impact on SNARE assembly in vivo. Recent work provides strong support for the idea that SM proteins function as chaperones, their essential role being to enable fast, accurate SNARE assembly. Finally, we review the evidence that SM proteins collaborate with other SNARE chaperones, especially Munc13-1, and briefly discuss some roles of SNARE and SM protein deficiencies in human disease.
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Affiliation(s)
- Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520, USA;
| | - Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA;
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18
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Fais M, Sanna G, Galioto M, Nguyen TTD, Trần MUT, Sini P, Carta F, Turrini F, Xiong Y, Dawson TM, Dawson VL, Crosio C, Iaccarino C. LRRK2 Modulates the Exocyst Complex Assembly by Interacting with Sec8. Cells 2021; 10:203. [PMID: 33498474 PMCID: PMC7909581 DOI: 10.3390/cells10020203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 01/12/2021] [Accepted: 01/18/2021] [Indexed: 11/17/2022] Open
Abstract
Mutations in LRRK2 play a critical role in both familial and sporadic Parkinson's disease (PD). Up to date, the role of LRRK2 in PD onset and progression remains largely unknown. However, experimental evidence highlights a critical role of LRRK2 in the control of vesicle trafficking, likely by Rab phosphorylation, that in turn may regulate different aspects of neuronal physiology. Here we show that LRRK2 interacts with Sec8, one of eight subunits of the exocyst complex. The exocyst complex is an evolutionarily conserved multisubunit protein complex mainly involved in tethering secretory vesicles to the plasma membrane and implicated in the regulation of multiple biological processes modulated by vesicle trafficking. Interestingly, Rabs and exocyst complex belong to the same protein network. Our experimental evidence indicates that LRRK2 kinase activity or the presence of the LRRK2 kinase domain regulate the assembly of exocyst subunits and that the over-expression of Sec8 significantly rescues the LRRK2 G2019S mutant pathological effect. Our findings strongly suggest an interesting molecular mechanism by which LRRK2 could modulate vesicle trafficking and may have important implications to decode the complex role that LRRK2 plays in neuronal physiology.
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Affiliation(s)
- Milena Fais
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Giovanna Sanna
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Manuela Galioto
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Thi Thanh Duyen Nguyen
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Mai Uyên Thi Trần
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Paola Sini
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | | | - Franco Turrini
- Nurex Srl, 07100 Sassari, Italy; (F.C.); (F.T.)
- Department of Oncology, University of Turin, 10126 Turin, Italy
| | - Yulan Xiong
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ted M. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Valina L. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Claudia Crosio
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Ciro Iaccarino
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
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19
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Chen F, Amgalan D, Kitsis RN, Pessin JE, Feng D. ATG16L1 autophagy pathway regulates BAX protein levels and programmed cell death. J Biol Chem 2020; 295:15045-15053. [PMID: 32848017 PMCID: PMC7606669 DOI: 10.1074/jbc.ra120.013999] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 08/20/2020] [Indexed: 01/05/2023] Open
Abstract
Previously we reported that adipocyte SNAP23 (synaptosome-associated protein of 23 kDa) deficiency blocks the activation of macroautophagy, leading to an increased abundance of BAX, a pro-death Bcl-2 family member, and activation and adipocyte cell death both in vitro and in vivo Here, we found that knockdown of SNAP23 inhibited the association of the autophagosome regulators ATG16L1 and ATG9 compartments by nutrient depletion and reduced the formation of ATG16L1 membrane puncta. ATG16L1 knockdown inhibited autophagy flux and increased BAX protein levels by suppressing BAX degradation. The elevation in BAX protein had no effect on BAX activation or cell death in the nutrient-replete state. However, following nutrient depletion, BAX was activated with a concomitant induction of cell death. Co-immunoprecipitation analyses demonstrated that SNAP23 and ATG16L1 proteins form a stable complex independent of nutrient condition, whereas in the nutrient-depleted state, BAX binds to SNAP23 to form a ternary BAX-SNAP23-ATG16L1 protein complex. Taken together, these data support a model in which SNAP23 plays a crucial function as a scaffold for ATG16L1 necessary for the suppression of BAX activation and induction of the intrinsic cell death program.
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Affiliation(s)
- Fenfen Chen
- Fleischer Institute of Diabetes and Metabolism, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Dulguun Amgalan
- Fleischer Institute of Diabetes and Metabolism, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Richard N. Kitsis
- Fleischer Institute of Diabetes and Metabolism, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA,Einstein-Mount Sinai Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York, USA,Wilf Family Cardiovascular Research Center, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Jeffrey E. Pessin
- Fleischer Institute of Diabetes and Metabolism, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York, USA,Einstein-Mount Sinai Diabetes Research Center, Albert Einstein College of Medicine, Bronx, New York, USA,Wilf Family Cardiovascular Research Center, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Daorong Feng
- Fleischer Institute of Diabetes and Metabolism, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA,Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York, USA,For correspondence: Daorong Feng,
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20
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Rossi G, Lepore D, Kenner L, Czuchra AB, Plooster M, Frost A, Munson M, Brennwald P. Exocyst structural changes associated with activation of tethering downstream of Rho/Cdc42 GTPases. J Cell Biol 2020; 219:133563. [PMID: 31904797 PMCID: PMC7041683 DOI: 10.1083/jcb.201904161] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 07/26/2019] [Accepted: 11/19/2019] [Indexed: 12/16/2022] Open
Abstract
The exocyst complex plays a critical role in determining both temporal and spatial dynamics of exocytic vesicle tethering and fusion with the plasma membrane. However, the mechanism by which the exocyst functions and how it is regulated remain poorly understood. Here we describe a novel biochemical assay for the examination of exocyst function in vesicle tethering. Importantly, the assay is stimulated by gain-of-function mutations in the Exo70 component of the exocyst, selected for their ability to bypass Rho/Cdc42 activation in vivo. Single-particle electron microscopy and 3D reconstructions of negatively stained exocyst complexes reveal a structural change in the mutant exocyst that exposes a binding site for the v-SNARE. We demonstrate a v-SNARE requirement in our tethering assay and increased v-SNARE binding to exocyst gain-of-function complexes. Together, these data suggest an allosteric mechanism for activation involving a conformational change in one subunit of the complex, which is relayed through the complex to regulate its biochemical activity in vitro, as well as overall function in vivo.
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Affiliation(s)
- Guendalina Rossi
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC
| | - Dante Lepore
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA
| | - Lillian Kenner
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA
| | - Alexander B Czuchra
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA
| | - Melissa Plooster
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC
| | - Adam Frost
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA.,Chan Zuckerberg Biohub, University of California, San Francisco, San Francisco, CA.,California Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA
| | - Patrick Brennwald
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC
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21
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Larson ER, Ortmannová J, Donald NA, Alvim J, Blatt MR, Žárský V. Synergy among Exocyst and SNARE Interactions Identifies a Functional Hierarchy in Secretion during Vegetative Growth. THE PLANT CELL 2020; 32:2951-2963. [PMID: 32699172 PMCID: PMC7474273 DOI: 10.1105/tpc.20.00280] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 06/23/2020] [Accepted: 07/20/2020] [Indexed: 05/28/2023]
Abstract
Vesicle exocytosis underpins signaling and development in plants and is vital for cell expansion. Vesicle tethering and fusion are thought to occur sequentially, with tethering mediated by the exocyst and fusion driven by assembly of soluble NSF attachment protein receptor (SNARE) proteins from the vesicle membrane (R-SNAREs or vesicle-associated membrane proteins [VAMPs]) and the target membrane (Q-SNAREs). Interactions between exocyst and SNARE protein complexes are known, but their functional consequences remain largely unexplored. We now identify a hierarchy of interactions leading to secretion in Arabidopsis (Arabidopsis thaliana). Mating-based split-ubiquitin screens and in vivo Förster resonance energy transfer analyses showed that exocyst EXO70 subunits bind preferentially to cognate plasma membrane SNAREs, notably SYP121 and VAMP721. The exo70A1 mutant affected SNARE distribution and suppressed vesicle traffic similarly to the dominant-negative truncated protein SYP121ΔC, which blocks secretion at the plasma membrane. These phenotypes are consistent with the epistasis of exo70A1 in the exo70A1 syp121 double mutant, which shows decreased growth similar to exo70A1 single mutants. However, the exo70A1 vamp721 mutant showed a strong, synergy, suppressing growth and cell expansion beyond the phenotypic sum of the two single mutants. These data are best explained by a hierarchy of SNARE recruitment to the exocyst at the plasma membrane, dominated by the R-SNARE and plausibly with the VAMP721 longin domain as a nexus for binding.
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Affiliation(s)
- Emily R Larson
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Jitka Ortmannová
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02 Prague 6, Czech Republic
| | - Naomi A Donald
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Jonas Alvim
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Michael R Blatt
- Laboratory of Plant Physiology and Biophysics, Bower Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Viktor Žárský
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 165 02 Prague 6, Czech Republic
- Department of Experimental Plant Biology, Faculty of Science, Charles University, 128 44 Prague 2, Czech Republic
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22
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Wang X, Gong J, Zhu L, Wang S, Yang X, Xu Y, Yang X, Ma C. Munc13 activates the Munc18-1/syntaxin-1 complex and enables Munc18-1 to prime SNARE assembly. EMBO J 2020; 39:e103631. [PMID: 32643828 PMCID: PMC7429736 DOI: 10.15252/embj.2019103631] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 05/20/2020] [Accepted: 06/02/2020] [Indexed: 11/09/2022] Open
Abstract
Priming of synaptic vesicles involves Munc13-catalyzed transition of the Munc18-1/syntaxin-1 complex to the SNARE complex in the presence of SNAP-25 and synaptobrevin-2; Munc13 drives opening of syntaxin-1 via the MUN domain while Munc18-1 primes SNARE assembly via domain 3a. However, the underlying mechanism remains unclear. In this study, we have identified a number of residues in domain 3a of Munc18-1 that are crucial for Munc13 and Munc18-1 actions in SNARE complex assembly and synaptic vesicle priming. Our results showed that two residues (Q301/K308) at the side of domain 3a mediate the interaction between the Munc18-1/syntaxin-1 complex and the MUN domain. This interaction enables the MUN domain to drive the opening of syntaxin-1 linker region, thereby leading to the extension of domain 3a and promoting synaptobrevin-2 binding. In addition, we identified two residues (K332/K333) at the bottom of domain 3a that mediate the interaction between Munc18-1 and the SNARE motif of syntaxin-1. This interaction ensures Munc18-1 to persistently associate with syntaxin-1 during the conformational change of syntaxin-1 from closed to open, which reinforces the role of Munc18-1 in templating SNARE assembly. Taken together, our data suggest a mechanism by which Munc13 activates the Munc18-1/syntaxin-1 complex and enables Munc18-1 to prime SNARE assembly.
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Affiliation(s)
- Xianping Wang
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Jihong Gong
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Le Zhu
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Shen Wang
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Xiaoyu Yang
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Yuanyuan Xu
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
| | - Xiaofei Yang
- Key Laboratory of Cognitive ScienceHubei Key Laboratory of Medical Information Analysis and Tumor Diagnosis & TreatmentLaboratory of Membrane Ion Channels and MedicineCollege of Biomedical EngineeringSouth‐Central University for NationalitiesWuhanChina
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of EducationCollege of Life Science and TechnologyHuazhong University of Science and TechnologyWuhanChina
- Institute of Brain ResearchHuazhong University of Science and TechnologyWuhanChina
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23
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Gerien KS, Zhang S, Russell AC, Zhu YH, Purde V, Wu JQ. Roles of Mso1 and the SM protein Sec1 in efficient vesicle fusion during fission yeast cytokinesis. Mol Biol Cell 2020; 31:1570-1583. [PMID: 32432970 PMCID: PMC7521796 DOI: 10.1091/mbc.e20-01-0067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Membrane trafficking during cytokinesis is essential for the delivery of membrane lipids and cargoes to the division site. However, the molecular mechanisms are still incompletely understood. In this study, we demonstrate the importance of uncharacterized fission yeast proteins Mso1 and Sec1 in membrane trafficking during cytokinesis. Fission yeast Mso1 shares homology with budding yeast Mso1 and human Mint1, proteins that interact with Sec1/Munc18 family proteins during vesicle fusion. Sec1/Munc18 proteins and their interactors are important regulators of SNARE complex formation during vesicle fusion. The roles of these proteins in vesicle trafficking during cytokinesis have been barely studied. Here, we show that fission yeast Mso1 is also a Sec1-binding protein and Mso1 and Sec1 localize to the division site interdependently during cytokinesis. The loss of Sec1 localization in mso1Δ cells results in a decrease in vesicle fusion and cytokinesis defects such as slow ring constriction, defective ring disassembly, and delayed plasma membrane closure. We also find that Mso1 and Sec1 may have functions independent of the exocyst tethering complex on the plasma membrane at the division site. Together, Mso1 and Sec1 play essential roles in regulating vesicle fusion and cargo delivery at the division site during cytokinesis.
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Affiliation(s)
- Kenneth S Gerien
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210.,Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Sha Zhang
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Alexandra C Russell
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Yi-Hua Zhu
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Vedud Purde
- Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210.,Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | - Jian-Qiu Wu
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210.,Department of Biological Chemistry and Pharmacology, The Ohio State University, Columbus, OH 43210
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24
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Ganesan SJ, Feyder MJ, Chemmama IE, Fang F, Rout MP, Chait BT, Shi Y, Munson M, Sali A. Integrative structure and function of the yeast exocyst complex. Protein Sci 2020; 29:1486-1501. [PMID: 32239688 DOI: 10.1002/pro.3863] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 12/13/2022]
Abstract
Exocyst is an evolutionarily conserved hetero-octameric tethering complex that plays a variety of roles in membrane trafficking, including exocytosis, endocytosis, autophagy, cell polarization, cytokinesis, pathogen invasion, and metastasis. Exocyst serves as a platform for interactions between the Rab, Rho, and Ral small GTPases, SNARE proteins, and Sec1/Munc18 regulators that coordinate spatial and temporal fidelity of membrane fusion. However, its mechanism is poorly described at the molecular level. Here, we determine the molecular architecture of the yeast exocyst complex by an integrative approach, based on a 3D density map from negative-stain electron microscopy (EM) at ~16 Å resolution, 434 disuccinimidyl suberate and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride cross-links from chemical-crosslinking mass spectrometry, and partial atomic models of the eight subunits. The integrative structure is validated by a previously determined cryo-EM structure, cross-links, and distances from in vivo fluorescence microscopy. Our subunit configuration is consistent with the cryo-EM structure, except for Sec5. While not observed in the cryo-EM map, the integrative model localizes the N-terminal half of Sec3 near the Sec6 subunit. Limited proteolysis experiments suggest that the conformation of Exo70 is dynamic, which may have functional implications for SNARE and membrane interactions. This study illustrates how integrative modeling based on varied low-resolution structural data can inform biologically relevant hypotheses, even in the absence of high-resolution data.
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Affiliation(s)
- Sai J Ganesan
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA.,Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
| | - Michael J Feyder
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Ilan E Chemmama
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA.,Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
| | - Fei Fang
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, New York, USA
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, New York, USA
| | - Yi Shi
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA.,Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
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25
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Torng T, Song H, Wickner W. Asymmetric Rab activation of vacuolar HOPS to catalyze SNARE complex assembly. Mol Biol Cell 2020; 31:1060-1068. [PMID: 32160129 PMCID: PMC7346727 DOI: 10.1091/mbc.e20-01-0019] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Intracellular membrane fusion requires Rab-family GTPases, their effector tethers, soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, and SNARE chaperones of the Sec1/Munc18 (SM), Sec17/α-SNAP, and Sec18/NSF families. We have developed an assay using fluorescence resonance energy transfer to measure SNARE complex formation in real time. We now show that yeast vacuolar SNAREs assemble spontaneously into RQaQbQc complexes when the R- and Qa-SNAREs are concentrated in the same micelles or in cis on the same membrane. When SNAREs are free in solution or are tethered to distinct membranes, assembly requires catalysis by HOPS, the vacuolar SM and tethering complex. The Rab Ypt7 and vacuole lipids together allosterically activate the bound HOPS for catalyzing SNARE assembly, even if none of the SNAREs are membrane bound. HOPS-dependent fusion between proteoliposomes bearing R- or Qa-SNAREs shows a strict requirement for Ypt7 on the R-SNARE proteoliposomes but not on the Qa-SNARE proteoliposomes. This asymmetry is reflected in the strikingly different capacity of Ypt7 in cis to either the R- or Qa-SNARE to stimulate SNARE complex assembly. Membrane-bound Ypt7 activates HOPS to catalyze 4-SNARE complex assembly when it is on the same membrane as the R-SNARE but not the Qa-SNARE, thus explaining the asymmetric need for Ypt7 for fusion.
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Affiliation(s)
- Thomas Torng
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Hongki Song
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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26
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Glomb O, Wu Y, Rieger L, Rüthnick D, Mulaw MA, Johnsson N. The cell polarity proteins Boi1 and Boi2 direct an actin nucleation complex to sites of exocytosis in Saccharomyces cerevisiae. J Cell Sci 2020; 133:jcs.237982. [PMID: 31964708 DOI: 10.1242/jcs.237982] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 12/19/2019] [Indexed: 01/13/2023] Open
Abstract
Owing to the local enrichment of factors that influence its dynamics and organization, the actin cytoskeleton displays different shapes and functions within the same cell. In yeast cells, post-Golgi vesicles ride on long actin cables to the bud tip. The proteins Boi1 and Boi2 (Boi1/2) participate in tethering and docking these vesicles to the plasma membrane. Here, we show in Saccharomyces cerevisiae that Boi1/2 also recruit nucleation and elongation factors to form actin filaments at sites of exocytosis. Disrupting the connection between Boi1/2 and the nucleation factor Bud6 impairs filament formation, reduces the directed movement of the vesicles to the tip and shortens the vesicles' tethering time at the cortex. Transplanting Boi1 from the bud tip to the peroxisomal membrane partially redirects the actin cytoskeleton and the vesicular flow towards the peroxisome, and creates an alternative, rudimentary vesicle-docking zone. We conclude that Boi1/2, through interactions with Bud6 and Bni1, induce the formation of a cortical actin structure that receives and aligns incoming vesicles before fusion with the membrane.
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Affiliation(s)
- Oliver Glomb
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Yehui Wu
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Lucia Rieger
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Diana Rüthnick
- ZMBH, University of Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany
| | - Medhanie A Mulaw
- Comprehensive Cancer Center Ulm, Institute of Experimental Cancer Research, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Nils Johnsson
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
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27
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Žárský V, Sekereš J, Kubátová Z, Pečenková T, Cvrčková F. Three subfamilies of exocyst EXO70 family subunits in land plants: early divergence and ongoing functional specialization. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:49-62. [PMID: 31647563 DOI: 10.1093/jxb/erz423] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 10/10/2019] [Indexed: 05/27/2023]
Abstract
Localized delivery of plasma membrane and cell wall components is an essential process in all plant cells. The vesicle-tethering complex, the exocyst, an ancient eukaryotic hetero-octameric protein cellular module, assists in targeted delivery of exocytosis vesicles to specific plasma membrane domains. Analyses of Arabidopsis and later other land plant genomes led to the surprising prediction of multiple putative EXO70 exocyst subunit paralogues. All land plant EXO70 exocyst subunits (including those of Bryophytes) form three distinct subfamilies-EXO70.1, EXO70.2, and EXO70.3. Interestingly, while the basal well-conserved EXO70.1 subfamily consists of multiexon genes, the remaining two subfamilies contain mostly single exon genes. Published analyses as well as public transcriptomic and proteomic data clearly indicate that most cell types in plants express and also use several different EXO70 isoforms. Here we sum up recent advances in the characterization of the members of the family of plant EXO70 exocyst subunits and present evidence that members of the EXO70.2 subfamily are often recruited to non-canonical functions in plant membrane trafficking pathways. Engagement of the most evolutionarily dynamic EXO70.2 subfamily of EXO70s in biotic interactions and defence correlates well with massive proliferation and conservation of new protein variants in this subfamily.
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Affiliation(s)
- Viktor Žárský
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová, Prague, Czech Republic
| | - Juraj Sekereš
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová, Prague, Czech Republic
| | - Zdeňka Kubátová
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
| | - Tamara Pečenková
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
- Institute of Experimental Botany, v.v.i., Czech Academy of Sciences, Rozvojová, Prague, Czech Republic
| | - Fatima Cvrčková
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Viničná, Prague, Czech Republic
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28
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Wang S, Crisman L, Miller J, Datta I, Gulbranson DR, Tian Y, Yin Q, Yu H, Shen J. Inducible Exoc7/Exo70 knockout reveals a critical role of the exocyst in insulin-regulated GLUT4 exocytosis. J Biol Chem 2019; 294:19988-19996. [PMID: 31740584 PMCID: PMC6937574 DOI: 10.1074/jbc.ra119.010821] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/13/2019] [Indexed: 12/20/2022] Open
Abstract
Insulin promotes glucose uptake by triggering the translocation of glucose transporter type 4 (GLUT4) from intracellular vesicles to the plasma membrane through exocytosis. GLUT4 exocytosis is a vesicle fusion event involving fusion of GLUT4-containing vesicles with the plasma membrane. For GLUT4 vesicle fusion to occur, GLUT4 vesicles must first be tethered to the plasma membrane. A key tethering factor in exocytosis is a heterooctameric protein complex called the exocyst. The role of the exocyst in GLUT4 exocytosis, however, remains incompletely understood. Here we first systematically analyzed data from a genome-scale CRISPR screen in HeLa cells that targeted virtually all known genes in the human genome, including 12 exocyst genes. The screen recovered only a subset of the exocyst genes, including exocyst complex component 7 (Exoc7/Exo70). Other exocyst genes, however, were not isolated in the screen, likely because of functional redundancy. Our findings suggest that selection of an appropriate exocyst gene is critical for genetic studies of exocyst functions. Next we developed an inducible adipocyte genome editing system that enabled Exoc7 gene deletion in adipocytes without interfering with adipocyte differentiation. We observed that insulin-stimulated GLUT4 exocytosis was markedly inhibited in Exoc7 KO adipocytes. Insulin signaling, however, remained intact in these KO cells. These results indicate that the exocyst plays a critical role in insulin-stimulated GLUT4 exocytosis in adipocytes. We propose that the strategy outlined in this work could be instrumental in genetically dissecting other membrane-trafficking pathways in adipocytes.
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Affiliation(s)
- Shifeng Wang
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
- Department of Chinese Medicine Information Science, Beijing University of Chinese Medicine, Beijing 102488, China
| | - Lauren Crisman
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Jessica Miller
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Ishara Datta
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Daniel R Gulbranson
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Yuan Tian
- Department of Biological Sciences and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306
| | - Qian Yin
- Department of Biological Sciences and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida 32306
| | - Haijia Yu
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Jingshi Shen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
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29
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Saeed B, Brillada C, Trujillo M. Dissecting the plant exocyst. CURRENT OPINION IN PLANT BIOLOGY 2019; 52:69-76. [PMID: 31509792 DOI: 10.1016/j.pbi.2019.08.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/12/2019] [Accepted: 08/08/2019] [Indexed: 06/10/2023]
Abstract
The exocyst is an evolutionary conserved complex that mediates tethering of post-Golgi vesicles derived from the conventional secretory pathway to the plasma membrane (PM), before SNARE-mediated fusion. Through its tethering function, connecting secretory vesicles to the PM, it mediates spatiotemporal regulation of exocytosis. As an integral element of the secretory machinery, the exocyst has been implicated in a large variety of processes. However, emerging evidence suggests that it may also cater for unconventional secretory pathways, as well as autophagy. The exocyst entertains a multitude of interactions with proteins and membrane phospholipids, reflecting its highly dynamic nature and the complex regulatory processes that hardwire it with cellular signalling networks. However, our molecular understanding of this essential complex remains fragmentary. Here we review recent work focusing on the molecular features that have revealed both commonalities with yeast and animals, as well as unique characteristics of the plant exocyst.
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Affiliation(s)
- Bushra Saeed
- Albert-Ludwigs-University Freiburg, Faculty of Biology, Institute of Biology II, 79104 Freiburg, Germany
| | - Carla Brillada
- Albert-Ludwigs-University Freiburg, Faculty of Biology, Institute of Biology II, 79104 Freiburg, Germany
| | - Marco Trujillo
- Albert-Ludwigs-University Freiburg, Faculty of Biology, Institute of Biology II, 79104 Freiburg, Germany.
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30
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Boehm C, Field MC. Evolution of late steps in exocytosis: conservation and specialization of the exocyst complex. Wellcome Open Res 2019; 4:112. [PMID: 31633057 PMCID: PMC6784791 DOI: 10.12688/wellcomeopenres.15142.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2019] [Indexed: 01/09/2023] Open
Abstract
Background: The eukaryotic endomembrane system most likely arose via paralogous expansions of genes encoding proteins that specify organelle identity, coat complexes and govern fusion specificity. While the majority of these gene families were established by the time of the last eukaryotic common ancestor (LECA), subsequent evolutionary events has moulded these systems, likely reflecting adaptations retained for increased fitness. As well as sequence evolution, these adaptations include loss of otherwise canonical components, the emergence of lineage-specific proteins and paralog expansion. The exocyst complex is involved in late exocytosis and additional trafficking pathways and a member of the complexes associated with tethering containing helical rods (CATCHR) tethering complex family. CATCHR includes the conserved oligomeric Golgi (COG) complex, homotypic fusion and vacuole protein sorting (HOPS)/class C core vacuole/endosome tethering (CORVET) complexes and several others. The exocyst is integrated into a complex GTPase signalling network in animals, fungi and other lineages. Prompted by discovery of Exo99, a non-canonical subunit in the excavate protist Trypanosoma brucei, and availability of significantly increased genome sequence data, we re-examined evolution of the exocyst. Methods: We examined the evolution of exocyst components by comparative genomics, phylogenetics and structure prediction. Results: The exocyst composition is highly conserved, but with substantial losses of subunits in the Apicomplexa and expansions in Streptophyta plants, Metazoa and land plants, where for the latter, massive paralog expansion of Exo70 represents an extreme and unique example. Significantly, few taxa retain a partial complex, suggesting that, in general, all subunits are probably required for functionality. Further, the ninth exocyst subunit, Exo99, is specific to the Euglenozoa with a distinct architecture compared to the other subunits and which possibly represents a coat system. Conclusions: These data reveal a remarkable degree of evolutionary flexibility within the exocyst complex, suggesting significant diversity in exocytosis mechanisms.
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Affiliation(s)
- Cordula Boehm
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovic, 37005, Czech Republic
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31
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Cao S, Chen H, Liang X, Fu J, Wang S, Zheng J, Zhang Z, Pang Y, Wang J, Shen B, Jia H. The Sec1/Munc18-like proteins TgSec1 and TgVps45 play pivotal roles in assembly of the pellicle and sub-pellicle network in Toxoplasma gondii. Mol Microbiol 2019; 113:208-221. [PMID: 31670849 DOI: 10.1111/mmi.14411] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/28/2019] [Indexed: 12/28/2022]
Abstract
Post-Golgi vesicle trafficking is indispensable for precise movement of proteins to the pellicle, the sub-pellicle network and apical secretory organelles in Apicomplexa. However, only a small number of molecular complexes involved in trafficking, tethering and fusion of vesicles have been identified in Toxoplasma gondii. Consequently, it is unclear how complicated vesicle trafficking is accomplished in this parasite. Sec1/Munc18-like (SM) proteins are essential components of protein complexes involved in vesicle fusion. Here, we found that depletion of the SM protein TgSec1 using an auxin-inducible degron-based conditional knockout strategy led to mislocalization of plasma membrane proteins. By contrast, conditional depletion of the SM protein TgVps45 led to morphological changes, asymmetrical loss of the inner membrane complex and defects in nucleation of sub-pellicular microtubules, polarization and symmetrical assembly of daughter parasites during repeated endodyogeny. TgVps45 interacts with the SNARE protein TgStx16 and TgVAMP4-1. Conditional ablation of TgStx16 causes the similar growth defect like TgVps45 deficiency suggested they work together for the vesicle fusion at TGN. These findings indicate that these two SM proteins are crucial for assembly of pellicle and sub-pellicle network in T. gondii respectively.
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Affiliation(s)
- Shinuo Cao
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Heming Chen
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Xiaohan Liang
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, People's Republic of China
| | - Jiawen Fu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Shida Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Jun Zheng
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Zhaoxia Zhang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Yu Pang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Jingfei Wang
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
| | - Bang Shen
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei Province, People's Republic of China
| | - Honglin Jia
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, People's Republic of China
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32
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Boehm C, Field MC. Evolution of late steps in exocytosis: conservation, specialization. Wellcome Open Res 2019; 4:112. [PMID: 31633057 PMCID: PMC6784791 DOI: 10.12688/wellcomeopenres.15142.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/11/2019] [Indexed: 01/05/2025] Open
Abstract
Background: The eukaryotic endomembrane system likely arose via paralogous expansion of genes encoding proteins specifying organelle identity, coat complexes and government of fusion specificity. While the majority of these gene families were established by the time of the last eukaryotic common ancestor (LECA), subsequent evolutionary events molded these systems, likely reflecting adaptations retained for increased fitness. As well as sequence evolution, these adaptations include loss of otherwise canonical subunits, emergence of lineage-specific proteins and paralog expansion. The exocyst complex is involved in late exocytosis, and possibly additional pathways, and is a member of the complexes associated with tethering containing helical rods (CATCHR) tethering complex family, which includes conserved oligomeric Golgi (COG), homotypic fusion and vacuole protein sorting (HOPS), class C core vacuole/endosome tethering (CORVET) and others. The exocyst is integrated into a complex GTPase signaling network in animals, fungi and other lineages. Prompted by discovery of Exo99, a non-canonical subunit in the excavate protist Trypanosoma brucei, and significantly increased genome sequence data, we examined evolution of the exocyst. Methods: We examined evolution of the exocyst by comparative genomics, phylogenetics and structure prediction. Results: The exocyst is highly conserved, but with substantial losses of subunits in the Apicomplexa and expansions in Streptophyta plants and Metazoa. Significantly, few taxa retain a partial complex, suggesting that, in the main, all subunits are required for functionality. Further, the ninth exocyst subunit Exo99 is specific to the Euglenozoa with a distinct architecture compared to the other subunits and which possibly represents a coat system. Conclusions: These data reveal a remarkable degree of evolutionary flexibility within the exocyst complex, suggesting significant diversity in exocytosis mechanisms.
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Affiliation(s)
- Cordula Boehm
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovic, 37005, Czech Republic
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33
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Sáez JJ, Diaz J, Ibañez J, Bozo JP, Cabrera Reyes F, Alamo M, Gobert FX, Obino D, Bono MR, Lennon-Duménil AM, Yeaman C, Yuseff MI. The exocyst controls lysosome secretion and antigen extraction at the immune synapse of B cells. J Cell Biol 2019; 218:2247-2264. [PMID: 31197029 PMCID: PMC6605794 DOI: 10.1083/jcb.201811131] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 04/11/2019] [Accepted: 05/22/2019] [Indexed: 02/06/2023] Open
Abstract
BCR engagement enhances microtubule stability, which triggers the mobilization of Exo70 from the centrosome to the immune synapse. BCR engagement activates GEF-H1, which promotes exocyst assembly required for the docking and secretion of lysosomes, facilitating the extraction of surface-tethered antigens. B lymphocytes capture antigens from the surface of presenting cells by forming an immune synapse. Local secretion of lysosomes, which are guided to the synaptic membrane by centrosome repositioning, can facilitate the extraction of immobilized antigens. However, the molecular basis underlying their delivery to precise domains of the plasma membrane remains elusive. Here we show that microtubule stabilization, triggered by engagement of the B cell receptor, acts as a cue to release centrosome-associated Exo70, which is redistributed to the immune synapse. This process is coupled to the recruitment and activation of GEF-H1, which is required for assembly of the exocyst complex, used to promote tethering and fusion of lysosomes at the immune synapse. B cells silenced for GEF-H1 or Exo70 display defective lysosome secretion, which results in impaired antigen extraction and presentation. Thus, centrosome repositioning coupled to changes in microtubule stability orchestrates the spatial-temporal distribution of the exocyst complex to promote polarized lysosome secretion at the immune synapse.
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Affiliation(s)
- Juan José Sáez
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile.,Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
| | - Jheimmy Diaz
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Jorge Ibañez
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan Pablo Bozo
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Fernanda Cabrera Reyes
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Martina Alamo
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - François-Xavier Gobert
- INSERM U932, Institut Curie, Centre de Recherche, PSL Research University, Paris, Île-de-France, France
| | - Dorian Obino
- INSERM U932, Institut Curie, Centre de Recherche, PSL Research University, Paris, Île-de-France, France
| | - María Rosa Bono
- Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile
| | - Ana-María Lennon-Duménil
- INSERM U932, Institut Curie, Centre de Recherche, PSL Research University, Paris, Île-de-France, France
| | - Charles Yeaman
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA
| | - María-Isabel Yuseff
- Department of Cellular and Molecular Biology, Faculty of Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
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Ungermann C, Kümmel D. Structure of membrane tethers and their role in fusion. Traffic 2019; 20:479-490. [DOI: 10.1111/tra.12655] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 04/26/2019] [Accepted: 05/03/2019] [Indexed: 12/27/2022]
Affiliation(s)
- Christian Ungermann
- Biochemistry Section, Department of Biology/ChemistryUniversity of Osnabrück Osnabrück Germany
- Center for Cellular Nanoanalytics (CellNanOs)University of Osnabrück Osnabrück Germany
| | - Daniel Kümmel
- Biochemistry & Structural Biology Section, Institute of BiochemistryUniversity of Münster Münster Germany
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Tang H, de Keijzer J, Overdijk EJR, Sweep E, Steentjes M, Vermeer JEM, Janson ME, Ketelaar T. Exocyst subunit Sec6 is positioned by microtubule overlaps in the moss phragmoplast prior to cell plate membrane arrival. J Cell Sci 2019; 132:jcs222430. [PMID: 30635445 DOI: 10.1242/jcs.222430] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 01/02/2019] [Indexed: 12/21/2022] Open
Abstract
During plant cytokinesis a radially expanding membrane-enclosed cell plate is formed from fusing vesicles that compartmentalizes the cell in two. How fusion is spatially restricted to the site of cell plate formation is unknown. Aggregation of cell-plate membrane starts near regions of microtubule overlap within the bipolar phragmoplast apparatus of the moss Physcomitrella patens Since vesicle fusion generally requires coordination of vesicle tethering and subsequent fusion activity, we analyzed the subcellular localization of several subunits of the exocyst, a tethering complex active during plant cytokinesis. We found that the exocyst complex subunit Sec6 but not the Sec3 or Sec5 subunits localized to microtubule overlap regions in advance of cell plate construction in moss. Moreover, Sec6 exhibited a conserved physical interaction with an ortholog of the Sec1/Munc18 protein KEULE, an important regulator for cell-plate membrane vesicle fusion in Arabidopsis Recruitment of the P. patens protein KEULE and vesicles to the early cell plate was delayed upon Sec6 gene silencing. Our findings, thus, suggest that vesicle-vesicle fusion is, in part, enabled by a pool of exocyst subunits at microtubule overlaps, which is recruited independently of vesicle delivery.
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Affiliation(s)
- Han Tang
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Jeroen de Keijzer
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Elysa J R Overdijk
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Els Sweep
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Maikel Steentjes
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Joop E M Vermeer
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
- Department of Plant and Microbial Biology and Zurich-Basel Plant Science Center, University of Zurich, 8008 Zurich, Switzerland
| | - Marcel E Janson
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Tijs Ketelaar
- Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
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36
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Lepore DM, Martínez-Núñez L, Munson M. Exposing the Elusive Exocyst Structure. Trends Biochem Sci 2018; 43:714-725. [PMID: 30055895 PMCID: PMC6108956 DOI: 10.1016/j.tibs.2018.06.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 06/18/2018] [Accepted: 06/29/2018] [Indexed: 11/18/2022]
Abstract
A major challenge for a molecular understanding of membrane trafficking has been the elucidation of high-resolution structures of large, multisubunit tethering complexes that spatially and temporally control intracellular membrane fusion. Exocyst is a large hetero-octameric protein complex proposed to tether secretory vesicles at the plasma membrane to provide quality control of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated membrane fusion. Breakthroughs in methodologies, including sample preparation, biochemical characterization, fluorescence microscopy, and single-particle cryoelectron microscopy, are providing critical insights into the structure and function of the exocyst. These studies now pose more questions than answers for understanding fundamental functional mechanisms, and they open wide the door for future studies to elucidate interactions with protein and membrane partners, potential conformational changes, and molecular insights into tethering reactions.
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Affiliation(s)
- Dante M Lepore
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Leonora Martínez-Núñez
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
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Exocyst Complex Member EXOC5 Is Required for Survival of Hair Cells and Spiral Ganglion Neurons and Maintenance of Hearing. Mol Neurobiol 2018; 55:6518-6532. [PMID: 29327200 PMCID: PMC6984595 DOI: 10.1007/s12035-017-0857-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 12/20/2017] [Indexed: 10/18/2022]
Abstract
The exocyst, an octameric protein complex consisting of Exoc1 through Exoc8, was first determined to regulate exocytosis by targeting vesicles to the plasma membrane in yeast to mice. In addition to this fundamental role, the exocyst complex has been implicated in other cellular processes. In this study, we investigated the role of the exocyst in cochlear development and hearing by targeting EXOC5, a central exocyst component. Deleting Exoc5 in the otic epithelium with widely used Cre lines resulted in early lethality. Thus, we generated two different inner ear-specific Exoc5 knockout models by crossing Gfi1Cre mice with Exoc5f/f mice for hair cell-specific deletion (Gfi1Cre/+;Exoc5f/f) and by in utero delivery of rAAV-iCre into the otocyst of embryonic day 12.5 for deletion throughout the otic epithelium (rAAV2/1-iCre;Exoc5f/f). Gfi1Cre/+;Exoc5f/f mice showed relatively normal hair cell morphology until postnatal day 20, after which hair cells underwent apoptosis accompanied by disorganization of stereociliary bundles, resulting in progressive hearing loss. rAAV2/1-iCre;Exoc5f/f mice exhibited abnormal neurite morphology, followed by apoptotic degeneration of spiral ganglion neurons (SGNs) and hair cells, which led to profound and early-onset hearing loss. These results demonstrate that Exoc5 is essential for the normal development and survival of cochlear hair cells and SGNs, as well as the functional maintenance of hearing.
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38
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Liu D, Li X, Shen D, Novick P. Two subunits of the exocyst, Sec3p and Exo70p, can function exclusively on the plasma membrane. Mol Biol Cell 2018; 29:736-750. [PMID: 29343551 PMCID: PMC6003224 DOI: 10.1091/mbc.e17-08-0518] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/09/2018] [Accepted: 01/10/2018] [Indexed: 11/18/2022] Open
Abstract
The exocyst is an octameric complex that tethers secretory vesicles to the plasma membrane in preparation for fusion. We anchored each subunit with a transmembrane (TM) domain at its N- or C-terminus. Only N-terminally anchored TM-Sec3p and C-terminally anchored Exo70p-TM proved functional. These findings orient the complex with respect to the membrane and establish that Sec3p and Exo70p can function exclusively on the membrane. The functions of TM-Sec3p and Exo70p-TM were largely unaffected by blocks in endocytic recycling, suggesting that they act on the plasma membrane rather than on secretory vesicles. Cytosolic pools of the other exocyst subunits were unaffected in TM-sec3 cells, while they were partially depleted in exo70-TM cells. Blocking actin-dependent delivery of secretory vesicles in act1-3 cells results in loss of Sec3p from the purified complex. Our results are consistent with a model in which Sec3p and Exo70p can function exclusively on the plasma membrane while the other subunits are brought to them on secretory vesicles.
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Affiliation(s)
- Dongmei Liu
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92130
| | - Xia Li
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92130
| | - David Shen
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92130
| | - Peter Novick
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92130
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39
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Abstract
Polarized exocytosis is generally considered as the multistep vesicular trafficking process in which membrane-bounded carriers are transported from the Golgi or endosomal compartments to specific sites of the plasma membrane. Polarized exocytosis in cells is achieved through the coordinated actions of membrane trafficking machinery and cytoskeleton orchestrated by signaling molecules such as the Rho family of small GTPases. Elucidating the molecular mechanisms of polarized exocytosis is essential to our understanding of a wide range of pathophysiological processes from neuronal development to tumor invasion.
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Affiliation(s)
- Jingwen Zeng
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
| | - Shanshan Feng
- Key Laboratory for Regenerative Medicine of Ministry of Education and Department of Developmental & Regenerative Biology, Jinan University, Guangzhou 510632, P.R. China
| | - Bin Wu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
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40
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D'Agostino M, Risselada HJ, Lürick A, Ungermann C, Mayer A. A tethering complex drives the terminal stage of SNARE-dependent membrane fusion. Nature 2017; 551:634-638. [PMID: 29088698 DOI: 10.1038/nature24469] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 10/03/2017] [Indexed: 11/09/2022]
Abstract
Membrane fusion in eukaryotic cells mediates the biogenesis of organelles, vesicular traffic between them, and exo- and endocytosis of important signalling molecules, such as hormones and neurotransmitters. Distinct tasks in intracellular membrane fusion have been assigned to conserved protein systems. Tethering proteins mediate the initial recognition and attachment of membranes, whereas SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein complexes are considered as the core fusion engine. SNARE complexes provide mechanical energy to distort membranes and drive them through a hemifusion intermediate towards the formation of a fusion pore. This last step is highly energy-demanding. Here we combine the in vivo and in vitro fusion of yeast vacuoles with molecular simulations to show that tethering proteins are critical for overcoming the final energy barrier to fusion pore formation. SNAREs alone drive vacuoles only into the hemifused state. Tethering proteins greatly increase the volume of SNARE complexes and deform the site of hemifusion, which lowers the energy barrier for pore opening and provides the driving force. Thereby, tethering proteins assume a crucial mechanical role in the terminal stage of membrane fusion that is likely to be conserved at multiple steps of vesicular traffic. We therefore propose that SNAREs and tethering proteins should be considered as a single, non-dissociable device that drives fusion. The core fusion machinery may then be larger and more complex than previously thought.
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Affiliation(s)
- Massimo D'Agostino
- Département de Biochimie, Université de Lausanne, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland
| | - Herre Jelger Risselada
- Georg-August University, Department of Theoretical Physics, Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.,Leibniz Institute of Surface Modification, Chemical Department, Permoserstrasse 15, D-04318, Leipzig, Germany
| | - Anna Lürick
- University of Osnabrück, Department of Biology/Chemistry, Barbarastrasse 13, D-49076 Osnabrück, Germany
| | - Christian Ungermann
- University of Osnabrück, Department of Biology/Chemistry, Barbarastrasse 13, D-49076 Osnabrück, Germany
| | - Andreas Mayer
- Département de Biochimie, Université de Lausanne, Chemin des Boveresses 155, CH-1066 Epalinges, Switzerland
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41
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Wang T, Li L, Hong W. SNARE proteins in membrane trafficking. Traffic 2017; 18:767-775. [PMID: 28857378 DOI: 10.1111/tra.12524] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 08/25/2017] [Accepted: 08/25/2017] [Indexed: 12/25/2022]
Abstract
SNAREs are the core machinery mediating membrane fusion. In this review, we provide an update on the recent progress on SNAREs regulating membrane fusion events, especially the more detailed fusion processes dissected by well-developed biophysical methods and in vitro single molecule analysis approaches. We also briefly summarize the relevant research from Chinese laboratories and highlight the significant contributions on our understanding of SNARE-mediated membrane trafficking from scientists in China.
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Affiliation(s)
- Tuanlao Wang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Liangcheng Li
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Wanjin Hong
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China.,Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
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42
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Munc18a clusters SNARE-bearing liposomes prior to trans-SNARE zippering. Biochem J 2017; 474:3339-3354. [PMID: 28827281 DOI: 10.1042/bcj20170494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/16/2017] [Accepted: 08/17/2017] [Indexed: 12/16/2022]
Abstract
Sec1-Munc18 (SM) proteins co-operate with SNAREs {SNAP [soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein] receptors} to mediate membrane fusion in eukaryotic cells. Studies of Munc18a/Munc18-1/Stxbp1 in neurotransmission suggest that SM proteins accelerate fusion kinetics primarily by activating the partially zippered trans-SNARE complex. However, accumulating evidence has argued for additional roles for SM proteins in earlier steps in the fusion cascade. Here, we investigate the function of Munc18a in reconstituted exocytic reactions mediated by neuronal and non-neuronal SNAREs. We show that Munc18a plays a direct role in promoting proteoliposome clustering, underlying vesicle docking during exocytosis. In the three different fusion reactions examined, Munc18a-dependent clustering requires an intact N-terminal peptide (N-peptide) motif in syntaxin that mediates the binary interaction between syntaxin and Munc18a. Importantly, clustering is preserved under inhibitory conditions that abolish both trans-SNARE complex formation and lipid mixing, indicating that Munc18a promotes membrane clustering in a step that is independent of trans-SNARE zippering and activation.
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43
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Ahmed SM, Macara IG. The Par3 polarity protein is an exocyst receptor essential for mammary cell survival. Nat Commun 2017; 8:14867. [PMID: 28358000 PMCID: PMC5379108 DOI: 10.1038/ncomms14867] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 02/01/2017] [Indexed: 12/11/2022] Open
Abstract
The exocyst is an essential component of the secretory pathway required for delivery of basolateral proteins to the plasma membranes of epithelial cells. Delivery occurs adjacent to tight junctions (TJ), suggesting that it recognizes a receptor at this location. However, no such receptor has been identified. The Par3 polarity protein associates with TJs but has no known function in membrane traffic. We now show that, unexpectedly, Par3 is essential for mammary cell survival. Par3 silencing causes apoptosis, triggered by phosphoinositide trisphosphate depletion and decreased Akt phosphorylation, resulting from failure of the exocyst to deliver basolateral proteins to the cortex. A small region of PAR3 binds directly to Exo70 and is sufficient for exocyst docking, membrane-protein delivery and cell survival. PAR3 lacking this domain can associate with the cortex but cannot support exocyst function. We conclude that Par3 is the long-sought exocyst receptor required for targeted membrane-protein delivery. The exocyst delivers basolateral proteins from the secretory pathway to the plasma membrane of epithelial cells close to tight junctions. Here the authors show that Par3 acts as a docking site for the exocyst to regulate polarized delivery of basolateral proteins and this is essential to prevent apoptosis and promote mammary cell survival.
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Affiliation(s)
- Syed Mukhtar Ahmed
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | - Ian G Macara
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
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Sekereš J, Pejchar P, Šantrůček J, Vukašinović N, Žárský V, Potocký M. Analysis of Exocyst Subunit EXO70 Family Reveals Distinct Membrane Polar Domains in Tobacco Pollen Tubes. PLANT PHYSIOLOGY 2017; 173:1659-1675. [PMID: 28082718 PMCID: PMC5338673 DOI: 10.1104/pp.16.01709] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 01/10/2017] [Indexed: 05/05/2023]
Abstract
The vesicle-tethering complex exocyst is one of the crucial cell polarity regulators. The EXO70 subunit is required for the targeting of the complex and is represented by many isoforms in angiosperm plant cells. This diversity could be partly responsible for the establishment and maintenance of membrane domains with different composition. To address this hypothesis, we employed the growing pollen tube, a well-established cell polarity model system, and performed large-scale expression, localization, and functional analysis of tobacco (Nicotiana tabacum) EXO70 isoforms. Various isoforms localized to different regions of the pollen tube plasma membrane, apical vesicle-rich inverted cone region, nucleus, and cytoplasm. The overexpression of major pollen-expressed EXO70 isoforms resulted in growth arrest and characteristic phenotypic deviations of tip swelling and apical invaginations. NtEXO70A1a and NtEXO70B1 occupied two distinct and mutually exclusive plasma membrane domains. Both isoforms partly colocalized with the exocyst subunit NtSEC3a at the plasma membrane, possibly forming different exocyst complex subpopulations. NtEXO70A1a localized to the small area previously characterized as the site of exocytosis in the tobacco pollen tube, while NtEXO70B1 surprisingly colocalized with the zone of clathrin-mediated endocytosis. Both NtEXO70A1a and NtEXO70B1 colocalized to different degrees with markers for the anionic signaling phospholipids phosphatidylinositol 4,5-bisphosphate and phosphatidic acid. In contrast, members of the EXO70 C class, which are specifically expressed in tip-growing cells, exhibited exocytosis-related functional effects in pollen tubes despite the absence of apparent plasma membrane localization. Taken together, our data support the existence of multiple membrane-trafficking domains regulated by different EXO70-containing exocyst complexes within a single cell.
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Affiliation(s)
- Juraj Sekereš
- Institute of Experimental Botany, Czech Academy of Sciences, Prague 6, Czech Republic (J.S., P.P., N.V., V.Ž., M.P.)
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague 2, Czech Republic (J.S., V.Ž.); and
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague 6, Czech Republic (J.Š.)
| | - Přemysl Pejchar
- Institute of Experimental Botany, Czech Academy of Sciences, Prague 6, Czech Republic (J.S., P.P., N.V., V.Ž., M.P.)
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague 2, Czech Republic (J.S., V.Ž.); and
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague 6, Czech Republic (J.Š.)
| | - Jiří Šantrůček
- Institute of Experimental Botany, Czech Academy of Sciences, Prague 6, Czech Republic (J.S., P.P., N.V., V.Ž., M.P.)
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague 2, Czech Republic (J.S., V.Ž.); and
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague 6, Czech Republic (J.Š.)
| | - Nemanja Vukašinović
- Institute of Experimental Botany, Czech Academy of Sciences, Prague 6, Czech Republic (J.S., P.P., N.V., V.Ž., M.P.)
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague 2, Czech Republic (J.S., V.Ž.); and
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague 6, Czech Republic (J.Š.)
| | - Viktor Žárský
- Institute of Experimental Botany, Czech Academy of Sciences, Prague 6, Czech Republic (J.S., P.P., N.V., V.Ž., M.P.)
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague 2, Czech Republic (J.S., V.Ž.); and
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague 6, Czech Republic (J.Š.)
| | - Martin Potocký
- Institute of Experimental Botany, Czech Academy of Sciences, Prague 6, Czech Republic (J.S., P.P., N.V., V.Ž., M.P.);
- Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague 2, Czech Republic (J.S., V.Ž.); and
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, Prague 6, Czech Republic (J.Š.)
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Yue P, Zhang Y, Mei K, Wang S, Lesigang J, Zhu Y, Dong G, Guo W. Sec3 promotes the initial binary t-SNARE complex assembly and membrane fusion. Nat Commun 2017; 8:14236. [PMID: 28112172 PMCID: PMC5267525 DOI: 10.1038/ncomms14236] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 12/12/2016] [Indexed: 01/04/2023] Open
Abstract
The soluble N-ethylmaleimide-sensitive factor-attachment protein receptors (SNAREs) constitute the core machinery for membrane fusion during eukaryotic cell vesicular trafficking. However, how the assembly of the SNARE complex is initiated is unknown. Here we report that Sec3, a component of the exocyst complex that mediates vesicle tethering during exocytosis, directly interacts with the t-SNARE protein Sso2. This interaction promotes the formation of an Sso2-Sec9 'binary' t-SNARE complex, the early rate-limiting step in SNARE complex assembly, and stimulates membrane fusion. The crystal structure of the Sec3-Sso2 complex suggests that Sec3 binding induces conformational changes of Sso2 that are crucial for the relief of its auto-inhibition. Interestingly, specific disruption of the Sec3-Sso2 interaction in cells blocks exocytosis without affecting the function of Sec3 in vesicle tethering. Our study reveals an activation mechanism for SNARE complex assembly, and uncovers a role of the exocyst in promoting membrane fusion in addition to vesicle tethering.
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Affiliation(s)
- Peng Yue
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Yubo Zhang
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, 1030 Vienna, Austria
| | - Kunrong Mei
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Shaoxiao Wang
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Johannes Lesigang
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, 1030 Vienna, Austria
| | - Yueyao Zhu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Gang Dong
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, 1030 Vienna, Austria
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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46
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Kustermann J, Wu Y, Rieger L, Dedden D, Phan T, Walther P, Dünkler A, Johnsson N. The cell polarity proteins Boi1p and Boi2p stimulate vesicle fusion at the plasma membrane of yeast cells. J Cell Sci 2017; 130:2996-3008. [DOI: 10.1242/jcs.206334] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 07/24/2017] [Indexed: 12/20/2022] Open
Abstract
Eukaryotic cells can direct secretion to defined regions of their plasma membrane. These regions are distinguished by an elaborate architecture of proteins and lipids that are specialized to capture and fuse post-Golgi vesicles. Here we show that the proteins Boi1p and Boi2p are important elements of this area of active exocytosis at the tip of growing yeast cells. Cells lacking Boi1p and Boi2p accumulate secretory vesicles in their bud. The essential PH domains of Boi1p and Boi2p interact with Sec1p, a protein required for SNARE complex formation and vesicle fusion. Sec1p loses its tip localization in cells depleted of Boi1p and Boi2p but can partially compensate for their loss upon overexpression. The capacity to simultaneously bind phospholipids, Sec1p, multiple subunits of the exocyst, Cdc42p, and the module for generating active Cdc42p identify Boi1p and Boi2p as essential mediators between exocytosis and polar growth.
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Affiliation(s)
- Jochen Kustermann
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Yehui Wu
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Lucia Rieger
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Dirk Dedden
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Tamara Phan
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Paul Walther
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Alexander Dünkler
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
| | - Nils Johnsson
- Institute of Molecular Genetics and Cell Biology, Department of Biology, Ulm University, James-Franck-Ring N27, D-89081 Ulm, Germany
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Boehm CM, Obado S, Gadelha C, Kaupisch A, Manna PT, Gould GW, Munson M, Chait BT, Rout MP, Field MC. The Trypanosome Exocyst: A Conserved Structure Revealing a New Role in Endocytosis. PLoS Pathog 2017; 13:e1006063. [PMID: 28114397 PMCID: PMC5256885 DOI: 10.1371/journal.ppat.1006063] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 11/14/2016] [Indexed: 01/10/2023] Open
Abstract
Membrane transport is an essential component of pathogenesis for most infectious organisms. In African trypanosomes, transport to and from the plasma membrane is closely coupled to immune evasion and antigenic variation. In mammals and fungi an octameric exocyst complex mediates late steps in exocytosis, but comparative genomics suggested that trypanosomes retain only six canonical subunits, implying mechanistic divergence. We directly determined the composition of the Trypanosoma brucei exocyst by affinity isolation and demonstrate that the parasite complex is nonameric, retaining all eight canonical subunits (albeit highly divergent at the sequence level) plus a novel essential subunit, Exo99. Exo99 and Sec15 knockdowns have remarkably similar phenotypes in terms of viability and impact on morphology and trafficking pathways. Significantly, both Sec15 and Exo99 have a clear function in endocytosis, and global proteomic analysis indicates an important role in maintaining the surface proteome. Taken together these data indicate additional exocyst functions in trypanosomes, which likely include endocytosis, recycling and control of surface composition. Knockdowns in HeLa cells suggest that the role in endocytosis is shared with metazoan cells. We conclude that, whilst the trypanosome exocyst has novel components, overall functionality appears conserved, and suggest that the unique subunit may provide therapeutic opportunities.
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Affiliation(s)
- Cordula M. Boehm
- Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
| | - Samson Obado
- The Rockefeller University, 1230 York Avenue, New York, NY, United States of America
| | - Catarina Gadelha
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Alexandra Kaupisch
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Paul T. Manna
- Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
| | - Gwyn W. Gould
- Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, United States of America
| | - Brian T. Chait
- The Rockefeller University, 1230 York Avenue, New York, NY, United States of America
| | - Michael P. Rout
- The Rockefeller University, 1230 York Avenue, New York, NY, United States of America
| | - Mark C. Field
- Wellcome Trust Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dow Street, Dundee, United Kingdom
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Lürick A, Gao J, Kuhlee A, Yavavli E, Langemeyer L, Perz A, Raunser S, Ungermann C. Multivalent Rab interactions determine tether-mediated membrane fusion. Mol Biol Cell 2016; 28:322-332. [PMID: 27852901 PMCID: PMC5231900 DOI: 10.1091/mbc.e16-11-0764] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 11/10/2016] [Indexed: 12/22/2022] Open
Abstract
Membrane fusion at endomembranes requires cross-talk between Rab GTPases and tethers to drive SNARE-mediated lipid bilayer mixing. Several tethers have multiple Rab-binding sites with largely untested function. Here we dissected the lysosomal HOPS complex as a tethering complex with just two binding sites for the Rab7-like Ypt7 protein to determine their relevance for fusion. Using tethering and fusion assays combined with HOPS mutants, we show that HOPS-dependent fusion requires both Rab-binding sites, with Vps39 being the stronger Ypt7 interactor than Vps41. The intrinsic amphipathic lipid packaging sensor (ALPS) motif within HOPS Vps41, a target of the vacuolar kinase Yck3, is dispensable for tethering and fusion but can affect tethering if phosphorylated. In combination, our data demonstrate that a multivalent tethering complex uses its two Rab bindings to determine the place of SNARE assembly and thus fusion at endomembranes.
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Affiliation(s)
- Anna Lürick
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany
| | - Jieqiong Gao
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany
| | - Anne Kuhlee
- Department of Physical Biochemistry, Max-Planck Institute of Molecular Physiology; 44227 Dortmund, Germany
| | - Erdal Yavavli
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany
| | - Lars Langemeyer
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany
| | - Angela Perz
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany
| | - Stefan Raunser
- Department of Physical Biochemistry, Max-Planck Institute of Molecular Physiology; 44227 Dortmund, Germany
| | - Christian Ungermann
- Biochemistry Section, Department of Biology/Chemistry, University of Osnabrück, 49076 Osnabrück, Germany
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Identification of Multiple Cryptococcal Fungicidal Drug Targets by Combined Gene Dosing and Drug Affinity Responsive Target Stability Screening. mBio 2016; 7:mBio.01073-16. [PMID: 27486194 PMCID: PMC4981720 DOI: 10.1128/mbio.01073-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Cryptococcus neoformans is a pathogenic fungus that is responsible for up to half a million cases of meningitis globally, especially in immunocompromised individuals. Common fungistatic drugs, such as fluconazole, are less toxic for patients but have low efficacy for initial therapy of the disease. Effective therapy against the disease is provided by the fungicidal drug amphotericin B; however, due to its high toxicity and the difficulty in administering its intravenous formulation, it is imperative to find new therapies targeting the fungus. The antiparasitic drug bithionol has been recently identified as having potent fungicidal activity. In this study, we used a combined gene dosing and drug affinity responsive target stability (GD-DARTS) screen as well as protein modeling to identify a common drug binding site of bithionol within multiple NAD-dependent dehydrogenase drug targets. This combination genetic and proteomic method thus provides a powerful method for identifying novel fungicidal drug targets for further development. Cryptococcosis is a neglected fungal meningitis that causes approximately half a million deaths annually. The most effective antifungal agent, amphotericin B, was developed in the 1950s, and no effective medicine has been developed for this disease since that time. A key aspect of amphotericin B’s effectiveness is thought to be because of its ability to kill the fungus (fungicidal activity), rather than just stop or slow its growth. The present study utilized a recently identified fungicidal agent, bithionol, to identify potential fungicidal drug targets that can be used in developing modern fungicidal agents. A combined protein and genetic analysis approach was used to identify a class of enzymes, dehydrogenases, that the fungus uses to maintain homeostasis with regard to sugar nutrients. Similarities in the drug target site were found that resulted in simultaneous inhibition and killing of the fungus by bithionol. These studies thus identify a common, multitarget site for antifungal development.
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Abstract
Intracellular membrane fusion is mediated in most cases by membrane-bridging complexes of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). However, the assembly of such complexes in vitro is inefficient, and their uncatalysed disassembly is undetectably slow. Here, we focus on the cellular machinery that orchestrates assembly and disassembly of SNARE complexes, thereby regulating processes ranging from vesicle trafficking to organelle fusion to neurotransmitter release. Rapid progress is being made on many fronts, including the development of more realistic cell-free reconstitutions, the application of single-molecule biophysics, and the elucidation of X-ray and high-resolution electron microscopy structures of the SNARE assembly and disassembly machineries 'in action'.
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Affiliation(s)
- Richard W Baker
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA.,Present address: Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Frederick M Hughson
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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