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Palfreyman MT, West SE, Jorgensen EM. SNARE Proteins in Synaptic Vesicle Fusion. ADVANCES IN NEUROBIOLOGY 2023; 33:63-118. [PMID: 37615864 DOI: 10.1007/978-3-031-34229-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
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Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
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2
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Sardar A, Dewangan N, Panda B, Bhowmick D, Tarafdar PK. Lipid and Lipidation in Membrane Fusion. J Membr Biol 2022; 255:691-703. [PMID: 36102950 PMCID: PMC9472184 DOI: 10.1007/s00232-022-00267-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/23/2022] [Indexed: 12/24/2022]
Abstract
Membrane fusion plays a lead role in the transport of vesicles, neurotransmission, mitochondrial dynamics, and viral infection. There are fusion proteins that catalyze and regulate the fusion. Interestingly, various types of fusion proteins are present in nature and they possess diverse mechanisms of action. We have highlighted the importance of the functional domains of intracellular heterotypic fusion, homotypic endoplasmic reticulum (ER), homotypic mitochondrial, and type-I viral fusion. During intracellular heterotypic fusion, the SNAREs and four-helix bundle formation are prevalent. Type-I viral fusion is controlled by the membrane destabilizing properties of fusion peptide and six-helix bundle formation. The ER/mitochondrial homotypic fusion is controlled by GTPase activity and the membrane destabilization properties of the amphipathic helix(s). Although the mechanism of action of these fusion proteins is diverse, they have some similarities. In all cases, the lipid composition of the membrane greatly affects membrane fusion. Next, examples of lipidation of the fusion proteins were discussed. We suggest that the fatty acyl hydrophobic tail not only acts as an anchor but may also modulate the energetics of membrane fusion intermediates. Lipidation is also important to design more effective peptide-based fusion inhibitors. Together, we have shown that membrane lipid composition and lipidation are important to modulate membrane fusion.
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Affiliation(s)
- Avijit Sardar
- grid.417960.d0000 0004 0614 7855Indian Institute of Science Education and Research Kolkata, Nadia, Mohanpur, West Bengal 741246 India
| | - Nikesh Dewangan
- grid.417960.d0000 0004 0614 7855Indian Institute of Science Education and Research Kolkata, Nadia, Mohanpur, West Bengal 741246 India
| | - Bishvanwesha Panda
- grid.417960.d0000 0004 0614 7855Indian Institute of Science Education and Research Kolkata, Nadia, Mohanpur, West Bengal 741246 India
| | - Debosmita Bhowmick
- grid.417960.d0000 0004 0614 7855Indian Institute of Science Education and Research Kolkata, Nadia, Mohanpur, West Bengal 741246 India
| | - Pradip K. Tarafdar
- grid.417960.d0000 0004 0614 7855Indian Institute of Science Education and Research Kolkata, Nadia, Mohanpur, West Bengal 741246 India
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3
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Salinas-Cornejo J, Madrid-Espinoza J, Verdugo I, Pérez-Díaz J, Martín-Davison AS, Norambuena L, Ruiz-Lara S. The Exocytosis Associated SNAP25-Type Protein, SlSNAP33, Increases Salt Stress Tolerance by Modulating Endocytosis in Tomato. PLANTS 2021; 10:plants10071322. [PMID: 34209492 PMCID: PMC8309203 DOI: 10.3390/plants10071322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 06/22/2021] [Accepted: 06/26/2021] [Indexed: 11/29/2022]
Abstract
In plants, vesicular trafficking is crucial for the response and survival to environmental challenges. The active trafficking of vesicles is essential to maintain cell homeostasis during salt stress. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are regulatory proteins of vesicular trafficking. They mediate membrane fusion and guarantee cargo delivery to the correct cellular compartments. SNAREs from the Qbc subfamily are the best-characterized plasma membrane SNAREs, where they control exocytosis during cell division and defense response. The Solanum lycopersicum gene SlSNAP33.2 encodes a Qbc-SNARE protein and is induced under salt stress conditions. SlSNAP33.2 localizes on the plasma membrane of root cells of Arabidopsis thaliana. In order to study its role in endocytosis and salt stress response, we overexpressed the SlSNAP33.2 cDNA in a tomato cultivar. Constitutive overexpression promoted endocytosis along with the accumulation of sodium (Na+) in the vacuoles. It also protected the plant from cell damage by decreasing the accumulation of hydrogen peroxide (H2O2) in the cytoplasm of stressed root cells. Subsequently, the higher level of SlSNAP33.2 conferred tolerance to salt stress in tomato plants. The analysis of physiological and biochemical parameters such as relative water content, the efficiency of the photosystem II, performance index, chlorophyll, and MDA contents showed that tomato plants overexpressing SlSNAP33.2 displayed a better performance under salt stress than wild type plants. These results reveal a role for SlSNAP33.2 in the endocytosis pathway involved in plant response to salt stress. This research shows that SlSNAP33.2 can be an effective tool for the genetic improvement of crop plants.
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Affiliation(s)
- Josselyn Salinas-Cornejo
- Laboratorio de Genómica Funcional, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3460000, Chile; (J.S.-C.); (J.M.-E.); (I.V.); (J.P.-D.); (A.S.M.-D.)
| | - José Madrid-Espinoza
- Laboratorio de Genómica Funcional, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3460000, Chile; (J.S.-C.); (J.M.-E.); (I.V.); (J.P.-D.); (A.S.M.-D.)
| | - Isabel Verdugo
- Laboratorio de Genómica Funcional, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3460000, Chile; (J.S.-C.); (J.M.-E.); (I.V.); (J.P.-D.); (A.S.M.-D.)
| | - Jorge Pérez-Díaz
- Laboratorio de Genómica Funcional, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3460000, Chile; (J.S.-C.); (J.M.-E.); (I.V.); (J.P.-D.); (A.S.M.-D.)
| | - Alex San Martín-Davison
- Laboratorio de Genómica Funcional, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3460000, Chile; (J.S.-C.); (J.M.-E.); (I.V.); (J.P.-D.); (A.S.M.-D.)
| | - Lorena Norambuena
- Facultad de Ciencias, Universidad de Chile, Santiago, Ñuñoa 7750000, Chile;
| | - Simón Ruiz-Lara
- Laboratorio de Genómica Funcional, Instituto de Ciencias Biológicas, Universidad de Talca, Talca 3460000, Chile; (J.S.-C.); (J.M.-E.); (I.V.); (J.P.-D.); (A.S.M.-D.)
- Correspondence:
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4
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Sena RM, Twiss JL, Gardiner AS, Dell’Orco M, Linsenbardt DN, Perrone-Bizzozero NI. The RNA-Binding Protein HuD Regulates Alternative Splicing and Alternative Polyadenylation in the Mouse Neocortex. Molecules 2021; 26:2836. [PMID: 34064652 PMCID: PMC8151252 DOI: 10.3390/molecules26102836] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/03/2021] [Accepted: 05/05/2021] [Indexed: 11/18/2022] Open
Abstract
The neuronal Hu/ELAV-like proteins HuB, HuC and HuD are a class of RNA-binding proteins that are crucial for proper development and maintenance of the nervous system. These proteins bind to AU-rich elements (AREs) in the untranslated regions (3'-UTRs) of target mRNAs regulating mRNA stability, transport and translation. In addition to these cytoplasmic functions, Hu proteins have been implicated in alternative splicing and alternative polyadenylation in the nucleus. The purpose of this study was to identify transcriptome-wide effects of HuD deletion on both of these nuclear events using RNA sequencing data obtained from the neocortex of Elavl4-/- (HuD KO) mice. HuD KO affected alternative splicing of 310 genes, including 17 validated HuD targets such as Cbx3, Cspp1, Snap25 and Gria2. In addition, deletion of HuD affected polyadenylation of 53 genes, with the majority of significantly altered mRNAs shifting towards usage of proximal polyadenylation signals (PAS), resulting in shorter 3'-UTRs. None of these genes overlapped with those showing alternative splicing events. Overall, HuD KO had a greater effect on alternative splicing than polyadenylation, with many of the affected genes implicated in several neuronal functions and neuropsychiatric disorders.
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Affiliation(s)
- Rebecca M. Sena
- Department Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA; (R.M.S.); (A.S.G.); (M.D.)
| | - Jeffery L. Twiss
- Department Biological Sciences, University of South Carolina, Columbia, SC 29208, USA;
| | - Amy S. Gardiner
- Department Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA; (R.M.S.); (A.S.G.); (M.D.)
- Department Cell Biology and Physiology, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA
| | - Michela Dell’Orco
- Department Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA; (R.M.S.); (A.S.G.); (M.D.)
| | - David N. Linsenbardt
- Department Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA; (R.M.S.); (A.S.G.); (M.D.)
| | - Nora I. Perrone-Bizzozero
- Department Neurosciences, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA; (R.M.S.); (A.S.G.); (M.D.)
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5
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Milosevic I. Spatial and Temporal Aspects of Exocytosis Studied on the Isolated Plasma Membranes. Methods Mol Biol 2021; 2233:311-325. [PMID: 33222144 DOI: 10.1007/978-1-0716-1044-2_21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Exocytosis of large-dense core vesicles in neuroendocrine cells is a highly regulated, calcium-dependent process, mediated by networks of interrelated proteins and lipids. Here, I describe experimental procedures for studies of selective spatial and temporal aspects of exocytosis at the plasma membrane, or in its proximity, using adrenal chromaffin cells. The assay utilizes primary cells subjected to a brief ultrasonic pulse, resulting in the formation of thin, flat inside-out plasma membranes with attached secretory vesicles and elements of cell cytoskeleton. In this model, secretion of plasma membrane-attached secretory vesicles was found to be dependent on calcium and sensitive to clostridial neurotoxins. Depending on the probe selected for secretory vesicle cargo, protein, and/or lipid detection, this simple assay is versatile, fast and inexpensive, and offers excellent spatial resolution.
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Affiliation(s)
- Ira Milosevic
- European Neuroscience Institute (ENI), A Joint Initiative of the University Medical Center Göttingen and the Max Planck Society, Göttingen, Germany. .,Wellcome Centre for Human Genetics, Nuffield Department of Medicine, NIHR Oxford Biomedical Research Centre, University of Oxford, Oxford, UK.
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6
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Sundaram RVK, Jin H, Li F, Shu T, Coleman J, Yang J, Pincet F, Zhang Y, Rothman JE, Krishnakumar SS. Munc13 binds and recruits SNAP25 to chaperone SNARE complex assembly. FEBS Lett 2021; 595:297-309. [PMID: 33222163 PMCID: PMC8068094 DOI: 10.1002/1873-3468.14006] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/15/2020] [Accepted: 11/19/2020] [Indexed: 11/10/2022]
Abstract
Synaptic vesicle fusion is mediated by SNARE proteins-VAMP2 on the vesicle and Syntaxin-1/SNAP25 on the presynaptic membrane. Chaperones Munc18-1 and Munc13-1 cooperatively catalyze SNARE assembly via an intermediate 'template' complex containing Syntaxin-1 and VAMP2. How SNAP25 enters this reaction remains a mystery. Here, we report that Munc13-1 recruits SNAP25 to initiate the ternary SNARE complex assembly by direct binding, as judged by bulk FRET spectroscopy and single-molecule optical tweezer studies. Detailed structure-function analyses show that the binding is mediated by the Munc13-1 MUN domain and is specific for the SNAP25 'linker' region that connects the two SNARE motifs. Consequently, freely diffusing SNAP25 molecules on phospholipid bilayers are concentrated and bound in ~ 1 : 1 stoichiometry by the self-assembled Munc13-1 nanoclusters.
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Affiliation(s)
- R Venkat Kalyana Sundaram
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Huaizhou Jin
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Feng Li
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Tong Shu
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Jeff Coleman
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Jie Yang
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Frederic Pincet
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
- Laboratoire de Physique de Ecole Normale Supérieure, Université PSL, CNRS, Sorbonne Université, Université de Paris 06, F-75005 Paris, France
| | - Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - James E. Rothman
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Shyam S. Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, Queens Square House, London WC1 3BG, UK
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7
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Holz RW, Bittner MA. Roles for the SNAP25 linker domain in the fusion pore and a dynamic plasma membrane SNARE "acceptor" complex. J Gen Physiol 2020; 152:151980. [PMID: 32722752 PMCID: PMC7478873 DOI: 10.1085/jgp.202012619] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Central to the exocytotic release of hormones and neurotransmitters is the interaction of four SNARE motifs in proteins on the secretory granule/synaptic vesicle membrane (synaptobrevin/VAMP, v-SNARE) and on the plasma membrane (syntaxin and SNAP25, t-SNAREs). The interaction is thought to bring the opposing membranes together to enable fusion. An underlying motivation for this Viewpoint is to synthesize from recent diverse studies possible new insights about these events. We focus on a recent paper that demonstrates the importance of the linker region joining the two SNARE motifs of the neuronal t-SNARE SNAP25 for maintaining rates of secretion with roles for distinct segments in speeding fusion pore expansion. Remarkably, lipid-perturbing agents rescue a palmitoylation-deficient mutant whose phenotype includes slow fusion pore expansion, suggesting that protein–protein interactions have a role not only in bringing together the granule or vesicle membrane with the plasma membrane but also in orchestrating protein–lipid interactions leading to the fusion reaction. Unexpectedly, biochemical investigations demonstrate the importance of the C-terminal domain of the linker in the formation of the plasma membrane t-SNARE “acceptor” complex for synaptobrevin2. This insight, together with biophysical and optical studies from other laboratories, suggests that the plasma membrane SNARE acceptor complex between SNAP25 and syntaxin and the subsequent trans-SNARE complex with the v-SNARE synaptobrevin form within 100 ms before fusion.
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Affiliation(s)
- Ronald W Holz
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Mary A Bittner
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
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8
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Won KH, Kim H. Functions of the Plant Qbc SNARE SNAP25 in Cytokinesis and Biotic and Abiotic Stress Responses. Mol Cells 2020; 43:313-322. [PMID: 32274918 PMCID: PMC7191049 DOI: 10.14348/molcells.2020.2245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 03/26/2020] [Accepted: 03/29/2020] [Indexed: 12/29/2022] Open
Abstract
Eukaryotes transport biomolecules between intracellular organelles and between cells and the environment via vesicle trafficking. Soluble N -ethylmaleimide-sensitive factor attachment protein receptors (SNARE proteins) play pivotal roles in vesicle and membrane trafficking. These proteins are categorized as Qa, Qb, Qc, and R SNAREs and form a complex that induces vesicle fusion for targeting of vesicle cargos. As the core components of the SNARE complex, the SNAP25 Qbc SNAREs perform various functions related to cellular homeostasis. The Arabidopsis thaliana SNAP25 homolog AtSNAP33 interacts with Qa and R SNAREs and plays a key role in cytokinesis and in triggering innate immune responses. However, other Arabidopsis SNAP25 homologs, such as AtSNAP29 and AtSNAP30, are not well studied; this includes their localization, interactions, structures, and functions. Here, we discuss three biological functions of plant SNAP25 orthologs in the context of AtSNAP33 and highlight recent findings on SNAP25 orthologs in various plants. We propose future directions for determining the roles of the less well-characterized AtSNAP29 and AtSNAP30 proteins.
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Affiliation(s)
- Kang-Hee Won
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
| | - Hyeran Kim
- Department of Biological Sciences, Kangwon National University, Chuncheon 24341, Korea
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9
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The SNAP-25 Protein Family. Neuroscience 2019; 420:50-71. [DOI: 10.1016/j.neuroscience.2018.09.020] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Revised: 08/31/2018] [Accepted: 09/14/2018] [Indexed: 01/04/2023]
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10
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Jiang X, Zhang Z, Cheng K, Wu Q, Jiang L, Pielak GJ, Liu M, Li C. Membrane-mediated disorder-to-order transition of SNAP25 flexible linker facilitates its interaction with syntaxin-1 and SNARE-complex assembly. FASEB J 2019; 33:7985-7994. [PMID: 30916996 DOI: 10.1096/fj.201802796r] [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] [Indexed: 01/15/2023]
Abstract
The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex comprises synaptosome-associated protein of 25 kDa (SNAP25), syntaxin-1a (syx-1), and synaptobrevin 2, which is essential for many physiologic processes requiring membrane fusion. Several studies imply that the loop region of SNAP25 plays important roles in SNARE-complex assembly. However, why and how the flexible loop facilitates the complex assembly remains poorly understood because it is purposely deleted in almost all structural studies. By using NMR spectroscopy and circular dichroism spectropolarimetry, we characterized SNAP25 structure and interactions with other SNAREs in aqueous buffer and in the membrane. We found that the N-terminal of the SNAP25 loop region binds with membrane, and this interaction induced a disorder-to-order conformational change of the loop, resulting in enhanced interaction between the C-terminal of the SNAP25 loop and syx-1. We further proved that SNARE-complex assembly efficiency decreased when we disrupted the electrostatic interaction between C-terminal of the SNAP25 loop and syx-1, suggesting that the SNAP25 loop region facilitates SNARE-complex assembly through promoting prefusion SNARE binary complex formation. Our work elucidates the role of the flexible loop and the membrane environment in SNARE-complex assembly at the residue level, which helps to understand membrane fusion, a fundamental transport and communication process in cells.-Jiang, X., Zhang, Z., Cheng, K., Wu, Q., Jiang, L., Pielak, G. J., Liu, M., Li, C. Membrane-mediated disorder-to-order transition of SNAP25 flexible linker facilitates its interaction with syntaxin-1 and SNARE-complex assembly.
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Affiliation(s)
- Xin Jiang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China.,Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Zeting Zhang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Kai Cheng
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Qiong Wu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China
| | - Ling Jiang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China.,Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Gary J Pielak
- Department of Chemistry and Department of Biochemistry and Biophysics, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA.,Integrative Program for Biological and Genome Sciences, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Maili Liu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China.,Graduate University of Chinese Academy of Sciences, Beijing, China
| | - Conggang Li
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan National Laboratory for Optoelectronics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, China.,Graduate University of Chinese Academy of Sciences, Beijing, China
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11
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Shaaban A, Dhara M, Frisch W, Harb A, Shaib AH, Becherer U, Bruns D, Mohrmann R. The SNAP-25 linker supports fusion intermediates by local lipid interactions. eLife 2019; 8:41720. [PMID: 30883328 PMCID: PMC6422494 DOI: 10.7554/elife.41720] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 03/05/2019] [Indexed: 12/22/2022] Open
Abstract
SNAP-25 is an essential component of SNARE complexes driving fast Ca2+-dependent exocytosis. Yet, the functional implications of the tandem-like structure of SNAP-25 are unclear. Here, we have investigated the mechanistic role of the acylated “linker” domain that concatenates the two SNARE motifs within SNAP-25. Refuting older concepts of an inert connector, our detailed structure-function analysis in murine chromaffin cells demonstrates that linker motifs play a crucial role in vesicle priming, triggering, and fusion pore expansion. Mechanistically, we identify two synergistic functions of the SNAP-25 linker: First, linker motifs support t-SNARE interactions and accelerate ternary complex assembly. Second, the acylated N-terminal linker segment engages in local lipid interactions that facilitate fusion triggering and pore evolution, putatively establishing a favorable membrane configuration by shielding phospholipid headgroups and affecting curvature. Hence, the linker is a functional part of the fusion complex that promotes secretion by SNARE interactions as well as concerted lipid interplay.
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Affiliation(s)
- Ahmed Shaaban
- ZHMB, Saarland University, Homburg, Germany.,Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Madhurima Dhara
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Walentina Frisch
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Ali Harb
- ZHMB, Saarland University, Homburg, Germany
| | - Ali H Shaib
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, Göttingen, Germany
| | - Ute Becherer
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Dieter Bruns
- Institute for Physiology, Center of Integrative Physiology and Molecular Medicine, Saarland University, Homburg, Germany
| | - Ralf Mohrmann
- ZHMB, Saarland University, Homburg, Germany.,Institute for Physiology, Otto-von-Guericke University, Magdeburg, Germany.,Center for Behavioral Brain Science, Otto-von-Guericke University, Magdeburg, Germany
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12
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Spatial and Temporal Aspects of Phosphoinositides in Endocytosis Studied in the Isolated Plasma Membranes. Methods Mol Biol 2018; 1847:147-160. [PMID: 30129015 DOI: 10.1007/978-1-4939-8719-1_11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Endocytosis is a well-orchestrated cascade of lipid-protein and protein-protein interactions resulting in formation and internalization of vesicles. Membrane phospholipids have key regulatory functions in endocytosis and membrane traffic. I have previously described an in vitro assay based on the isolated, substrate-attached plasma membrane to study the spatial distribution and levels of phosphoinositides, in particular phosphatidylinositol-4,5-bisphospate [PI(4,5)P2]. This assay utilizes cultured cells subjected to a brief ultrasonic pulse, resulting in the formation of thin, flat inside-out plasma membrane sheets with elements of cell cytoskeleton. Here, I describe an experimental procedure for "on-stage" and "off-stage" detection of PI(4,5)P2 spatial distribution, and semi-quantification of PI(4,5)P2 levels in the plasma membrane using fluorescence microscopy. Depending on the probe selected for lipid detection, this simple assay can be modified to study other plasmalemmal phospholipids and/or proteins.
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Wang P, Sun Y, Pei Y, Li X, Zhang X, Li F, Hou Y. GhSNAP33, a t-SNARE Protein From Gossypium hirsutum, Mediates Resistance to Verticillium dahliae Infection and Tolerance to Drought Stress. FRONTIERS IN PLANT SCIENCE 2018; 9:896. [PMID: 30018623 PMCID: PMC6038728 DOI: 10.3389/fpls.2018.00896] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 06/07/2018] [Indexed: 05/06/2023]
Abstract
Soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) proteins mediate membrane fusion and deliver cargo to specific cellular locations through vesicle trafficking. Synaptosome-associated protein of 25 kDa (SNAP25) is a target membrane SNARE that drives exocytosis by fusing plasma and vesicular membranes. In this study, we isolated GhSNAP33, a gene from cotton (Gossypium hirsutum), encoding a SNAP25-type protein containing glutamine (Q)b- and Qc-SNARE motifs connected by a linker. GhSNAP33 expression was induced by H2O2, salicylic acid, abscisic acid, and polyethylene glycol 6000 treatment and Verticillium dahliae inoculation. Ectopic expression of GhSNAP33 enhanced the tolerance of yeast cells to oxidative and osmotic stresses. Virus-induced gene silencing of GhSNAP33 induced spontaneous cell death and reactive oxygen species accumulation in true leaves at a later stage of cotton development. GhSNAP33-deficient cotton was susceptible to V. dahliae infection, which resulted in severe wilt on leaves, an elevated disease index, enhanced vascular browning and thylose accumulation. Conversely, Arabidopsis plants overexpressing GhSNAP33 showed significant resistance to V. dahliae, with reduced disease index and fungal biomass and elevated expression of PR1 and PR5. Leaves from GhSNAP33-transgenic plants showed increased callose deposition and reduced mycelia growth. Moreover, GhSNAP33 overexpression enhanced drought tolerance in Arabidopsis, accompanied with reduced water loss rate and enhanced expression of DERB2A and RD29A during dehydration. Thus, GhSNAP33 positively mediates plant defense against stress conditions and V. dahliae infection, rendering it a candidate for the generation of stress-resistant engineered cotton.
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Affiliation(s)
- Ping Wang
- College of Science, China Agricultural University, Beijing, China
| | - Yun Sun
- College of Science, China Agricultural University, Beijing, China
| | - Yakun Pei
- College of Science, China Agricultural University, Beijing, China
| | - Xiancai Li
- College of Science, China Agricultural University, Beijing, China
| | - Xueyan Zhang
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of The Chinese Academy of Agricultural Sciences, Anyang, China
| | - Fuguang Li
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of The Chinese Academy of Agricultural Sciences, Anyang, China
- *Correspondence: Fuguang Li, Yuxia Hou,
| | - Yuxia Hou
- College of Science, China Agricultural University, Beijing, China
- *Correspondence: Fuguang Li, Yuxia Hou,
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14
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Extended Synaptotagmin 1 Interacts with Herpes Simplex Virus 1 Glycoprotein M and Negatively Modulates Virus-Induced Membrane Fusion. J Virol 2017; 92:JVI.01281-17. [PMID: 29046455 DOI: 10.1128/jvi.01281-17] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 10/11/2017] [Indexed: 12/18/2022] Open
Abstract
Enveloped viruses typically encode their own fusion machinery to enter cells. Herpesviruses are unusual, as they fuse with a number of cellular compartments throughout their life cycles. As uncontrolled fusion of the host membranes should be avoided in these events, tight regulation of the viral fusion machinery is critical. While studying herpes simplex virus 1 (HSV-1) glycoprotein gM, we identified the cellular protein E-Syt1 (extended synaptotagmin 1) as an interaction partner. The interaction took place in both infected and transfected cells, suggesting other viral proteins were not required for the interaction. Most interestingly, E-Syt1 is a member of the synaptotagmin family of membrane fusion regulators. However, the protein is known to promote the tethering of the endoplasmic reticulum (ER) to the plasma membrane. We now show that E-Syt1, along with the related E-Syt3, negatively modulates viral release into the extracellular milieu, cell-to-cell viral spread, and viral entry, all processes that implicate membrane fusion events. Similarly, these E-Syt proteins impacted the formation of virus-induced syncytia. Altogether, these findings hint at the modulation of the viral fusion machinery by the E-Syt family of proteins.IMPORTANCE Viruses typically encode their own fusion apparatus to enable them to enter cells. For many viruses, this means a single fusogenic protein. However, herpesviruses are large entities that express several accessory viral proteins to regulate their fusogenic activity. The present study hints at the additional participation of cellular proteins in this process, suggesting the host can also modulate viral fusion to some extent. Hence E-Syt proteins 1 and 3 seem to negatively modulate the different viral fusion events that take place during the HSV-1 life cycle. This could represent yet another innate immunity response to the virus.
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Rothman JE, Krishnakumar SS, Grushin K, Pincet F. Hypothesis - buttressed rings assemble, clamp, and release SNAREpins for synaptic transmission. FEBS Lett 2017; 591:3459-3480. [PMID: 28983915 PMCID: PMC5698743 DOI: 10.1002/1873-3468.12874] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 10/02/2017] [Accepted: 10/02/2017] [Indexed: 11/21/2022]
Abstract
Neural networks are optimized to detect temporal coincidence on the millisecond timescale. Here, we offer a synthetic hypothesis based on recent structural insights into SNAREs and the C2 domain proteins to explain how synaptic transmission can keep this pace. We suggest that an outer ring of up to six curved Munc13 ‘MUN’ domains transiently anchored to the plasma membrane via its flanking domains surrounds a stable inner ring comprised of synaptotagmin C2 domains to serve as a work‐bench on which SNAREpins are templated. This ‘buttressed‐ring hypothesis’ affords straightforward answers to many principal and long‐standing questions concerning how SNAREpins can be assembled, clamped, and then released synchronously with an action potential.
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Affiliation(s)
- James E Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Shyam S Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Kirill Grushin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Frederic Pincet
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Laboratoire de Physique Statistique, Ecole Normale Supérieure, PSL Research University, Université Paris Diderot Sorbonne Paris Cité, Sorbonne Universités UPMC Univ, CNRS, Paris, France
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16
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Song Y, Botvinnik OB, Lovci MT, Kakaradov B, Liu P, Xu JL, Yeo GW. Single-Cell Alternative Splicing Analysis with Expedition Reveals Splicing Dynamics during Neuron Differentiation. Mol Cell 2017; 67:148-161.e5. [PMID: 28673540 DOI: 10.1016/j.molcel.2017.06.003] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 03/29/2017] [Accepted: 06/02/2017] [Indexed: 12/28/2022]
Abstract
Alternative splicing (AS) generates isoform diversity for cellular identity and homeostasis in multicellular life. Although AS variation has been observed among single cells, little is known about the biological or evolutionary significance of such variation. We developed Expedition, a computational framework consisting of outrigger, a de novo splice graph transversal algorithm to detect AS; anchor, a Bayesian approach to assign modalities; and bonvoyage, a visualization tool using non-negative matrix factorization to display modality changes. Applying Expedition to single pluripotent stem cells undergoing neuronal differentiation, we discover that up to 20% of AS exons exhibit bimodality. Bimodal exons are flanked by more conserved intronic sequences harboring distinct cis-regulatory motifs, constitute much of cell-type-specific splicing, are highly dynamic during cellular transitions, preserve reading frame, and reveal intricacy of cell states invisible to conventional gene expression analysis. Systematic AS characterization in single cells redefines our understanding of AS complexity in cell biology.
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Affiliation(s)
- Yan Song
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Olga B Botvinnik
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Bioinformatics and Systems Biology Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Michael T Lovci
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Boyko Kakaradov
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Bioinformatics and Systems Biology Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Patrick Liu
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jia L Xu
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, Stem Cell Program and Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Bioinformatics and Systems Biology Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119077, Singapore; Molecular Engineering Laboratory, A(∗)STAR, Singapore 138632, Singapore.
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17
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Weber JP, Toft-Bertelsen TL, Mohrmann R, Delgado-Martinez I, Sørensen JB. Synaptotagmin-7 is an asynchronous calcium sensor for synaptic transmission in neurons expressing SNAP-23. PLoS One 2014; 9:e114033. [PMID: 25422940 PMCID: PMC4244210 DOI: 10.1371/journal.pone.0114033] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 11/03/2014] [Indexed: 12/25/2022] Open
Abstract
Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetitive stimulation, and can even play a dominant role in some synapses. Here, we show that substitution of SNAP-23 for SNAP-25 in mouse autaptic glutamatergic hippocampal neurons results in asynchronous release and a higher frequency of spontaneous release events (mEPSCs). Use of neurons from double-knock-out (SNAP-25, synaptotagmin-7) mice in combination with viral transduction showed that SNAP-23-driven release is triggered by endogenous synaptotagmin-7. In the absence of synaptotagmin-7 release became even more asynchronous, and the spontaneous release rate increased even more, indicating that synaptotagmin-7 acts to synchronize release and suppress spontaneous release. However, compared to synaptotagmin-1, synaptotagmin-7 is a both leaky and asynchronous calcium sensor. In the presence of SNAP-25, consequences of the elimination of synaptotagmin-7 were small or absent, indicating that the protein pairs SNAP-25/synaptotagmin-1 and SNAP-23/synaptotagmin-7 might act as mutually exclusive calcium sensors. Expression of fusion proteins between pHluorin (pH-sensitive GFP) and synaptotagmin-1 or -7 showed that vesicles that fuse using the SNAP-23/synaptotagmin-7 combination contained synaptotagmin-1, while synaptotagmin-7 barely displayed activity-dependent trafficking between vesicle and plasma membrane, implying that it acts as a plasma membrane calcium sensor. Overall, these findings support the idea of alternative syt∶SNARE combinations driving release with different kinetics and fidelity.
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Affiliation(s)
- Jens P. Weber
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, Vrije Universiteit, Amsterdam, The Netherlands
| | - Trine L. Toft-Bertelsen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ralf Mohrmann
- Department of Physiology, University of Saarland, Homburg, Germany
| | | | - Jakob B. Sørensen
- Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
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18
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Chen G, Hu T, Li Q, Li J, Jia Y, Wang Z. Expression of synaptosomal-associated protein-25 in the rat brain after subarachnoid hemorrhage. Neural Regen Res 2014; 8:2693-702. [PMID: 25206580 PMCID: PMC4145993 DOI: 10.3969/j.issn.1673-5374.2013.29.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 08/09/2013] [Indexed: 11/18/2022] Open
Abstract
Synaptosomal-associated protein-25 is an important factor for synaptic functions and cognition. In this study, subarachnoid hemorrhage models with spatial learning disorder were established through a blood injection into the chiasmatic cistern. Immunohistochemical staining and western blot analysis results showed that synaptosomal-associated protein-25 expression in the temporal lobe, hippocampus, and cerebellum significantly lower at days 1 and 3 following subarachnoid morrhage. Our findings indicate that synaptosomal-associated protein-25 expression was down-regulated in the rat brain after subarachnoid hemorrhage.
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Affiliation(s)
- Gang Chen
- Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
| | - Tong Hu
- Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China ; Department of Neurosurgery, Yixing People's Hospital, Yixing 214200, Jiangsu Province, China
| | - Qi Li
- Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
| | - Jianke Li
- Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
| | - Yang Jia
- Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
| | - Zhong Wang
- Department of Neurosurgery, the First Affiliated Hospital of Soochow University, Suzhou 215006, Jiangsu Province, China
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19
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Kasai H, Takahashi N, Tokumaru H. Distinct Initial SNARE Configurations Underlying the Diversity of Exocytosis. Physiol Rev 2012; 92:1915-64. [DOI: 10.1152/physrev.00007.2012] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The dynamics of exocytosis are diverse and have been optimized for the functions of synapses and a wide variety of cell types. For example, the kinetics of exocytosis varies by more than five orders of magnitude between ultrafast exocytosis in synaptic vesicles and slow exocytosis in large dense-core vesicles. However, in all cases, exocytosis is mediated by the same fundamental mechanism, i.e., the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins. It is often assumed that vesicles need to be docked at the plasma membrane and SNARE proteins must be preassembled before exocytosis is triggered. However, this model cannot account for the dynamics of exocytosis recently reported in synapses and other cells. For example, vesicles undergo exocytosis without prestimulus docking during tonic exocytosis of synaptic vesicles in the active zone. In addition, epithelial and hematopoietic cells utilize cAMP and kinases to trigger slow exocytosis of nondocked vesicles. In this review, we summarize the manner in which the diversity of exocytosis reflects the initial configurations of SNARE assembly, including trans-SNARE, binary-SNARE, unitary-SNARE, and cis-SNARE configurations. The initial SNARE configurations depend on the particular SNARE subtype (syntaxin, SNAP25, or VAMP), priming proteins (Munc18, Munc13, CAPS, complexin, or snapin), triggering proteins (synaptotagmins, Doc2, and various protein kinases), and the submembraneous cytomatrix, and they are the key to determining the kinetics of subsequent exocytosis. These distinct initial configurations will help us clarify the common SNARE assembly processes underlying exocytosis and membrane trafficking in eukaryotic cells.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Noriko Takahashi
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
| | - Hiroshi Tokumaru
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; and Faculty of Pharmaceutical Sciences at Kagawa, Tokushima Bunri University, Kagawa, Japan
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20
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Bykhovskaia M. Synapsin regulation of vesicle organization and functional pools. Semin Cell Dev Biol 2011; 22:387-92. [PMID: 21827866 DOI: 10.1016/j.semcdb.2011.07.003] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 07/13/2011] [Indexed: 11/18/2022]
Abstract
Synaptic vesicles are organized in clusters, and synapsin maintains vesicle organization and abundance in nerve terminals. At the functional level, vesicles can be subdivided into three pools: the releasable pool, the recycling pool, and the reserve pool, and synapsin mediates transitions between these pools. Synapsin directs vesicles into the reserve pool, and synapsin II isoform has a primary role in this function. In addition, synapsin actively delivers vesicles to active zones. Finally, synapsin I isoform mediates coupling release events to action potentials at the latest stages of exocytosis. Thus, synapsin is involved in multiple stages of the vesicle cycle, including vesicle clustering, maintaining the reserve pool, vesicle delivery to active zones, and synchronizing release events. These processes are regulated via a dynamic synapsin phosphorylation/dephosphorylation cycle which involves multiple phosphorylation sites and several pathways. Different synapsin isoforms have unique and non-redundant roles in the multifaceted synapsin function.
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Affiliation(s)
- Maria Bykhovskaia
- Universidad Central del Caribe, Neuroscience Department, 2U6 Ave Laurel, Bayamon, PR 00956, USA.
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21
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Hirano AA, Brandstätter JH, Morgans CW, Brecha NC. SNAP25 expression in mammalian retinal horizontal cells. J Comp Neurol 2011; 519:972-88. [PMID: 21280047 DOI: 10.1002/cne.22562] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Horizontal cells mediate inhibitory feedforward and feedback lateral interactions in the outer retina at photoreceptor terminals and bipolar cell dendrites; however, the mechanisms that underlie synaptic transmission from mammalian horizontal cells are poorly understood. The localization of a vesicular γ-aminobutyric acid (GABA) transporter (VGAT) to horizontal cell processes in primate and rodent retinae suggested that mammalian horizontal cells release transmitter in a vesicular manner. Toward determining whether the molecular machinery for vesicular transmitter release is present in horizontal cells, we investigated the expression of SNAP25 (synaptosomal-associated protein of 25 kDa), a key SNARE protein, by immunocytochemistry with cell type-specific markers in the retinae of mouse, rat, rabbit, and monkey. Different commercial antibodies to SNAP25 were tested on vertical sections of retina. We report the robust expression of SNAP25 in both plexiform layers. Double labeling with SNAP25 and calbindin antibodies demonstrated that horizontal cell processes and their endings in photoreceptor triad synapses were strongly labeled for both proteins in mouse, rat, rabbit, and monkey retinae. Double labeling with parvalbumin antibodies in monkey retina verified SNAP25 immunoreactivity in all horizontal cells. Pre-embedding immunoelectron microscopy in rabbit retina confirmed expression of SNAP25 in lateral elements within photoreceptor triad synapses. The SNAP25 immunoreactivity in the plexiform layers and outer nuclear layer fell into at least three patterns depending on the antibody, suggesting a differential distribution of SNAP25 isoforms. The presence of SNAP25a and SNAP25b isoforms in mouse retina was established by reverse transcriptase-polymerase chain reaction. SNAP25 expression in mammalian horizontal cells along with other SNARE proteins is consistent with vesicular exocytosis.
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Affiliation(s)
- Arlene A Hirano
- Department of Neurobiology, David Geffen School of Medicine at the University of California-Los Angeles, Los Angeles, California 90095, USA.
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22
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Geumann C, Grønborg M, Hellwig M, Martens H, Jahn R. A sandwich enzyme-linked immunosorbent assay for the quantification of insoluble membrane and scaffold proteins. Anal Biochem 2010; 402:161-9. [DOI: 10.1016/j.ab.2010.03.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Revised: 03/29/2010] [Accepted: 03/30/2010] [Indexed: 10/19/2022]
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23
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Walter AM, Wiederhold K, Bruns D, Fasshauer D, Sørensen JB. Synaptobrevin N-terminally bound to syntaxin-SNAP-25 defines the primed vesicle state in regulated exocytosis. ACTA ACUST UNITED AC 2010; 188:401-13. [PMID: 20142423 PMCID: PMC2819690 DOI: 10.1083/jcb.200907018] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Time-resolved measurements of exocytosis identify a domain of the SNARE complex required to keep vesicles readily releasable. Rapid neurotransmitter release depends on the ability to arrest the SNAP receptor (SNARE)–dependent exocytosis pathway at an intermediate “cocked” state, from which fusion can be triggered by Ca2+. It is not clear whether this state includes assembly of synaptobrevin (the vesicle membrane SNARE) to the syntaxin–SNAP-25 (target membrane SNAREs) acceptor complex or whether the reaction is arrested upstream of that step. In this study, by a combination of in vitro biophysical measurements and time-resolved exocytosis measurements in adrenal chromaffin cells, we find that mutations of the N-terminal interaction layers of the SNARE bundle inhibit assembly in vitro and vesicle priming in vivo without detectable changes in triggering speed or fusion pore properties. In contrast, mutations in the last C-terminal layer decrease triggering speed and fusion pore duration. Between the two domains, we identify a region exquisitely sensitive to mutation, possibly constituting a switch. Our data are consistent with a model in which the N terminus of the SNARE complex assembles during vesicle priming, followed by Ca2+-triggered C-terminal assembly and membrane fusion.
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Affiliation(s)
- Alexander M Walter
- Molecular Mechanism of Exocytosis, Department of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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24
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Plattner H. Membrane Trafficking in Protozoa. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 280:79-184. [DOI: 10.1016/s1937-6448(10)80003-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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25
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Brunger AT, Weninger K, Bowen M, Chu S. Single-molecule studies of the neuronal SNARE fusion machinery. Annu Rev Biochem 2009; 78:903-28. [PMID: 19489736 DOI: 10.1146/annurev.biochem.77.070306.103621] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
SNAREs are essential components of the machinery for Ca(2+)-triggered fusion of synaptic vesicles with the plasma membrane, resulting in neurotransmitter release into the synaptic cleft. Although much is known about their biophysical and structural properties and their interactions with accessory proteins such as the Ca(2+) sensor synaptotagmin, their precise role in membrane fusion remains an enigma. Ensemble studies of liposomes with reconstituted SNAREs have demonstrated that SNAREs and accessory proteins can trigger lipid mixing/fusion, but the inability to study individual fusion events has precluded molecular insights into the fusion process. Thus, this field is ripe for studies with single-molecule methodology. In this review, we discuss applications of single-molecule approaches to observe reconstituted SNAREs, their complexes, associated proteins, and their effect on biological membranes. Some of the findings are provocative, such as the possibility of parallel and antiparallel SNARE complexes or of vesicle docking with only syntaxin and synaptobrevin, but have been confirmed by other experiments.
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Affiliation(s)
- Axel T Brunger
- The Howard Hughes Medical Institute and Departments of Molecular and Cellular Physiology, Neurology and Neurological Sciences, Structural Biology, and Photon Science, Stanford University, CA 94305, USA.
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26
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Prescott GR, Gorleku OA, Greaves J, Chamberlain LH. Palmitoylation of the synaptic vesicle fusion machinery. J Neurochem 2009; 110:1135-49. [PMID: 19508429 DOI: 10.1111/j.1471-4159.2009.06205.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fusion of synaptic vesicles with the pre-synaptic plasma membrane mediates the secretion of neurotransmitters at nerve terminals. This pathway is regulated by an array of protein-protein interactions. Of central importance are the soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor (SNARE) proteins syntaxin 1 and SNAP25, which are associated with the pre-synaptic plasma membrane and vesicle-associated membrane protein (VAMP2), a synaptic vesicle SNARE. Syntaxin 1, SNAP25 and VAMP2 interact to form a tight complex bridging the vesicle and plasma membranes, which has been suggested to represent the minimal membrane fusion machinery. Synaptic vesicle fusion is stimulated by a rise in intraterminal Ca2+ levels, and a major Ca2+ sensor for vesicle fusion is synaptotagmin I. Synaptotagmin is likely to couple Ca2+ entry to vesicle fusion via Ca2+-dependent and independent interactions with membrane phospholipids and the SNARE proteins. Intriguingly, syntaxin 1, SNAP25, VAMP2 and synaptotagmin I have all been reported to be modified by palmitoylation in neurons. In this review, we discuss the mechanisms and dynamics of palmitoylation of these proteins and speculate on how palmitoylation might contribute to the regulation of synaptic vesicle fusion.
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Affiliation(s)
- Gerald R Prescott
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
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27
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Montana V, Liu W, Mohideen U, Parpura V. Single molecule measurements of mechanical interactions within ternary SNARE complexes and dynamics of their disassembly: SNAP25 vs. SNAP23. J Physiol 2009; 587:1943-60. [PMID: 19273577 DOI: 10.1113/jphysiol.2009.168575] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Regulated exocytosis is a crucial event for intercellular communication between neurons and astrocytes within the CNS. The soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) complex, composed of synaptobrevin 2, syntaxin and synaptosome-associated protein of 25 kDa or 23 kDa (SNAP25 or SNAP23), is essential in this process. It was reported that SNAP25 and SNAP23 have distinct roles in exocytotic release, where SNAP25, but not SNAP23, supports an exocytotic burst. It is not clear, however, whether this is due to the intrinsic properties of the ternary SNARE complex, containing either SNAP25 or SNAP23, or perhaps due to the differential association of these proteins with ancillary proteins to the complex. Here, using force spectroscopy, we show from single molecule investigations of the SNARE complex, that SNAP23A created a local interaction at the ionic layer by cuffing syntaxin 1A and synaptobrevin 2, similar to the action of SNAP25B; thus either of the ternary complexes would allow positioning of vesicles at a maximal distance of approximately 13 nm from the plasma membrane. However, the stability of the ternary SNARE complex containing SNAP23A is less than half of that for the complex containing SNAP25B. Thus, differences in the stability of the two different ternary complexes could underlie some of the SNAP25/23 differential ability to control the exocytotic burst.
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Affiliation(s)
- Vedrana Montana
- Department of Neurobiology, University of Alabama, Birmingham, AL 35294, USA
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