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Vardar G, Salazar-Lázaro A, Zobel S, Trimbuch T, Rosenmund C. Syntaxin-1A modulates vesicle fusion in mammalian neurons via juxtamembrane domain dependent palmitoylation of its transmembrane domain. eLife 2022; 11:78182. [PMID: 35638903 PMCID: PMC9183232 DOI: 10.7554/elife.78182] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 05/30/2022] [Indexed: 11/16/2022] Open
Abstract
SNAREs are undoubtedly one of the core elements of synaptic transmission. Contrary to the well characterized function of their SNARE domains bringing the plasma and vesicular membranes together, the level of contribution of their juxtamembrane domain (JMD) and the transmembrane domain (TMD) to the vesicle fusion is still under debate. To elucidate this issue, we analyzed three groups of STX1A mutations in cultured mouse hippocampal neurons: (1) elongation of STX1A’s JMD by three amino acid insertions in the junction of SNARE-JMD or JMD-TMD; (2) charge reversal mutations in STX1A’s JMD; and (3) palmitoylation deficiency mutations in STX1A’s TMD. We found that both JMD elongations and charge reversal mutations have position-dependent differential effects on Ca2+-evoked and spontaneous neurotransmitter release. Importantly, we show that STX1A’s JMD regulates the palmitoylation of STX1A’s TMD and loss of STX1A palmitoylation either through charge reversal mutation K260E or by loss of TMD cysteines inhibits spontaneous vesicle fusion. Interestingly, the retinal ribbon specific STX3B has a glutamate in the position corresponding to the K260E mutation in STX1A and mutating it with E259K acts as a molecular on-switch. Furthermore, palmitoylation of post-synaptic STX3A can be induced by the exchange of its JMD with STX1A’s JMD together with the incorporation of two cysteines into its TMD. Forced palmitoylation of STX3A dramatically enhances spontaneous vesicle fusion suggesting that STX1A regulates spontaneous release through two distinct mechanisms: one through the C-terminal half of its SNARE domain and the other through the palmitoylation of its TMD.
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Affiliation(s)
- Gülçin Vardar
- Department of Neurophysiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Andrea Salazar-Lázaro
- Department of Neurophysiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Sina Zobel
- Department of Neurophysiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Thorsten Trimbuch
- Department of Neurophysiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Christian Rosenmund
- Department of Neurophysiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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Orr A, Song H, Wickner W. Fusion with wild-type SNARE domains is controlled by juxtamembrane domains, transmembrane anchors, and Sec17. Mol Biol Cell 2022; 33:ar38. [PMID: 35171720 PMCID: PMC9282010 DOI: 10.1091/mbc.e21-11-0583] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Membrane fusion requires tethers, SNAREs of R, Qa, Qb, and Qc families, and chaperones of the SM, Sec17/SNAP, and Sec18/NSF families. SNAREs have N-domains, SNARE domains that zipper into 4-helical RQaQbQc coiled coils, a short juxtamembrane (Jx) domain, and (often) a C-terminal transmembrane anchor. We reconstitute fusion with purified components from yeast vacuoles, where the HOPS protein combines tethering and SM functions. The vacuolar Rab, lipids, and R-SNARE activate HOPS to bind Q-SNAREs and catalyze trans-SNARE associations. With SNAREs initially disassembled, as they are on the organelle, we now report that R- and Qa-SNAREs require their physiological juxtamembrane (Jx) regions for fusion. Swap of the Jx domain between the R- and Qa-SNAREs blocks fusion after SNARE association in trans. This block is bypassed by either Sec17, which drives fusion without requiring complete SNARE zippering, or transmembrane-anchored Qb-SNARE in complex with Qa. The abundance of the trans-SNARE complex is not the sole fusion determinant, as it is unaltered by Sec17, Jx swap, or the Qb-transmembrane anchor. The sensitivity of fusion to Jx swap in the absence of a Qb transmembrane anchor is inherent to the SNAREs, because it remains when a synthetic tether replaces HOPS.
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Affiliation(s)
- Amy Orr
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, 7200 Vail Building, Hanover, NH 03755
| | - Hongki Song
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, 7200 Vail Building, Hanover, NH 03755
| | - William Wickner
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, 7200 Vail Building, Hanover, NH 03755
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Barak-Broner N, Singer-Lahat D, Chikvashvili D, Lotan I. CK2 Phosphorylation Is Required for Regulation of Syntaxin 1A Activity in Ca 2+-Triggered Release in Neuroendocrine Cells. Int J Mol Sci 2021; 22:ijms222413556. [PMID: 34948351 PMCID: PMC8708312 DOI: 10.3390/ijms222413556] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 12/29/2022] Open
Abstract
The polybasic juxtamembrane region (5RK) of the plasma membrane neuronal SNARE, syntaxin1A (Syx), was previously shown by us to act as a fusion clamp in PC12 cells, as charge neutralization of 5RK promotes spontaneous and inhibits Ca2+-triggered release. Using a Syx-based FRET probe (CSYS), we demonstrated that 5RK is required for a depolarization-induced Ca+2-dependent opening (close-to-open transition; CDO) of Syx, which involves the vesicular SNARE synaptobrevin2 and occurs concomitantly with Ca2+-triggered release. Here, we investigated the mechanism underlying the CDO requirement for 5RK and identified phosphorylation of Syx at Ser-14 (S14) by casein kinase 2 (CK2) as a crucial molecular determinant. Thus, following biochemical verification that both endogenous Syx and CSYS are constitutively S14 phosphorylated in PC12 cells, dynamic FRET analysis of phospho-null and phospho-mimetic mutants of CSYS and the use of a CK2 inhibitor revealed that the S14 phosphorylation confers the CDO requirement for 5RK. In accord, amperometric analysis of catecholamine release revealed that the phospho-null mutant does not support Ca2+-triggered release. These results identify a functionally important CK2 phosphorylation of Syx that is required for the 5RK-regulation of CDO and for concomitant Ca2+-triggered release. Further, also spontaneous release, conferred by charge neutralization of 5RK, was abolished in the phospho-null mutant.
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Affiliation(s)
- Noa Barak-Broner
- Department of Neurobiology Biochemistry & Biophysics, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel;
| | - Dafna Singer-Lahat
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
| | - Dodo Chikvashvili
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
| | - Ilana Lotan
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel; (D.S.-L.); (D.C.)
- Sagol School of Neuroscience, Tel Aviv University, Ramat Aviv, Tel Aviv-Yafo 69978, Israel
- Correspondence:
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Yang Y, Margam NN. Structural Insights into Membrane Fusion Mediated by Convergent Small Fusogens. Cells 2021; 10:cells10010160. [PMID: 33467484 PMCID: PMC7830690 DOI: 10.3390/cells10010160] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/07/2021] [Accepted: 01/13/2021] [Indexed: 12/30/2022] Open
Abstract
From lifeless viral particles to complex multicellular organisms, membrane fusion is inarguably the important fundamental biological phenomena. Sitting at the heart of membrane fusion are protein mediators known as fusogens. Despite the extensive functional and structural characterization of these proteins in recent years, scientists are still grappling with the fundamental mechanisms underlying membrane fusion. From an evolutionary perspective, fusogens follow divergent evolutionary principles in that they are functionally independent and do not share any sequence identity; however, they possess structural similarity, raising the possibility that membrane fusion is mediated by essential motifs ubiquitous to all. In this review, we particularly emphasize structural characteristics of small-molecular-weight fusogens in the hope of uncovering the most fundamental aspects mediating membrane–membrane interactions. By identifying and elucidating fusion-dependent functional domains, this review paves the way for future research exploring novel fusogens in health and disease.
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Rathore SS, Liu Y, Yu H, Wan C, Lee M, Yin Q, Stowell MHB, Shen J. Intracellular Vesicle Fusion Requires a Membrane-Destabilizing Peptide Located at the Juxtamembrane Region of the v-SNARE. Cell Rep 2019; 29:4583-4592.e3. [PMID: 31875562 PMCID: PMC6990648 DOI: 10.1016/j.celrep.2019.11.107] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/13/2019] [Accepted: 11/26/2019] [Indexed: 12/11/2022] Open
Abstract
Intracellular vesicle fusion is mediated by soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) and Sec1/Munc18 (SM) proteins. It is generally accepted that membrane fusion occurs when the vesicle and target membranes are brought into close proximity by SNAREs and SM proteins. In this work, we demonstrate that, for fusion to occur, membrane bilayers must be destabilized by a conserved membrane-embedded motif located at the juxtamembrane region of the vesicle-anchored v-SNARE. Comprised of basic and hydrophobic residues, the juxtamembrane motif perturbs the lipid bilayer structure and promotes SNARE-SM-mediated membrane fusion. The juxtamembrane motif can be functionally substituted with an unrelated membrane-disrupting peptide in the membrane fusion reaction. These findings establish the juxtamembrane motif of the v-SNARE as a membrane-destabilizing peptide. Requirement of membrane-destabilizing peptides is likely a common feature of biological membrane fusion.
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Affiliation(s)
- Shailendra S Rathore
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - Yinghui Liu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA; Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China
| | - Haijia Yu
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA; Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
| | - Chun Wan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - MyeongSeon Lee
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - Qian Yin
- Department of Biological Sciences and Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA
| | - Michael H B Stowell
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA
| | - Jingshi Shen
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, 347 UCB, Boulder, CO 80309, USA.
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Liu X, Tong Y, Fang PP. Recent development in amperometric measurements of vesicular exocytosis. Trends Analyt Chem 2019. [DOI: 10.1016/j.trac.2019.01.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Wheeler S, Schmid R, Sillence DJ. Lipid⁻Protein Interactions in Niemann⁻Pick Type C Disease: Insights from Molecular Modeling. Int J Mol Sci 2019; 20:E717. [PMID: 30736449 PMCID: PMC6387118 DOI: 10.3390/ijms20030717] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 01/31/2019] [Accepted: 02/03/2019] [Indexed: 12/19/2022] Open
Abstract
The accumulation of lipids in the late endosomes and lysosomes of Niemann⁻Pick type C disease (NPCD) cells is a consequence of the dysfunction of one protein (usually NPC1) but induces dysfunction in many proteins. We used molecular docking to propose (a) that NPC1 exports not just cholesterol, but also sphingosine, (b) that the cholesterol sensitivity of big potassium channel (BK) can be traced to a previously unappreciated site on the channel's voltage sensor, (c) that transient receptor potential mucolipin 1 (TRPML1) inhibition by sphingomyelin is likely an indirect effect, and (d) that phosphoinositides are responsible for both the mislocalization of annexin A2 (AnxA2) and a soluble NSF (N-ethylmaleimide Sensitive Fusion) protein attachment receptor (SNARE) recycling defect. These results are set in the context of existing knowledge of NPCD to sketch an account of the endolysosomal pathology key to this disease.
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Affiliation(s)
- Simon Wheeler
- School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, UK.
| | - Ralf Schmid
- Leicester Institute of Structural and Chemical Biology, Henry Wellcome Building, University of Leicester, Lancaster Road, Leicester LE1 7RH, UK.
| | - Dan J Sillence
- School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, UK.
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