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Toulmé E, Lázaro AS, Trimbuch T, Rizo J, Rosenmund C. Neurotransmitter release is triggered by a calcium-induced rearrangement in the Synaptotagmin-1/SNARE complex primary interface. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.599435. [PMID: 38948868 PMCID: PMC11213007 DOI: 10.1101/2024.06.17.599435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
The Ca2+ sensor synaptotagmin-1 triggers neurotransmitter release together with the neuronal SNARE complex formed by syntaxin-1, SNAP25 and synaptobrevin. Moreover, synaptotagmin-1 increases synaptic vesicle priming and impairs spontaneous vesicle release. The synaptotagmin-1 C2B domain binds to the SNARE complex through a primary interface via two regions (I and II), but how exactly this interface mediates distinct functions of synaptotagmin-1, and the mechanism underlying Ca2+-triggering of release is unknown. Using mutagenesis and electrophysiological experiments, we show that region II is functionally and spatially subdivided: binding of C2B domain arginines to SNAP-25 acidic residues at one face of region II is crucial for Ca2+-evoked release but not for vesicle priming or clamping of spontaneous release, whereas other SNAP-25 and syntaxin-1 acidic residues at the other face mediate priming and clamping of spontaneous release but not evoked release. Mutations that disrupt region I impair the priming and clamping functions of synaptotagmin-1 while, strikingly, mutations that enhance binding through this region increase vesicle priming and clamping of spontaneous release, but strongly inhibit evoked release and vesicle fusogenicity. These results support previous findings that the primary interface mediates the functions of synaptotagmin-1 in vesicle priming and clamping of spontaneous release, and, importantly, show that Ca2+-triggering of release requires a rearrangement of the primary interface involving dissociation of region I, while region II remains bound. Together with modeling and biophysical studies presented in the accompanying paper, our data suggest a model whereby this rearrangement pulls the SNARE complex to facilitate fast synaptic vesicle fusion.
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Affiliation(s)
- Estelle Toulmé
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Andrea Salazar Lázaro
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Thorsten Trimbuch
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Christian Rosenmund
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
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Jaczynska K, Esser V, Xu J, Sari L, Lin MM, Rosenmund C, Rizo J. A lever hypothesis for Synaptotagmin-1 action in neurotransmitter release. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.599417. [PMID: 38948826 PMCID: PMC11212951 DOI: 10.1101/2024.06.17.599417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Neurotransmitter release is triggered in microseconds by Ca2+-binding to the Synaptotagmin-1 C2 domains and by SNARE complexes that form four-helix bundles between synaptic vesicles and plasma membranes, but the coupling mechanism between Ca2+-sensing and membrane fusion is unknown. Release requires extension of SNARE helices into juxtamembrane linkers that precede transmembrane regions (linker zippering) and binding of the Synaptotagmin-1 C2B domain to SNARE complexes through a 'primary interface' comprising two regions (I and II). The Synaptotagmin-1 Ca2+-binding loops were believed to accelerate membrane fusion by inducing membrane curvature, perturbing lipid bilayers or helping bridge the membranes, but SNARE complex binding orients the Ca2+-binding loops away from the fusion site, hindering these putative activities. Molecular dynamics simulations now suggest that Synaptotagmin-1 C2 domains near the site of fusion hinder SNARE action, providing an explanation for this paradox and arguing against previous models of Sytnaptotagmin-1 action. NMR experiments reveal that binding of C2B domain arginines to SNARE acidic residues at region II remains after disruption of region I. These results and fluorescence resonance energy transfer assays, together with previous data, suggest that Ca2+ causes reorientation of the C2B domain on the membrane and dissociation from the SNAREs at region I but not region II. Based on these results and molecular modeling, we propose that Synaptotagmin-1 acts as a lever that pulls the SNARE complex when Ca2+ causes reorientation of the C2B domain, facilitating linker zippering and fast membrane fusion. This hypothesis is supported by the electrophysiological data described in the accompanying paper.
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Affiliation(s)
- Klaudia Jaczynska
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Victoria Esser
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Junjie Xu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Levent Sari
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Milo M. Lin
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Christian Rosenmund
- Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Neurophysiology, Berlin, Germany
- NeuroCure Cluster of Excellence, Berlin, Germany
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Bykhovskaia M. Dynamic Formation of the Protein-Lipid Pre-fusion Complex. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.17.589983. [PMID: 38659925 PMCID: PMC11042276 DOI: 10.1101/2024.04.17.589983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Synaptic vesicles (SVs) fuse with the presynaptic membrane (PM) to release neuronal transmitters. The SV protein Synaptotagmin 1 (Syt1) serves as a Ca2+ sensor for evoked fusion. Syt1 is thought to trigger fusion by penetrating into PM upon Ca2+ binding, however the mechanistic detail of this process is still debated. Syt1 interacts with the SNARE complex, a coiled-coil four-helical bundle that enables the SV-PM attachment. The SNARE-associated protein Complexin (Cpx) promotes the Ca2+-dependent fusion, possibly interacting with Syt1. We employed all-atom molecular dynamics (MD) to investigate the formation of the Syt1-SNARE-Cpx complex interacting with the lipid bilayers of PM and SV. Our simulations demonstrated that the PM-Syt1-SNARE-Cpx complex can transition to a "dead-end" state, wherein Syt1 attaches tightly to PM but does not immerse into it, as opposed to a pre-fusion state, which has the tips of the Ca2+-bound C2 domains of Syt1 inserted into PM. Our simulations unraveled the sequence of Syt1 conformational transitions, including the simultaneous Syt1 docking to the SNARE-Cpx bundle and PM, followed by the Ca2+ chelation and the penetration of the tips of Syt1 domains into PM, leading to the pre-fusion state of the protein-lipid complex. Importantly, we found that the direct Syt1-Cpx interactions are required to promote these transitions. Thus, we developed the all-atom dynamic model of the conformational transitions that lead to the formation of the pre-fusion PM-Syt1-SNARE-Cpx complex. Our simulations also revealed an alternative "dead-end" state of the protein-lipid complex that can be formed if this pathway is disrupted.
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Courtney KC, Mandal T, Mehta N, Wu L, Li Y, Das D, Cui Q, Chapman ER. Synaptotagmin-7 outperforms synaptotagmin-1 to promote the formation of large, stable fusion pores via robust membrane penetration. Nat Commun 2023; 14:7761. [PMID: 38012142 PMCID: PMC10681989 DOI: 10.1038/s41467-023-42497-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 10/11/2023] [Indexed: 11/29/2023] Open
Abstract
Synaptotagmin-1 and synaptotagmin-7 are two prominent calcium sensors that regulate exocytosis in neuronal and neuroendocrine cells. Upon binding calcium, both proteins partially penetrate lipid bilayers that bear anionic phospholipids, but the specific underlying mechanisms that enable them to trigger exocytosis remain controversial. Here, we examine the biophysical properties of these two synaptotagmin isoforms and compare their interactions with phospholipid membranes. We discover that synaptotagmin-1-membrane interactions are greatly influenced by membrane order; tight packing of phosphatidylserine inhibits binding due to impaired membrane penetration. In contrast, synaptotagmin-7 exhibits robust membrane binding and penetration activity regardless of phospholipid acyl chain structure. Thus, synaptotagmin-7 is a super-penetrator. We exploit these observations to specifically isolate and examine the role of membrane penetration in synaptotagmin function. Using nanodisc-black lipid membrane electrophysiology, we demonstrate that membrane penetration is a critical component that underlies how synaptotagmin proteins regulate reconstituted, exocytic fusion pores in response to calcium.
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Affiliation(s)
- Kevin C Courtney
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biochemistry and Molecular Medicine, West Virginia University, Morgantown, WV, 26506, USA
| | - Taraknath Mandal
- Department of Chemistry, Boston University, Boston, MA, 02215, USA
- Department of Physics, Indian Institute of Technology - Kanpur, Kanpur, 208016, India
| | - Nikunj Mehta
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Lanxi Wu
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - Yueqi Li
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
- Center for Bioanalytical Chemistry, University of Science and Technology of China, Hefei, 230026, China
| | - Debasis Das
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Navy Nagar, Colaba, Mumbai, 400005, India
| | - Qiang Cui
- Department of Chemistry, Boston University, Boston, MA, 02215, USA
| | - Edwin R Chapman
- Howard Hughes Medical Institute and the Department of Neuroscience, University of Wisconsin, 1111 Highland Avenue, Madison, WI, 53705, USA.
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Norman CA, Krishnakumar SS, Timofeeva Y, Volynski KE. The release of inhibition model reproduces kinetics and plasticity of neurotransmitter release in central synapses. Commun Biol 2023; 6:1091. [PMID: 37891212 PMCID: PMC10611806 DOI: 10.1038/s42003-023-05445-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
Calcium-evoked release of neurotransmitters from synaptic vesicles (SVs) is catalysed by SNARE proteins. The predominant view is that, at rest, complete assembly of SNARE complexes is inhibited ('clamped') by synaptotagmin and complexin molecules. Calcium binding by synaptotagmins releases this fusion clamp and triggers fast SV exocytosis. However, this model has not been quantitatively tested over physiological timescales. Here we describe an experimentally constrained computational modelling framework to quantitatively assess how the molecular architecture of the fusion clamp affects SV exocytosis. Our results argue that the 'release-of-inhibition' model can indeed account for fast calcium-activated SV fusion, and that dual binding of synaptotagmin-1 and synaptotagmin-7 to the same SNARE complex enables synergistic regulation of the kinetics and plasticity of neurotransmitter release. The developed framework provides a powerful and adaptable tool to link the molecular biochemistry of presynaptic proteins to physiological data and efficiently test the plausibility of calcium-activated neurotransmitter release models.
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Affiliation(s)
- Christopher A Norman
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK
- Department of Computer Science, University of Warwick, Coventry, CV4 7AL, UK
- Mathematics for Real-World Systems Centre for Doctoral Training, University of Warwick, Coventry, CV4 7AL, UK
| | - Shyam S Krishnakumar
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK.
- Department of Neurology, Yale Nanobiology Institute, Yale University School of Medicine, New Haven, CT, 06510, USA.
| | - Yulia Timofeeva
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK.
- Department of Computer Science, University of Warwick, Coventry, CV4 7AL, UK.
| | - Kirill E Volynski
- University College London Institute of Neurology, University College London, London, WC1N 3BG, UK.
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, 06510, USA.
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Chen X, Perry S, Wang B, Wang S, Hu J, Loxterkamp E, Dickman D, Han C. Tissue-specific knockout in Drosophila neuromuscular system reveals ESCRT's role in formation of synapse-derived extracellular vesicles. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.25.559303. [PMID: 37808853 PMCID: PMC10557614 DOI: 10.1101/2023.09.25.559303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Tissue-specific gene knockout by CRISPR/Cas9 is a powerful approach for characterizing gene functions in animal development. However, this approach has been successfully applied in only a small number of Drosophila tissues. The Drosophila motor nervous system is an excellent model system for studying the biology of neuromuscular junction (NMJ). To expand tissue-specific CRISPR to the Drosophila motor system, here we present a CRISPR-mediated tissue-restricted mutagenesis (CRISPR-TRiM) toolkit for knocking out genes in motoneurons, muscles, and glial cells. We validated the efficacy of this toolkit by knocking out known genes in each tissue, demonstrated its orthogonal use with the Gal4/UAS binary expression system, and showed simultaneous knockout of multiple redundant genes. Using these tools, we discovered an essential role for SNARE pathways in NMJ maintenance. Furthermore, we demonstrate that the canonical ESCRT pathway suppresses NMJ bouton growth by downregulating the retrograde Gbb signaling. Lastly, we found that axon termini of motoneurons rely on ESCRT-mediated intra-axonal membrane trafficking to lease extracellular vesicles at the NMJ.
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Affiliation(s)
- Xinchen Chen
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Sarah Perry
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Bei Wang
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Shuran Wang
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Jiayi Hu
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
| | - Elizabeth Loxterkamp
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Chun Han
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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Zhuang R, Zhou Y, Wang Z, Cao Y, Chen J, Xu L, Ren Y, Zheng Y, Wei Z, Qiu H, Li L, Han Y, Yun Y, Chen X, Hong W, Wang T. Rab26 restricts insulin secretion via sequestering Synaptotagmin-1. PLoS Biol 2023; 21:e3002142. [PMID: 37289842 DOI: 10.1371/journal.pbio.3002142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 04/28/2023] [Indexed: 06/10/2023] Open
Abstract
Rab26 is known to regulate multiple membrane trafficking events, but its role in insulin secretion in pancreatic β cells remains unclear despite it was first identified in the pancreas. In this study, we generated Rab26-/- mice through CRISPR/Cas9 technique. Surprisingly, insulin levels in the blood of the Rab26-/- mice do not decrease upon glucose stimulation but conversely increase. Deficiency of Rab26 promotes insulin secretion, which was independently verified by Rab26 knockdown in pancreatic insulinoma cells. Conversely, overexpression of Rab26 suppresses insulin secretion in both insulinoma cell lines and isolated mouse islets. Islets overexpressing Rab26, upon transplantation, also failed to restore glucose homeostasis in type 1 diabetic mice. Immunofluorescence microscopy revealed that overexpression of Rab26 results in clustering of insulin granules. GST-pulldown experiments reveal that Rab26 interacts with synaptotagmin-1 (Syt1) through directly binding to its C2A domain, which interfering with the interaction between Syt1 and SNAP25, and consequently inhibiting the exocytosis of newcomer insulin granules revealed by TIRF microscopy. Our results suggest that Rab26 serves as a negative regulator of insulin secretion, via suppressing insulin granule fusion with plasma membrane through sequestering Syt1.
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Affiliation(s)
- Ruijuan Zhuang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Yuxia Zhou
- School of Basic Medical Sciences, Guizhou Provincial Key Laboratory of Pathogenesis and Drug Research on Common Chronic Diseases, Guizhou Medical University, Guiyang, China
| | - Ziyan Wang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Yating Cao
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Fujian, China
| | - Jun Chen
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Liju Xu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Yandan Ren
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Yige Zheng
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Ziheng Wei
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Hantian Qiu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Liangcheng Li
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Yang Han
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Ye Yun
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
| | - Xin Chen
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Fujian, China
| | - Wanjin Hong
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
- Institute of Molecular and Cell Biology, A STAR (Agency of Science, Technology and Research), Singapore, Singapore
| | - Tuanlao Wang
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Fujian Provincial Key Laboratory of Innovative Drug Target Research, Xiamen University, Fujian, China
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Brunger AT, Leitz J. The Core Complex of the Ca 2+-Triggered Presynaptic Fusion Machinery. J Mol Biol 2023; 435:167853. [PMID: 36243149 PMCID: PMC10578080 DOI: 10.1016/j.jmb.2022.167853] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 09/30/2022] [Accepted: 10/03/2022] [Indexed: 11/05/2022]
Abstract
Synaptic neurotransmitter release is mediated by an orchestra of presynaptic proteins that precisely control and trigger fusion between synaptic vesicles and the neuron terminal at the active zone upon the arrival of an action potential. Critical to this process are the neuronal SNAREs (Soluble N-ethylmaleimide sensitive factor Attachment protein REceptor), the Ca2+-sensor synaptotagmin, the activator/regulator complexin, and other factors. Here, we review the interactions between the SNARE complex and synaptotagmin, with focus on the so-called primary interface between synaptotagmin and the SNARE complex that has been validated in terms of its physiological relevance. We discuss several other but less validated interfaces as well, including the so-called tripartite interface, and we discuss the pros and cons for these possible alternative interfaces. We also present new molecular dynamics simulations of the tripartite interface and new data of an inhibitor of the primary interface in a reconstituted system of synaptic vesicle fusion.
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Affiliation(s)
- Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States; Department of Neurology and Neurological Sciences, Stanford University, Stanford, United States; Department of Structural Biology, Stanford University, Stanford, United States; Department of Photon Science, Stanford University, Stanford, United States; Howard Hughes Medical Institute, Stanford University, Stanford, United States.
| | - Jeremy Leitz
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States; Department of Neurology and Neurological Sciences, Stanford University, Stanford, United States; Department of Structural Biology, Stanford University, Stanford, United States; Department of Photon Science, Stanford University, Stanford, United States; Howard Hughes Medical Institute, Stanford University, Stanford, United States
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9
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Pugliese A, Holland SH, Rodolico C, Lochmüller H, Spendiff S. Presynaptic Congenital Myasthenic Syndromes: Understanding Clinical Phenotypes through In vivo Models. J Neuromuscul Dis 2023; 10:731-759. [PMID: 37212067 PMCID: PMC10578258 DOI: 10.3233/jnd-221646] [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] [Accepted: 04/30/2023] [Indexed: 05/23/2023]
Abstract
Presynaptic congenital myasthenic syndromes (CMS) are a group of genetic disorders affecting the presynaptic side of the neuromuscular junctions (NMJ). They can result from a dysfunction in acetylcholine (ACh) synthesis or recycling, in its packaging into synaptic vesicles, or its subsequent release into the synaptic cleft. Other proteins involved in presynaptic endplate development and maintenance can also be impaired.Presynaptic CMS usually presents during the prenatal or neonatal period, with a severe phenotype including congenital arthrogryposis, developmental delay, and apnoeic crisis. However, milder phenotypes with proximal muscle weakness and good response to treatment have been described. Finally, many presynaptic genes are expressed in the brain, justifying the presence of additional central nervous system symptoms.Several animal models have been developed to study CMS, providing the opportunity to identify disease mechanisms and test treatment options. In this review, we describe presynaptic CMS phenotypes with a focus on in vivo models, to better understand CMS pathophysiology and define new causative genes.
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Affiliation(s)
- Alessia Pugliese
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Stephen H. Holland
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Carmelo Rodolico
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - Hanns Lochmüller
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
- Department of Medicine, Division of Neurology, The Ottawa Hospital, Ottawa, ON, Canada
- Brain and Mind Research Institute, University of Ottawa, Ottawa, ON, Canada
- Department of Neuropediatrics and Muscle Disorders, Medical Center – University of Freiburg, Faculty of Medicine, Freiburg, Germany
- Centro Nacional de Análisis Genómico (CNAG-CRG), Center for Genomic Regulation, Barcelona Institute of Science and Technology (BIST), Barcelona, Catalonia, Spain
| | - Sally Spendiff
- Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada
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10
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Zhou Q. Calcium Sensors of Neurotransmitter Release. ADVANCES IN NEUROBIOLOGY 2023; 33:119-138. [PMID: 37615865 DOI: 10.1007/978-3-031-34229-5_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Calcium (Ca2+) plays a critical role in triggering all three primary modes of neurotransmitter release (synchronous, asynchronous, and spontaneous). Synaptotagmin1, a protein with two C2 domains, is the first isoform of the synaptotagmin family that was identified and demonstrated as the primary Ca2+ sensor for synchronous neurotransmitter release. Other isoforms of the synaptotagmin family as well as other C2 proteins such as the double C2 domain protein family were found to act as Ca2+ sensors for different modes of neurotransmitter release. Major recent advances and previous data suggest a new model, release-of-inhibition, for the initiation of Ca2+-triggered synchronous neurotransmitter release. Synaptotagmin1 binds Ca2+ via its two C2 domains and relieves a primed pre-fusion machinery. Before Ca2+ triggering, synaptotagmin1 interacts Ca2+ independently with partially zippered SNARE complexes, the plasma membrane, phospholipids, and other components to form a primed pre-fusion state that is ready for fast release. However, membrane fusion is inhibited until the arrival of Ca2+ reorients the Ca2+-binding loops of the C2 domain to perturb the lipid bilayers, help bridge the membranes, and/or induce membrane curvatures, which serves as a power stroke to activate fusion. This chapter reviews the evidence supporting these models and discusses the molecular interactions that may underlie these abilities.
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Affiliation(s)
- Qiangjun Zhou
- Department of Cell and Developmental Biology, Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN, USA.
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11
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Zhu J, McDargh ZA, Li F, Krishnakumar SS, Rothman JE, O’Shaughnessy B. Synaptotagmin rings as high-sensitivity regulators of synaptic vesicle docking and fusion. Proc Natl Acad Sci U S A 2022; 119:e2208337119. [PMID: 36103579 PMCID: PMC9499556 DOI: 10.1073/pnas.2208337119] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 07/05/2022] [Indexed: 11/18/2022] Open
Abstract
Synchronous release at neuronal synapses is accomplished by a machinery that senses calcium influx and fuses the synaptic vesicle and plasma membranes to release neurotransmitters. Previous studies suggested the calcium sensor synaptotagmin (Syt) is a facilitator of vesicle docking and both a facilitator and inhibitor of fusion. On phospholipid monolayers, the Syt C2AB domain spontaneously oligomerized into rings that are disassembled by Ca2+, suggesting Syt rings may clamp fusion as membrane-separating "washers" until Ca2+-mediated disassembly triggers fusion and release [J. Wang et al., Proc. Natl. Acad. Sci. U.S.A. 111, 13966-13971 (2014)].). Here, we combined mathematical modeling with experiment to measure the mechanical properties of Syt rings and to test this mechanism. Consistent with experimental results, the model quantitatively recapitulates observed Syt ring-induced dome and volcano shapes on phospholipid monolayers and predicts rings are stabilized by anionic phospholipid bilayers or bulk solution with ATP. The selected ring conformation is highly sensitive to membrane composition and bulk ATP levels, a property that may regulate vesicle docking and fusion in ATP-rich synaptic terminals. We find the Syt molecules hosted by a synaptic vesicle oligomerize into a halo, unbound from the vesicle, but in proximity to sufficiently phosphatidylinositol 4,5-bisphosphate (PIP2)-rich plasma membrane (PM) domains, the PM-bound trans Syt ring conformation is preferred. Thus, the Syt halo serves as landing gear for spatially directed docking at PIP2-rich sites that define the active zones of exocytotic release, positioning the Syt ring to clamp fusion and await calcium. Our results suggest the Syt ring is both a Ca2+-sensitive fusion clamp and a high-fidelity sensor for directed docking.
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Affiliation(s)
- Jie Zhu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Zachary A. McDargh
- Department of Chemical Engineering, Columbia University, New York, NY 10027
| | - Feng Li
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | | | - James E. Rothman
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520
| | - Ben O’Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, NY 10027
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12
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Kobbersmed JRL, Berns MMM, Ditlevsen S, Sørensen JB, Walter AM. Allosteric stabilization of calcium and phosphoinositide dual binding engages several synaptotagmins in fast exocytosis. eLife 2022; 11:74810. [PMID: 35929728 PMCID: PMC9489213 DOI: 10.7554/elife.74810] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 08/04/2022] [Indexed: 12/04/2022] Open
Abstract
Synaptic communication relies on the fusion of synaptic vesicles with the plasma membrane, which leads to neurotransmitter release. This exocytosis is triggered by brief and local elevations of intracellular Ca2+ with remarkably high sensitivity. How this is molecularly achieved is unknown. While synaptotagmins confer the Ca2+ sensitivity of neurotransmitter exocytosis, biochemical measurements reported Ca2+ affinities too low to account for synaptic function. However, synaptotagmin’s Ca2+ affinity increases upon binding the plasma membrane phospholipid PI(4,5)P2 and, vice versa, Ca2+ binding increases synaptotagmin’s PI(4,5)P2 affinity, indicating a stabilization of the Ca2+/PI(4,5)P2 dual-bound state. Here, we devise a molecular exocytosis model based on this positive allosteric stabilization and the assumptions that (1.) synaptotagmin Ca2+/PI(4,5)P2 dual binding lowers the energy barrier for vesicle fusion and that (2.) the effect of multiple synaptotagmins on the energy barrier is additive. The model, which relies on biochemically measured Ca2+/PI(4,5)P2 affinities and protein copy numbers, reproduced the steep Ca2+ dependency of neurotransmitter release. Our results indicate that each synaptotagmin engaging in Ca2+/PI(4,5)P2 dual-binding lowers the energy barrier for vesicle fusion by ~5 kBT and that allosteric stabilization of this state enables the synchronized engagement of several (typically three) synaptotagmins for fast exocytosis. Furthermore, we show that mutations altering synaptotagmin’s allosteric properties may show dominant-negative effects, even though synaptotagmins act independently on the energy barrier, and that dynamic changes of local PI(4,5)P2 (e.g. upon vesicle movement) dramatically impact synaptic responses. We conclude that allosterically stabilized Ca2+/PI(4,5)P2 dual binding enables synaptotagmins to exert their coordinated function in neurotransmission. For our brains and nervous systems to work properly, the nerve cells within them must be able to ‘talk’ to each other. They do this by releasing chemical signals called neurotransmitters which other cells can detect and respond to. Neurotransmitters are packaged in tiny membrane-bound spheres called vesicles. When a cell of the nervous system needs to send a signal to its neighbours, the vesicles fuse with the outer membrane of the cell, discharging their chemical contents for other cells to detect. The initial trigger for neurotransmitter release is a short, fast increase in the amount of calcium ions inside the signalling cell. One of the main proteins that helps regulate this process is synaptotagmin which binds to calcium and gives vesicles the signal to start unloading their chemicals. Despite acting as a calcium sensor, synaptotagmin actually has a very low affinity for calcium ions by itself, meaning that it would not be efficient for the protein to respond alone. Synpatotagmin is more likely to bind to calcium if it is attached to a molecule called PIP2, which is found in the membranes of cells The effect also occurs in reverse, as the binding of calcium to synaptotagmin increases the protein’s affinity for PIP2. However, how these three molecules – synaptotagmin, PIP2, and calcium – work together to achieve the physiological release of neurotransmitters is poorly understood. To help answer this question, Kobbersmed, Berns et al. set up a computer simulation of ‘virtual vesicles’ using available experimental data on synaptotagmin’s affinity with calcium and PIP2. In this simulation, synaptotagmin could only trigger the release of neurotransmitters when bound to both calcium and PIP2. The model also showed that each ‘complex’ of synaptotagmin/calcium/PIP2 made the vesicles more likely to fuse with the outer membrane of the cell – to the extent that only a handful of synaptotagmin molecules were needed to start neurotransmitter release from a single vesicle. These results shed new light on a biological process central to the way nerve cells communicate with each other. In the future, Kobbersmed, Berns et al. hope that this insight will help us to understand the cause of diseases where communication in the nervous system is impaired.
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Affiliation(s)
- Janus R L Kobbersmed
- Department of Mathematical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Manon M M Berns
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Susanne Ditlevsen
- Department of Mathematical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Alexander M Walter
- Department of Mathematical Sciences, University of Copenhagen, Copenhagen, Denmark
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13
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Atlas D. Revisiting the molecular basis of synaptic transmission. Prog Neurobiol 2022; 216:102312. [PMID: 35760141 DOI: 10.1016/j.pneurobio.2022.102312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 06/12/2022] [Accepted: 06/20/2022] [Indexed: 10/17/2022]
Abstract
Measurements of the time elapsed during synaptic transmission has shown that synaptic vesicle (SV) fusion lags behind Ca2+-influx by approximately 60 microseconds (µsec). The conventional model cannot explain this extreme rapidity of the release event. Synaptic transmission occurs at the active zone (AZ), which comprises of two pools of SV, non-releasable "tethered" vesicles, and a readily-releasable pool of channel-associated Ca2+-primed vesicles, "RRP". A recent TIRF study at cerebellar-mossy fiber-terminal, showed that subsequent to an action potential, newly "tethered" vesicles, became fusion-competent in a Ca2+-dependent manner, 300-400 milliseconds after tethering, but were not fused. This time resolution may correspond to priming of tethered vesicles through Ca2+-binding to Syt1/Munc13-1/complexin. It confirms that Ca2+-priming and Ca2+-influx-independent fusion, are two distinct events. Notably, we have established that Ca2+ channel signals evoked-release in an ion flux-independent manner, demonstrated by Ca2+-impermeable channel, or a Ca2+ channel in which Ca2+ is replaced by impermeable La3+. Thus, conformational changes in a channel coupled to RRP appear to directly activate the release machinery and account for a µsec Ca2+-influx-independent vesicle fusion. Rapid vesicle fusion driven by non-ionotropic channel signaling strengthens a conformational-coupling mechanism of synaptic transmission, and contributes to better understanding of neuronal communication vital for brain function.
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Affiliation(s)
- Daphne Atlas
- Dept. of Biological Chemistry, Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904 Israel.
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14
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Restrepo LJ, DePew AT, Moese ER, Tymanskyj SR, Parisi MJ, Aimino MA, Duhart JC, Fei H, Mosca TJ. γ-secretase promotes Drosophila postsynaptic development through the cleavage of a Wnt receptor. Dev Cell 2022; 57:1643-1660.e7. [PMID: 35654038 DOI: 10.1016/j.devcel.2022.05.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 04/06/2022] [Accepted: 05/10/2022] [Indexed: 12/27/2022]
Abstract
Developing synapses mature through the recruitment of specific proteins that stabilize presynaptic and postsynaptic structure and function. Wnt ligands signaling via Frizzled (Fz) receptors play many crucial roles in neuronal and synaptic development, but whether and how Wnt and Fz influence synaptic maturation is incompletely understood. Here, we show that Fz2 receptor cleavage via the γ-secretase complex is required for postsynaptic development and maturation. In the absence of γ-secretase, Drosophila neuromuscular synapses fail to recruit postsynaptic scaffolding and cytoskeletal proteins, leading to behavioral deficits. Introducing presenilin mutations linked to familial early-onset Alzheimer's disease into flies leads to synaptic maturation phenotypes that are identical to those seen in null alleles. This conserved role for γ-secretase in synaptic maturation and postsynaptic development highlights the importance of Fz2 cleavage and suggests that receptor processing by proteins linked to neurodegeneration may be a shared mechanism with aspects of synaptic development.
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Affiliation(s)
- Lucas J Restrepo
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Alison T DePew
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Elizabeth R Moese
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Stephen R Tymanskyj
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Michael J Parisi
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Michael A Aimino
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Juan Carlos Duhart
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Hong Fei
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA
| | - Timothy J Mosca
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Bluemle Life Sciences Building, Philadelphia, PA 19107, USA.
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15
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Abstract
Major recent advances and previous data have led to a plausible model of how key proteins mediate neurotransmitter release. In this model, the soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor (SNARE) proteins syntaxin-1, SNAP-25, and synaptobrevin form tight complexes that bring the membranes together and are crucial for membrane fusion. NSF and SNAPs disassemble SNARE complexes and ensure that fusion occurs through an exquisitely regulated pathway that starts with Munc18-1 bound to a closed conformation of syntaxin-1. Munc18-1 also binds to synaptobrevin, forming a template to assemble the SNARE complex when Munc13-1 opens syntaxin-1 while bridging the vesicle and plasma membranes. Synaptotagmin-1 and complexin bind to partially assembled SNARE complexes, likely stabilizing them and preventing fusion until Ca2+ binding to synaptotagmin-1 causes dissociation from the SNARE complex and induces interactions with phospholipids that help trigger release. Although fundamental questions remain about the mechanism of membrane fusion, these advances provide a framework to investigate the mechanisms underlying presynaptic plasticity.
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Affiliation(s)
- Josep Rizo
- Departments of Biophysics, Biochemistry, and Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA;
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16
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Henry D, Joselevitch C, Matthews GG, Wollmuth LP. Expression and distribution of synaptotagmin family members in the zebrafish retina. J Comp Neurol 2022; 530:705-728. [PMID: 34468021 PMCID: PMC8792163 DOI: 10.1002/cne.25238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 08/21/2021] [Accepted: 08/24/2021] [Indexed: 11/10/2022]
Abstract
Synaptotagmins belong to a large family of proteins. Although various synaptotagmins have been implicated as Ca2+ sensors for vesicle replenishment and release at conventional synapses, their roles at retinal ribbon synapses remain incompletely understood. Zebrafish is a widely used experimental model for retinal research. We therefore investigated the homology between human, rat, mouse, and zebrafish synaptotagmins 1-10 using a bioinformatics approach. We also characterized the expression and distribution of various synaptotagmin (syt) genes in the zebrafish retina using RT-PCR, qPCR, and in situhybridization, focusing on the family members whose products likely underlie Ca2+ -dependent exocytosis in the central nervous system (synaptotagmins 1, 2, 5, and 7). Most zebrafish synaptotagmins are well conserved and can be grouped in the same classes as mammalian synaptotagmins, based on crucial amino acid residues needed for coordinating Ca2+ binding and determining phospholipid binding affinity. The only exception is synaptotagmin 1b, which lacks 34 amino acid residues in the C2B domain and is therefore unlikely to bind Ca2+ there. Additionally, the products of zebrafish syt5a and syt5b genes share identity with mammalian class 1 and 5 synaptotagmins. Zebrafish syt1, syt2, syt5, and syt7 paralogues are found in the zebrafish brain, eye, and retina, excepting syt1b, which is only present in the brain. The complementary expression pattern of the remaining paralogues in the retina suggests that syt1a and syt5a may underlie synchronous release and syt7a and syt7b may mediate asynchronous release or other Ca2+ -dependent processes in different retinal neurons.
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Affiliation(s)
- Diane Henry
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
| | - Christina Joselevitch
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
| | - Gary G. Matthews
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
| | - Lonnie P. Wollmuth
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY 11794-5230,Department of Biochemistry & Cell Biology, Stony Brook University, Stony Brook, NY 11794-5230,Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794-5230
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17
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Szule JA. Hypothesis Relating the Structure, Biochemistry and Function of Active Zone Material Macromolecules at a Neuromuscular Junction. Front Synaptic Neurosci 2022; 13:798225. [PMID: 35069169 PMCID: PMC8766674 DOI: 10.3389/fnsyn.2021.798225] [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] [Received: 10/19/2021] [Accepted: 12/14/2021] [Indexed: 12/22/2022] Open
Abstract
This report integrates knowledge of in situ macromolecular structures and synaptic protein biochemistry to propose a unified hypothesis for the regulation of certain vesicle trafficking events (i.e., docking, priming, Ca2+-triggering, and membrane fusion) that lead to neurotransmitter secretion from specialized “active zones” of presynaptic axon terminals. Advancements in electron tomography, to image tissue sections in 3D at nanometer scale resolution, have led to structural characterizations of a network of different classes of macromolecules at the active zone, called “Active Zone Material’. At frog neuromuscular junctions, the classes of Active Zone Material macromolecules “top-masts”, “booms”, “spars”, “ribs” and “pins” direct synaptic vesicle docking while “pins”, “ribs” and “pegs” regulate priming to influence Ca2+-triggering and membrane fusion. Other classes, “beams”, “steps”, “masts”, and “synaptic vesicle luminal filaments’ likely help organize and maintain the structural integrity of active zones. Extensive studies on the biochemistry that regulates secretion have led to comprehensive characterizations of the many conserved proteins universally involved in these trafficking events. Here, a hypothesis including a partial proteomic atlas of Active Zone Material is presented which considers the common roles, binding partners, physical features/structure, and relative positioning in the axon terminal of both the proteins and classes of macromolecules involved in the vesicle trafficking events. The hypothesis designates voltage-gated Ca2+ channels and Ca2+-gated K+ channels to ribs and pegs that are connected to macromolecules that span the presynaptic membrane at the active zone. SNARE proteins (Syntaxin, SNAP25, and Synaptobrevin), SNARE-interacting proteins Synaptotagmin, Munc13, Munc18, Complexin, and NSF are designated to ribs and/or pins. Rab3A and Rabphillin-3A are designated to top-masts and/or booms and/or spars. RIM, Bassoon, and Piccolo are designated to beams, steps, masts, ribs, spars, booms, and top-masts. Spectrin is designated to beams. Lastly, the luminal portions of SV2 are thought to form the bulk of the observed synaptic vesicle luminal filaments. The goal here is to help direct future studies that aim to bridge Active Zone Material structure, biochemistry, and function to ultimately determine how it regulates the trafficking events in vivo that lead to neurotransmitter secretion.
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18
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Li X, Chien C, Han Y, Sun Z, Chen X, Dickman D. Autocrine inhibition by a glutamate-gated chloride channel mediates presynaptic homeostatic depression. SCIENCE ADVANCES 2021; 7:eabj1215. [PMID: 34851664 PMCID: PMC8635443 DOI: 10.1126/sciadv.abj1215] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 10/14/2021] [Indexed: 06/13/2023]
Abstract
Homeostatic modulation of presynaptic neurotransmitter release is a fundamental form of plasticity that stabilizes neural activity, where presynaptic homeostatic depression (PHD) can adaptively diminish synaptic strength. PHD has been proposed to operate through an autocrine mechanism to homeostatically depress release probability in response to excess glutamate release at the Drosophila neuromuscular junction. This model implies the existence of a presynaptic glutamate autoreceptor. We systematically screened all neuronal glutamate receptors in the fly genome and identified the glutamate-gated chloride channel (GluClα) to be required for the expression of PHD. Pharmacological, genetic, and Ca2+ imaging experiments demonstrate that GluClα acts locally at axonal terminals to drive PHD. Unexpectedly, GluClα localizes and traffics with synaptic vesicles to drive presynaptic inhibition through an activity-dependent anionic conductance. Thus, GluClα operates as both a sensor and effector of PHD to adaptively depress neurotransmitter release through an elegant autocrine inhibitory signaling mechanism at presynaptic terminals.
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Affiliation(s)
- Xiling Li
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
- USC Neuroscience Graduate Program, Los Angeles, CA, 90089, USA
| | - Chun Chien
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
- USC Neuroscience Graduate Program, Los Angeles, CA, 90089, USA
| | - Yifu Han
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
- USC Neuroscience Graduate Program, Los Angeles, CA, 90089, USA
| | - Zihan Sun
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Xun Chen
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
- USC Neuroscience Graduate Program, Los Angeles, CA, 90089, USA
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
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19
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Synaptotagmin 1 oligomerization via the juxtamembrane linker regulates spontaneous and evoked neurotransmitter release. Proc Natl Acad Sci U S A 2021; 118:2113859118. [PMID: 34810248 PMCID: PMC8694047 DOI: 10.1073/pnas.2113859118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2021] [Indexed: 11/18/2022] Open
Abstract
Synaptotagmin 1 (syt1) is a synaptic vesicle (SV) protein that is rapidly activated by Ca2+ influx into presynaptic nerve terminals, triggering SV exocytosis. Syt1 also inhibits exocytosis, prior to Ca2+ influx, and thus helps synchronize evoked exocytosis upon Ca2+ binding. Herein, we identified a cluster of lysine residues, in the oft-ignored juxtamembrane linker region of syt1, that governs homo-multimerization in an anionic lipid-dependent manner. Neutralization of this positively charged region abolished syt1 self-association on phospholipid bilayers in vitro. Subsequently, in neurons, we found mutations that disrupted syt1 self-association were correlated with defects in clamping spontaneous SV release and in triggering and synchronizing evoked exocytosis. Thus, syt1 regulates SV exocytosis as an oligomer via charged residues in the juxtamembrane linker. Synaptotagmin 1 (syt1) is a Ca2+ sensor that regulates synaptic vesicle exocytosis. Cell-based experiments suggest that syt1 functions as a multimer; however, biochemical and electron microscopy studies have yielded contradictory findings regarding putative self-association. Here, we performed dynamic light scattering on syt1 in solution, followed by electron microscopy, and we used atomic force microscopy to study syt1 self-association on supported lipid bilayers under aqueous conditions. Ring-like multimers were clearly observed. Multimerization was enhanced by Ca2+ and required anionic phospholipids. Large ring-like structures (∼180 nm) were reduced to smaller rings (∼30 nm) upon neutralization of a cluster of juxtamembrane lysine residues; further substitution of residues in the second C2-domain completely abolished self-association. When expressed in neurons, syt1 mutants with graded reductions in self-association activity exhibited concomitant reductions in 1) clamping spontaneous release and 2) triggering and synchronizing evoked release. Thus, the juxtamembrane linker of syt1 plays a crucial role in exocytosis by mediating multimerization.
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20
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Li L, Liu H, Krout M, Richmond JE, Wang Y, Bai J, Weeratunga S, Collins BM, Ventimiglia D, Yu Y, Xia J, Tang J, Liu J, Hu Z. A novel dual Ca2+ sensor system regulates Ca2+-dependent neurotransmitter release. J Cell Biol 2021; 220:211787. [PMID: 33570571 PMCID: PMC7883739 DOI: 10.1083/jcb.202008121] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 12/19/2020] [Accepted: 01/15/2021] [Indexed: 02/08/2023] Open
Abstract
Ca2+-dependent neurotransmitter release requires synaptotagmins as Ca2+ sensors to trigger synaptic vesicle (SV) exocytosis via binding of their tandem C2 domains—C2A and C2B—to Ca2+. We have previously demonstrated that SNT-1, a mouse synaptotagmin-1 (Syt1) homologue, functions as the fast Ca2+ sensor in Caenorhabditis elegans. Here, we report a new Ca2+ sensor, SNT-3, which triggers delayed Ca2+-dependent neurotransmitter release. snt-1;snt-3 double mutants abolish evoked synaptic transmission, demonstrating that C. elegans NMJs use a dual Ca2+ sensor system. SNT-3 possesses canonical aspartate residues in both C2 domains, but lacks an N-terminal transmembrane (TM) domain. Biochemical evidence demonstrates that SNT-3 binds both Ca2+ and the plasma membrane. Functional analysis shows that SNT-3 is activated when SNT-1 function is impaired, triggering SV release that is loosely coupled to Ca2+ entry. Compared with SNT-1, which is tethered to SVs, SNT-3 is not associated with SV. Eliminating the SV tethering of SNT-1 by removing the TM domain or the whole N terminus rescues fast release kinetics, demonstrating that cytoplasmic SNT-1 is still functional and triggers fast neurotransmitter release, but also exhibits decreased evoked amplitude and release probability. These results suggest that the fast and slow properties of SV release are determined by the intrinsically different C2 domains in SNT-1 and SNT-3, rather than their N-termini–mediated membrane tethering. Our findings therefore reveal a novel dual Ca2+ sensor system in C. elegans and provide significant insights into Ca2+-regulated exocytosis.
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Affiliation(s)
- Lei Li
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Haowen Liu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Mia Krout
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL
| | - Yu Wang
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Jihong Bai
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA
| | - Saroja Weeratunga
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Brett M Collins
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Donovan Ventimiglia
- Lulu and Anthony Wang Laboratory of Neural Circuits and Behavior, The Rockefeller University, New York, NY
| | - Yi Yu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Jingyao Xia
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Jing Tang
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia
| | - Jie Liu
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Zhitao Hu
- Queensland Brain Institute, Clem Jones Centre for Ageing Dementia Research, The University of Queensland, Brisbane, Queensland, Australia
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21
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Xue R, Meng H, Yin J, Xia J, Hu Z, Liu H. The Role of Calmodulin vs. Synaptotagmin in Exocytosis. Front Mol Neurosci 2021; 14:691363. [PMID: 34421537 PMCID: PMC8375295 DOI: 10.3389/fnmol.2021.691363] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 07/19/2021] [Indexed: 12/04/2022] Open
Abstract
Exocytosis is a Ca2+-regulated process that requires the participation of Ca2+ sensors. In the 1980s, two classes of Ca2+-binding proteins were proposed as putative Ca2+ sensors: EF-hand protein calmodulin, and the C2 domain protein synaptotagmin. In the next few decades, numerous studies determined that in the final stage of membrane fusion triggered by a micromolar boost in the level of Ca2+, the low affinity Ca2+-binding protein synaptotagmin, especially synaptotagmin 1 and 2, acts as the primary Ca2+ sensor, whereas calmodulin is unlikely to be functional due to its high Ca2+ affinity. However, in the meantime emerging evidence has revealed that calmodulin is involved in the earlier exocytotic steps prior to fusion, such as vesicle trafficking, docking and priming by acting as a high affinity Ca2+ sensor activated at submicromolar level of Ca2+. Calmodulin directly interacts with multiple regulatory proteins involved in the regulation of exocytosis, including VAMP, myosin V, Munc13, synapsin, GAP43 and Rab3, and switches on key kinases, such as type II Ca2+/calmodulin-dependent protein kinase, to phosphorylate a series of exocytosis regulators, including syntaxin, synapsin, RIM and Ca2+ channels. Moreover, calmodulin interacts with synaptotagmin through either direct binding or indirect phosphorylation. In summary, calmodulin and synaptotagmin are Ca2+ sensors that play complementary roles throughout the process of exocytosis. In this review, we discuss the complementary roles that calmodulin and synaptotagmin play as Ca2+ sensors during exocytosis.
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Affiliation(s)
- Renhao Xue
- Shanghai Key Laboratory of Maternal Fetal Medicine, Clinical and Translational Research Center of Shanghai First Maternity & Infant Hospital, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Hao Meng
- Guangzhou Laboratory, Guangzhou, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
| | - Jiaxiang Yin
- Guangzhou Laboratory, Guangzhou, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
| | - Jingyao Xia
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Zhitao Hu
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia
| | - Huisheng Liu
- Guangzhou Laboratory, Guangzhou, China.,Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou, China
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22
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Sauvola CW, Littleton JT. SNARE Regulatory Proteins in Synaptic Vesicle Fusion and Recycling. Front Mol Neurosci 2021; 14:733138. [PMID: 34421538 PMCID: PMC8377282 DOI: 10.3389/fnmol.2021.733138] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/20/2021] [Indexed: 01/01/2023] Open
Abstract
Membrane fusion is a universal feature of eukaryotic protein trafficking and is mediated by the soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) family. SNARE proteins embedded in opposing membranes spontaneously assemble to drive membrane fusion and cargo exchange in vitro. Evolution has generated a diverse complement of SNARE regulatory proteins (SRPs) that ensure membrane fusion occurs at the right time and place in vivo. While a core set of SNAREs and SRPs are common to all eukaryotic cells, a specialized set of SRPs within neurons confer additional regulation to synaptic vesicle (SV) fusion. Neuronal communication is characterized by precise spatial and temporal control of SNARE dynamics within presynaptic subdomains specialized for neurotransmitter release. Action potential-elicited Ca2+ influx at these release sites triggers zippering of SNAREs embedded in the SV and plasma membrane to drive bilayer fusion and release of neurotransmitters that activate downstream targets. Here we discuss current models for how SRPs regulate SNARE dynamics and presynaptic output, emphasizing invertebrate genetic findings that advanced our understanding of SRP regulation of SV cycling.
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Affiliation(s)
- Chad W Sauvola
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
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23
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Wu Z, Dharan N, McDargh ZA, Thiyagarajan S, O'Shaughnessy B, Karatekin E. The neuronal calcium sensor Synaptotagmin-1 and SNARE proteins cooperate to dilate fusion pores. eLife 2021; 10:68215. [PMID: 34190041 PMCID: PMC8294851 DOI: 10.7554/elife.68215] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 06/29/2021] [Indexed: 02/07/2023] Open
Abstract
All membrane fusion reactions proceed through an initial fusion pore, including calcium-triggered release of neurotransmitters and hormones. Expansion of this small pore to release cargo is energetically costly and regulated by cells, but the mechanisms are poorly understood. Here, we show that the neuronal/exocytic calcium sensor Synaptotagmin-1 (Syt1) promotes expansion of fusion pores induced by SNARE proteins. Pore dilation relied on calcium-induced insertion of the tandem C2 domain hydrophobic loops of Syt1 into the membrane, previously shown to reorient the C2 domain. Mathematical modelling suggests that C2B reorientation rotates a bound SNARE complex so that it exerts force on the membranes in a mechanical lever action that increases the height of the fusion pore, provoking pore dilation to offset the bending energy penalty. We conclude that Syt1 exerts novel non-local calcium-dependent mechanical forces on fusion pores that dilate pores and assist neurotransmitter and hormone release.
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Affiliation(s)
- Zhenyong Wu
- Department of Cellular and Molecular Physiology, Yale University, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States
| | - Nadiv Dharan
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Zachary A McDargh
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Sathish Thiyagarajan
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Ben O'Shaughnessy
- Department of Chemical Engineering, Columbia University, New York, United States
| | - Erdem Karatekin
- Department of Cellular and Molecular Physiology, Yale University, New Haven, United States.,Nanobiology Institute, Yale University, West Haven, United States.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, United States.,Saints-Pères Paris Institute for the Neurosciences (SPPIN), Université de Paris, Centre National de la Recherche Scientifique (CNRS) UMR 8003, Paris, France
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24
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Beijer D, Baets J. The expanding genetic landscape of hereditary motor neuropathies. Brain 2021; 143:3540-3563. [PMID: 33210134 DOI: 10.1093/brain/awaa311] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/15/2020] [Accepted: 07/27/2020] [Indexed: 12/12/2022] Open
Abstract
Hereditary motor neuropathies are clinically and genetically diverse disorders characterized by length-dependent axonal degeneration of lower motor neurons. Although currently as many as 26 causal genes are known, there is considerable missing heritability compared to other inherited neuropathies such as Charcot-Marie-Tooth disease. Intriguingly, this genetic landscape spans a discrete number of key biological processes within the peripheral nerve. Also, in terms of underlying pathophysiology, hereditary motor neuropathies show striking overlap with several other neuromuscular and neurological disorders. In this review, we provide a current overview of the genetic spectrum of hereditary motor neuropathies highlighting recent reports of novel genes and mutations or recent discoveries in the underlying disease mechanisms. In addition, we link hereditary motor neuropathies with various related disorders by addressing the main affected pathways of disease divided into five major processes: axonal transport, tRNA aminoacylation, RNA metabolism and DNA integrity, ion channels and transporters and endoplasmic reticulum.
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Affiliation(s)
- Danique Beijer
- Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.,Laboratory of Neuromuscular Pathology, Institute Born-Bunge, University of Antwerp, Belgium
| | - Jonathan Baets
- Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.,Laboratory of Neuromuscular Pathology, Institute Born-Bunge, University of Antwerp, Belgium.,Neuromuscular Reference Centre, Department of Neurology, Antwerp University Hospital, Belgium
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25
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Function of Drosophila Synaptotagmins in membrane trafficking at synapses. Cell Mol Life Sci 2021; 78:4335-4364. [PMID: 33619613 PMCID: PMC8164606 DOI: 10.1007/s00018-021-03788-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/29/2021] [Accepted: 02/09/2021] [Indexed: 12/13/2022]
Abstract
The Synaptotagmin (SYT) family of proteins play key roles in regulating membrane trafficking at neuronal synapses. Using both Ca2+-dependent and Ca2+-independent interactions, several SYT isoforms participate in synchronous and asynchronous fusion of synaptic vesicles (SVs) while preventing spontaneous release that occurs in the absence of stimulation. Changes in the function or abundance of the SYT1 and SYT7 isoforms alter the number and route by which SVs fuse at nerve terminals. Several SYT family members also regulate trafficking of other subcellular organelles at synapses, including dense core vesicles (DCV), exosomes, and postsynaptic vesicles. Although SYTs are linked to trafficking of multiple classes of synaptic membrane compartments, how and when they interact with lipids, the SNARE machinery and other release effectors are still being elucidated. Given mutations in the SYT family cause disorders in both the central and peripheral nervous system in humans, ongoing efforts are defining how these proteins regulate vesicle trafficking within distinct neuronal compartments. Here, we review the Drosophila SYT family and examine their role in synaptic communication. Studies in this invertebrate model have revealed key similarities and several differences with the predicted activity of their mammalian counterparts. In addition, we highlight the remaining areas of uncertainty in the field and describe outstanding questions on how the SYT family regulates membrane trafficking at nerve terminals.
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26
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Fujii T, Sakurai A, Littleton JT, Yoshihara M. Synaptotagmin 7 switches short-term synaptic plasticity from depression to facilitation by suppressing synaptic transmission. Sci Rep 2021; 11:4059. [PMID: 33603074 PMCID: PMC7892890 DOI: 10.1038/s41598-021-83397-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 01/22/2021] [Indexed: 01/25/2023] Open
Abstract
Short-term synaptic plasticity is a fast and robust modification in neuronal presynaptic output that can enhance release strength to drive facilitation or diminish it to promote depression. The mechanisms that determine whether neurons display short-term facilitation or depression are still unclear. Here we show that the Ca2+-binding protein Synaptotagmin 7 (Syt7) determines the sign of short-term synaptic plasticity by controlling the initial probability of synaptic vesicle (SV) fusion. Electrophysiological analysis of Syt7 null mutants at Drosophila embryonic neuromuscular junctions demonstrate loss of the protein converts the normally observed synaptic facilitation response during repetitive stimulation into synaptic depression. In contrast, overexpression of Syt7 dramatically enhanced the magnitude of short-term facilitation. These changes in short-term plasticity were mirrored by corresponding alterations in the initial evoked response, with SV release probability enhanced in Syt7 mutants and suppressed following Syt7 overexpression. Indeed, Syt7 mutants were able to display facilitation in lower [Ca2+] where release was reduced. These data suggest Syt7 does not act by directly sensing residual Ca2+ and argues for the existence of a distinct Ca2+ sensor beyond Syt7 that mediates facilitation. Instead, Syt7 normally suppresses synaptic transmission to maintain an output range where facilitation is available to the neuron.
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Affiliation(s)
- Takaaki Fujii
- Memory Neurobiology Project, National Institute of Information and Communications Technology, Kobe, Japan
| | - Akira Sakurai
- Memory Neurobiology Project, National Institute of Information and Communications Technology, Kobe, Japan
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Motojiro Yoshihara
- Memory Neurobiology Project, National Institute of Information and Communications Technology, Kobe, Japan.
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27
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Fionda L, Turon‐Sans J, Fuentes Prior P, Bernal Noguera S, Cortés‐Vicente E, López‐Pérez MA, Gallardo E, Rojas‐García R. A new
de novo SYT2
mutation presenting as distal weakness. Neuropathy or neuromuscular junction dysfunction? J Peripher Nerv Syst 2020; 26:113-117. [DOI: 10.1111/jns.12425] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 12/08/2020] [Accepted: 12/08/2020] [Indexed: 01/10/2023]
Affiliation(s)
- Laura Fionda
- Neuromuscular and Rare Disease Center, Department of Neuroscience Mental Health and Sensory Organs (NESMOS), Sant'Andrea Hospital, Sapienza University of Rome Rome Italy
| | - Janina Turon‐Sans
- Neuromuscular Diseases Unit, Department of Neurology Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona Barcelona Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras CIBERER IICS‐Madrid Spain
| | - Pablo Fuentes Prior
- Biomedical Research Institute (IIB) Molecular Bases of Disease Hospital de la Santa Creu i Sant Pau Barcelona Spain
| | - Sara Bernal Noguera
- Centro de Investigación Biomédica en Red de Enfermedades Raras CIBERER IICS‐Madrid Spain
- Biomedical Research Institute (IIB) Molecular Bases of Disease Hospital de la Santa Creu i Sant Pau Barcelona Spain
| | - Elena Cortés‐Vicente
- Neuromuscular Diseases Unit, Department of Neurology Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona Barcelona Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras CIBERER IICS‐Madrid Spain
| | | | - Eduard Gallardo
- Neuromuscular Diseases Unit, Department of Neurology Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona Barcelona Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras CIBERER IICS‐Madrid Spain
| | - Ricard Rojas‐García
- Neuromuscular Diseases Unit, Department of Neurology Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona Barcelona Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras CIBERER IICS‐Madrid Spain
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28
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Bauché S, Sureau A, Sternberg D, Rendu J, Buon C, Messéant J, Boëx M, Furling D, Fauré J, Latypova X, Gelot AB, Mayer M, Mary P, Whalen S, Fournier E, Cloix I, Remerand G, Laffargue F, Nougues MC, Fontaine B, Eymard B, Isapof A, Strochlic L. New recessive mutations in SYT2 causing severe presynaptic congenital myasthenic syndromes. NEUROLOGY-GENETICS 2020; 6:e534. [PMID: 33659639 PMCID: PMC7803339 DOI: 10.1212/nxg.0000000000000534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 09/25/2020] [Indexed: 11/15/2022]
Abstract
Objective To report the identification of 2 new homozygous recessive mutations in the synaptotagmin 2 (SYT2) gene as the genetic cause of severe and early presynaptic forms of congenital myasthenic syndromes (CMSs). Methods Next-generation sequencing identified new homozygous intronic and frameshift mutations in the SYT2 gene as a likely cause of presynaptic CMS. We describe the clinical and electromyographic patient phenotypes, perform ex vivo splicing analyses to characterize the effect of the intronic mutation on exon splicing, and analyze the functional impact of this variation at the neuromuscular junction (NMJ). Results The 2 infants presented a similar clinical phenotype evoking first a congenital myopathy characterized by muscle weakness and hypotonia. Next-generation sequencing allowed to the identification of 1 homozygous intronic mutation c.465+1G>A in patient 1 and another homozygous frameshift mutation c.328_331dup in patient 2, located respectively in the 5' splice donor site of SYT2 intron 4 and in exon 3. Functional studies of the intronic mutation validated the abolition of the splice donor site of exon 4 leading to its skipping. In-frame skipping of exon 4 that encodes part of the C2A calcium-binding domain of SYT2 is associated with a loss-of-function effect resulting in a decrease of neurotransmitter release and severe pre- and postsynaptic NMJ defects. Conclusions This study identifies new homozygous recessive SYT2 mutations as the underlying cause of severe and early presynaptic form of CMS expanding the genetic spectrum of recessive SYT2-related CMS associated with defects in neurotransmitter release.
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Affiliation(s)
- Stéphanie Bauché
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Alain Sureau
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Damien Sternberg
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - John Rendu
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Céline Buon
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Julien Messéant
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Myriam Boëx
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Denis Furling
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Julien Fauré
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Xénia Latypova
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Antoinette Bernabe Gelot
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Michèle Mayer
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Pierre Mary
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Sandra Whalen
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Emmanuel Fournier
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Isabelle Cloix
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Ganaelle Remerand
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Fanny Laffargue
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Marie-Christine Nougues
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Bertrand Fontaine
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Bruno Eymard
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Arnaud Isapof
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
| | - Laure Strochlic
- Sorbonne Université, INSERM, UMRS974, Centre de Recherche en Myologie, Hôpital de la Pitié-Salpêtrière, Paris, (S.B., A.S., C. B., J.M., M.B., D.F., E. F., B.F., B.E., A.I., L.S.); CHU APHP (D.S., J.R., J.F., X.L., A.B.G., M.M., P.M., S.W., E.F., I.C., G.R., F.L., M.C.N., B.F., B.E., A.I.); Aix-Marseille University, INSERM, INMED, Campus de Luminy, Marseille, France (A.B.G.); UFR Cardiogénétique et Myogénétique, Hôpital de la Pitié-Salpêtrière, APHP, Paris (D.S.); UF de génétique clinique, CRMR Anomalies du développement et syndromes malformatifs, APHP, Hôpital Armand Trousseau, Paris, France (S.W.); Université de Grenoble Alpes, INSERM, CHU Grenoble Alpes, GIN (J.R., J.F., X.L.); CHU Clermont Ferrand (I.C., G.R., F.L.); and Reference Centre for Neuromuscular Pathologies "Nord/Est/Ile-de France" Paris (A.B.G., M.M., P.M., S.W., M.C.N., B.F., B.E., A.I.)
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Mironovich O, Dadali E, Malmberg S, Markova T, Ryzhkova O, Poliakov A. Identification of a Novel de Novo Variant in the SYT2 Gene Causing a Rare Type of Distal Hereditary Motor Neuropathy. Genes (Basel) 2020; 11:genes11111238. [PMID: 33105646 PMCID: PMC7690400 DOI: 10.3390/genes11111238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 01/31/2023] Open
Abstract
Objective: To report the first de novo missense mutation in the SYT2 gene causing distal hereditary motor neuropathy. Methods: Genetic testing was carried out, including clinical exome sequencing for the proband and Sanger sequencing for the proband and his parents. We described the clinical and electrophysiological features found in the patient. Results: We reported a proband with a new de novo missense mutation, c.917C>T (p.Ser306Leu), in the C2B domain of SYT2. The clinical presentation was similar to that of phenotypes described in previous studies. A notable feature in our study was normal electrophysiological testing results of the patient. Conclusions: In this study we reinforced the association between SYT2 mutations and distal hereditary motor neuropathy. We also described the clinical presentation of the patient carrying this pathogenic variant and provided unusual results of electrophysiological testing. The results showed that a diagnosis of SYT2-associated neuropathy should be based on the similarity of clinical manifestations, rather than the results of electrophysiological testing.
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Affiliation(s)
- Olga Mironovich
- Federal State Budgetary Institution “Research Centre For Medical Genetics”, Moscow 115478, Russia; (E.D.); (T.M.); (O.R.); (A.P.)
- Correspondence: ; Tel.: +7-909-687-3104
| | - Elena Dadali
- Federal State Budgetary Institution “Research Centre For Medical Genetics”, Moscow 115478, Russia; (E.D.); (T.M.); (O.R.); (A.P.)
| | - Sergey Malmberg
- Federal State Budget Healthcare Institution “Central Children Clinical Hospital” at FMBA of Russia, Moscow 115409, Russia;
| | - Tatyana Markova
- Federal State Budgetary Institution “Research Centre For Medical Genetics”, Moscow 115478, Russia; (E.D.); (T.M.); (O.R.); (A.P.)
| | - Oxana Ryzhkova
- Federal State Budgetary Institution “Research Centre For Medical Genetics”, Moscow 115478, Russia; (E.D.); (T.M.); (O.R.); (A.P.)
| | - Aleksander Poliakov
- Federal State Budgetary Institution “Research Centre For Medical Genetics”, Moscow 115478, Russia; (E.D.); (T.M.); (O.R.); (A.P.)
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Synaptotagmin-1 membrane binding is driven by the C2B domain and assisted cooperatively by the C2A domain. Sci Rep 2020; 10:18011. [PMID: 33093513 PMCID: PMC7581758 DOI: 10.1038/s41598-020-74923-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Accepted: 07/23/2020] [Indexed: 11/08/2022] Open
Abstract
Synaptotagmin interaction with anionic lipid (phosphatidylserine/phosphatidylinositol) containing membranes, both in the absence and presence of calcium ions (Ca2+), is critical to its central role in orchestrating neurotransmitter release. The molecular surfaces involved, namely the conserved polylysine motif in the C2B domain and Ca2+-binding aliphatic loops on both C2A and C2B domains, are known. Here we use surface force apparatus combined with systematic mutational analysis of the functional surfaces to directly measure Syt1-membrane interaction and fully map the site-binding energetics of Syt1 both in the absence and presence of Ca2+. By correlating energetics data with the molecular rearrangements measured during confinement, we find that both C2 domains cooperate in membrane binding, with the C2B domain functioning as the main energetic driver, and the C2A domain acting as a facilitator.
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Voleti R, Jaczynska K, Rizo J. Ca 2+-dependent release of synaptotagmin-1 from the SNARE complex on phosphatidylinositol 4,5-bisphosphate-containing membranes. eLife 2020; 9:57154. [PMID: 32808925 PMCID: PMC7498268 DOI: 10.7554/elife.57154] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 08/12/2020] [Indexed: 11/13/2022] Open
Abstract
The Ca2+ sensor synaptotagmin-1 and the SNARE complex cooperate to trigger neurotransmitter release. Structural studies elucidated three distinct synaptotagmin-1-SNARE complex binding modes involving 'polybasic', 'primary' and 'tripartite' interfaces of synaptotagmin-1. We investigated these interactions using NMR and fluorescence spectroscopy. Synaptotagmin-1 binds to the SNARE complex through the polybasic and primary interfaces in solution. Ca2+-free synaptotagmin-1 binds to SNARE complexes anchored on PIP2-containing nanodiscs. R398Q/R399Q and E295A/Y338W mutations at the primary interface, which strongly impair neurotransmitter release, disrupt and enhance synaptotagmin-1-SNARE complex binding, respectively. Ca2+ induces tight binding of synaptotagmin-1 to PIP2-containing nanodiscs, disrupting synaptotagmin-1-SNARE interactions. Specific effects of mutations in the polybasic region on Ca2+-dependent synaptotagmin-1-PIP2-membrane interactions correlate with their effects on release. Our data suggest that synaptotagmin-1 binds to the SNARE complex through the primary interface and that Ca2+ releases this interaction, inducing PIP2/membrane binding and allowing cooperation between synaptotagmin-1 and the SNAREs in membrane fusion to trigger release.
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Affiliation(s)
- Rashmi Voleti
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Klaudia Jaczynska
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, United States
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Donkervoort S, Mohassel P, Laugwitz L, Zaki MS, Kamsteeg EJ, Maroofian R, Chao KR, Verschuuren-Bemelmans CC, Horber V, Fock AJM, McCarty RM, Jain MS, Biancavilla V, McMacken G, Nalls M, Voermans NC, Elbendary HM, Snyder M, Cai C, Lehky TJ, Stanley V, Iannaccone ST, Foley AR, Lochmüller H, Gleeson J, Houlden H, Haack TB, Horvath R, Bönnemann CG. Biallelic loss of function variants in SYT2 cause a treatable congenital onset presynaptic myasthenic syndrome. Am J Med Genet A 2020; 182:2272-2283. [PMID: 32776697 DOI: 10.1002/ajmg.a.61765] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 05/25/2020] [Accepted: 06/13/2020] [Indexed: 12/15/2022]
Abstract
Synaptotagmins are integral synaptic vesicle membrane proteins that function as calcium sensors and regulate neurotransmitter release at the presynaptic nerve terminal. Synaptotagmin-2 (SYT2), is the major isoform expressed at the neuromuscular junction. Recently, dominant missense variants in SYT2 have been reported as a rare cause of distal motor neuropathy and myasthenic syndrome, manifesting with stable or slowly progressive distal weakness of variable severity along with presynaptic NMJ impairment. These variants are thought to have a dominant-negative effect on synaptic vesicle exocytosis, although the precise pathomechanism remains to be elucidated. Here we report seven patients of five families, with biallelic loss of function variants in SYT2, clinically manifesting with a remarkably consistent phenotype of severe congenital onset hypotonia and weakness, with variable degrees of respiratory involvement. Electrodiagnostic findings were consistent with a presynaptic congenital myasthenic syndrome (CMS) in some. Treatment with an acetylcholinesterase inhibitor pursued in three patients showed clinical improvement with increased strength and function. This series further establishes SYT2 as a CMS-disease gene and expands its clinical and genetic spectrum to include recessive loss-of-function variants, manifesting as a severe congenital onset presynaptic CMS with potential treatment implications.
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Affiliation(s)
- Sandra Donkervoort
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Payam Mohassel
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Lucia Laugwitz
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany.,Department of Paediatric Neurology, University Children's Hospital, Tübingen, Germany
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Erik-Jan Kamsteeg
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Reza Maroofian
- Department of Neuromuscular Disorders, University College London Institute of Neurology, London, UK
| | - Katherine R Chao
- Center for Mendelian Genomics, Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | | | - Veronka Horber
- Department of Paediatric Neurology, University Children's Hospital, Tübingen, Germany
| | - Annemarie J M Fock
- Department of Neurology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Riley M McCarty
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Minal S Jain
- Rehabilitation Medicine Department, Clinical Research Center, National Institutes of Health, Bethesda, Maryland, USA
| | - Victoria Biancavilla
- Rehabilitation Medicine Department, Clinical Research Center, National Institutes of Health, Bethesda, Maryland, USA
| | - Grace McMacken
- Department of Neurosciences, Royal Victoria Hospital, Belfast, UK
| | - Matthew Nalls
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Nicol C Voermans
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Hasnaa M Elbendary
- Clinical Genetics Department, Human Genetics and Genome Research Division, National Research Centre, Cairo, Egypt
| | - Molly Snyder
- Department of Neurology, Children's Health, Dallas, Texas, USA
| | - Chunyu Cai
- Department of Pathology, UT Southwestern Medical Center, Dallas, Texas, USA
| | - Tanya J Lehky
- EMG Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Valentina Stanley
- Laboratory for Pediatric Brain Disease, Howard Hughes Medical Institute, University of California, San Diego, California, USA.,Rady Children's Institute for Genomic Medicine, Rady Children's Hospital, San Diego, California, USA
| | - Susan T Iannaccone
- Department of Pediatrics, UT Southwestern Medical Center, Dallas, Texas, USA
| | - A Reghan Foley
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Hanns Lochmüller
- Department of Neuropediatrics and Muscle Disorders, Medical Center - University of Freiburg, Faculty of Medicine, Freiburg, Germany.,Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, Ontario, Canada.,Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada
| | - Joseph Gleeson
- Laboratory for Pediatric Brain Disease, Howard Hughes Medical Institute, University of California, San Diego, California, USA.,Rady Children's Institute for Genomic Medicine, Rady Children's Hospital, San Diego, California, USA
| | - Henry Houlden
- Department of Neuromuscular Disorders, University College London Institute of Neurology, London, UK
| | - Tobias B Haack
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Rita Horvath
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Carsten G Bönnemann
- Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
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33
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Sleiman M, Stevens DR, Chitirala P, Rettig J. Cytotoxic Granule Trafficking and Fusion in Synaptotagmin7-Deficient Cytotoxic T Lymphocytes. Front Immunol 2020; 11:1080. [PMID: 32547563 PMCID: PMC7273742 DOI: 10.3389/fimmu.2020.01080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 05/05/2020] [Indexed: 11/13/2022] Open
Abstract
Granules of cytotoxic T lymphocytes (CTL) are derived from the lysosomal compartment. Synaptotagmin7 (Syt7) appears to be the calcium sensor triggering fusion of lysosomes in fibroblasts. Syt7 has been proposed to control cytotoxic granule (CG) fusion in lymphocytes and mice lacking Syt7 have reduced ability to clear infections. However, fusion of CG persists in the absence of Syt7. To clarify the role of Syt7 in CTL function, we have examined the fusion of cytotoxic granules of CD8+ T-lymphocytes from Syt7 knock-out mice. We have recorded granule fusion in living CTL, using total internal reflection microscopy. Since Syt7 is considered a high affinity calcium-sensor specialized for fusion under low calcium conditions, we have compared cytotoxic granule fusion under low and high calcium conditions in the same CTL. There was no difference in latencies or numbers of fusion events per CTL under low-calcium conditions, indicating that Syt7 is not required for cytotoxic granule fusion. A deficit of fusion in Syt7 KO CTL was seen when a high-calcium solution was introduced. Expressing wild type Syt7 in Syt7 KO lymphocytes reversed this deficit, confirming its Syt7-dependence. Mutations of Syt7 which disrupt calcium binding to its C2A domain reduced the efficacy of this rescue. We counted the cytotoxic granules present at the plasma membrane to determine if the lack of fusion events in the Syt7 KO CTL was due to a lack of granules. In low calcium there were no differences in fusion events per CTL, and granule numbers were similar. In high calcium, granule number was similar though wild type CTL exhibited significantly more fusion than Syt7 KO CTL. The modest differences in granule counts do not account for the lack of fusion in high calcium in Syt7 KO CTL. In Syt7 KO CTL expressing wild type Syt7, delivery of cytotoxic granules to the plasma membrane was comparable to that of wild type CTL. Syt7 KO CTL expressing Syt7 with deficient calcium binding in the C2A domain had significantly less fusion and fewer CG at the plasma membrane. These results indicate that Syt7 is involved in trafficking of CG to the plasma membrane.
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Affiliation(s)
- Marwa Sleiman
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - David R Stevens
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Praneeth Chitirala
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
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34
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Shields MC, Bowers MR, Kramer HL, Fulcer MM, Perinet LC, Metz MJ, Reist NE. The role of the C2A domain of synaptotagmin 1 in asynchronous neurotransmitter release. PLoS One 2020; 15:e0232991. [PMID: 32407359 PMCID: PMC7224543 DOI: 10.1371/journal.pone.0232991] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 04/24/2020] [Indexed: 11/22/2022] Open
Abstract
Following nerve stimulation, there are two distinct phases of Ca2+-dependent neurotransmitter release: a fast, synchronous release phase, and a prolonged, asynchronous release phase. Each of these phases is tightly regulated and mediated by distinct mechanisms. Synaptotagmin 1 is the major Ca2+ sensor that triggers fast, synchronous neurotransmitter release upon Ca2+ binding by its C2A and C2B domains. It has also been implicated in the inhibition of asynchronous neurotransmitter release, as blocking Ca2+ binding by the C2A domain of synaptotagmin 1 results in increased asynchronous release. However, the mutation used to block Ca2+ binding in the previous experiments (aspartate to asparagine mutations, sytD-N) had the unintended side effect of mimicking Ca2+ binding, raising the possibility that the increase in asynchronous release was directly caused by ostensibly constitutive Ca2+ binding. Thus, rather than modulating an asynchronous sensor, sytD-N may be mimicking one. To directly test the C2A inhibition hypothesis, we utilized an alternate C2A mutation that we designed to block Ca2+ binding without mimicking it (an aspartate to glutamate mutation, sytD-E). Analysis of both the original sytD-N mutation and our alternate sytD-E mutation at the Drosophila neuromuscular junction showed differential effects on asynchronous release, as well as on synchronous release and the frequency of spontaneous release. Importantly, we found that asynchronous release is not increased in the sytD-E mutant. Thus, our work provides new mechanistic insight into synaptotagmin 1 function during Ca2+-evoked synaptic transmission and demonstrates that Ca2+ binding by the C2A domain of synaptotagmin 1 does not inhibit asynchronous neurotransmitter release in vivo.
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Affiliation(s)
- Mallory C. Shields
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Matthew R. Bowers
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Hannah L. Kramer
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - McKenzie M. Fulcer
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Lara C. Perinet
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
| | - Marissa J. Metz
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
| | - Noreen E. Reist
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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35
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Bradberry MM, Courtney NA, Dominguez MJ, Lofquist SM, Knox AT, Sutton RB, Chapman ER. Molecular Basis for Synaptotagmin-1-Associated Neurodevelopmental Disorder. Neuron 2020; 107:52-64.e7. [PMID: 32362337 DOI: 10.1016/j.neuron.2020.04.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/09/2020] [Accepted: 04/01/2020] [Indexed: 12/13/2022]
Abstract
At neuronal synapses, synaptotagmin-1 (syt1) acts as a Ca2+ sensor that synchronizes neurotransmitter release with Ca2+ influx during action potential firing. Heterozygous missense mutations in syt1 have recently been associated with a severe but heterogeneous developmental syndrome, termed syt1-associated neurodevelopmental disorder. Well-defined pathogenic mechanisms, and the basis for phenotypic heterogeneity in this disorder, remain unknown. Here, we report the clinical, physiological, and biophysical characterization of three syt1 mutations from human patients. Synaptic transmission was impaired in neurons expressing mutant variants, which demonstrated potent, graded dominant-negative effects. Biophysical interrogation of the mutant variants revealed novel mechanistic features concerning the cooperative action, and functional specialization, of the tandem Ca2+-sensing domains of syt1. These mechanistic studies led to the discovery that a clinically approved K+ channel antagonist is able to rescue the dominant-negative heterozygous phenotype. Our results establish a molecular cause, basis for phenotypic heterogeneity, and potential treatment approach for syt1-associated neurodevelopmental disorder.
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Affiliation(s)
- Mazdak M Bradberry
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA; Medical Scientist Training Program, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Nicholas A Courtney
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Matthew J Dominguez
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Sydney M Lofquist
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - Andrew T Knox
- Department of Neurology, Section of Pediatric Neurology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA
| | - R Bryan Sutton
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Edwin R Chapman
- Howard Hughes Medical Institute and Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53705, USA.
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36
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Guan Z, Quiñones-Frías MC, Akbergenova Y, Littleton JT. Drosophila Synaptotagmin 7 negatively regulates synaptic vesicle release and replenishment in a dosage-dependent manner. eLife 2020; 9:e55443. [PMID: 32343229 PMCID: PMC7224696 DOI: 10.7554/elife.55443] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 04/28/2020] [Indexed: 01/03/2023] Open
Abstract
Synchronous neurotransmitter release is triggered by Ca2+ binding to the synaptic vesicle protein Synaptotagmin 1, while asynchronous fusion and short-term facilitation is hypothesized to be mediated by plasma membrane-localized Synaptotagmin 7 (SYT7). We generated mutations in Drosophila Syt7 to determine if it plays a conserved role as the Ca2+ sensor for these processes. Electrophysiology and quantal imaging revealed evoked release was elevated 2-fold. Syt7 mutants also had a larger pool of readily-releasable vesicles, faster recovery following stimulation, and intact facilitation. Syt1/Syt7 double mutants displayed more release than Syt1 mutants alone, indicating SYT7 does not mediate the residual asynchronous release remaining in the absence of SYT1. SYT7 localizes to an internal membrane tubular network within the peri-active zone, but does not enrich at active zones. These findings indicate the two Ca2+ sensor model of SYT1 and SYT7 mediating all phases of neurotransmitter release and facilitation is not applicable at Drosophila synapses.
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Affiliation(s)
- Zhuo Guan
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Monica C Quiñones-Frías
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Yulia Akbergenova
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of TechnologyCambridgeUnited States
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37
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Bowers MR, Reist NE. Synaptotagmin: Mechanisms of an electrostatic switch. Neurosci Lett 2020; 722:134834. [DOI: 10.1016/j.neulet.2020.134834] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 02/06/2020] [Accepted: 02/09/2020] [Indexed: 02/09/2023]
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38
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Bowers MR, Reist NE. The C2A domain of synaptotagmin is an essential component of the calcium sensor for synaptic transmission. PLoS One 2020; 15:e0228348. [PMID: 32032373 PMCID: PMC7006929 DOI: 10.1371/journal.pone.0228348] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 01/13/2020] [Indexed: 01/27/2023] Open
Abstract
The synaptic vesicle protein, synaptotagmin, is the principle Ca2+ sensor for synaptic transmission. Ca2+ influx into active nerve terminals is translated into neurotransmitter release by Ca2+ binding to synaptotagmin’s tandem C2 domains, triggering the fast, synchronous fusion of multiple synaptic vesicles. Two hydrophobic residues, shown to mediate Ca2+-dependent membrane insertion of these C2 domains, are required for this process. Previous research suggested that one of its tandem C2 domains (C2B) is critical for fusion, while the other domain (C2A) plays only a facilitatory role. However, the function of the two hydrophobic residues in C2A have not been adequately tested in vivo. Here we show that these two hydrophobic residues are absolutely required for synaptotagmin to trigger vesicle fusion. Using in vivo electrophysiological recording at the Drosophila larval neuromuscular junction, we found that mutation of these two key C2A hydrophobic residues almost completely abolished neurotransmitter release. Significantly, mutation of both hydrophobic residues resulted in more severe deficits than those seen in synaptotagmin null mutants. Thus, we report the most severe phenotype of a C2A mutation to date, demonstrating that the C2A domain is absolutely essential for synaptotagmin’s function as the electrostatic switch. The postulated role of synaptotagmin’s C2A domain in triggering neurotransmitter release has fluctuated wildly over the years. Early biochemical experiments suggested that the C2A domain was essential, while the C2B domain was superfluous. Then, functional experiments measuring neurotransmitter release in vivo following disruptions in Ca2+ binding suggested that C2B was essential, while C2A was superfluous. Subsequently, the use of more refined mutations to disrupt Ca2+ binding indicated that C2A played a facilitatory role. Here we show two hydrophobic residues of the C2A domain are absolutely required for synaptotagmin-triggered neurotransmitter release. Thus, after over twenty years of research, we now demonstrate that the C2A domain of synaptotagmin is an essential component of the Ca2+ sensor for triggering synaptic transmission in vivo.
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Affiliation(s)
- Matthew R. Bowers
- Department of Biomedical Sciences, Molecular, Cellular, Integrative Neurosciences Program, Colorado State University, Fort Collins, CO, United States of America
| | - Noreen E. Reist
- Department of Biomedical Sciences, Molecular, Cellular, Integrative Neurosciences Program, Colorado State University, Fort Collins, CO, United States of America
- * E-mail:
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39
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Silva B, Niehage C, Maglione M, Hoflack B, Sigrist SJ, Wassmer T, Pavlowsky A, Preat T. Interactions between amyloid precursor protein-like (APPL) and MAGUK scaffolding proteins contribute to appetitive long-term memory in Drosophila melanogaster. J Neurogenet 2020; 34:92-105. [PMID: 31965876 DOI: 10.1080/01677063.2020.1712597] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Amyloid precursor protein (APP), the precursor of amyloid beta peptide, plays a central role in Alzheimer's disease (AD), a pathology characterized by memory decline and synaptic loss upon aging. Understanding the physiological role of APP is fundamental in deciphering the progression of AD, and several studies suggest a synaptic function via protein-protein interactions. Nevertheless, it remains unclear whether and how these interactions contribute to memory. In Drosophila, we previously showed that APP-like (APPL), the fly APP homolog, is required for aversive associative memory in the olfactory memory center, the mushroom body (MB). In the present study, we show that APPL is required for appetitive long-term memory (LTM), another form of associative memory, in a specific neuronal subpopulation of the MB, the α'/β' Kenyon cells. Using a biochemical approach, we identify the synaptic MAGUK (membrane-associated guanylate kinase) proteins X11, CASK, Dlgh2 and Dlgh4 as interactants of the APP intracellular domain (AICD). Next, we show that the Drosophila homologs CASK and Dlg are also required for appetitive LTM in the α'/β' neurons. Finally, using a double RNAi approach, we demonstrate that genetic interactions between APPL and CASK, as well as between APPL and Dlg, are critical for appetitive LTM. In summary, our results suggest that APPL contributes to associative long-term memory through its interactions with the main synaptic scaffolding proteins CASK and Dlg. This function should be conserved across species.
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Affiliation(s)
- Bryon Silva
- Genes and Dynamics of Memory Systems, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | | | - Marta Maglione
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | | | - Stephan J Sigrist
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | - Thomas Wassmer
- School of Life and Health Sciences, Aston University, Birmingham, UK
| | - Alice Pavlowsky
- Genes and Dynamics of Memory Systems, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
| | - Thomas Preat
- Genes and Dynamics of Memory Systems, Brain Plasticity Unit, CNRS, ESPCI Paris, PSL Research University, Paris, France
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40
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Baker K, Gordon SL, Melland H, Bumbak F, Scott DJ, Jiang TJ, Owen D, Turner BJ, Boyd SG, Rossi M, Al-Raqad M, Elpeleg O, Peck D, Mancini GMS, Wilke M, Zollino M, Marangi G, Weigand H, Borggraefe I, Haack T, Stark Z, Sadedin S, Tan TY, Jiang Y, Gibbs RA, Ellingwood S, Amaral M, Kelley W, Kurian MA, Cousin MA, Raymond FL. SYT1-associated neurodevelopmental disorder: a case series. Brain 2019; 141:2576-2591. [PMID: 30107533 PMCID: PMC6113648 DOI: 10.1093/brain/awy209] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 06/19/2018] [Indexed: 12/25/2022] Open
Abstract
Synaptotagmin 1 (SYT1) is a critical mediator of fast, synchronous, calcium-dependent neurotransmitter release and also modulates synaptic vesicle endocytosis. This paper describes 11 patients with de novo heterozygous missense mutations in SYT1. All mutations alter highly conserved residues, and cluster in two regions of the SYT1 C2B domain at positions Met303 (M303K), Asp304 (D304G), Asp366 (D366E), Ile368 (I368T) and Asn371 (N371K). Phenotypic features include infantile hypotonia, congenital ophthalmic abnormalities, childhood-onset hyperkinetic movement disorders, motor stereotypies, and developmental delay varying in severity from moderate to profound. Behavioural characteristics include sleep disturbance and episodic agitation. Absence of epileptic seizures and normal orbitofrontal head circumference are important negative features. Structural MRI is unremarkable but EEG disturbance is universal, characterized by intermittent low frequency high amplitude oscillations. The functional impact of these five de novo SYT1 mutations has been assessed by expressing rat SYT1 protein containing the equivalent human variants in wild-type mouse primary hippocampal cultures. All mutant forms of SYT1 were expressed at levels approximately equal to endogenous wild-type protein, and correctly localized to nerve terminals at rest, except for SYT1M303K, which was expressed at a lower level and failed to localize at nerve terminals. Following stimulation, SYT1I368T and SYT1N371K relocalized to nerve terminals at least as efficiently as wild-type SYT1. However, SYT1D304G and SYT1D366E failed to relocalize to nerve terminals following stimulation, indicative of impairments in endocytic retrieval and trafficking of SYT1. In addition, the presence of SYT1 variants at nerve terminals induced a slowing of exocytic rate following sustained action potential stimulation. The extent of disturbance to synaptic vesicle kinetics is mirrored by the severity of the affected individuals' phenotypes, suggesting that the efficiency of SYT1-mediated neurotransmitter release is critical to cognitive development. In summary, de novo dominant SYT1 missense mutations are associated with a recognizable neurodevelopmental syndrome, and further cases can now be diagnosed based on clinical features, electrophysiological signature and mutation characteristics. Variation in phenotype severity may reflect mutation-specific impact on the diverse physiological functions of SYT1.
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Affiliation(s)
- Kate Baker
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, Wellcome Trust / MRC Building, Hills Road, Cambridge, UK.,MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge, UK
| | - Sarah L Gordon
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Holly Melland
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Fabian Bumbak
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Daniel J Scott
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia.,Department of Biochemistry and Molecular Biology, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Tess J Jiang
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - David Owen
- Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Hills Road, Cambridge, UK
| | - Bradley J Turner
- The Florey Institute of Neuroscience and Mental Health, University of Melbourne, 30 Royal Parade, Parkville, VIC, Australia
| | - Stewart G Boyd
- Developmental Neurosciences, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London, UK
| | - Mari Rossi
- Ambry Genetics, 15 Argonaut, Aliso Viejo, CA, USA
| | - Mohammed Al-Raqad
- Department of Clinical Genetics, Queen Rania Al-Abdullah Children Hospital, King Hussein Medical Centre, Royal Medical Services, Amman, Jordan
| | - Orly Elpeleg
- Monique and Jacques Roboh Department of Genetic Research, Hadassah, Hebrew University Medical Center, Jerusalem, Israel
| | - Dawn Peck
- University of Missouri Health Care, Columbia, MO, USA
| | - Grazia M S Mancini
- Department of Clinical Genetics, Erasmus Medical Center, 3015 CN Rotterdam, The Netherlands
| | - Martina Wilke
- Department of Clinical Genetics, Erasmus Medical Center, 3015 CN Rotterdam, The Netherlands
| | - Marcella Zollino
- Institute of Genomic Medicine, Catholic University, A. Gemelli Foundation, Roma, Italy
| | - Giuseppe Marangi
- Institute of Genomic Medicine, Catholic University, A. Gemelli Foundation, Roma, Italy
| | - Heike Weigand
- Department of Pediatric Neurology, Developmental Medicine and Social Pediatrics, Dr. von Hauner's Children's Hospital, University of Munich, Munich, Germany
| | - Ingo Borggraefe
- Department of Pediatric Neurology, Developmental Medicine and Social Pediatrics, Dr. von Hauner's Children's Hospital, University of Munich, Munich, Germany
| | - Tobias Haack
- Institute of Human Genetics, Technische Universität München, Munich, Germany.,Institute of Medical Genetics and Applied Genomics, University of Tuebingen, Tuebingen, Germany
| | - Zornitza Stark
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Flemington Road, Parkville VIC, Australia
| | - Simon Sadedin
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Flemington Road, Parkville VIC, Australia.,Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | | | - Tiong Yang Tan
- Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Flemington Road, Parkville VIC, Australia
| | - Yunyun Jiang
- Human Genome Sequencing Center, Baylor College of Medicine, Texas, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Texas, USA
| | - Sara Ellingwood
- Maine Medical Partners Pediatric Specialty Care, Congress St, Portland ME, USA
| | - Michelle Amaral
- HudsonAlpha Institute for Biotechnology, 601 Genome Way NW, Huntsville, AL, USA
| | - Whitley Kelley
- HudsonAlpha Institute for Biotechnology, 601 Genome Way NW, Huntsville, AL, USA
| | - Manju A Kurian
- Developmental Neurosciences, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, Hugh Robson Building, George Square, University of Edinburgh, Edinburgh, UK
| | - F Lucy Raymond
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, Wellcome Trust / MRC Building, Hills Road, Cambridge, UK
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41
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Grushin K, Wang J, Coleman J, Rothman JE, Sindelar CV, Krishnakumar SS. Structural basis for the clamping and Ca 2+ activation of SNARE-mediated fusion by synaptotagmin. Nat Commun 2019; 10:2413. [PMID: 31160571 PMCID: PMC6546687 DOI: 10.1038/s41467-019-10391-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 05/08/2019] [Indexed: 12/22/2022] Open
Abstract
Synapotagmin-1 (Syt1) interacts with both SNARE proteins and lipid membranes to synchronize neurotransmitter release to calcium (Ca2+) influx. Here we report the cryo-electron microscopy structure of the Syt1-SNARE complex on anionic-lipid containing membranes. Under resting conditions, the Syt1 C2 domains bind the membrane with a magnesium (Mg2+)-mediated partial insertion of the aliphatic loops, alongside weak interactions with the anionic lipid headgroups. The C2B domain concurrently interacts the SNARE bundle via the 'primary' interface and is positioned between the SNAREpins and the membrane. In this configuration, Syt1 is projected to sterically delay the complete assembly of the associated SNAREpins and thus, contribute to clamping fusion. This Syt1-SNARE organization is disrupted upon Ca2+-influx as Syt1 reorients into the membrane, likely displacing the attached SNAREpins and reversing the fusion clamp. We thus conclude that the cation (Mg2+/Ca2+) dependent membrane interaction is a key determinant of the dual clamp/activator function of Synaptotagmin-1.
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Affiliation(s)
- Kirill Grushin
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
| | - Jing Wang
- 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
| | - James E Rothman
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT, 06520, USA
| | - Charles V Sindelar
- Department of Molecular Biophysics and Biochemistry, 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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42
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Lee SE, Jeong S, Lee U, Chang S. SGIP1α functions as a selective endocytic adaptor for the internalization of synaptotagmin 1 at synapses. Mol Brain 2019; 12:41. [PMID: 31053155 PMCID: PMC6499997 DOI: 10.1186/s13041-019-0464-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 04/16/2019] [Indexed: 11/10/2022] Open
Abstract
Proper sorting of exocytosed synaptic vesicle (SV) proteins into individual SVs during endocytosis is of the utmost importance for the fidelity of subsequent neurotransmission. Recent studies suggest that each SV protein is sorted into individual SVs by its own dedicated adaptors as well as by association between SV proteins. The SH3-containing GRB2-like protein 3-interacting protein 1 (SGIP1), an ortholog of Fer/Cip4 homology domain-only (FCHo) proteins, contains a μ-homology domain (μHD) and binds AP-2 and Eps15, thus functioning as an endocytic regulator of clathrin-mediated endocytosis (CME). Its longest isoform SGIP1α is predominantly expressed in the brain but the functional significance of SGIP1 in SV recycling remains unknown. Here, we found that SGIP1α, a brain-specific long isoform of SGIP1 binds synaptotagmin1 (Syt1) via its μHD and promotes the internalization of Syt1 on the neuronal surface. The small hairpin RNA (shRNA)-mediated knockdown (KD) of SGIP1α caused selective impairment of Syt1 internalization at hippocampal synapses and it was fully rescued by coexpression of the shRNA-resistant form of SGIP1α in KD neurons. We further found that the μHD of SGIP1α is structurally similar to those of AP-2 and stonin2, and mutations at Trp771 and Lys781, which correspond to Syt1-recognition motifs of AP-2 and stonin2, to Ala bound less efficiently to Syt1 and failed to rescue the endocytic defect of Syt1 caused by KD. Our results indicate that SGIP1α is an endocytic adaptor dedicated to the retrieval of surface-stranded Syt1. Since endocytic sorting of Syt1 is also mediated by the overlapping activities of synaptic vesicle glycoprotein 2A/B (SV2A/B) and stonin2, our results suggest that complementary fail-safe mechanism by these proteins ensures high fidelity of Syt1 retrieval.
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Affiliation(s)
- Sang-Eun Lee
- Department of Physiology and Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Soomin Jeong
- Department of Physiology and Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Unghwi Lee
- Department of Physiology and Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Sunghoe Chang
- Department of Physiology and Biomedical Sciences, Neuroscience Research Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea.
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43
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Burgoyne RD, Helassa N, McCue HV, Haynes LP. Calcium Sensors in Neuronal Function and Dysfunction. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a035154. [PMID: 30833454 DOI: 10.1101/cshperspect.a035154] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Calcium signaling in neurons as in other cell types can lead to varied changes in cellular function. Neuronal Ca2+ signaling processes have also become adapted to modulate the function of specific pathways over a wide variety of time domains and these can have effects on, for example, axon outgrowth, neuronal survival, and changes in synaptic strength. Ca2+ also plays a key role in synapses as the trigger for fast neurotransmitter release. Given its physiological importance, abnormalities in neuronal Ca2+ signaling potentially underlie many different neurological and neurodegenerative diseases. The mechanisms by which changes in intracellular Ca2+ concentration in neurons can bring about diverse responses is underpinned by the roles of ubiquitous or specialized neuronal Ca2+ sensors. It has been established that synaptotagmins have key functions in neurotransmitter release, and, in addition to calmodulin, other families of EF-hand-containing neuronal Ca2+ sensors, including the neuronal calcium sensor (NCS) and the calcium-binding protein (CaBP) families, play important physiological roles in neuronal Ca2+ signaling. It has become increasingly apparent that these various Ca2+ sensors may also be crucial for aspects of neuronal dysfunction and disease either indirectly or directly as a direct consequence of genetic variation or mutations. An understanding of the molecular basis for the regulation of the targets of the Ca2+ sensors and the physiological roles of each protein in identified neurons may contribute to future approaches to the development of treatments for a variety of human neuronal disorders.
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Affiliation(s)
- Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Nordine Helassa
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Hannah V McCue
- Centre for Genomic Research, University of Liverpool, Liverpool, United Kingdom
| | - Lee P Haynes
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
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44
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Goel P, Dufour Bergeron D, Böhme MA, Nunnelly L, Lehmann M, Buser C, Walter AM, Sigrist SJ, Dickman D. Homeostatic scaling of active zone scaffolds maintains global synaptic strength. J Cell Biol 2019; 218:1706-1724. [PMID: 30914419 PMCID: PMC6504899 DOI: 10.1083/jcb.201807165] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 12/14/2018] [Accepted: 03/06/2019] [Indexed: 12/23/2022] Open
Abstract
Synaptic terminals grow and retract throughout life, yet synaptic strength is maintained within stable physiological ranges. To study this process, we investigated Drosophila endophilin (endo) mutants. Although active zone (AZ) number is doubled in endo mutants, a compensatory reduction in their size homeostatically adjusts global neurotransmitter output to maintain synaptic strength. We find an inverse adaptation in rab3 mutants. Additional analyses using confocal, STED, and electron microscopy reveal a stoichiometric tuning of AZ scaffolds and nanoarchitecture. Axonal transport of synaptic cargo via the lysosomal kinesin adapter Arl8 regulates AZ abundance to modulate global synaptic output and sustain the homeostatic potentiation of neurotransmission. Finally, we find that this AZ scaling can interface with two independent homeostats, depression and potentiation, to remodel AZ structure and function, demonstrating a robust balancing of separate homeostatic adaptations. Thus, AZs are pliable substrates with elastic and modular nanostructures that can be dynamically sculpted to stabilize and tune both local and global synaptic strength.
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Affiliation(s)
- Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA
| | | | - Mathias A Böhme
- Neurocure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | - Luke Nunnelly
- Department of Neurobiology, University of Southern California, Los Angeles, CA
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, Berlin, Germany
| | | | - Alexander M Walter
- Neurocure Cluster of Excellence, Charité Universitätsmedizin, Berlin, Germany
| | | | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA
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45
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Tran HT, Anderson LH, Knight JD. Membrane-Binding Cooperativity and Coinsertion by C2AB Tandem Domains of Synaptotagmins 1 and 7. Biophys J 2019; 116:1025-1036. [PMID: 30795874 DOI: 10.1016/j.bpj.2019.01.035] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 12/21/2018] [Accepted: 01/30/2019] [Indexed: 02/04/2023] Open
Abstract
Synaptotagmin-1 (Syt-1) and synaptotagmin-7 (Syt-7) contain analogous tandem C2 domains, C2A and C2B, which together sense Ca2+ to bind membranes and promote the stabilization of exocytotic fusion pores. Syt-1 triggers fast release of neurotransmitters, whereas Syt-7 functions in processes that involve lower Ca2+ concentrations such as hormone secretion. Syt-1 C2 domains are reported to bind membranes cooperatively, based on the observation that they penetrate farther into membranes as the C2AB tandem than as individual C2 domains. In contrast, we previously suggested that the two C2 domains of Syt-7 bind membranes independently, based in part on measurements of their liposome dissociation kinetics. Here, we investigated C2A-C2B interdomain cooperativity with Syt-1 and Syt-7 using directly comparable measurements. Equilibrium Ca2+ titrations demonstrate that the Syt-7 C2AB tandem binds liposomes lacking phosphatidylinositol-4,5-bisphosphate (PIP2) with greater Ca2+ sensitivity than either of its individual domains and binds to membranes containing PIP2 even in the absence of Ca2+. Stopped-flow kinetic measurements show differences in cooperativity between Syt-1 and Syt-7: Syt-1 C2AB dissociates from PIP2-free liposomes much more slowly than either of its individual C2 domains, indicating cooperativity, whereas the major population of Syt-7 C2AB has a dissociation rate comparable to its C2A domain, suggesting a lack of cooperativity. A minor subpopulation of Syt-7 C2AB dissociates at a slower rate, which could be due to a small cooperative component and/or liposome clustering. Measurements using an environment-sensitive fluorescent probe indicate that the Syt-7 C2B domain inserts deeply into membranes as part of the C2AB tandem, similar to the coinsertion previously reported for Syt-1. Overall, coinsertion of C2A and C2B domains is coupled to cooperative energetic effects in Syt-1 to a much greater extent than in Syt-7. The difference can be understood in terms of the relative contributions of C2A and C2B domains toward membrane binding in the two proteins.
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Affiliation(s)
- Hai T Tran
- Department of Chemistry, University of Colorado Denver, Denver, Colorado
| | - Lauren H Anderson
- Department of Chemistry, University of Colorado Denver, Denver, Colorado
| | - Jefferson D Knight
- Department of Chemistry, University of Colorado Denver, Denver, Colorado.
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46
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DePew AT, Aimino MA, Mosca TJ. The Tenets of Teneurin: Conserved Mechanisms Regulate Diverse Developmental Processes in the Drosophila Nervous System. Front Neurosci 2019; 13:27. [PMID: 30760977 PMCID: PMC6363694 DOI: 10.3389/fnins.2019.00027] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 01/11/2019] [Indexed: 01/26/2023] Open
Abstract
To successfully integrate a neuron into a circuit, a myriad of developmental events must occur correctly and in the correct order. Neurons must be born and grow out toward a destination, responding to guidance cues to direct their path. Once arrived, each neuron must segregate to the correct sub-region before sorting through a milieu of incorrect partners to identify the correct partner with which they can connect. Finally, the neuron must make a synaptic connection with their correct partner; a connection that needs to be broadly maintained throughout the life of the animal while remaining responsive to modes of plasticity and pruning. Though many intricate molecular mechanisms have been discovered to regulate each step, recent work showed that a single family of proteins, the Teneurins, regulates a host of these developmental steps in Drosophila – an example of biological adaptive reuse. Teneurins first influence axon guidance during early development. Once neurons arrive in their target regions, Teneurins enable partner matching and synapse formation in both the central and peripheral nervous systems. Despite these diverse processes and systems, the Teneurins use conserved mechanisms to achieve these goals, as defined by three tenets: (1) transsynaptic interactions with each other, (2) membrane stabilization via an interaction with and regulation of the cytoskeleton, and (3) a role for presynaptic Ten-a in regulating synaptic function. These processes are further distinguished by (1) the nature of the transsynaptic interaction – homophilic interactions (between the same Teneurins) to engage partner matching and heterophilic interactions (between different Teneurins) to enable synaptic connectivity and the proper apposition of pre- and postsynaptic sites and (2) the location of cytoskeletal regulation (presynaptic cytoskeletal regulation in the CNS and postsynaptic regulation of the cytoskeleton at the NMJ). Thus, both the roles and the mechanisms governing them are conserved across processes and synapses. Here, we will highlight the contributions of Drosophila synaptic biology to our understanding of the Teneurins, discuss the mechanistic conservation that allows the Teneurins to achieve common neurodevelopmental goals, and present new data in support of these points. Finally, we will posit the next steps for understanding how this remarkably versatile family of proteins functions to control multiple distinct events in the creation of a nervous system.
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Affiliation(s)
- Alison T DePew
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA, United States
| | - Michael A Aimino
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA, United States
| | - Timothy J Mosca
- Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA, United States
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47
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Abstract
Modulation of neurotransmitter exocytosis by activated Gi/o coupled G-protein coupled receptors (GPCRs) is a universal regulatory mechanism used both to avoid overstimulation and to influence circuitry. One of the known modulation mechanisms is the interaction between Gβγ and the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNAREs). There are 5 Gβ and 12 Gγ subunits, but specific Gβγs activated by a given GPCR and the specificity to effectors, such as SNARE, in vivo are not known. Although less studied, Gβγ binding to the exocytic fusion machinery (i.e. SNARE) provides a more direct regulatory mechanism for neurotransmitter release. Here, we review some recent insights in the architecture of the synaptic terminal, modulation of synaptic transmission, and implications of G protein modulation of synaptic transmission in diseases. Numerous presynaptic proteins are involved in the architecture of synaptic terminals, particularly the active zone, and their importance in the regulation of exocytosis is still not completely understood. Further understanding of the Gβγ-SNARE interaction and the architecture and mechanisms of exocytosis may lead to the discovery of novel therapeutic targets to help patients with various disorders such as hypertension, attention-deficit/hyperactivity disorder, post-traumatic stress disorder, and acute/chronic pain.
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Affiliation(s)
- Yun Young Yim
- Department of Pharmacology, Vanderbilt University, Nashville 37232-6600, TN, United States
| | - Zack Zurawski
- Department of Pharmacology, Vanderbilt University, Nashville 37232-6600, TN, United States
| | - Heidi Hamm
- Department of Pharmacology, Vanderbilt University, Nashville 37232-6600, TN, United States.
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48
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Abstract
In 1992, Brose et al. showed that the synaptic vesicle (SV) protein p65/synaptotagmin (syt) 1 binds - in a mutually dependent manner - Ca2+ and anionic phospholipids, prompting the idea that it functions as a Ca2+ sensor for exocytosis. These findings now define two key aspects of excitation-secretion coupling.
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Affiliation(s)
- Edwin R Chapman
- Department of Neuroscience and Howard Hughes Medical Institute, University of Wisconsin-Madison, 1111 Highland Ave., Madison, WI 53705, USA.
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49
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Montes-Chinea NI, Guan Z, Coutts M, Vidal C, Courel S, Rebelo AP, Abreu L, Zuchner S, Littleton JT, Saporta MA. Identification of a new SYT2 variant validates an unusual distal motor neuropathy phenotype. NEUROLOGY-GENETICS 2018; 4:e282. [PMID: 30533528 PMCID: PMC6244021 DOI: 10.1212/nxg.0000000000000282] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 08/21/2018] [Indexed: 11/15/2022]
Abstract
Objective To report a new SYT2 missense mutation causing distal hereditary motor neuropathy and presynaptic neuromuscular junction (NMJ) transmission dysfunction. Methods We report a multigenerational family with a new missense mutation, c. 1112T>A (p. Ile371Lys), in the C2B domain of SYT2, describe the clinical and electrophysiologic phenotype associated with this variant, and validate its pathogenicity in a Drosophila model. Results Both proband and her mother present a similar clinical phenotype characterized by a slowly progressive, predominantly motor neuropathy and clear evidence of presynaptic NMJ dysfunction on nerve conduction studies. Validation of this new variant was accomplished by characterization of the mutation homologous to the human c. 1112T>A variant in Drosophila, confirming its dominant-negative effect on neurotransmitter release. Conclusions This report provides further confirmation of the role of SYT2 in human disease and corroborates the resultant unique clinical phenotype consistent with heriditary distal motor neuropathy. SYT2-related motor neuropathy is a rare disease but should be suspected in patients presenting with a combination of presynaptic NMJ dysfunction (resembling Lambert-Eaton myasthenic syndrome) and a predominantly motor neuropathy, especially in the context of a positive family history.
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Affiliation(s)
- Nataly I Montes-Chinea
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Zhuo Guan
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Marcella Coutts
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Cecilia Vidal
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Steve Courel
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Adriana P Rebelo
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Lisa Abreu
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Stephan Zuchner
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - J Troy Littleton
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
| | - Mario A Saporta
- Department of Neurology (N.I.M.-C., M.C., C.V., M.A.S.), University of Miami Miller School of Medicine FL; Department of Biology (Z.G., J.T.L.) and Department of Brain and Cognitive Sciences (Z.G., J.T.L.), The Picower Institute for Learning & Memory, Massachusetts Institute of Technology, Cambridge; and Department of Human Genetics (S.C., A.P.R., L.A., S.Z., M.A.S.), Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL
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50
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Brunger AT, Leitz J, Zhou Q, Choi UB, Lai Y. Ca 2+-Triggered Synaptic Vesicle Fusion Initiated by Release of Inhibition. Trends Cell Biol 2018; 28:631-645. [PMID: 29706534 PMCID: PMC6056330 DOI: 10.1016/j.tcb.2018.03.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/17/2018] [Accepted: 03/26/2018] [Indexed: 12/20/2022]
Abstract
Recent structural and functional studies of the synaptic vesicle fusion machinery suggest an inhibited tripartite complex consisting of neuronal soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs), synaptotagmin, and complexin prior to Ca2+-triggered synaptic vesicle fusion. We speculate that Ca2+-triggered fusion commences with the release of inhibition by Ca2+ binding to synaptotagmin C2 domains. Subsequently, fusion is assisted by SNARE complex zippering and by active membrane remodeling properties of synaptotagmin. This additional, inhibitory role of synaptotagmin may be a general principle since other recent studies suggest that Ca2+ binding to extended synaptotagmin C2 domains enables lipid transport by releasing an inhibited state of the system, and that Munc13 may nominally be in an inhibited state, which is released upon Ca2+ binding to one of its C2 domains.
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Affiliation(s)
- Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA.
| | - Jeremy Leitz
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Qiangjun Zhou
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Ucheor B Choi
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Ying Lai
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
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