51
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Egawa J, Hoya S, Watanabe Y, Nunokawa A, Shibuya M, Ikeda M, Inoue E, Okuda S, Kondo K, Saito T, Kaneko N, Muratake T, Igeta H, Iwata N, Someya T. Rare UNC13B variations and risk of schizophrenia: Whole-exome sequencing in a multiplex family and follow-up resequencing and a case-control study. Am J Med Genet B Neuropsychiatr Genet 2016; 171:797-805. [PMID: 26990377 DOI: 10.1002/ajmg.b.32444] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 02/25/2016] [Indexed: 01/03/2023]
Abstract
Rare genomic variations inherited in multiplex schizophrenia families are suggested to play a role in the genetic etiology of the disease. To identify rare variations with large effects on the risk of developing schizophrenia, we performed whole-exome sequencing (WES) in two affected and one unaffected individual of a multiplex family with 10 affected individuals. We also performed follow-up resequencing of the unc-13 homolog B (Caenorhabditis elegans) (UNC13B) gene, a potential risk gene identified by WES, in the multiplex family and undertook a case-control study to investigate association between UNC13B and schizophrenia. UNC13B coding regions (39 exons) from 15 individuals of the multiplex family and 111 affected offspring for whom parental DNA samples were available were resequenced. Rare missense UNC13B variations identified by resequencing were further tested for association with schizophrenia in two independent case-control populations comprising a total of 1,753 patients and 1,602 controls. A rare missense variation (V1525M) in UNC13B was identified by WES in the multiplex family; this variation was present in five of six affected individuals, but not in eight unaffected individuals or one individual of unknown disease status. Resequencing UNC13B coding regions identified five rare missense variations (T103M, M813T, P1349T, I1362T, and V1525M). In the case-control study, there was no significant association between rare missense UNC13B variations and schizophrenia, although single-variant meta-analysis indicated that M813T was nominally associated with schizophrenia. These results do not support a contribution of rare missense UNC13B variations to the genetic etiology of schizophrenia in the Japanese population. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Jun Egawa
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Satoshi Hoya
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Yuichiro Watanabe
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Ayako Nunokawa
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.,Oojima Hospital, Sanjo, Niigata, Japan
| | - Masako Shibuya
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Masashi Ikeda
- Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Emiko Inoue
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Shujiro Okuda
- Division of Bioinformatics, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kenji Kondo
- Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Takeo Saito
- Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Naoshi Kaneko
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.,Oojima Hospital, Sanjo, Niigata, Japan
| | - Tatsuyuki Muratake
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.,Furumachi Mental Clinic, Niigata, Japan
| | - Hirofumi Igeta
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Nakao Iwata
- Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Toshiyuki Someya
- Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
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52
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Shinoda Y, Ishii C, Fukazawa Y, Sadakata T, Ishii Y, Sano Y, Iwasato T, Itohara S, Furuichi T. CAPS1 stabilizes the state of readily releasable synaptic vesicles to fusion competence at CA3-CA1 synapses in adult hippocampus. Sci Rep 2016; 6:31540. [PMID: 27545744 PMCID: PMC4992871 DOI: 10.1038/srep31540] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/21/2016] [Indexed: 01/06/2023] Open
Abstract
Calcium-dependent activator protein for secretion 1 (CAPS1) regulates exocytosis of dense-core vesicles in neuroendocrine cells and of synaptic vesicles in neurons. However, the synaptic function of CAPS1 in the mature brain is unclear because Caps1 knockout (KO) results in neonatal death. Here, using forebrain-specific Caps1 conditional KO (cKO) mice, we demonstrate, for the first time, a critical role of CAPS1 in adult synapses. The amplitude of synaptic transmission at CA3–CA1 synapses was strongly reduced, and paired-pulse facilitation was significantly increased, in acute hippocampal slices from cKO mice compared with control mice, suggesting a perturbation in presynaptic function. Morphological analysis revealed an accumulation of synaptic vesicles in the presynapse without any overall morphological change. Interestingly, however, the percentage of docked vesicles was markedly decreased in the Caps1 cKO. Taken together, our findings suggest that CAPS1 stabilizes the state of readily releasable synaptic vesicles, thereby enhancing neurotransmitter release at hippocampal synapses.
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Affiliation(s)
- Yo Shinoda
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba 278-8510, Japan.,School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
| | - Chiaki Ishii
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Yugo Fukazawa
- Department of Brain Structure and Function, Faculty of Medical Sciences, University of Fukui, Yoshida-gun, Fukui 910-1193, Japan
| | - Tetsushi Sadakata
- Advanced Scientific Research Leaders Development Unit, Gunma University, Maebashi, Gunma 371-8511, Japan
| | - Yuki Ishii
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Yoshitake Sano
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba 278-8510, Japan
| | - Takuji Iwasato
- Division of Neurogenetics, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.,Department of Genetics, SOKENDAI, Mishima, Shizuoka 411-8540, Japan
| | - Shigeyoshi Itohara
- Laboratory for Behavioral Genetics, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Teiichi Furuichi
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba 278-8510, Japan
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53
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Netrakanti PR, Cooper BH, Dere E, Poggi G, Winkler D, Brose N, Ehrenreich H. Fast cerebellar reflex circuitry requires synaptic vesicle priming by munc13-3. THE CEREBELLUM 2016; 14:264-83. [PMID: 25617111 PMCID: PMC4441738 DOI: 10.1007/s12311-015-0645-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Munc13-3 is a member of the Munc13 family of synaptic vesicle priming proteins and mainly expressed in cerebellar neurons. Munc13-3 null mutant (Munc13-3−/−) mice show decreased synaptic release probability at parallel fiber to Purkinje cell, granule cell to Golgi cell, and granule cell to basket cell synapses and exhibit a motor learning deficit at highest rotarod speeds. Since we detected Munc13-3 immunoreactivity in the dentate gyrus, as reported here for the first time, and current studies indicated a crucial role for the cerebellum in hippocampus-dependent spatial memory, we systematically investigated Munc13-3−/− mice versus wild-type littermates of both genders with respect to hippocampus-related cognition and a range of basic behaviors, including tests for anxiety, sensory functions, motor performance and balance, sensorimotor gating, social interaction and competence, and repetitive and compulsive behaviors. Neither basic behavior nor hippocampus-dependent cognitive performance, evaluated by Morris water maze, hole board working and reference memory, IntelliCage-based place learning including multiple reversals, and fear conditioning, showed any difference between genotypes. However, consistent with a disturbed cerebellar reflex circuitry, a reliable reduction in the acoustic startle response in both male and female Munc13-3−/− mice was found. To conclude, complete deletion of Munc13-3 leads to a robust decrease in the acoustic startle response. This readout of a fast cerebellar reflex circuitry obviously requires synaptic vesicle priming by Munc13-3 for full functionality, in contrast to other behavioral or cognitive features, where a nearly perfect compensation of Munc13-3 deficiency by related synaptic proteins has to be assumed.
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Affiliation(s)
- Pallavi Rao Netrakanti
- Clinical Neuroscience, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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54
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Kabachinski G, Kielar-Grevstad DM, Zhang X, James DJ, Martin TFJ. Resident CAPS on dense-core vesicles docks and primes vesicles for fusion. Mol Biol Cell 2016; 27:654-68. [PMID: 26700319 PMCID: PMC4750925 DOI: 10.1091/mbc.e15-07-0509] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 12/12/2015] [Accepted: 12/18/2015] [Indexed: 11/11/2022] Open
Abstract
The Ca(2+)-dependent exocytosis of dense-core vesicles in neuroendocrine cells requires a priming step during which SNARE protein complexes assemble. CAPS (aka CADPS) is one of several factors required for vesicle priming; however, the localization and dynamics of CAPS at sites of exocytosis in live neuroendocrine cells has not been determined. We imaged CAPS before, during, and after single-vesicle fusion events in PC12 cells by TIRF micro-scopy. In addition to being a resident on cytoplasmic dense-core vesicles, CAPS was present in clusters of approximately nine molecules near the plasma membrane that corresponded to docked/tethered vesicles. CAPS accompanied vesicles to the plasma membrane and was present at all vesicle exocytic events. The knockdown of CAPS by shRNA eliminated the VAMP-2-dependent docking and evoked exocytosis of fusion-competent vesicles. A CAPS(ΔC135) protein that does not localize to vesicles failed to rescue vesicle docking and evoked exocytosis in CAPS-depleted cells, showing that CAPS residence on vesicles is essential. Our results indicate that dense-core vesicles carry CAPS to sites of exocytosis, where CAPS promotes vesicle docking and fusion competence, probably by initiating SNARE complex assembly.
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Affiliation(s)
- Greg Kabachinski
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | | | - Xingmin Zhang
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | - Declan J James
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
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55
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Man KNM, Imig C, Walter AM, Pinheiro PS, Stevens DR, Rettig J, Sørensen JB, Cooper BH, Brose N, Wojcik SM. Identification of a Munc13-sensitive step in chromaffin cell large dense-core vesicle exocytosis. eLife 2015; 4. [PMID: 26575293 PMCID: PMC4798968 DOI: 10.7554/elife.10635] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 11/16/2015] [Indexed: 01/16/2023] Open
Abstract
It is currently unknown whether the molecular steps of large dense-core vesicle (LDCV) docking and priming are identical to the corresponding reactions in synaptic vesicle (SV) exocytosis. Munc13s are essential for SV docking and priming, and we systematically analyzed their role in LDCV exocytosis using chromaffin cells lacking individual isoforms. We show that particularly Munc13-2 plays a fundamental role in LDCV exocytosis, but in contrast to synapses lacking Munc13s, the corresponding chromaffin cells do not exhibit a vesicle docking defect. We further demonstrate that ubMunc13-2 and Munc13-1 confer Ca(2+)-dependent LDCV priming with similar affinities, but distinct kinetics. Using a mathematical model, we identify an early LDCV priming step that is strongly dependent upon Munc13s. Our data demonstrate that the molecular steps of SV and LDCV priming are very similar while SV and LDCV docking mechanisms are distinct.
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Affiliation(s)
- Kwun Nok M Man
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | | | - Paulo S Pinheiro
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - David R Stevens
- Department of Physiology, Saarland University, Homburg, Germany
| | - Jens Rettig
- Department of Physiology, Saarland University, Homburg, Germany
| | - Jakob B Sørensen
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences and Lundbeck Foundation Center for Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
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56
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Bruckner JJ, Zhan H, O'Connor-Giles KM. Advances in imaging ultrastructure yield new insights into presynaptic biology. Front Cell Neurosci 2015; 9:196. [PMID: 26052269 PMCID: PMC4440913 DOI: 10.3389/fncel.2015.00196] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 05/05/2015] [Indexed: 11/13/2022] Open
Abstract
Synapses are the fundamental functional units of neural circuits, and their dysregulation has been implicated in diverse neurological disorders. At presynaptic terminals, neurotransmitter-filled synaptic vesicles are released in response to calcium influx through voltage-gated calcium channels activated by the arrival of an action potential. Decades of electrophysiological, biochemical, and genetic studies have contributed to a growing understanding of presynaptic biology. Imaging studies are yielding new insights into how synapses are organized to carry out their critical functions. The development of techniques for rapid immobilization and preservation of neuronal tissues for electron microscopy (EM) has led to a new renaissance in ultrastructural imaging that is rapidly advancing our understanding of synapse structure and function.
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Affiliation(s)
- Joseph J Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison Madison, WI, USA
| | - Hong Zhan
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison Madison, WI, USA
| | - Kate M O'Connor-Giles
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison Madison, WI, USA ; Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison Madison, WI, USA ; Laboratory of Genetics, University of Wisconsin-Madison Madison, WI, USA
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57
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Brusich DJ, Spring AM, Frank CA. A single-cross, RNA interference-based genetic tool for examining the long-term maintenance of homeostatic plasticity. Front Cell Neurosci 2015; 9:107. [PMID: 25859184 PMCID: PMC4374470 DOI: 10.3389/fncel.2015.00107] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/09/2015] [Indexed: 11/15/2022] Open
Abstract
Homeostatic synaptic plasticity (HSP) helps neurons and synapses maintain physiologically appropriate levels of output. The fruit fly Drosophila melanogaster larval neuromuscular junction (NMJ) is a valuable model for studying HSP. Here we introduce a genetic tool that allows fruit fly researchers to examine the lifelong maintenance of HSP with a single cross. The tool is a fruit fly stock that combines the GAL4/UAS expression system with RNA interference (RNAi)-based knock down of a glutamate receptor subunit gene. With this stock, we uncover important new information about the maintenance of HSP. We address an open question about the role that presynaptic CaV2-type Ca2+ channels play in NMJ homeostasis. Published experiments have demonstrated that hypomorphic missense mutations in the CaV2 α1a subunit gene cacophony (cac) can impair homeostatic plasticity at the NMJ. Here we report that reducing cac expression levels by RNAi is not sufficient to impair homeostatic plasticity. The presence of wild-type channels appears to support HSP—even when total CaV2 function is severely reduced. We also conduct an RNAi- and electrophysiology-based screen to identify new factors required for sustained homeostatic signaling throughout development. We uncover novel roles in HSP for Drosophila homologs of Cysteine string protein (CSP) and Phospholipase Cβ (Plc21C). We characterize those roles through follow-up genetic tests. We discuss how CSP, Plc21C, and associated factors could modulate presynaptic CaV2 function, presynaptic Ca2+ handling, or other signaling processes crucial for sustained homeostatic regulation of NMJ function throughout development. Our findings expand the scope of signaling pathways and processes that contribute to the durable strength of the NMJ.
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Affiliation(s)
- Douglas J Brusich
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| | - Ashlyn M Spring
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA ; Interdisciplinary Graduate Program in Genetics, University of Iowa Iowa City, IA, USA
| | - C Andrew Frank
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA ; Interdisciplinary Programs in Genetics, Neuroscience, and MCB, University of Iowa Iowa City, IA, USA
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58
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Nguyen Truong CQ, Nestvogel D, Ratai O, Schirra C, Stevens DR, Brose N, Rhee J, Rettig J. Secretory vesicle priming by CAPS is independent of its SNARE-binding MUN domain. Cell Rep 2014; 9:902-9. [PMID: 25437547 DOI: 10.1016/j.celrep.2014.09.050] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 09/12/2014] [Accepted: 09/28/2014] [Indexed: 01/27/2023] Open
Abstract
Priming of secretory vesicles is a prerequisite for their Ca(2+)-dependent fusion with the plasma membrane. The key vesicle priming proteins, Munc13s and CAPSs, are thought to mediate vesicle priming by regulating the conformation of the t-SNARE syntaxin, thereby facilitating SNARE complex assembly. Munc13s execute their priming function through their MUN domain. Given that the MUN domain of Ca(2+)-dependent activator protein for secretion (CAPS) also binds syntaxin, it was assumed that CAPSs prime vesicles through the same mechanism as Munc13s. We studied naturally occurring splice variants of CAPS2 in CAPS1/CAPS2-deficient cells and found that CAPS2 primes vesicles independently of its MUN domain. Instead, the pleckstrin homology domain of CAPS2 seemingly is essential for its priming function. Our findings indicate a priming mode for secretory vesicles. This process apparently requires membrane phospholipids, does not involve the binding or direct conformational regulation of syntaxin by MUN domains of CAPSs, and is therefore not redundant with Munc13 action.
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Affiliation(s)
| | - Dennis Nestvogel
- Neurophysiology Group, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany; Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Olga Ratai
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany
| | - Claudia Schirra
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany
| | - David R Stevens
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - JeongSeop Rhee
- Neurophysiology Group, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany; Department of Molecular Neurobiology, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jens Rettig
- Institute of Physiology, Saarland University, Building 59, 66421 Homburg/Saar, Germany.
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59
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Martin TFJ. PI(4,5)P₂-binding effector proteins for vesicle exocytosis. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:785-93. [PMID: 25280637 DOI: 10.1016/j.bbalip.2014.09.017] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 09/20/2014] [Accepted: 09/23/2014] [Indexed: 12/27/2022]
Abstract
PI(4,5)P₂participates directly in priming and possibly in fusion steps of Ca²⁺-triggered vesicle exocytosis. High concentration nanodomains of PI(4,5)P₂reside on the plasma membrane of neuroendocrine cells. A subset of vesicles that co-localize with PI(4,5)P₂ domains appear to undergo preferential exocytosis in stimulated cells. PI(4,5)P₂directly regulates vesicle exocytosis by recruiting and activating PI(4,5)P₂-binding proteins that regulate SNARE protein function including CAPS, Munc13-1/2, synaptotagmin-1, and other C2 domain-containing proteins. These PI(4,5)P₂effector proteins are coincidence detectors that engage in multiple interactions at vesicle exocytic sites. The SNARE protein syntaxin-1 also binds to PI(4,5)P₂, which promotes clustering, but an activating role for PI(4,5)P₂in syntaxin-1 function remains to be fully characterized. Similar principles underlie polarized constitutive vesicle fusion mediated in part by the PI(4,5)P₂-binding subunits of the exocyst complex (Sec3, Exo70). Overall, focal vesicle exocytosis occurs at sites landmarked by PI(4,5)P2, which serves to recruit and/or activate multifunctional PI(4,5)P₂-binding proteins. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Thomas F J Martin
- Biochemistry Department, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706, USA.
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60
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Chua JJE. Macromolecular complexes at active zones: integrated nano-machineries for neurotransmitter release. Cell Mol Life Sci 2014; 71:3903-16. [PMID: 24912984 PMCID: PMC11113288 DOI: 10.1007/s00018-014-1657-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/22/2014] [Accepted: 05/23/2014] [Indexed: 02/06/2023]
Abstract
The release of neurotransmitters from synaptic vesicles exocytosing at presynaptic nerve terminals is a critical event in the initiation of synaptic transmission. This event occurs at specialized sites known as active zones. The task of faithfully executing various steps in the process is undertaken by careful orchestration of overlapping sets of molecular nano-machineries upon a core macromolecular scaffold situated at active zones. However, their composition remains incompletely elucidated. This review provides an overview of the role of the active zone in mediating neurotransmitter release and summarizes the recent progress using neuroproteomic approaches to decipher their composition. Key proteins of these nano-machineries are highlighted.
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Affiliation(s)
- John Jia En Chua
- Department of Neurobiology, Max-Planck-Institute for Biophysical Chemistry, Am Fassberg 11, 37077, Göttingen, Germany,
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61
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Önel SF, Rust MB, Jacob R, Renkawitz-Pohl R. Tethering membrane fusion: common and different players in myoblasts and at the synapse. J Neurogenet 2014; 28:302-15. [PMID: 24957080 PMCID: PMC4245166 DOI: 10.3109/01677063.2014.936014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Drosophila Membrane fusion is essential for the communication of membrane-defined compartments, development of multicellular organisms and tissue homeostasis. Although membrane fusion has been studied extensively, still little is known about the molecular mechanisms. Especially the intercellular fusion of cells during development and tissue homeostasis is poorly understood. Somatic muscle formation in Drosophila depends on the intercellular fusion of myoblasts. In this process, myoblasts recognize each other and adhere, thereby triggering a protein machinery that leads to electron-dense plaques, vesicles and F-actin formation at apposing membranes. Two models of how local membrane stress is achieved to induce the merging of the myoblast membranes have been proposed: the electron-dense vesicles transport and release a fusogen and F-actin bends the plasma membrane. In this review, we highlight cell-adhesion molecules and intracellular proteins known to be involved in myoblast fusion. The cell-adhesion proteins also mediate the recognition and adhesion of other cell types, such as neurons that communicate with each other via special intercellular junctions, termed chemical synapses. At these synapses, neurotransmitters are released through the intracellular fusion of synaptic vesicles with the plasma membrane. As the targeting of electron-dense vesicles in myoblasts shares some similarities with the targeting of synaptic vesicle fusion, we compare molecules required for synaptic vesicle fusion to recently identified molecules involved in myoblast fusion.
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Affiliation(s)
- Susanne Filiz Önel
- Developmental Biology, Philipps University of Marburg , 35043 Marburg , Germany
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62
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Messenger SW, Falkowski MA, Groblewski GE. Ca²⁺-regulated secretory granule exocytosis in pancreatic and parotid acinar cells. Cell Calcium 2014; 55:369-75. [PMID: 24742357 DOI: 10.1016/j.ceca.2014.03.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/04/2014] [Accepted: 03/09/2014] [Indexed: 01/09/2023]
Abstract
Protein secretion from acinar cells of the pancreas and parotid glands is controlled by G-protein coupled receptor activation and generation of the cellular messengers Ca(2+), diacylglycerol and cAMP. Secretory granule (SG) exocytosis shares some common characteristics with nerve, neuroendocrine and endocrine cells which are regulated mainly by elevated cell Ca(2+). However, in addition to diverse signaling pathways, acinar cells have large ∼1 μm diameter SGs (∼30 fold larger diameter than synaptic vesicles), respond to stimulation at slower rates (seconds versus milliseconds), demonstrate significant constitutive secretion, and in isolated acini, undergo sequential compound SG-SG exocytosis at the apical membrane. Exocytosis proceeds as an initial rapid phase that peaks and declines over 3 min followed by a prolonged phase that decays to near basal levels over 20-30 min. Studies indicate the early phase is triggered by Ca(2+) and involves the SG proteins VAMP2 (vesicle associated membrane protein2), Ca(2+)-sensing protein synatotagmin 1 (syt1) and the accessory protein complexin 2. The molecular details for regulation of VAMP8-mediated SG exocytosis and the prolonged phase of secretion are still emerging. Here we review the known regulatory molecules that impact the sequential exocytic process of SG tethering, docking, priming and fusion in acinar cells.
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Affiliation(s)
- Scott W Messenger
- Department of Nutritional Sciences, Graduate Program in Biochemical and Molecular Nutrition, University of Wisconsin, Madison, WI 53706, United States
| | - Michelle A Falkowski
- Department of Nutritional Sciences, Graduate Program in Biochemical and Molecular Nutrition, University of Wisconsin, Madison, WI 53706, United States
| | - Guy E Groblewski
- Department of Nutritional Sciences, Graduate Program in Biochemical and Molecular Nutrition, University of Wisconsin, Madison, WI 53706, United States.
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63
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Vazquez-Martinez R, Gasman S. The regulated secretory pathway in neuroendocrine cells. Front Endocrinol (Lausanne) 2014; 5:48. [PMID: 24782828 PMCID: PMC3986512 DOI: 10.3389/fendo.2014.00048] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 03/24/2014] [Indexed: 12/25/2022] Open
Affiliation(s)
- Rafael Vazquez-Martinez
- Department of Cell Biology, Physiology and Immunology, Instituto Maimónides de Investigaciones Biomédicas de Córdoba (IMIBIC), Reina Sofia University Hospital, University of Córdoba, Córdoba, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn), Córdoba, Spain
- *Correspondence: ;
| | - Stéphane Gasman
- Centre National de la Recherche Scientifique (CNRS UPR 3212), Institut des Neurosciences Cellulaires et Intégratives (INCI), Université de Strasbourg, Strasbourg, France
- *Correspondence: ;
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