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Altas B, Tuffy LP, Patrizi A, Dimova K, Soykan T, Brandenburg C, Romanowski AJ, Whitten JR, Robertson CD, Khim SN, Crutcher GW, Ambrozkiewicz MC, Yagensky O, Krueger-Burg D, Hammer M, Hsiao HH, Laskowski PR, Dyck L, Puche AC, Sassoè-Pognetto M, Chua JJE, Urlaub H, Jahn O, Brose N, Poulopoulos A. Region-Specific Phosphorylation Determines Neuroligin-3 Localization to Excitatory Versus Inhibitory Synapses. Biol Psychiatry 2023:S0006-3223(23)01799-7. [PMID: 38154503 PMCID: PMC11209832 DOI: 10.1016/j.biopsych.2023.12.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/19/2023] [Accepted: 12/19/2023] [Indexed: 12/30/2023]
Abstract
BACKGROUND Neuroligin-3 is a postsynaptic adhesion molecule involved in synapse development and function. It is implicated in rare, monogenic forms of autism, and its shedding is critical to the tumor microenvironment of gliomas. While other members of the neuroligin family exhibit synapse-type specificity in localization and function through distinct interactions with postsynaptic scaffold proteins, the specificity of neuroligin-3 synaptic localization remains largely unknown. METHODS We investigated the synaptic localization of neuroligin-3 across regions in mouse and human brain samples after validating antibody specificity in knockout animals. We raised a phospho-specific neuroligin antibody and used phosphoproteomics, cell-based assays, and in utero CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/Cas9) knockout and gene replacement to identify mechanisms that regulate neuroligin-3 localization to distinct synapse types. RESULTS Neuroligin-3 exhibits region-dependent synapse specificity, largely localizing to excitatory synapses in cortical regions and inhibitory synapses in subcortical regions of the brain in both mice and humans. We identified specific phosphorylation of cortical neuroligin-3 at a key binding site for recruitment to inhibitory synapses, while subcortical neuroligin-3 remained unphosphorylated. In vitro, phosphomimetic mutation of that site disrupted neuroligin-3 association with the inhibitory postsynaptic scaffolding protein gephyrin. In vivo, phosphomimetic mutants of neuroligin-3 localized to excitatory postsynapses, while phospho-null mutants localized to inhibitory postsynapses. CONCLUSIONS These data reveal an unexpected region-specific pattern of neuroligin-3 synapse specificity, as well as a phosphorylation-dependent mechanism that regulates its recruitment to either excitatory or inhibitory synapses. These findings add to our understanding of how neuroligin-3 is involved in conditions that may affect the balance of excitation and inhibition.
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Affiliation(s)
- Bekir Altas
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Liam P Tuffy
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Annarita Patrizi
- Department of Neuroscience Rita Levi Montalcini, University of Turin, Turin, Italy
| | - Kalina Dimova
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Neuroproteomics Group, Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Tolga Soykan
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Cheryl Brandenburg
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Andrea J Romanowski
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Julia R Whitten
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Colin D Robertson
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Saovleak N Khim
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Garrett W Crutcher
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Mateusz C Ambrozkiewicz
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Oleksandr Yagensky
- Research Group Protein Trafficking in Synaptic Development and Function, Laboratory of Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Dilja Krueger-Burg
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Matthieu Hammer
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - He-Hsuan Hsiao
- Bioanalytical Mass Spectrometry, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Pawel R Laskowski
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Lydia Dyck
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Adam C Puche
- Department of Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland
| | | | - John J E Chua
- Research Group Protein Trafficking in Synaptic Development and Function, Laboratory of Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Bioanalytics Group, Institute of Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Olaf Jahn
- Neuroproteomics Group, Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany; Translational Neuroproteomics Group, Department of Psychiatry and Psychotherapy, University Medical Center Göttingen, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Alexandros Poulopoulos
- Department of Pharmacology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany.
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Das J, You Y, Mathukumalli K, Ann J, Lee J, Marquez VE. Activation of Munc13-1 by Diacylglycerol (DAG)-Lactones. Biochemistry 2023; 62:2717-2726. [PMID: 37651159 DOI: 10.1021/acs.biochem.3c00375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Munc13-1 is a key protein necessary for vesicle fusion and neurotransmitter release in the brain. Diacylglycerol (DAG)/phorbol ester binds to its C1 domain in the plasma membrane and activates it. The C1 domain of Munc13-1 and protein kinase C (PKC) are homologous in terms of sequence and structure. In order to identify small-molecule modulators of Munc13-1 targeting the C1 domain, we studied the effect of three DAG-lactones, (R,Z)-(2-(hydroxymethyl)-4-(3-isobutyl-5-methylhexylidene)-5-oxotetrahydrofuran-2-yl)methyl pivalate (JH-131e-153), (E)-(2-(hydroxymethyl)-4-(3-isobutyl-5-methylhexylidene)-5-oxotetrahydrofuran-2-yl)methyl pivalate (AJH-836), and (E)-(2-(hydroxymethyl)-4-(4-nitrobenzylidene)-5-oxotetrahydrofuran-2-yl)methyl 4-(dimethylamino)benzoate (130C037), on Munc13-1 activation using the ligand-induced membrane translocation assay. JH-131e-153 showed higher activation than AJH-836, and 130C037 was not able to activate Munc13-1. To understand the role of the ligand-binding site residues in the activation process, three alanine mutants were generated. For AJH-836, the order of activation was wild-type (WT) Munc13-1 > R592A > W588A > I590A. For JH-131e-153, the order of activation was WT > I590 ≈ R592A ≈ W588A. Overall, the Z isomer of DAG-lactones showed higher potency than the E isomer and Trp-588, Ile-590, and Arg-592 were important for its binding. When comparing the activation of Munc13-1 and PKC, the order of activation for JH-131e-153 was PKCα > Munc13-1 > PKCε and for AJH-836, the order of activation was PKCε > PKCα > Munc13-1. Molecular docking supported higher binding of JH-131e-153 than AJH-836 with the Munc13-1 C1 domain. Our results suggest that DAG-lactones have the potential to modulate neuronal processes via Munc13-1 and can be further developed for therapeutic intervention for neurodegenerative diseases.
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Affiliation(s)
- Joydip Das
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204, United States
| | - Youngki You
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204, United States
| | - Kavya Mathukumalli
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204, United States
| | - Jihyae Ann
- College of Pharmacy, Seoul National University, Building 143, Room 507, 1 Gwanak-Ro, Gwanak-Gu, Seoul 08826, Korea
| | - Jeewoo Lee
- College of Pharmacy, Seoul National University, Building 143, Room 507, 1 Gwanak-Ro, Gwanak-Gu, Seoul 08826, Korea
| | - Victor E Marquez
- Center for Cancer Research, Chemical Biology Laboratory, NCI-Frederick, 376 Boyles Street, Frederick, Maryland 21702, United States
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Daniel JA, Elizarova S, Shaib AH, Chouaib AA, Magnussen HM, Wang J, Brose N, Rhee J, Tirard M. An intellectual-disability-associated mutation of the transcriptional regulator NACC1 impairs glutamatergic neurotransmission. Front Mol Neurosci 2023; 16:1115880. [PMID: 37533751 PMCID: PMC10393139 DOI: 10.3389/fnmol.2023.1115880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 06/14/2023] [Indexed: 08/04/2023] Open
Abstract
Advances in genome sequencing technologies have favored the identification of rare de novo mutations linked to neurological disorders in humans. Recently, a de novo autosomal dominant mutation in NACC1 was identified (NM_052876.3: c.892C > T, NP_443108.1; p.Arg298Trp), associated with severe neurological symptoms including intellectual disability, microcephaly, and epilepsy. As NACC1 had never before been associated with neurological diseases, we investigated how this mutation might lead to altered brain function. We examined neurotransmission in autaptic glutamatergic mouse neurons expressing the murine homolog of the human mutant NACC1, i.e., Nacc1-R284W. We observed that expression of Nacc1-R284W impaired glutamatergic neurotransmission in a cell-autonomous manner, likely through a dominant negative mechanism. Furthermore, by screening for Nacc1 interaction targets in the brain, we identified SynGAP1, GluK2A, and several SUMO E3 ligases as novel Nacc1 interaction partners. At a biochemical level, Nacc1-R284W exhibited reduced binding to SynGAP1 and GluK2A, and also showed greatly increased SUMOylation. Ablating the SUMOylation of Nacc1-R284W partially restored its interaction with SynGAP1 but did not restore binding to GluK2A. Overall, these data indicate a role for Nacc1 in regulating glutamatergic neurotransmission, which is substantially impaired by the expression of a disease-associated Nacc1 mutant. This study provides the first functional insights into potential deficits in neuronal function in patients expressing the de novo mutant NACC1 protein.
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Affiliation(s)
- James A. Daniel
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Sofia Elizarova
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Ali H. Shaib
- Institute for Neuro- and Sensory Physiology, University Medical Center Göttingen, Göttingen, Germany
| | - Abed A. Chouaib
- Department of Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Helge M. Magnussen
- MRC Protein Phosphorylation and Ubiquitination Unit, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Jianlong Wang
- Department of Medicine, Columbia Center for Human Development and Stem Cell Therapies, Columbia University Irving Medical Center, New York, NY, United States
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - JeongSeop Rhee
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Marilyn Tirard
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
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Palfreyman MT, West SE, Jorgensen EM. SNARE Proteins in Synaptic Vesicle Fusion. ADVANCES IN NEUROBIOLOGY 2023; 33:63-118. [PMID: 37615864 DOI: 10.1007/978-3-031-34229-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
Neurotransmitters are stored in small membrane-bound vesicles at synapses; a subset of synaptic vesicles is docked at release sites. Fusion of docked vesicles with the plasma membrane releases neurotransmitters. Membrane fusion at synapses, as well as all trafficking steps of the secretory pathway, is mediated by SNARE proteins. The SNAREs are the minimal fusion machinery. They zipper from N-termini to membrane-anchored C-termini to form a 4-helix bundle that forces the apposed membranes to fuse. At synapses, the SNAREs comprise a single helix from syntaxin and synaptobrevin; SNAP-25 contributes the other two helices to complete the bundle. Unc13 mediates synaptic vesicle docking and converts syntaxin into the permissive "open" configuration. The SM protein, Unc18, is required to initiate and proofread SNARE assembly. The SNAREs are then held in a half-zippered state by synaptotagmin and complexin. Calcium removes the synaptotagmin and complexin block, and the SNAREs drive vesicle fusion. After fusion, NSF and alpha-SNAP unwind the SNAREs and thereby recharge the system for further rounds of fusion. In this chapter, we will describe the discovery of the SNAREs, their relevant structural features, models for their function, and the central role of Unc18. In addition, we will touch upon the regulation of SNARE complex formation by Unc13, complexin, and synaptotagmin.
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Affiliation(s)
- Mark T Palfreyman
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Sam E West
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA
| | - Erik M Jorgensen
- School of Biological Sciences, and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT, USA.
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Jin Y, Zhai RG. Presynaptic Cytomatrix Proteins. ADVANCES IN NEUROBIOLOGY 2023; 33:23-42. [PMID: 37615862 DOI: 10.1007/978-3-031-34229-5_2] [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
The Cytomatrix Assembled at the active Zone (CAZ) of a presynaptic terminal displays electron-dense appearance and defines the center of the synaptic vesicle release. The protein constituents of CAZ are multiple-domain scaffolds that interact extensively with each other and also with an ensemble of synaptic vesicle proteins to ensure docking, fusion, and recycling. Reflecting the central roles of the active zone in synaptic transmission, CAZ proteins are highly conserved throughout evolution. As the nervous system increases complexity and diversity in types of neurons and synapses, CAZ proteins expand in the number of gene and protein isoforms and interacting partners. This chapter summarizes the discovery of the core CAZ proteins and current knowledge of their functions.
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Affiliation(s)
- Yishi Jin
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA.
| | - R Grace Zhai
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, USA.
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6
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Meunier FA, Hu Z. Functional Roles of UNC-13/Munc13 and UNC-18/Munc18 in Neurotransmission. ADVANCES IN NEUROBIOLOGY 2023; 33:203-231. [PMID: 37615868 DOI: 10.1007/978-3-031-34229-5_8] [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
Neurotransmitters are released from synaptic and secretory vesicles following calcium-triggered fusion with the plasma membrane. These exocytotic events are driven by assembly of a ternary SNARE complex between the vesicle SNARE synaptobrevin and the plasma membrane-associated SNAREs syntaxin and SNAP-25. Proteins that affect SNARE complex assembly are therefore important regulators of synaptic strength. In this chapter, we review our current understanding of the roles played by two SNARE interacting proteins: UNC-13/Munc13 and UNC-18/Munc18. We discuss results from both invertebrate and vertebrate model systems, highlighting recent advances, focusing on the current consensus on molecular mechanisms of action and nanoscale organization, and pointing out some unresolved aspects of their functions.
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Affiliation(s)
- Frédéric A Meunier
- Clem Jones Centre for Ageing Dementia Research (CJCADR), Queensland Brain Institute, The University of Queensland, Brisbane, QLD, Australia.
- School of Biomedical Sciences, 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.
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Parra-Rivas LA, Palfreyman MT, Vu TN, Jorgensen EM. Interspecies complementation identifies a pathway to assemble SNAREs. iScience 2022; 25:104506. [PMID: 35754735 PMCID: PMC9213704 DOI: 10.1016/j.isci.2022.104506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 03/23/2022] [Accepted: 05/27/2022] [Indexed: 11/18/2022] Open
Abstract
Unc18 and SNARE proteins form the core of the membrane fusion complex at synapses. To understand the functional interactions within the core machinery, we adopted an "interspecies complementation" approach in Caenorhabditis elegans. Substitutions of individual SNAREs and Unc18 proteins with those from yeast fail to rescue fusion. However, synaptic transmission could be restored in worm-yeast chimeras when two key interfaces were present: an Habc-Unc18 contact site and an Unc18-SNARE motif contact site. A constitutively open form of Unc18 bypasses the requirement for the Habc-Unc18 interface. These data suggest that the Habc domain of syntaxin is required for Unc18 to adopt an open conformation; open Unc18 then templates SNARE complex formation. Finally, we demonstrate that the SNARE and Unc18 machinery in the nematode C. elegans can be replaced by yeast proteins and still carry out synaptic transmission, pointing to the deep evolutionary conservation of these two interfaces.
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Affiliation(s)
- Leonardo A. Parra-Rivas
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Mark T. Palfreyman
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Thien N. Vu
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
| | - Erik M. Jorgensen
- Howard Hughes Medical Institute, School of Biological Sciences, University of Utah, Salt Lake City, UT 84112-0840, USA
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8
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Ghosh A, Muthuraju S, Badal S, Wooden J, Leasure JL, Roman G, Das J. Differential Expression of Presynaptic Munc13-1 and Munc13-2 in Mouse Hippocampus Following Ethanol Drinking. Neuroscience 2022; 487:166-183. [PMID: 35167938 PMCID: PMC8930510 DOI: 10.1016/j.neuroscience.2022.02.008] [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: 08/30/2021] [Revised: 01/22/2022] [Accepted: 02/08/2022] [Indexed: 10/19/2022]
Abstract
The Munc13 family of proteins is critically involved in synaptic vesicle priming and release in glutamatergic neurons in the brain. Munc13-1 binds to alcohol and, in Drosophila, modulates sedation sensitivity and self-administration. We examined the effect of alcohol consumption on the expression of Munc13-1 and Munc13-2, NMDA receptor subunits GluN1, GluN2A and GluN2B in the hippocampus-derived HT22 cells, hippocampal primary neuron culture, and wild-type and Munc13-1+/- male mouse hippocampus after ethanol consumption (Drinking in the Dark (DID) paradigm). In HT22 cells, Munc13-1 was upregulated following 25 mM ethanol treatment for 24 h. In the primary neuronal culture, however, the expression of both Munc13-1 and Munc13-2 increased after ethanol exposure. While Munc13-1 was upregulated in the hippocampus, Munc13-2 was downregulated following DID. This differential effect was found in the CA1 subfield of the hippocampus. Although Munc13-1+/- mice had approximately 50% Munc13-1 expression compared to wild-type, it was nonetheless significantly increased following DID. Munc13-1 and Munc13-2 were expressed in vesicular glutamate transporter1 (VGLUT1) immunoreactive neurons in the hippocampus, but ethanol did not alter the expression of VGLUT1. The NMDA receptor subunits, GluN1, GluN2A and GluN2B were upregulated in the hippocampal primary culture and in the CA1. Ethanol exerts a differential effect on the expression of Munc13-1 and Munc13-2 in the CA1 in male mice. Our study also found that ethanol's effect on Munc13 expression is dependent on the experimental paradigm, and both Munc13-1 and Munc13-2 could contribute to the ethanol-induced augmentation of glutamatergic neurotransmission.
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Affiliation(s)
- Anamitra Ghosh
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204, United States
| | - Sangu Muthuraju
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204, United States
| | - Sean Badal
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204, United States
| | - Jessica Wooden
- Department of Psychology, University of Houston, Houston, TX 77204, United States
| | - J Leigh Leasure
- Department of Psychology, University of Houston, Houston, TX 77204, United States
| | - Gregg Roman
- Department of BioMolecular Sciences, University of Mississippi, Oxford, MS 38677, United States
| | - Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, TX 77204, United States.
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9
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Munc13 structural transitions and oligomers that may choreograph successive stages in vesicle priming for neurotransmitter release. Proc Natl Acad Sci U S A 2022; 119:2121259119. [PMID: 35135883 PMCID: PMC8851502 DOI: 10.1073/pnas.2121259119] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2021] [Indexed: 12/24/2022] Open
Abstract
The speed of neural information processing in the human central nervous system is ultimately determined by the speed of chemical transmission at synapses, because action potentials have relatively short distances to traverse. The release of synaptic vesicles containing neurotransmitters must therefore be remarkably fast as compared to other forms of membrane fusion. Six separate SNARE complexes cooperate to achieve this. But how can exactly six copies be assembled under every vesicle? Here we report that six copies of the key molecular chaperone that assembles the SNAREs can arrange themselves into a closed hexagon, providing the likely answer. How can exactly six SNARE complexes be assembled under each synaptic vesicle? Here we report cryo-EM crystal structures of the core domain of Munc13, the key chaperone that initiates SNAREpin assembly. The functional core of Munc13, consisting of C1–C2B–MUN–C2C (Munc13C) spontaneously crystallizes between phosphatidylserine-rich bilayers in two distinct conformations, each in a radically different oligomeric state. In the open conformation (state 1), Munc13C forms upright trimers that link the two bilayers, separating them by ∼21 nm. In the closed conformation, six copies of Munc13C interact to form a lateral hexamer elevated ∼14 nm above the bilayer. Open and closed conformations differ only by a rigid body rotation around a flexible hinge, which when performed cooperatively assembles Munc13 into a lateral hexamer (state 2) in which the key SNARE assembly-activating site of Munc13 is autoinhibited by its neighbor. We propose that each Munc13 in the lateral hexamer ultimately assembles a single SNAREpin, explaining how only and exactly six SNARE complexes are templated. We suggest that state 1 and state 2 may represent two successive states in the synaptic vesicle supply chain leading to “primed” ready-release vesicles in which SNAREpins are clamped and ready to release (state 3).
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Banerjee A, Imig C, Balakrishnan K, Kershberg L, Lipstein N, Uronen RL, Wang J, Cai X, Benseler F, Rhee JS, Cooper BH, Liu C, Wojcik SM, Brose N, Kaeser PS. Molecular and functional architecture of striatal dopamine release sites. Neuron 2022; 110:248-265.e9. [PMID: 34767769 PMCID: PMC8859508 DOI: 10.1016/j.neuron.2021.10.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2020] [Revised: 09/22/2021] [Accepted: 10/19/2021] [Indexed: 01/21/2023]
Abstract
Despite the importance of dopamine for striatal circuit function, mechanistic understanding of dopamine transmission remains incomplete. We recently showed that dopamine secretion relies on the presynaptic scaffolding protein RIM, indicating that it occurs at active zone-like sites similar to classical synaptic vesicle exocytosis. Here, we establish using a systematic gene knockout approach that Munc13 and Liprin-α, active zone proteins for vesicle priming and release site organization, are important for dopamine secretion. Furthermore, RIM zinc finger and C2B domains, which bind to Munc13 and Liprin-α, respectively, are needed to restore dopamine release after RIM ablation. In contrast, and different from typical synapses, the active zone scaffolds RIM-BP and ELKS, and RIM domains that bind to them, are expendable. Hence, dopamine release necessitates priming and release site scaffolding by RIM, Munc13, and Liprin-α, but other active zone proteins are dispensable. Our work establishes that efficient release site architecture mediates fast dopamine exocytosis.
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Affiliation(s)
- Aditi Banerjee
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Cordelia Imig
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | | | - Lauren Kershberg
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Riikka-Liisa Uronen
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jiexin Wang
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Xintong Cai
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Fritz Benseler
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Jeong Seop Rhee
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Benjamin H Cooper
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Changliang Liu
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Pascal S Kaeser
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA.
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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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12
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You Y, Das J. Molecular dynamics simulation studies on binding of activator and inhibitor to Munc13-1 C1 in the presence of membrane. J Biomol Struct Dyn 2022; 40:14160-14175. [PMID: 34779746 PMCID: PMC9482821 DOI: 10.1080/07391102.2021.2001375] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Munc13-1 is a presynaptic active zone protein that plays a critical role in priming the synaptic vesicle and releasing neurotransmitters in the brain. Munc13-1 acts as a scaffold and is activated when diacylglycerol (DAG)/phorbol ester binds to its C1 domain in the plasma membrane. Our previous studies showed that bryostatin 1 activated the Munc13-1, but resveratrol inhibited the phorbol ester-induced Munc13-1 activity. To gain structural insights into the binding of the ligand into Munc13-1 C1 in the membrane, we conducted 1.0 μs molecular dynamics (MD) simulation on Munc13-1 C1-ligand-lipid ternary system using phorbol 13-acetate, bryostatin 1 and resveratrol as ligands. Munc13-1 C1 shows higher conformational stability and less mobility along membrane with phorbol 13-acetate and bryostatin 1 than with resveratrol. Bryostatin 1 and phorbol ester remained in the protein active site, but resveratrol moved out of Munc13-1 C1 during the MD simulation. While bryostatin 1-bound Munc13-1 C1 showed two different positioning in the membrane, phorbol 13-acetate and resveratrol-bound Munc13-1 C1 only showed one positioning. Phorbol 13-acetate formed hydrogen bond with Ala-574 and Gly-589. Bryostatin 1 had more hydrogen bonds with Trp-588 and Arg-592 than with other residues. Resveratrol formed hydrogen bond with Ile-590. This study suggests that different ligands control Munc13-1 C1's mobility and positioning in the membrane differently. Ligand also has a critical role in the interaction between Munc13-1 C1 and lipid membrane. Our results provide structural basis of the pharmacological activity of the ligands and highlight the importance of membrane in Munc13-1 activity.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
| | - Joydip Das
- To whom to address correspondence at: Joydip Das, Department of Pharmacological and Pharmaceutical Sciences, Health 2, 4849 Calhoun Road, Room 3044, Houston TX 77204-5037. ; Tel: 713-743-1708; FAX 713-743-1229
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13
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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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14
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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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15
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You Y, Katti S, Yu B, Igumenova TI, Das J. Probing the Diacylglycerol Binding Site of Presynaptic Munc13-1. Biochemistry 2021; 60:1286-1298. [PMID: 33818064 PMCID: PMC8906797 DOI: 10.1021/acs.biochem.1c00165] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Munc13-1 is a presynaptic active zone protein that acts as a master regulator of synaptic vesicle priming and neurotransmitter release in the brain. It has been implicated in the pathophysiology of several neurodegenerative diseases. Diacylglycerol and phorbol ester activate Munc13-1 by binding to its C1 domain. The objective of this study is to identify the structural determinants of ligand binding activity of the Munc13-1 C1 domain. Molecular docking suggested that residues Trp-588, Ile-590, and Arg-592 of Munc13-1 are involved in ligand interactions. To elucidate the role of these three residues in ligand binding, we generated W588A, I590A, and R592A mutants in full-length Munc13-1, expressed them as GFP-tagged proteins in HT22 cells, and measured their ligand-induced membrane translocation by confocal microscopy and immunoblotting. The extent of 1,2-dioctanoyl-sn-glycerol (DOG)- and phorbol ester-induced membrane translocation decreased in the following order: wild type > I590A > W588A > R592A and wild type > W588A > I590A > R592A, respectively. To understand the effect of the mutations on ligand binding, we also measured the DOG binding affinity of the isolated wild-type C1 domain and its mutants in membrane-mimicking micelles using nuclear magnetic resonance methods. The DOG binding affinity decreased in the following order: wild type > I590A > R592A. No binding was detected for W588A with DOG in micelles. This study shows that Trp-588, Ile-590, and Arg-592 are essential determinants for the activity of Munc13-1 and the effects of the three residues on the activity are ligand-dependent. This study bears significance for the development of selective modulators of Munc13-1.
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Affiliation(s)
- Youngki You
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, Health 2, University of Houston, Houston, Texas 77204, United States
| | - Sachin Katti
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, Texas 77843, United States
| | - Binhan Yu
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, Texas 77843, United States
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, Texas 77843, United States
| | - Joydip Das
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, Health 2, University of Houston, Houston, Texas 77204, United States
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16
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Sundaram RVK, Jin H, Li F, Shu T, Coleman J, Yang J, Pincet F, Zhang Y, Rothman JE, Krishnakumar SS. Munc13 binds and recruits SNAP25 to chaperone SNARE complex assembly. FEBS Lett 2021; 595:297-309. [PMID: 33222163 PMCID: PMC8068094 DOI: 10.1002/1873-3468.14006] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 11/15/2020] [Accepted: 11/19/2020] [Indexed: 11/10/2022]
Abstract
Synaptic vesicle fusion is mediated by SNARE proteins-VAMP2 on the vesicle and Syntaxin-1/SNAP25 on the presynaptic membrane. Chaperones Munc18-1 and Munc13-1 cooperatively catalyze SNARE assembly via an intermediate 'template' complex containing Syntaxin-1 and VAMP2. How SNAP25 enters this reaction remains a mystery. Here, we report that Munc13-1 recruits SNAP25 to initiate the ternary SNARE complex assembly by direct binding, as judged by bulk FRET spectroscopy and single-molecule optical tweezer studies. Detailed structure-function analyses show that the binding is mediated by the Munc13-1 MUN domain and is specific for the SNAP25 'linker' region that connects the two SNARE motifs. Consequently, freely diffusing SNAP25 molecules on phospholipid bilayers are concentrated and bound in ~ 1 : 1 stoichiometry by the self-assembled Munc13-1 nanoclusters.
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Affiliation(s)
- R Venkat Kalyana Sundaram
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Huaizhou Jin
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Feng Li
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Tong Shu
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Jeff Coleman
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Jie Yang
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Frederic Pincet
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
- Laboratoire de Physique de Ecole Normale Supérieure, Université PSL, CNRS, Sorbonne Université, Université de Paris 06, F-75005 Paris, France
| | - Yongli Zhang
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - James E. Rothman
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
| | - Shyam S. Krishnakumar
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
- Department of Clinical and Experimental Epilepsy, Institute of Neurology, University College London, Queens Square House, London WC1 3BG, UK
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17
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Heterogeneous Presynaptic Distribution of Munc13 Isoforms at Retinal Synapses and Identification of an Unconventional Bipolar Cell Type with Dual Expression of Munc13 Isoforms: A Study Using Munc13-EXFP Knock-in Mice. Int J Mol Sci 2020; 21:ijms21217848. [PMID: 33105896 PMCID: PMC7660176 DOI: 10.3390/ijms21217848] [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: 09/28/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 12/19/2022] Open
Abstract
Munc13 isoforms are constituents of the presynaptic compartment of chemical synapses, where they govern important steps in preparing synaptic vesicles for exocytosis. The role of Munc13-1, -2 and -3 is well documented in brain neurons, but less is known about their function and distribution among the neurons of the retina and their conventional and ribbon-type chemical synapses. Here, we examined the retinae of Munc13-1-, -2-, and -3-EXFP knock-in (KI) mice with a combination of immunocytochemistry, physiology, and electron microscopy. We show that knock-in of Munc13-EXFP fusion proteins did not affect overall retinal anatomy or synapse structure, but slightly affected synaptic transmission. By labeling Munc13-EXFP KI retinae with specific antibodies against Munc13-1, -2 and -3, we found that unlike in the brain, most retinal synapses seem to operate with a single Munc13 isoform. A surprising exception to this rule was type 6 ON bipolar cells, which expressed two Munc13 isoforms in their synaptic terminals, ubMunc13-2 and Munc13-3. The results of this study provide an important basis for future studies on the contribution of Munc13 isoforms in visual signal processing in the mammalian retina.
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18
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You Y, Das J. Effect of ethanol on Munc13-1 C1 in Membrane: A Molecular Dynamics Simulation Study. Alcohol Clin Exp Res 2020; 44:1344-1355. [PMID: 32424866 DOI: 10.1111/acer.14363] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 05/06/2020] [Indexed: 12/26/2022]
Abstract
BACKGROUND EtOH has a significant effect on synaptic plasticity. Munc13-1 is an essential presynaptic active zone protein involved in priming the synaptic vesicle and releasing neurotransmitter in the brain. It is a peripheral membrane protein and binds to the activator, diacylglycerol (DAG)/phorbol ester at its membrane-targeting C1 domain. Our previous studies identified Glu-582 of C1 domain as the alcohol-binding residue (Das, J. et al, J. Neurochem., 126, 715-726, 2013). METHODS Here, we describe a 250 ns molecular dynamics (MD) simulation study on the interaction of EtOH and the activator-bound Munc13-1 C1 in the presence of varying concentrations of phosphatidylserine (PS). RESULTS In this study, Munc13-1 C1 shows higher conformational stability in EtOH than in water. It forms fewer hydrogen bonds with phorbol 13-acetate in the presence of EtOH than in water. EtOH also affected the interaction between the protein and the membrane and between the activator and the membrane. Similar studies in a E582A mutant suggest that these effects of EtOH are mostly mediated through Glu-582. CONCLUSIONS EtOH forms hydrogen bonds with Glu-582. While occupancy of the EtOH molecules at the vicinity (4Å) of Glu-582 is 34.4%, the occupancy in the E582A mutant is 26.5% of the simulation time. In addition, the amount of PS in the membrane influences the conformational stability of the C1 domain and interactions in the ternary complex. This study is important in providing the structural basis of EtOH's effects on synaptic plasticity.
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Affiliation(s)
- Youngki You
- From the Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas
| | - Joydip Das
- From the Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas
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19
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Magdziarek M, Bolembach AA, Stepien KP, Quade B, Liu X, Rizo J. Re-examining how Munc13-1 facilitates opening of syntaxin-1. Protein Sci 2020; 29:1440-1458. [PMID: 32086964 DOI: 10.1002/pro.3844] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/19/2020] [Accepted: 02/20/2020] [Indexed: 11/06/2022]
Abstract
Munc13-1 is crucial for neurotransmitter release and, together with Munc18-1, orchestrates assembly of the neuronal SNARE complex formed by syntaxin-1, SNAP-25, and synaptobrevin. Assembly starts with syntaxin-1 folded into a self-inhibited closed conformation that binds to Munc18-1. Munc13-1 is believed to catalyze the opening of syntaxin-1 to facilitate SNARE complex formation. However, different types of Munc13-1-syntaxin-1 interactions have been reported to underlie this activity, and the critical nature of Munc13-1 for release may arise because of its key role in bridging the vesicle and plasma membranes. To shed light into the mechanism of action of Munc13-1, we have used NMR spectroscopy, SNARE complex assembly experiments, and liposome fusion assays. We show that point mutations in a linker region of syntaxin-1 that forms intrinsic part of the closed conformation strongly impair stimulation of SNARE complex assembly and liposome fusion mediated by Munc13-1 fragments, even though binding of this linker region to Munc13-1 is barely detectable. Conversely, the syntaxin-1 SNARE motif clearly binds to Munc13-1, but a mutation that disrupts this interaction does not affect SNARE complex assembly or liposome fusion. We also show that Munc13-1 cannot be replaced by an artificial tethering factor to mediate liposome fusion. Overall, these results emphasize how very weak interactions can play fundamental roles in promoting conformational transitions and strongly support a model whereby the critical nature of Munc13-1 for neurotransmitter release arises not only from its ability to bridge two membranes but also from an active role in opening syntaxin-1 via interactions with the linker.
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Affiliation(s)
- Magdalena Magdziarek
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Agnieszka A Bolembach
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Karolina P Stepien
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Bradley Quade
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Xiaoxia Liu
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Department of Pathophysiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Josep Rizo
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA.,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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20
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Wooden JI, Schuller K, Roman G, Das J, Leasure JL. MUNC13-1 heterozygosity does not alter voluntary ethanol consumption or sensitivity in mice. Alcohol 2020; 83:89-97. [PMID: 31265903 PMCID: PMC7043798 DOI: 10.1016/j.alcohol.2019.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 06/12/2019] [Accepted: 06/21/2019] [Indexed: 02/06/2023]
Abstract
The role of the munc13-1 presynaptic protein in alcohol-related behaviors has been little-studied, despite being a known site of action for ethanol binding. Munc13-1 is an active zone protein that plays a vital role in vesicle maturation and the release of neurotransmitters in excitatory neurons. Ethanol binds munc13-1, which decreases its functionality. In Drosophila, loss of the homologous protein Dunc13 is associated with an increase in ethanol preference, and is associated with a resistance to sedation following ethanol exposure. The current study assessed the effects of munc13-1 heterozygosity on ethanol sensitivity and consumption in mice, as well as on learning and anxiety-like behaviors, which can influence alcohol intake. Wild-type and mutant mice underwent 6 cycles of drinking-in-the-dark (DID) as well as rotarod testing following ethanol injection, to probe for differences in ethanol consumption and sensitivity, respectively. We did not detect genotype-based differences in our measures of anxiety, spatial learning, ethanol consumption, or ethanol sensitivity. However, heterozygotes showed increased use of a spatial navigation strategy in a dual-solution water maze, as opposed to a stimulus-response strategy. To summarize, although reduction of Dunc13 in flies produces clear effects on ethanol consumption and sensitivity, heterozygosity for munc13-1 does not, potentially due to compensatory adaptation by other munc-13 isoforms.
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Affiliation(s)
- Jessica I Wooden
- Department of Psychology, University of Houston, Houston, TX 77204, United States
| | - Kyle Schuller
- Department of Psychology, University of Houston, Houston, TX 77204, United States
| | - Gregg Roman
- Department of Biology, University of Mississippi, Oxford, MS 38677, United States
| | - Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
| | - J Leigh Leasure
- Department of Psychology, University of Houston, Houston, TX 77204, United States; Department of Biology & Biochemistry, University of Houston, Houston, TX 77204, United States.
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21
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Das J. SNARE Complex-Associated Proteins and Alcohol. Alcohol Clin Exp Res 2019; 44:7-18. [PMID: 31724225 DOI: 10.1111/acer.14238] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 11/07/2019] [Indexed: 12/23/2022]
Abstract
Alcohol addiction causes major health problems throughout the world, causing numerous deaths and incurring a huge economic burden to society. To develop an intervention for alcohol addiction, it is necessary to identify molecular target(s) of alcohol and associated molecular mechanisms of alcohol action. The functions of many central and peripheral synapses are impacted by low concentrations of ethanol (EtOH). While the postsynaptic targets and mechanisms are studied extensively, there are limited studies on the presynaptic targets and mechanisms. This article is an endeavor in this direction, focusing on the effect of EtOH on the presynaptic proteins associated with the neurotransmitter release machinery. Studies on the effects of EtOH at the levels of gene, protein, and behavior are highlighted in this article.
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Affiliation(s)
- Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas
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22
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Abstract
Ca2+-dependent secretion is a process by which important signaling molecules that are produced within a cell-including proteins and neurotransmitters-are expelled to the extracellular environment. The cellular mechanism that underlies secretion is referred to as exocytosis. Many years of work have revealed that exocytosis in neurons and neuroendocrine cells is tightly coupled to Ca2+ and orchestrated by a series of protein-protein/protein-lipid interactions. Here, we highlight landmark discoveries that have informed our current understanding of the process. We focus principally on reductionist studies performed using powerful model secretory systems and cell-free reconstitution assays. In recent years, molecular cloning and genetics have implicated the involvement of a sizeable number of proteins in exocytosis. We expect reductionist approaches will be central to attempts to resolve their roles. The Journal of General Physiology will continue to be an outlet for much of this work, befitting its tradition of publishing strongly mechanistic, basic research.
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Affiliation(s)
- Arun Anantharam
- Department of Pharmacology, University of Michigan, Ann Arbor, MI
| | - Alex J B Kreutzberger
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA
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23
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Quade B, Camacho M, Zhao X, Orlando M, Trimbuch T, Xu J, Li W, Nicastro D, Rosenmund C, Rizo J. Membrane bridging by Munc13-1 is crucial for neurotransmitter release. eLife 2019; 8:42806. [PMID: 30816091 PMCID: PMC6407922 DOI: 10.7554/elife.42806] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 02/22/2019] [Indexed: 11/13/2022] Open
Abstract
Munc13-1 plays a crucial role in neurotransmitter release. We recently proposed that the C-terminal region encompassing the C1, C2B, MUN and C2C domains of Munc13-1 (C1C2BMUNC2C) bridges the synaptic vesicle and plasma membranes through interactions involving the C2C domain and the C1-C2B region. However, the physiological relevance of this model has not been demonstrated. Here we show that C1C2BMUNC2C bridges membranes through opposite ends of its elongated structure. Mutations in putative membrane-binding sites of the C2C domain disrupt the ability of C1C2BMUNC2C to bridge liposomes and to mediate liposome fusion in vitro. These mutations lead to corresponding disruptive effects on synaptic vesicle docking, priming, and Ca2+-triggered neurotransmitter release in mouse neurons. Remarkably, these effects include an almost complete abrogation of release by a single residue substitution in this 200 kDa protein. These results show that bridging the synaptic vesicle and plasma membranes is a central function of Munc13-1.
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Affiliation(s)
- Bradley Quade
- 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
| | - Marcial Camacho
- Institut für Neurophysiologie, Charité - Universitätsmedizin, Berlin, Germany.,NeuroCure Cluster of Excellence, Berlin, Germany
| | - Xiaowei Zhao
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Marta Orlando
- Institut für Neurophysiologie, Charité - Universitätsmedizin, Berlin, Germany.,NeuroCure Cluster of Excellence, Berlin, Germany
| | - Thorsten Trimbuch
- Institut für Neurophysiologie, Charité - Universitätsmedizin, Berlin, Germany.,NeuroCure Cluster of Excellence, Berlin, Germany
| | - Junjie Xu
- 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
| | - Wei Li
- 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
| | - Daniela Nicastro
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Christian Rosenmund
- Institut für Neurophysiologie, Charité - Universitätsmedizin, Berlin, Germany.,NeuroCure Cluster of Excellence, Berlin, Germany
| | - 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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24
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Rizo J. Mechanism of neurotransmitter release coming into focus. Protein Sci 2018; 27:1364-1391. [PMID: 29893445 DOI: 10.1002/pro.3445] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 05/10/2018] [Indexed: 12/11/2022]
Abstract
Research for three decades and major recent advances have provided crucial insights into how neurotransmitters are released by Ca2+ -triggered synaptic vesicle exocytosis, leading to reconstitution of basic steps that underlie Ca2+ -dependent membrane fusion and yielding a model that assigns defined functions for central components of the release machinery. The soluble N-ethyl maleimide sensitive factor attachment protein receptors (SNAREs) syntaxin-1, SNAP-25, and synaptobrevin-2 form a tight SNARE complex that brings the vesicle and plasma membranes together and is key for membrane fusion. N-ethyl maleimide sensitive factor (NSF) and soluble NSF attachment proteins (SNAPs) disassemble the SNARE complex to recycle the SNAREs for another round of fusion. Munc18-1 and Munc13-1 orchestrate SNARE complex formation in an NSF-SNAP-resistant manner by a mechanism whereby Munc18-1 binds to synaptobrevin and to a self-inhibited "closed" conformation of syntaxin-1, thus forming a template to assemble the SNARE complex, and Munc13-1 facilitates assembly by bridging the vesicle and plasma membranes and catalyzing opening of syntaxin-1. Synaptotagmin-1 functions as the major Ca2+ sensor that triggers release by binding to membrane phospholipids and to the SNAREs, in a tight interplay with complexins that accelerates membrane fusion. Many of these proteins act as both inhibitors and activators of exocytosis, which is critical for the exquisite regulation of neurotransmitter release. It is still unclear how the actions of these various proteins and multiple other components that control release are integrated and, in particular, how they induce membrane fusion, but it can be expected that these fundamental questions can be answered in the near future, building on the extensive knowledge already available.
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Affiliation(s)
- Josep Rizo
- Departments of Biophysics, Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas, 75390
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25
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Bin NR, Ma K, Tien CW, Wang S, Zhu D, Park S, Turlova E, Sugita K, Shirakawa R, van der Sluijs P, Horiuchi H, Sun HS, Monnier PP, Gaisano HY, Sugita S. C2 Domains of Munc13-4 Are Crucial for Ca 2+-Dependent Degranulation and Cytotoxicity in NK Cells. THE JOURNAL OF IMMUNOLOGY 2018; 201:700-713. [PMID: 29884704 DOI: 10.4049/jimmunol.1800426] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 05/18/2018] [Indexed: 11/19/2022]
Abstract
In the immune system, degranulation/exocytosis from lymphocytes is crucial for life through facilitating eradication of infected and malignant cells. Dysfunction of the NK cell exocytosis process has been implicated with devastating immune diseases, such as familial hemophagocytic lymphohistiocytosis, yet the underlying molecular mechanisms of such processes have remained elusive. In particular, although the lytic granule exocytosis from NK cells is strictly Ca2+-dependent, the molecular identity of the Ca2+ sensor has yet to be identified. In this article, we show multiple lines of evidence in which point mutations in aspartic acid residues in both C2 domains of human Munc13-4, whose mutation underlies familial hemophagocytic lymphohistiocytosis type 3, diminished exocytosis with dramatically altered Ca2+ sensitivity in both mouse primary NK cells as well as rat mast cell lines. Furthermore, these mutations within the C2 domains severely impaired NK cell cytotoxicity against malignant cells. Total internal reflection fluorescence microscopy analysis revealed that the mutations strikingly altered Ca2+ dependence of fusion pore opening of each single granule and frequency of fusion events. Our results demonstrate that both C2 domains of Munc13-4 play critical roles in Ca2+-dependent exocytosis and cytotoxicity by regulating single-granule membrane fusion dynamics in immune cells.
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Affiliation(s)
- Na-Ryum Bin
- Division of Fundamental Neurobiology, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Ke Ma
- Division of Fundamental Neurobiology, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Chi-Wei Tien
- Division of Fundamental Neurobiology, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Siyan Wang
- Division of Fundamental Neurobiology, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Dan Zhu
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Seungmee Park
- Division of Fundamental Neurobiology, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Ekaterina Turlova
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Kyoko Sugita
- Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada
| | - Ryutaro Shirakawa
- Department of Molecular and Cellular Biology, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan; and
| | - Peter van der Sluijs
- Department of Cell Biology, University Medical Center Utrecht, 3584 CX Utrecht, the Netherlands
| | - Hisanori Horiuchi
- Department of Molecular and Cellular Biology, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan; and
| | - Hong-Shuo Sun
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Surgery, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Philippe P Monnier
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada
| | - Herbert Y Gaisano
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Shuzo Sugita
- Division of Fundamental Neurobiology, Krembil Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada; .,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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26
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Ethanol Regulates Presynaptic Activity and Sedation through Presynaptic Unc13 Proteins in Drosophila. eNeuro 2018; 5:eN-NWR-0125-18. [PMID: 29911175 PMCID: PMC6001265 DOI: 10.1523/eneuro.0125-18.2018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 05/09/2018] [Accepted: 05/12/2018] [Indexed: 11/21/2022] Open
Abstract
Ethanol has robust effects on presynaptic activity in many neurons, however, it is not yet clear how this drug acts within this compartment to change neural activity, nor the significance of this change on behavior and physiology in vivo. One possible presynaptic effector for ethanol is the Munc13-1 protein. Herein, we show that ethanol binding to the rat Munc13-1 C1 domain, at concentrations consistent with binge exposure, reduces diacylglycerol (DAG) binding. The inhibition of DAG binding is predicted to reduce the activity of Munc13-1 and presynaptic release. In Drosophila, we show that sedating concentrations of ethanol significantly reduce synaptic vesicle release in olfactory sensory neurons (OSNs), while having no significant impact on membrane depolarization and Ca2+ influx into the presynaptic compartment. These data indicate that ethanol targets the active zone in reducing synaptic vesicle exocytosis. Drosophila, haploinsufficent for the Munc13-1 ortholog Dunc13, are more resistant to the effect of ethanol on presynaptic inhibition. Genetically reducing the activity of Dunc13 through mutation or expression of RNAi transgenes also leads to a significant resistance to the sedative effects of ethanol. The neuronal expression of Munc13-1 in heterozygotes for a Dunc13 loss-of-function mutation can largely rescue the ethanol sedation resistance phenotype, indicating a conservation of function between Munc13-1 and Dunc13 in ethanol sedation. Hence, reducing Dunc13 activity leads to naïve physiological and behavioral resistance to sedating concentrations of ethanol. We propose that reducing Dunc13 activity, genetically or pharmacologically by ethanol binding to the C1 domain of Munc13-1/Dunc13, promotes a homeostatic response that leads to ethanol tolerance.
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27
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Calahorro F, Izquierdo PG. The presynaptic machinery at the synapse of C. elegans. INVERTEBRATE NEUROSCIENCE : IN 2018; 18:4. [PMID: 29532181 PMCID: PMC5851683 DOI: 10.1007/s10158-018-0207-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 02/22/2018] [Indexed: 11/17/2022]
Abstract
Synapses are specialized contact sites that mediate information flow between neurons and their targets. Important physical interactions across the synapse are mediated by synaptic adhesion molecules. These adhesions regulate formation of synapses during development and play a role during mature synaptic function. Importantly, genes regulating synaptogenesis and axon regeneration are conserved across the animal phyla. Genetic screens in the nematode Caenorhabditis elegans have identified a number of molecules required for synapse patterning and assembly. C. elegans is able to survive even with its neuronal function severely compromised. This is in comparison with Drosophila and mice where increased complexity makes them less tolerant to impaired function. Although this fact may reflect differences in the function of the homologous proteins in the synapses between these organisms, the most likely interpretation is that many of these components are equally important, but not absolutely essential, for synaptic transmission to support the relatively undemanding life style of laboratory maintained C. elegans. Here, we review research on the major group of synaptic proteins, involved in the presynaptic machinery in C. elegans, showing a strong conservation between higher organisms and highlight how C. elegans can be used as an informative tool for dissecting synaptic components, based on a simple nervous system organization.
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Affiliation(s)
- Fernando Calahorro
- Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton, SO17 1BJ, UK.
| | - Patricia G Izquierdo
- Biological Sciences, University of Southampton, Life Sciences Building 85, Southampton, SO17 1BJ, UK
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28
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Das J, Kedei N, Kelsey JS, You Y, Pany S, Mitchell GA, Lewin NE, Blumberg PM. Critical Role of Trp-588 of Presynaptic Munc13-1 for Ligand Binding and Membrane Translocation. Biochemistry 2018; 57:732-741. [PMID: 29244485 DOI: 10.1021/acs.biochem.7b00764] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Munc13-1 is a presynaptic active-zone protein essential for neurotransmitter release and presynaptic plasticity in the brain. This multidomain scaffold protein contains a C1 domain that binds to the activator diacylglycerol/phorbol ester. Although the C1 domain bears close structural homology with the C1 domains of protein kinase C (PKC), the tryptophan residue at position 22 (588 in the full-length Munc13-1) occludes the activator binding pocket, which is not the case for PKC. To elucidate the role of this tryptophan, we generated W22A, W22K, W22D, W22Y, and W22F substitutions in the full-length Munc13-1, expressed the GFP-tagged constructs in Neuro-2a cells, and measured their membrane translocation in response to phorbol ester treatment by imaging of the live cells using confocal microscopy. The extent of membrane translocation followed the order, wild-type > W22K > W22F > W22Y > W22A > W22D. The phorbol ester binding affinity of the wild-type Munc13-1C1 domain and its mutants was phosphatidylserine (PS)-dependent following the order, wild-type > W22K > W22A ≫ W22D in both 20% and 100% PS. Phorbol ester affinity was higher for Munc13-1 than the C1 domain. While Munc13-1 translocated to the plasma membrane, the C1 domain translocated to internal membranes in response to phorbol ester. Molecular dynamics (80 ns) studies reveal that Trp-22 is relatively less flexible than the homologous Trp-22 of PKCδ and PKCθ. Results are discussed in terms of the overall negative charge state of the Munc13-1C1 domain and its possible interaction with the PS-rich plasma membrane. This study shows that Trp-588 is an important structural element for ligand binding and membrane translocation in Munc13-1.
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Affiliation(s)
- Joydip Das
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, University of Houston , Houston, Texas 77204, United States
| | - Noemi Kedei
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland 20892, United States
| | - Jessica S Kelsey
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland 20892, United States
| | - Youngki You
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, University of Houston , Houston, Texas 77204, United States
| | - Satyabrata Pany
- Department of Pharmacological & Pharmaceutical Sciences, College of Pharmacy, University of Houston , Houston, Texas 77204, United States
| | - Gary A Mitchell
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland 20892, United States
| | - Nancy E Lewin
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland 20892, United States
| | - Peter M Blumberg
- Center for Cancer Research, National Cancer Institute , Bethesda, Maryland 20892, United States
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29
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Rodarte EM, Ramos MA, Davalos AJ, Moreira DC, Moreno DS, Cardenas EI, Rodarte AI, Petrova Y, Molina S, Rendon LE, Sanchez E, Breaux K, Tortoriello A, Manllo J, Gonzalez EA, Tuvim MJ, Dickey BF, Burns AR, Heidelberger R, Adachi R. Munc13 proteins control regulated exocytosis in mast cells. J Biol Chem 2017; 293:345-358. [PMID: 29141910 DOI: 10.1074/jbc.m117.816884] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 11/02/2017] [Indexed: 01/01/2023] Open
Abstract
Mast cells (MCs) are involved in host defenses against pathogens and inflammation. Stimulated MCs release substances stored in their granules via regulated exocytosis. In other cell types, Munc13 (mammalian homolog of Caenorhabditis elegans uncoordinated gene 13) proteins play essential roles in regulated exocytosis. Here, we found that MCs express Munc13-2 and -4, and we studied their roles using global and conditional knock-out (KO) mice. In a model of systemic anaphylaxis, we found no difference between WT and Munc13-2 KO mice, but global and MC-specific Munc13-4 KO mice developed less hypothermia. This protection correlated with lower plasma histamine levels and with histological evidence of defective MC degranulation but not with changes in MC development, distribution, numbers, or morphology. In vitro assays revealed that the defective response in Munc13-4-deficient MCs was limited to regulated exocytosis, leaving other MC secretory effector responses intact. Single cell capacitance measurements in MCs from mouse mutants differing in Munc13-4 expression levels in their MCs revealed that as levels of Munc13-4 decrease, the rate of exocytosis declines first, and then the total amount of exocytosis decreases. A requirement for Munc13-2 in MC exocytosis was revealed only in the absence of Munc13-4. Electrophysiology and EM studies uncovered that the number of multigranular compound events (i.e. granule-to-granule homotypic fusion) was severely reduced in the absence of Munc13-4. We conclude that although Munc13-2 plays a minor role, Munc13-4 is essential for regulated exocytosis in MCs, and that this MC effector response is required for a full anaphylactic response.
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Affiliation(s)
- Elsa M Rodarte
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Marco A Ramos
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Alfredo J Davalos
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Daniel C Moreira
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - David S Moreno
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Eduardo I Cardenas
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Alejandro I Rodarte
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Youlia Petrova
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Sofia Molina
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Luis E Rendon
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Elizabeth Sanchez
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Keegan Breaux
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Alejandro Tortoriello
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - John Manllo
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Erika A Gonzalez
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030; Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo León 64710, México
| | - Michael J Tuvim
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Burton F Dickey
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Alan R Burns
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Roberto Adachi
- Department of Pulmonary Medicine, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030.
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30
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Pany S, Ghosh A, You Y, Nguyen N, Das J. Resveratrol inhibits phorbol ester-induced membrane translocation of presynaptic Munc13-1. Biochim Biophys Acta Gen Subj 2017; 1861:2640-2651. [PMID: 28713022 DOI: 10.1016/j.bbagen.2017.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 06/23/2017] [Accepted: 07/12/2017] [Indexed: 12/13/2022]
Abstract
BACKGROUND Resveratrol (1) is a naturally occurring polyphenol that has been implicated in neuroprotection. One of resveratrol's several biological targets is Ca2+-sensitive protein kinase C alpha (PKCα). Resveratrol inhibits PKCα by binding to its activator-binding C1 domain. Munc13-1 is a C1 domain-containing Ca2+-sensitive SNARE complex protein essential for vesicle priming and neurotransmitter release. METHODS To test if resveratrol could also bind and inhibit Munc13-1, we studied the interaction of resveratrol and its derivatives, (E)-1,3-dimethoxy-5-(4-methoxystyryl)benzene, (E)-5,5'-(ethene-1,2-diyl)bis(benzene-1,2,3-triol), (E)-1,2-bis(3,4,5-trimethoxyphenyl)ethane, and (E)-5-(4-(hexadecyloxy)-3,5-dihydroxystyryl)benzene-1,2,3-triol with Munc13-1 by studying its membrane translocation from cytosol to plasma membrane in HT22 cells and primary hippocampal neurons. RESULTS Resveratrol, but not the derivatives inhibited phorbol ester-induced Munc13-1 translocation from cytosol to membrane in HT22 cells and primary hippocampal neurons, as evidenced by immunoblot analysis and confocal microscopy. Resveratrol did not show any effect on Munc13-1H567K, a mutant which is not sensitive to phorbol ester. Binding studies with Munc13-1 C1 indicated that resveratrol competes with phorbol ester for the binding site. Molecular docking and dynamics studies suggested that hydroxyl groups of resveratrol interact with phorbol-ester binding residues in the binding pocket. CONCLUSIONS AND SIGNIFICANCE This study characterizes Munc13-1 as a target of resveratrol and highlights the importance of dietary polyphenol in the management of neurodegenerative diseases.
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Affiliation(s)
- Satyabrata Pany
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
| | - Anamitra Ghosh
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
| | - Youngki You
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
| | - Nga Nguyen
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
| | - Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States.
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31
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Jakhanwal S, Lee CT, Urlaub H, Jahn R. An activated Q-SNARE/SM protein complex as a possible intermediate in SNARE assembly. EMBO J 2017; 36:1788-1802. [PMID: 28483813 DOI: 10.15252/embj.201696270] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 03/23/2017] [Accepted: 03/24/2017] [Indexed: 01/15/2023] Open
Abstract
Assembly of the SNARE proteins syntaxin1, SNAP25, and synaptobrevin into a SNARE complex is essential for exocytosis in neurons. For efficient assembly, SNAREs interact with additional proteins but neither the nature of the intermediates nor the sequence of protein assembly is known. Here, we have characterized a ternary complex between syntaxin1, SNAP25, and the SM protein Munc18-1 as a possible acceptor complex for the R-SNARE synaptobrevin. The ternary complex binds synaptobrevin with fast kinetics, resulting in the rapid formation of a fully zippered SNARE complex to which Munc18-1 remains tethered by the N-terminal domain of syntaxin1. Intriguingly, only one of the synaptobrevin truncation mutants (Syb1-65) was able to bind to the syntaxin1:SNAP25:Munc18-1 complex, suggesting either a cooperative zippering mechanism that proceeds bidirectionally or the progressive R-SNARE binding via an SM template. Moreover, the complex is resistant to disassembly by NSF Based on these findings, we consider the ternary complex as a strong candidate for a physiological intermediate in SNARE assembly.
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Affiliation(s)
- Shrutee Jakhanwal
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Chung-Tien Lee
- Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center, Göttingen, Germany
| | - Reinhard Jahn
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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32
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Chehab T, Santos NC, Holthenrich A, Koerdt SN, Disse J, Schuberth C, Nazmi AR, Neeft M, Koch H, Man KNM, Wojcik SM, Martin TFJ, van der Sluijs P, Brose N, Gerke V. A novel Munc13-4/S100A10/annexin A2 complex promotes Weibel-Palade body exocytosis in endothelial cells. Mol Biol Cell 2017; 28:1688-1700. [PMID: 28450451 PMCID: PMC5469611 DOI: 10.1091/mbc.e17-02-0128] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/17/2017] [Accepted: 04/18/2017] [Indexed: 11/17/2022] Open
Abstract
The tethering factor Munc13-4 is recruited to Weibel–Palade body (WPB) fusion sites after secretagogue stimulation to promote WPB exocytosis. Annexin A2-S100A10 is a novel Munc13-4 interaction partner assisting Munc13-4 tethering at the plasma membrane. Endothelial cells respond to blood vessel injury by the acute release of the procoagulant von Willebrand factor, which is stored in unique secretory granules called Weibel–Palade bodies (WPBs). Stimulated WPB exocytosis critically depends on their proper recruitment to the plasma membrane, but factors involved in WPB–plasma membrane tethering are not known. Here we identify Munc13-4, a protein mutated in familial hemophagocytic lymphohistiocytosis 3, as a WPB-tethering factor. Munc13-4 promotes histamine-evoked WPB exocytosis and is present on WPBs, and secretagogue stimulation triggers an increased recruitment of Munc13-4 to WPBs and a clustering of Munc13-4 at sites of WPB–plasma membrane contact. We also identify the S100A10 subunit of the annexin A2 (AnxA2)-S100A10 protein complex as a novel Munc13-4 interactor and show that AnxA2-S100A10 participates in recruiting Munc13-4 to WPB fusion sites. These findings indicate that Munc13-4 supports acute WPB exocytosis by tethering WPBs to the plasma membrane via AnxA2-S100A10.
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Affiliation(s)
- Tarek Chehab
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
| | - Nina Criado Santos
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
| | - Anna Holthenrich
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
| | - Sophia N Koerdt
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
| | - Jennifer Disse
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
| | - Christian Schuberth
- Institute of Cell Dynamics and Imaging, Centre for Molecular Biology of Inflammation, Cells-in-Motion Cluster of Excellence, University of Münster, 48149 Münster, Germany
| | - Ali Reza Nazmi
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
| | - Maaike Neeft
- Department of Cell Biology, Center of Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, Netherlands
| | - Henriette Koch
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Kwun Nok M Man
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Thomas F J Martin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
| | - Peter van der Sluijs
- Department of Cell Biology, Center of Molecular Medicine, University Medical Center Utrecht, 3584 CX Utrecht, Netherlands
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Volker Gerke
- Institute of Medical Biochemistry, University of Münster, 48149 Münster, Germany
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33
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Lipstein N, Verhoeven-Duif NM, Michelassi FE, Calloway N, van Hasselt PM, Pienkowska K, van Haaften G, van Haelst MM, van Empelen R, Cuppen I, van Teeseling HC, Evelein AMV, Vorstman JA, Thoms S, Jahn O, Duran KJ, Monroe GR, Ryan TA, Taschenberger H, Dittman JS, Rhee JS, Visser G, Jans JJ, Brose N. Synaptic UNC13A protein variant causes increased neurotransmission and dyskinetic movement disorder. J Clin Invest 2017; 127:1005-1018. [PMID: 28192369 DOI: 10.1172/jci90259] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 12/15/2016] [Indexed: 12/13/2022] Open
Abstract
Munc13 proteins are essential regulators of neurotransmitter release at nerve cell synapses. They mediate the priming step that renders synaptic vesicles fusion-competent, and their genetic elimination causes a complete block of synaptic transmission. Here we have described a patient displaying a disorder characterized by a dyskinetic movement disorder, developmental delay, and autism. Using whole-exome sequencing, we have shown that this condition is associated with a rare, de novo Pro814Leu variant in the major human Munc13 paralog UNC13A (also known as Munc13-1). Electrophysiological studies in murine neuronal cultures and functional analyses in Caenorhabditis elegans revealed that the UNC13A variant causes a distinct dominant gain of function that is characterized by increased fusion propensity of synaptic vesicles, which leads to increased initial synaptic vesicle release probability and abnormal short-term synaptic plasticity. Our study underscores the critical importance of fine-tuned presynaptic control in normal brain function. Further, it adds the neuronal Munc13 proteins and the synaptic vesicle priming process that they control to the known etiological mechanisms of psychiatric and neurological synaptopathies.
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34
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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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35
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Bonifacino T, Musazzi L, Milanese M, Seguini M, Marte A, Gallia E, Cattaneo L, Onofri F, Popoli M, Bonanno G. Altered mechanisms underlying the abnormal glutamate release in amyotrophic lateral sclerosis at a pre-symptomatic stage of the disease. Neurobiol Dis 2016; 95:122-33. [PMID: 27425885 DOI: 10.1016/j.nbd.2016.07.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 07/08/2016] [Accepted: 07/13/2016] [Indexed: 01/29/2023] Open
Abstract
Abnormal Glu release occurs in the spinal cord of SOD1(G93A) mice, a transgenic animal model for human ALS. Here we studied the mechanisms underlying Glu release in spinal cord nerve terminals of SOD1(G93A) mice at a pre-symptomatic disease stage (30days) and found that the basal release of Glu was more elevated in SOD1(G93A) with respect to SOD1 mice, and that the surplus of release relies on synaptic vesicle exocytosis. Exposure to high KCl or ionomycin provoked Ca(2+)-dependent Glu release that was likewise augmented in SOD1(G93A) mice. Equally, the Ca(2+)-independent hypertonic sucrose-induced Glu release was abnormally elevated in SOD1(G93A) mice. Also in this case, the surplus of Glu release was exocytotic in nature. We could determine elevated cytosolic Ca(2+) levels, increased phosphorylation of Synapsin-I, which was causally related to the abnormal Glu release measured in spinal cord synaptosomes of pre-symptomatic SOD1(G93A) mice, and increased phosphorylation of glycogen synthase kinase-3 at the inhibitory sites, an event that favours SNARE protein assembly. Western blot experiments revealed an increased number of SNARE protein complexes at the nerve terminal membrane, with no changes of the three SNARE proteins and increased expression of synaptotagmin-1 and β-Actin, but not of an array of other release-related presynaptic proteins. These results indicate that the abnormal exocytotic Glu release in spinal cord of pre-symptomatic SOD1(G93A) mice is mainly based on the increased size of the readily releasable pool of vesicles and release facilitation, supported by plastic changes of specific presynaptic mechanisms.
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Affiliation(s)
- Tiziana Bonifacino
- Department of Pharmacy, Unit of Pharmacology and Toxicology, and Center of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy.
| | - Laura Musazzi
- Department of Pharmacological and Biomolecular Sciences and Center of Excellence on Neurodegenerative Diseases, University of Milan, 20133 Milan, Italy.
| | - Marco Milanese
- Department of Pharmacy, Unit of Pharmacology and Toxicology, and Center of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy.
| | - Mara Seguini
- Department of Pharmacological and Biomolecular Sciences and Center of Excellence on Neurodegenerative Diseases, University of Milan, 20133 Milan, Italy.
| | - Antonella Marte
- Department of Experimental Medicine, Unit of Human Physiology, University of Genoa, Viale Benedetto XV, 16132 Genoa, Italy.
| | - Elena Gallia
- Department of Pharmacy, Unit of Pharmacology and Toxicology, and Center of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy.
| | - Luca Cattaneo
- Department of Pharmacy, Unit of Pharmacology and Toxicology, and Center of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy.
| | - Franco Onofri
- Department of Experimental Medicine, Unit of Human Physiology, University of Genoa, Viale Benedetto XV, 16132 Genoa, Italy.
| | - Maurizio Popoli
- Department of Pharmacological and Biomolecular Sciences and Center of Excellence on Neurodegenerative Diseases, University of Milan, 20133 Milan, Italy.
| | - Giambattista Bonanno
- Department of Pharmacy, Unit of Pharmacology and Toxicology, and Center of Excellence for Biomedical Research, University of Genoa, 16148 Genoa, Italy.
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36
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Okamoto Y, Lipstein N, Hua Y, Lin KH, Brose N, Sakaba T, Midorikawa M. Distinct modes of endocytotic presynaptic membrane and protein uptake at the calyx of Held terminal of rats and mice. eLife 2016; 5. [PMID: 27154627 PMCID: PMC4927297 DOI: 10.7554/elife.14643] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 05/06/2016] [Indexed: 11/15/2022] Open
Abstract
Neurotransmitter is released at synapses by fusion of synaptic vesicles with the plasma membrane. To sustain synaptic transmission, compensatory retrieval of membranes and vesicular proteins is essential. We combined capacitance measurements and pH-imaging via pH-sensitive vesicular protein marker (anti-synaptotagmin2-cypHer5E), and compared the retrieval kinetics of membranes and vesicular proteins at the calyx of Held synapse. Membrane and Syt2 were retrieved with a similar time course when slow endocytosis was elicited. When fast endocytosis was elicited, Syt2 was still retrieved together with the membrane, but endocytosed organelle re-acidification was slowed down, which provides strong evidence for two distinct endocytotic pathways. Strikingly, CaM inhibitors or the inhibition of the Ca2+-calmodulin-Munc13-1 signaling pathway only impaired the uptake of Syt2 while leaving membrane retrieval intact, indicating different recycling mechanisms for membranes and vesicle proteins. Our data identify a novel mechanism of stimulus- and Ca2+-dependent regulation of coordinated endocytosis of synaptic membranes and vesicle proteins. DOI:http://dx.doi.org/10.7554/eLife.14643.001 Nerve cells release chemicals called neurotransmitters to communicate with each other. The neurotransmitters are packaged inside membrane-encased sacs called vesicles that fuse with the cell’s membrane and release their contents into the space between the nerve cells. The vesicle membrane (which also has proteins embedded in it) can then be retrieved into the cell, and recycled to make new vesicles ready to release more neurotransmitters. Recycling vesicle components requires highly coordinated mechanisms that regulate how much membrane and vesicle protein is retrieved from the cell membrane. Researchers interested in these processes have often studied them at a part of the brainstem of mammals known as the calyx of Held. However, many of the details about how vesicle proteins are recycled remained unclear. Okamoto et al. have now measured vesicle membrane and protein retrieval at the same time and in the same cell at the calyx of Held from rats and mice. The cell surface area was also measured, and the experiments focused on a fluorescently tagged version of a vesicle protein called Synaptotagmin2 that could be tracked under a microscope. Okamoto et al. found that, in weakly active nerve cells, the vesicle membrane and Synaptotagmin2 were retrieved together at a slow rate. The process was faster in more active nerve cells, and Synaptotagmin2 was still retrieved with the membrane but it appeared to be stored first in larger sacs. This suggests that membrane and vesicle proteins may be retrieved via two distinct modes depending on the activity strength. The results of further experiments went on to suggest that vesicle membranes might be recycled in a different way from vesicle proteins. Finally, Okamoto et al. also found a signaling pathway that couples the uptake of vesicle membrane with uptake of Synaptotagmin2. Future studies could now explore how these processes work in other types of nerve cell. DOI:http://dx.doi.org/10.7554/eLife.14643.002
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Affiliation(s)
- Yuji Okamoto
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
| | - Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Yunfeng Hua
- Department of Connectomics, Max Planck Institute of Brain Research, Frankfurt, Germany.,Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Kun-Han Lin
- Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Takeshi Sakaba
- Graduate School of Brain Science, Doshisha University, Kyoto, Japan
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37
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Crescente M, Pluthero FG, Li L, Lo RW, Walsh TG, Schenk MP, Holbrook LM, Louriero S, Ali MS, Vaiyapuri S, Falet H, Jones IM, Poole AW, Kahr WHA, Gibbins JM. Intracellular Trafficking, Localization, and Mobilization of Platelet-Borne Thiol Isomerases. Arterioscler Thromb Vasc Biol 2016; 36:1164-73. [PMID: 27079884 DOI: 10.1161/atvbaha.116.307461] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 03/28/2016] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Thiol isomerases facilitate protein folding in the endoplasmic reticulum, and several of these enzymes, including protein disulfide isomerase and ERp57, are mobilized to the surface of activated platelets, where they influence platelet aggregation, blood coagulation, and thrombus formation. In this study, we examined the synthesis and trafficking of thiol isomerases in megakaryocytes, determined their subcellular localization in platelets, and identified the cellular events responsible for their movement to the platelet surface on activation. APPROACH AND RESULTS Immunofluorescence microscopy imaging was used to localize protein disulfide isomerase and ERp57 in murine and human megakaryocytes at various developmental stages. Immunofluorescence microscopy and subcellular fractionation analysis were used to localize these proteins in platelets to a compartment distinct from known secretory vesicles that overlaps with an inner cell-surface membrane region defined by the endoplasmic/sarcoplasmic reticulum proteins calnexin and sarco/endoplasmic reticulum calcium ATPase 3. Immunofluorescence microscopy and flow cytometry were used to monitor thiol isomerase mobilization in activated platelets in the presence and absence of actin polymerization (inhibited by latrunculin) and in the presence or absence of membrane fusion mediated by Munc13-4 (absent in platelets from Unc13d(Jinx) mice). CONCLUSIONS Platelet-borne thiol isomerases are trafficked independently of secretory granule contents in megakaryocytes and become concentrated in a subcellular compartment near the inner surface of the platelet outer membrane corresponding to the sarco/endoplasmic reticulum of these cells. Thiol isomerases are mobilized to the surface of activated platelets via a process that requires actin polymerization but not soluble N-ethylmaleimide-sensitive fusion protein attachment receptor/Munc13-4-dependent vesicular-plasma membrane fusion.
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Affiliation(s)
- Marilena Crescente
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Fred G Pluthero
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Ling Li
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Richard W Lo
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Tony G Walsh
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Michael P Schenk
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Lisa M Holbrook
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Silvia Louriero
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Marfoua S Ali
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Sakthivel Vaiyapuri
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Hervé Falet
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Ian M Jones
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Alastair W Poole
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.)
| | - Walter H A Kahr
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.).
| | - Jonathan M Gibbins
- From the School of Biological Sciences, University of Reading, Reading, United Kingdom (M.C., M.P.S., L.M.H., S.L., M.S.A., S.V., I.M.J., J.M.G.); Program in Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada (F.G.P., L.L., R.W.L., W.H.A.K.); Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, Canada (R.W.L., W.H.A.K.); School of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom (T.G.W., A.W.P.); and Division of Hematology, Brigham and Women's Hospital, Department of Medicine, Harvard Medical School, Boston, MA (H.F.).
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Higashio H, Satoh YI, Saino T. Mast cell degranulation is negatively regulated by the Munc13-4-binding small-guanosine triphosphatase Rab37. Sci Rep 2016; 6:22539. [PMID: 26931073 PMCID: PMC4773767 DOI: 10.1038/srep22539] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 02/17/2016] [Indexed: 02/07/2023] Open
Abstract
Mast cell degranulation is regulated by the small guanosine triphosphatases (GTPases) Rab27a and Rab27b, which have distinct and opposing roles: Rab27b acts as a positive regulator through its effector protein Munc13-4, a non-neuronal isoform of the vesicle-priming Munc13 family of proteins, whereas Rab27a acts as a negative regulator through its effector protein melanophilin, by maintaining integrity of cortical filamentous actin (F-actin), a barrier to degranulation. Here we investigated the role of Rab37, one of the Rab GTPases assumed to be implicated in regulated secretion during mast cell degranulation. Using the RBL-2H3 mast cell line, we detected Rab37 on the secretory granules and found that antigen-induced degranulation was extensively increased by either knockdown of Rab37 or overexpression of a dominant-active Rab37 mutant. This hypersecretion phenotype in the Rab37-knockdown cells was suppressed by simultaneous knockdown of Rab27a and Rab27b or of Munc13-4, but not by disruption of cortical F-actin. We further found that Rab37 interacted with Munc13-4 in a GTP-independent manner and formed a Rab27-Munc13-4-Rab37 complex. These results suggest that Rab37 is a Munc13-4-binding protein that inhibits mast cell degranulation through its effector protein, by counteracting the vesicle-priming activity of the Rab27-Munc13-4 system.
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Affiliation(s)
- Hironori Higashio
- Department of Chemistry, Center for Liberal Arts and Sciences, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan
| | - Yoh-ichi Satoh
- Division of Cell Biology, Department of Anatomy, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan.,Department of Medical Education, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan
| | - Tomoyuki Saino
- Division of Cell Biology, Department of Anatomy, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan
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Wu YJ, Tejero R, Arancillo M, Vardar G, Korotkova T, Kintscher M, Schmitz D, Ponomarenko A, Tabares L, Rosenmund C. Syntaxin 1B is important for mouse postnatal survival and proper synaptic function at the mouse neuromuscular junctions. J Neurophysiol 2015. [PMID: 26203110 DOI: 10.1152/jn.00577.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
STX1 is a major neuronal syntaxin protein located at the plasma membrane of the neuronal tissues. Rodent STX1 has two highly similar paralogs, STX1A and STX1B, that are thought to be functionally redundant. Interestingly, some studies have shown that the distribution patterns of STX1A and STX1B at the central and peripheral nervous systems only partially overlapped, implying that there might be differential functions between these paralogs. In the current study, we generated an STX1B knockout (KO) mouse line and studied the impact of STX1B removal in neurons of several brain regions and the neuromuscular junction (NMJ). We found that either complete removal of STX1B or selective removal of it from forebrain excitatory neurons in mice caused premature death. Autaptic hippocampal and striatal cultures derived from STX1B KO mice still maintained efficient neurotransmission compared with neurons from STX1B wild-type and heterozygous mice. Interestingly, examining high-density cerebellar cultures revealed a decrease in the spontaneous GABAergic transmission frequency, which was most likely due to a lower number of neurons in the STX1B KO cultures, suggesting that STX1B is essential for neuronal survival in vitro. Moreover, our study also demonstrated that although STX1B is dispensable for the formation of the mouse NMJ, it is required to maintain the efficiency of neurotransmission at the nerve-muscle synapse.
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Affiliation(s)
- Yuan-Ju Wu
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Rocio Tejero
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain; and
| | - Marife Arancillo
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Gülcin Vardar
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Tatiana Korotkova
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany; Leibniz Institute for Molecular Pharmacology, Berlin, Germany
| | - Michael Kintscher
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Dietmar Schmitz
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Alexey Ponomarenko
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany; Leibniz Institute for Molecular Pharmacology, Berlin, Germany
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain; and
| | - Christian Rosenmund
- NeuroCure Cluster of Excellence, Charité-Universitätsmedizin Berlin, Berlin, Germany;
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40
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Abstract
Large macromolecular assemblies, so-called molecular machines, are critical to ensuring proper cellular function. Understanding how proper function is achieved at the atomic level is crucial to advancing multiple avenues of biomedical research. Biophysical studies often include X-ray diffraction and cryo-electron microscopy, providing detailed structural descriptions of these machines. However, their inherent flexibility has complicated an understanding of the relation between structure and function. Solution NMR spectroscopy is well suited to the study of such dynamic complexes, and continued developments have increased size boundaries; insights into function have been obtained for complexes with masses as large as 1 MDa. We highlight methyl-TROSY (transverse relaxation optimized spectroscopy) NMR, which enables the study of such large systems, and include examples of applications to several cellular machines. We show how this emerging technique contributes to an understanding of cellular function and the role of molecular plasticity in regulating an array of biochemical activities.
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Gandasi NR, Barg S. Contact-induced clustering of syntaxin and munc18 docks secretory granules at the exocytosis site. Nat Commun 2014; 5:3914. [PMID: 24835618 DOI: 10.1038/ncomms4914] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2013] [Accepted: 04/17/2014] [Indexed: 02/06/2023] Open
Abstract
Docking of secretory vesicles at the plasma membrane is a poorly understood prerequisite for exocytosis. Current models propose raft-like clusters containing syntaxin as docking receptor, but direct evidence for this is lacking. Here we provide quantitative measurements of several exocytosis proteins (syntaxin, SNAP25, munc18, munc13 and rab3) at the insulin granule release site and show that docking coincides with rapid de novo formation of syntaxin1/munc18 clusters at the nascent docking site. Formation of such clusters prevents undocking and is not observed during failed docking attempts. Overexpression of syntaxins' N-terminal Habc-domain competitively interferes with both cluster formation and successful docking. SNAP25 and munc13 are recruited to the docking site more than a minute later, consistent with munc13's reported role in granule priming rather than docking. We conclude that secretory vesicles dock by inducing syntaxin1/munc18 clustering in the target membrane, and find no evidence for preformed docking receptors.
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Affiliation(s)
- Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
| | - Sebastian Barg
- Department of Medical Cell Biology, Uppsala University, BMC 571, 75123 Uppsala, Sweden
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42
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Doc2b synchronizes secretion from chromaffin cells by stimulating fast and inhibiting sustained release. J Neurosci 2013; 33:16459-70. [PMID: 24133251 DOI: 10.1523/jneurosci.2656-13.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Synaptotagmin-1 and -7 constitute the main calcium sensors mediating SNARE-dependent exocytosis in mouse chromaffin cells, but the role of a closely related calcium-binding protein, Doc2b, remains enigmatic. We investigated its role in chromaffin cells using Doc2b knock-out mice and high temporal resolution measurements of exocytosis. We found that the calcium dependence of vesicle priming and release triggering remained unchanged, ruling out an obligatory role for Doc2b in those processes. However, in the absence of Doc2b, release was shifted from the readily releasable pool to the subsequent sustained component. Conversely, upon overexpression of Doc2b, the sustained component was largely inhibited whereas the readily releasable pool was augmented. Electron microscopy revealed an increase in the total number of vesicles upon Doc2b overexpression, ruling out vesicle depletion as the cause for the reduced sustained component. Further experiments showed that, in the absence of Doc2b, the refilling of the readily releasable vesicle pools is faster, but incomplete. Faster refilling leads to an increase in the sustained component as newly primed vesicles fuse while the [Ca(2+)]i following stimulation is still high. We conclude that Doc2b acts to inhibit vesicle priming during prolonged calcium elevations, thus protecting unprimed vesicles from fusing prematurely, and redirecting them to refill the readily releasable pool after relaxation of the calcium signal. In sum, Doc2b favors fast, synchronized release, and limits out-of-phase secretion.
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43
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James DJ, Martin TFJ. CAPS and Munc13: CATCHRs that SNARE Vesicles. Front Endocrinol (Lausanne) 2013; 4:187. [PMID: 24363652 PMCID: PMC3849599 DOI: 10.3389/fendo.2013.00187] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 11/18/2013] [Indexed: 11/13/2022] Open
Abstract
CAPS (Calcium-dependent Activator Protein for Secretion, aka CADPS) and Munc13 (Mammalian Unc-13) proteins function to prime vesicles for Ca(2+)-triggered exocytosis in neurons and neuroendocrine cells. CAPS and Munc13 proteins contain conserved C-terminal domains that promote the assembly of SNARE complexes for vesicle priming. Similarities of the C-terminal domains of CAPS/Munc13 proteins with Complex Associated with Tethering Containing Helical Rods domains in multi-subunit tethering complexes (MTCs) have been reported. MTCs coordinate multiple interactions for SNARE complex assembly at constitutive membrane fusion steps. We review aspects of these diverse tethering and priming factors to identify common operating principles.
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Affiliation(s)
- Declan J. James
- Department of Biochemistry, University of Wisconsin, Madison, WI, USA
| | - Thomas F. J. Martin
- Department of Biochemistry, University of Wisconsin, Madison, WI, USA
- *Correspondence: Thomas F. J. Martin, Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706, USA e-mail:
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Zhou K, Stawicki TM, Goncharov A, Jin Y. Position of UNC-13 in the active zone regulates synaptic vesicle release probability and release kinetics. eLife 2013; 2:e01180. [PMID: 24220508 PMCID: PMC3821175 DOI: 10.7554/elife.01180] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The presynaptic active zone proteins UNC-13/Munc13s are essential for synaptic vesicle (SV) exocytosis by directly interacting with SV fusion apparatus. An open question is how their association with active zones, hence their position to Ca2+ entry sites, regulates SV release. The N-termini of major UNC-13/Munc13 isoforms contain a non-calcium binding C2A domain that mediates protein homo- or hetero-meric interactions. Here, we show that the C2A domain of Caenorhabditis elegans UNC-13 regulates release probability of evoked release and its precise active zone localization. Kinetics analysis of SV release supports that the proximity of UNC-13 to Ca2+ entry sites, mediated by the C2A-domain containing N-terminus, is critical for accelerating neurotransmitter release. Additionally, the C2A domain is specifically required for spontaneous release. These data reveal multiple roles of UNC-13 C2A domain, and suggest that spontaneous release and the fast phase of evoked release may involve a common pool of SVs at the active zone. DOI:http://dx.doi.org/10.7554/eLife.01180.001 Neurons are connected to each other by junctions called synapses. When an electrical signal travelling along a neuron arrives at a synapse, it causes the release of bubble-like structures called synaptic vesicles that contain chemicals called neurotransmitters. When released by the vesicles these neurotransmitters bind to receptors on a second neuron and allow the signal to continue on its way through the nervous system. The release of synaptic vesicles from the neuron depends largely on the number of calcium ions that enter this neuron via structures called ion channels, and also on the rate at which they enter. Vesicles are released in one of three ways: they can be released quickly (within a few milliseconds) in response to the influx of calcium ions; they can be released slowly (over a period of tens or hundreds of milliseconds) in response to the influx; or they can be released at random times that are not related to the influx. It is known that the sensitivity of certain calcium sensors near the synapse influences the release of the vesicles. It had been thought that the distance between the “active zone” where the calcium ions enter the neuron and the region where the vesicles reside might also influence rate of release, but the molecular mechanism underlying this hypothesis is poorly understood. Zhou et al. have now shed new light on this question by performing a series of experiments that involved manipulating a protein called UNC-13 – which is known to be involved in the release of vesicles – in neurons from C. elegans, a nematode worm. First it was shown that the precise position of UNC-13 in the active zone depended on a domain within the protein called the C2A domain. Next it was shown that the distance between the UNC-13 protein and the calcium ion channels strongly influences the quick mode of vesicle release. Finally, Zhou et al. showed that the C2A domain also had a significant influence on the spontaneous release of vesicles, which suggests that a common fleet of vesicles might be used for both the quick and the spontaneous modes of vesicle release. Zhou et al. also generated mutant worms that mimicked a neurological disease, epileptic seizure, and showed that eliminating the C2A domain can relieve some of the symptoms associated with the disease. Many neurological diseases are caused by signals not being transmitted properly at synapses, so in addition to providing insights into the basic mechanism underlying synaptic action, these results could also assist with the development of new strategies for managing neurological diseases. DOI:http://dx.doi.org/10.7554/eLife.01180.002
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Affiliation(s)
- Keming Zhou
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, United States
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45
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The Munc13 proteins differentially regulate readily releasable pool dynamics and calcium-dependent recovery at a central synapse. J Neurosci 2013; 33:8336-51. [PMID: 23658173 DOI: 10.1523/jneurosci.5128-12.2013] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Munc13 gene family encodes molecules located at the synaptic active zone that regulate the reliability of synapses to encode information over a wide range of frequencies in response to action potentials. In the CNS, proteins of the Munc13 family are critical in regulating neurotransmitter release and synaptic plasticity. Although Munc13-1 is essential for synaptic transmission, it is paradoxical that Munc13-2 and Munc13-3 are functionally dispensable at some synapses, although their loss in other synapses leads to increases in frequency-dependent facilitation. We addressed this issue at the calyx of Held synapse, a giant glutamatergic synapse that we found to express all these Munc13 isoforms. We studied their roles in the regulation of synaptic transmission and their impact on the reliability of information transfer. Through detailed electrophysiological analyses of Munc13-2, Munc13-3, and Munc13-2-3 knock-out and wild-type mice, we report that the combined loss of Munc13-2 and Munc13-3 led to an increase in the rate of calcium-dependent recovery and a change in kinetics of release of the readily releasable pool. Furthermore, viral-mediated overexpression of a dominant-negative form of Munc13-1 at the calyx demonstrated that these effects are Munc13-1 dependent. Quantitative immunohistochemistry using Munc13-fluorescent protein knock-in mice revealed that Munc13-1 is the most highly expressed Munc13 isoform at the calyx and the only one highly colocalized with Bassoon at the active zone. Based on these data, we conclude that Munc13-2 and Munc13-3 isoforms limit the ability of Munc13-1 to regulate calcium-dependent replenishment of readily releasable pool and slow pool to fast pool conversion in central synapses.
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46
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Dynamic Control of Synaptic Vesicle Replenishment and Short-Term Plasticity by Ca2+-Calmodulin-Munc13-1 Signaling. Neuron 2013; 79:82-96. [DOI: 10.1016/j.neuron.2013.05.011] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2013] [Indexed: 02/02/2023]
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47
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Parsaud L, Li L, Jung CH, Park S, Saw NMN, Park S, Kim MY, Sugita S. Calcium-dependent activator protein for secretion 1 (CAPS1) binds to syntaxin-1 in a distinct mode from Munc13-1. J Biol Chem 2013; 288:23050-63. [PMID: 23801330 DOI: 10.1074/jbc.m113.494088] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calcium-dependent activator protein for secretion 1 (CAPS1) is a multidomain protein containing a Munc13 homology domain 1 (MHD1). Although CAPS1 and Munc13-1 play crucial roles in the priming stage of secretion, their functions are non-redundant. Similar to Munc13-1, CAPS1 binds to syntaxin-1, a key t-SNARE protein in neurosecretion. However, whether CAPS1 interacts with syntaxin-1 in a similar mode to Munc13-1 remains unclear. Here, using yeast two-hybrid assays followed by biochemical binding experiments, we show that the region in CAPS1 consisting of the C-terminal half of the MHD1 with the corresponding C-terminal region can bind to syntaxin-1. Importantly, the binding mode of CAPS1 to syntaxin-1 is distinct from that of Munc13-1; CAPS1 binds to the full-length of cytoplasmic syntaxin-1 with preference to its "open" conformation, whereas Munc13-1 binds to the first 80 N-terminal residues of syntaxin-1. Unexpectedly, the majority of the MHD1 of CAPS1 is dispensable, whereas the C-terminal 69 residues are crucial for the binding to syntaxin-1. Functionally, a C-terminal truncation of 69 or 134 residues in CAPS1 abolishes its ability to reconstitute secretion in permeabilized PC12 cells. Our results reveal a novel mode of binding between CAPS1 and syntaxin-1, which play a crucial role in neurosecretion. We suggest that the distinct binding modes between CAPS1 and Munc13-1 can account for their non-redundant functions in neurosecretion. We also propose that the preferential binding of CAPS1 to open syntaxin-1 can contribute to the stabilization of the open state of syntaxin-1 during its transition from "closed" state to the SNARE complex formation.
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Affiliation(s)
- Leon Parsaud
- Division of Fundamental Neurobiology, University Health Network, Toronto, Ontario M5T 2S8, Canada
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48
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Das J, Xu S, Pany S, Guillory A, Shah V, Roman GW. The pre-synaptic Munc13-1 binds alcohol and modulates alcohol self-administration in Drosophila. J Neurochem 2013; 126:715-26. [PMID: 23692447 DOI: 10.1111/jnc.12315] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 05/09/2013] [Accepted: 05/17/2013] [Indexed: 11/30/2022]
Abstract
Munc13-1 is a pre-synaptic active-zone protein essential for neurotransmitter release and involved in pre-synaptic plasticity in brain. Ethanol, butanol, and octanol quenched the intrinsic fluorescence of the C1 domain of Munc13-1 with EC₅₀ s of 52 mM, 26 mM, and 0.7 mM, respectively. Photoactive azialcohols photolabeled Munc13-1 C1 exclusively at Glu-582, which was identified by mass spectrometry. Mutation of Glu-582 to alanine, leucine, and histidine reduced the alcohol binding two- to five-fold. Circular dichroism studies suggested that binding of alcohol increased the stability of the wild-type Munc13-1 compared with the mutants. If Munc13-1 plays some role in the neural effects of alcohol in vivo, changes in the activity of this protein should produce differences in the behavioral responses to ethanol. We tested this prediction with a loss-of-function mutation in the conserved Dunc-13 in Drosophila melanogaster. The Dunc-13(P84200) /+ heterozygotes have 50% wild-type levels of Dunc-13 mRNA and display a very robust increase in ethanol self-administration. This phenotype is reversed by the expression of the rat Munc13-1 protein within the Drosophila nervous system. The present studies indicate that Munc13-1 C1 has binding site(s) for alcohols and Munc13-1 activity is sufficient to restore normal self-administration to Drosophila mutants deficient in Dunc-13 activity. The pre-synaptic Mun13-1 protein is a critical regulator of synaptic vesicle fusion and may be involved in processes that lead to ethanol abuse and addiction. We studied its interaction with alcohol and identified Glu-582 as a critical residue for ethanol binding. Munc13-1 can functionally complement the Dunc13 haploinsufficient ethanol self-administration phenotype in Drosophila melanogaster, indicating that this protein participates in alcohol-induced behavioral plasticity.
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Affiliation(s)
- Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, Texas 77204, USA.
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Dudenhöffer-Pfeifer M, Schirra C, Pattu V, Halimani M, Maier-Peuschel M, Marshall MR, Matti U, Becherer U, Dirks J, Jung M, Lipp P, Hoth M, Sester M, Krause E, Rettig J. Different Munc13 isoforms function as priming factors in lytic granule release from murine cytotoxic T lymphocytes. Traffic 2013; 14:798-809. [PMID: 23590328 DOI: 10.1111/tra.12074] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 04/11/2013] [Accepted: 04/16/2013] [Indexed: 01/10/2023]
Abstract
In order to fuse lytic granules (LGs) with the plasma membrane at the immunological synapse, cytotoxic T lymphocytes (CTLs) have to render these LGs fusion-competent through the priming process. In secretory tissues such as brain and neuroendocrine glands, this process is mediated by members of the Munc13 protein family. In human CTLs, mutations in the Munc13-4 gene cause a severe loss in killing efficiency, resulting in familial hemophagocytic lymphohistiocytosis type 3, suggesting a similar role of other Munc13 isoforms in the immune system. Here, we investigate the contribution of different Munc13 isoforms to the priming process of murine CTLs at both the mRNA and protein level. We demonstrate that Munc13-1 and Munc13-4 are the only Munc13 isoforms present in mouse CTLs. Both isoforms rescue the drastical secretion defect of CTLs derived from Munc13-4-deficient Jinx mice. Mobility studies using total internal reflection fluorescence microscopy indicate that Munc13-4 and Munc13-1 are responsible for the priming process of LGs. Furthermore, the domains of the Munc13 protein, which is responsible for functional fusion, could be identified. We conclude from these data that both isoforms of the Munc13 family, Munc13-1 and Munc13-4, are functionally redundant in murine CTLs.
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50
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Rizo J, Südhof TC. The Membrane Fusion Enigma: SNAREs, Sec1/Munc18 Proteins, and Their Accomplices—Guilty as Charged? Annu Rev Cell Dev Biol 2012; 28:279-308. [DOI: 10.1146/annurev-cellbio-101011-155818] [Citation(s) in RCA: 318] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Josep Rizo
- Departments of Biophysics, Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390;
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology and Howard Hughes Medical Institute, Stanford University Medical School, Stanford, California 94305;
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