Negative regulation of syntaxin4/SNAP-23/VAMP2-mediated membrane fusion by Munc18c In Vitro

Brandie, F.M., Aran-Ponte, V., Verma, A., McNew, J.A., Bryant, N.J. and Gould, G.W. (2008) Negative regulation of syntaxin4/SNAP-23/VAMP2-mediated membrane fusion by Munc18c In Vitro. PLoS ONE, 3(12), e4074. (doi: 10.1371/journal.pone.0004074) (PMID:19116655) (PMCID:PMC2605266)

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Abstract

Background: Translocation of the facilitative glucose transporter GLUT4 from an intracellular store to the plasma membrane is responsible for the increased rate of glucose transport into fat and muscle cells in response to insulin. This represents a specialised form of regulated membrane trafficking. Intracellular membrane traffic is subject to multiple levels of regulation by conserved families of proteins in all eukaryotic cells. Notably, all intracellular fusion events require SNARE proteins and Sec1p/Munc18 family members. Fusion of GLUT4-containing vesicles with the plasma membrane of insulin-sensitive cells involves the SM protein Munc18c, and is regulated by the formation of syntaxin 4/SNAP23/VAMP2 SNARE complexes. Methodology/Principal Findings Here we have used biochemical approaches to characterise the interaction(s) of Munc18c with its cognate SNARE proteins and to examine the role of Munc18c in regulating liposome fusion catalysed by syntaxin 4/SNAP23/VAMP2 SNARE complex formation. We demonstrate that Munc18c makes contacts with both t- and v-SNARE proteins of this complex, and directly inhibits bilayer fusion mediated by the syntaxin 4/SNAP23/VAMP2 SNARE complex. Conclusion/Significance Our reductionist approach has enabled us to ascertain a direct inhibitory role for Munc18c in regulating membrane fusion mediated by syntaxin 4/SNAP23/VAMP2 SNARE complex formation. It is important to note that two different SM proteins have recently been shown to stimulate liposome fusion mediated by their cognate SNARE complexes. Given the structural similarities between SM proteins, it seems unlikely that different members of this family perform opposing regulatory functions. Hence, our findings indicate that Munc18c requires a further level of regulation in order to stimulate SNARE-mediated membrane fusion.

Item Type:Articles
Additional Information:This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Gould, Professor Gwyn and Bryant, Dr Nia and Brandie, Ms Fiona
Authors: Brandie, F.M., Aran-Ponte, V., Verma, A., McNew, J.A., Bryant, N.J., and Gould, G.W.
Subjects:Q Science > QR Microbiology
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:PLoS ONE
Publisher:Public Library of Science
ISSN:1932-6203
ISSN (Online):1932-6203
Published Online:31 December 2008
Copyright Holders:Copyright © 2008 Brandie et al.
First Published:First published in PLoS One 3(12): e4074
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
404401Functional analysis of Munc18c/Syntaxin4 interactionsNia BryantBiotechnology and Biological Sciences Research Council (BBSRC)BB/D000211/1Institute of Molecular Cell and Systems Biology