Tyrosine phosphorylation of Munc18c on residue 521 abrogates binding to Syntaxin 4

Aran, V., Bryant, N.J. and Gould, G.W. (2011) Tyrosine phosphorylation of Munc18c on residue 521 abrogates binding to Syntaxin 4. BMC Biochemistry, 12(19), (doi: 10.1186/1471-2091-12-19)

Abstract

Background: Insulin stimulates exocytosis of GLUT4 from an intracellular store to the cell surface of fat and muscle cells. Fusion of GLUT4-containing vesicles with the plasma membrane requires the SNARE proteins Syntaxin 4, VAMP2 and the regulatory Sec1/Munc18 protein, Munc18c. Syntaxin 4 and Munc18c form a complex that is disrupted upon insulin treatment of adipocytes. Munc18c is tyrosine phosphorylated in response to insulin in these cells. Here, we directly test the hypothesis that tyrosine phosphorylation of Munc18c is responsible for the observed insulin-dependent abrogation of binding between Munc18c and Syntaxin 4. Results: We show that Munc18c is directly phosphorylated by recombinant insulin receptor tyrosine kinase in vitro. Using pull-down assays, we show that phosphorylation abrogates binding of Munc18c to both Syntaxin 4 and the v-SNARE VAMP2, as does the introduction of a phosphomimetic mutation into Munc18c ( Y521E). Conclusion: Our data indicate that insulin-stimulated tyrosine phosphorylation of Munc18c impairs the ability of Munc18c to bind its cognate SNARE proteins, and may therefore represent a regulatory step in GLUT4 traffic.

• Item Type: Articles
• Additional Information: This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gould, Professor Gwyn and Bryant, Dr Nia
• Authors: Aran, V., Bryant, N.J., and Gould, G.W.
• College/School: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Journal Name: BMC Biochemistry
• Publisher: BioMed Central Ltd.
• ISSN (Online): 1471-2091
• Published Online: 06 May 2011
• Copyright Holders: Copyright © 2011 Aran et al; licensee BioMed Central Ltd.
• First Published: First published in BMC Biochemistry 12 (19)
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher