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Phosphorylation of cysteine string protein by protein kinase A. Implications for the modulation of exocytosis

Evans, G.J.O., Wilkinson, M.C., Graham, M.E., Turner, K.M., Chamberlain, L.H., Burgoyne, R.D. and Morgan, A. (2001) Phosphorylation of cysteine string protein by protein kinase A. Implications for the modulation of exocytosis. Journal of Biological Chemistry, 276 (51). pp. 47877-47885. ISSN 0021-9258

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Cyclic AMP-dependent protein kinase (PKA) enhances regulated exocytosis in neurons and most other secretory cells. To explore the molecular basis of this effect, known exocytotic proteins were screened for PKA substrates. Both cysteine string protein (CSP) and soluble NSF attachment protein- (-SNAP) were phosphorylated by PKA in vitro, but immunoprecipitation of cellular -SNAP failed to detect 32P incorporation. In contrast, endogenous CSP was phosphorylated in synaptosomes, PC12 cells, and chromaffin cells. In-gel kinase assays confirmed PKA to be a cellular CSP kinase, with phosphorylation occurring on Ser10. PKA phosphorylation of CSP reduced its binding to syntaxin by 10-fold but had little effect on its interaction with HSC70 or G-protein subunits. Furthermore, an in vivo role for Ser10 phosphorylation at a late stage of exocytosis is suggested by analysis of chromaffin cells transfected with wild type or non-phosphorylatable mutant CSP. We propose that PKA phosphorylation of CSP could modulate the exocytotic machinery, by selectively altering its availability for protein-protein interactions.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Biology (York)
Depositing User: York RAE Import
Date Deposited: 23 Apr 2009 09:40
Last Modified: 23 Apr 2009 09:40
Published Version: http://dx.doi.org/10.1074/jbc.M108186200
Status: Published
Publisher: The American Society for Biochemistry and Molecular Biology
Identification Number: 10.1074/jbc.M108186200
URI: http://eprints.whiterose.ac.uk/id/eprint/6591

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