Phosphorylation of SNAP-23 regulates exocytosis from mast cells

Régine Hepp, Niti Puri, Anita C. Hohenstein, Garland L. Crawford, Sidney W. Whiteheart, Paul A. Roche

Research output: Contribution to journalArticlepeer-review

105 Scopus citations

Abstract

Regulated exocytosis is a process in which a physiological trigger initiates the translocation, docking, and fusion of secretory granules with the plasma membrane. A class of proteins termed SNAREs (including SNAP-23, syntaxins, and VAMPs) are known regulators of secretory granule/plasma membrane fusion events. We have investigated the molecular mechanisms of regulated exocytosis in mast cells and find that SNAP-23 is phosphorylated when rat basophilic leukemia mast cells are triggered to degranulate. The kinetics of SNAP-23 phosphorylation mirror the kinetics of exocytosis. We have identified amino acid residues Ser95 and Ser120 as the major phosphorylation sites in SNAP-23 in rodent mast cells. Quantitative analysis revealed that ∼10% of SNAP-23 was phosphorylated when mast cell degranulation was induced. These same residues were phosphorylated when mouse platelet degranulation was induced with thrombin, demonstrating that phosphorylation of SNAP-23 Ser95 and Ser120 is not restricted to mast cells. Although triggering exocytosis did not alter the absolute amount of SNAP-23 bound to SNAREs, after stimulation essentially all of the SNAP-23 bound to the plasma membrane SNARE syntaxin 4 and the vesicle SNARE VAMP-2 was phosphorylated. Regulated exocytosis studies revealed that overexpression of SNAP-23 phosphorylation mutants inhibited exocytosis from rat basophilic leukemia mast cells, demonstrating that phosphorylation of SNAP-23 on Ser120 and Ser95 modulates regulated exocytosis by mast cells.

Original languageEnglish
Pages (from-to)6610-6620
Number of pages11
JournalJournal of Biological Chemistry
Volume280
Issue number8
DOIs
StatePublished - Feb 25 2005

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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