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Updated: Sep 28, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
Differential phosphorylation of SNAP-25 in vivo by protein kinase C and protein kinase A
Régine Hepp1, Jean-Pierre Cabaniols, Paul A Roche
1Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bldg. 10, Room 4B36, Bethesda, MD 20892, USA.
Abstract:
SNAP-25 is a key protein required for the fusion of synaptic vesicles with the plasma membrane during exocytosis. This study establishes that SNAP-25 is differentially phosphorylated by protein kinase C and protein kinase A in neuroendocrine PC12 cells. Using phosphopeptide mapping and site-directed mutagenesis we identified both Thr138 and Ser187 as the targets of SNAP-25 phosphorylation by protein kinase C and Thr138 as the exclusive site of SNAP-25 phosphorylation by protein kinase A in vivo. Finally, despite published data to the contrary, we demonstrate that stimulation of regulated exocytosis under physiological conditions is independent of a measurable increase in SNAP-25 phosphorylation in PC12 cells.
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