Differential phosphorylation of SNAP-25 in vivo by protein kinase C and protein kinase A.
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.
Hepp
Régine
R
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bldg. 10, Room 4B36, Bethesda, MD 20892, USA.
Cabaniols
Jean-Pierre
JP
Roche
Paul A
PA
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D016716:PC12 Cells; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D012694:Serine / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25; D013912:Threonine / Q000378:metabolism
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C494208:SNAP25 protein, human; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D013912:Threonine; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D009638:Norepinephrine