CAPS activity in priming vesicle exocytosis requires CK2 phosphorylation.

CAPS (Ca(2+)-dependent activator protein for secretion) functions in priming Ca(2+)-dependent vesicle exocytosis, but the regulation of CAPS activity has not been characterized. Here we show that phosphorylation by protein kinase CK2 is required for CAPS activity. Dephosphorylation eliminated CAPS activity in reconstituting Ca(2+)-dependent vesicle exocytosis in permeable and intact PC12 cells.