PHOSPHORYLATION OF RABPHILIN-3A BY CALMODULIN-DEPENDENT PROTEIN-KINASE-II

Rabphilin-3A is a putative target protein for Rab3A small GTP-binding protein which is implicated in neurotransmitter release. We have exami ned here whether Rabphilin-3A is phosphorylated by calmodulin-dependen t protein kinase II (CaMKII). Recombinant Rabphilin-3A was phosphoryla ted by CaMKII purified from rat brain. Two moles of phosphate were max imally incorporated into one mole of Rabphilin-3A. The phosphorylation sites were Ser(34), Thr(205), Thr(209), and Thr(537). These results s uggest that the CaMKII-catalyzed phosphorylation of Rabphilin-3A may m odulate neurotransmitter release. (C) 1994 Academic Press, Inc.