Phorbol-12-myristate-13-acetate, a stable analog of the important signaling membrane lipid diacylglycerol (DAG), is known to potentiate exocytosis and modulate vesicle fusion kinetics in neurons and endocrine cells. The exact mechanisms underlying the actions of PMA, however, is often not clear, largely because of the diversity of the DAG/PMA receptors involved in the exocytotic process, which include, most notably, various isoforms of protein kinase C (PKC). In this study, the roles of PKC alpha in PMA-mediated regulation of exocytosis were investigated by over-expressing wild-type PKC alpha (wt-PKC alpha) or dominant negative PKC alpha (dn-PKC alpha.). Amperometric measurements based on carbon fiber microelectrodes demonstrated that PKC alpha. has a key role in the PMA-mediated facilitation of exocytosis and vesicle fusion in neuroendocrine PC12 cells. (C) 2009 Elsevier Inc. All rights reserved.