Novel phosphorylation site markers of protein kinase C delta activation

Protein kinase C delta (PKC delta) is a Ser/Thr kinase which regulates numerous cellular processes, including proliferation, differentiation, migration and apoptosis. Here, we demonstrate that PKCS undergoes in vitro autophosphorylation at three sites within its V3 region (S299, S302, S304), each of which is unique to this PKC isoform and evolutionarily conserved. We demonstrate that S299 and S304 can be phosphorylated in mammalian cells following phorbol ester stimulation and that S299-phosphorylated PKC delta is localised to both the plasma and nuclear membranes. These data indicate that PKC delta is phosphorylated upon activation and that phospho-S299 represents a useful marker of the activated enzyme. (c) 2007 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.