Characterization of Serine 916 as an in VivoAutophosphorylation Site for Protein Kinase D/Protein Kinase CÎ

• Published in: The Journal of biological chemistry 1999-09, Vol.274 (37), p.26543
• Main Authors: Sharon A. Matthews, Enrique Rozengurt, Doreen Cantrell
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.37.26543

Activation of the serine kinase protein kinase D (PKD)/PKCμ is controlled by the phosphorylation of two serine residues within its activation loop via a PKC-dependent signaling cascade. In this study we have identified the C-terminal serine 916 residue as an in vivo phosphorylation site within active PKD/PKCμ. An antibody that recognized PKD/PKCμ proteins specifically phosphorylated on the serine 916 residue was generated and used to show that phosphorylation of Ser-916 is induced by phorbol ester treatment of cells. Thus, the pS916 antibody is a useful tool to study the regulation of PKD/PKCμ activity in vivo . Antigen receptor ligation of T and B lymphocytes also induced phosphorylation of the serine 916 residue of PKD/PKCμ. Furthermore the regulatory FcγRIIB receptor, which mediates vital negative feedback signals to the B cell antigen receptor complex, inhibited the antigen receptor-induced activation and serine 916 phosphorylation of PKD/PKCμ. The degree of serine 916 phosphorylation during lymphocyte activation and inhibition exactly correlated with the activation status of PKD/PKCμ. Moreover, using different mutants of PKD/PKCμ, we show that serine 916 is not trans-phosphorylated by an upstream kinase but is rather an autophosphorylation event that occurs following activation of PKD/PKCμ.