Characterization of the hydrophobic motif phosphorylation in activation of Protein Kinase C delta

초록

Protein Kinase C (PKC) is a multi-gene subfamily of serine-threonine kinases comprising of at least ten isoforms which play important roles in multitudes of cellular processes as proliferation, differentiation, growth, and apoptosis. PKCδ is one of the important isoforms among the PKCs in regulating various cellular processes including cell survival and apoptosis. Activation of PKCδ is correlated with apoptosis in various cell types. Phosphorylation of Thr505, Ser643 and Ser662 are crucial in activation of PKCδ. Furthermore, phosphorylation of tyrosine residues, in particular that of Tyr311, is related with PKCδ activation and induction of apoptosis. Here, we intended to study the hydrophobic motif Ser662 in specific and generated the phoshorylation-deficient and phosphorylation-mimic mutants: S662A and S662D. We studied the effect of these mutations in activation of PKCδ and induction of apoptosis in L929 murine fibroblsasts. We found that the phosphorylation-deficient mutant PKCδ-S662A is more active and induced more apoptosis in L929 cells. Furthermore, as compared with PKCδ-WT, this mutant is more tyrosine phosphorylated and translocated to the membrane faster.