Phosphorylation of poly(ADP-ribose)polymerase protein in human peripheral lymphocytes stimulated with phytohemagglutinin.

Intracellular phosphorylation of poly(ADP-ribose)polymerase was assayed in streptolysin-O-permeabilized human lymphocytes. Whereas 32P incorporation from [gamma-32P]ATP into immunoprecipitated enzyme protein was undetectable in resting cells, significant phosphorylation of this enzyme was observed in lymphocytes treated with phytohemagglutinin. The phosphorylation of poly(ADP-ribose)polymerase in permeabilized cells was not stimulated by phorbol ester, while phorbol-induced phosphorylation of other proteins and of a specific oligopeptide substrate of protein kinase C was observed. However, the specific inhibitory pseudosubstrate peptide of protein kinase C blocked the phosphorylation of poly(ADP-ribose)polymerase induced by phytohemagglutinin. Therefore, a potential role of a member of the protein kinase C family in the phytohemagglutinin stimulated intracellular phosphorylation of poly(ADP-ribose)polymerase is conceivable.