A novel type of phorbol ester-dependent protein phosphorylation in the particulate fraction of mouse epidermis

In a Triton X100-extract from the particulate fraction of mouse epidermis but also of other murine tissues, the phosphorylation of a protein with the relative molecular mass of 82,000 (p82) is found to be dependent on phosphatidyl serine and the tumor promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Unlike protein kinase C-catalyzed phosphorylation, p82 phosphorylation is neither observed in the presence of high concentrations of Ca2+ and phosphatidyl serine alone nor after addition of exogenous protein kinase C. Dioctanoylglycerol and the "incomplete" promoter 12-0-retinoylphorbol-13-acetate are also capable of stimulating p82 phosphorylation, whereas the non-promoting phorbol ester 4-0-methyl-TPA is at least 100-fold less active in this respect.