Proteolytic activation of protein kinase C in the extracts of cells treated for a short time with phorbol ester

Abstract

A 10 min treatment of human neutrophils with phorbol 12‐myristate 13‐acetate (PMA) has been reported to induce accumulation of the proteolytically activated Ca^{2 +}/phospholipid‐independent catalytic fragment of protein kinase C in the cytosol of intact cells [(1986) J. Biol. Chem. 261, 4101‐4105]. We investigated the proteolytic conversion of protein kinase C to the Ca^{2 +}/phospholipid‐independent form in the cytosol and membrane fractions of pig neutrophils. The activity of protein kinase C was measured with its specific oligopeptide substrate Ala‐Ala‐Ala‐Ser‐Phe‐Lys‐Ala‐Lys‐Lys‐amide designed previously. In our experiments the short‐term treatment of neutrophils with PMA did not induce the accumulation of the proteolytically activated form of protein kinase C in the cytosol of intact cells. However, treatment of cells with PMA enhanced the limited proteolysis of protein kinase C during the preparation of cell extracts.