Activation of Protein Kinase C by Oxidized Diacylglycerols

The effects of 1,2-diacylglycerol hydroperoxide (DAG-OOH), its alcohol (DAG-OH), "unoxidized" 1,2-diacylglycerol (DAG), 1,2-dioleoylglycerol (DOG), and phorbol 12-myristate acetate (PMA) on the activity of protein kinase C (PKC) isolated from rat brain were examined in the presence and absence of phosphatidylserine (PS) and calcium ion. Both DAG-OOH and DAG-OH stimulated the activity of PKC dose- and time-dependently, The ability of additives for PKC activation increased in the order of DOG, DAG ⪡ DAG-OOH, DAG-OH < PMA. DAG-OOH and DAG-OH activated PKC even in the absence of PS and calcium ion as PMA does. If DAG-OOH and DAG-OH are released from the oxidized biomembranes by the action of phospholipase C, these components may act like PMA and serve to activate the PKC-dependent signal transduction system.