STAUROSPORINE STIMULATES PHOSPHOLIPASE-D ACTIVATION IN HUMAN POLYMORPHONUCLEAR LEUKOCYTES

Treatment of 1-O-[H-3]alkyl-2-acyl-phosphatidylcholine-prelabeled human polymorphonuclear leukocytes (PMNs) with staurosporine (50 nM to 1 muM) induced a time- and concentration-dependent generation of tritiated phosphatidic acid (PA), reaching approximately 225% of the control value at 15-20 min. In the presence of ethanol, staurosporine induced a production of phosphatidylethanol (PEt) reaching, 250% of control values, and partial inhibition of PA production, consistent with PLD activation. The amount of ether-linked acylglycerol (EAG) was weakly enhanced (29%) after 5 min of PMN treatment; longer treatment resulted in no significant EAG production, suggesting a possible late inhibition of PA hydrolase activity. Staurosporine concentrations that induced an elevation in PA completely depressed protein kinase C (PKC) activity in both soluble and particulate cell fractions, suggesting that PLD activation may occur independently from PKC activation. PLD may thus represent a potential cellular target for staurosporine action.