THE ROLE OF PROTEIN-KINASE-C IN THE STIMULATION OF PHOSPHATIDYLCHOLINE SYNTHESIS BY PHOSPHOLIPASE-C

The role of protein kinase C in the stimulation of phosphatidylcholine (PC) synthesis by phospholipase C was investigated. Phospholipase C treatment of Chinese hamster ovary cells (CHO) generates diacylglycerol, which is an activator of protein kinase C. The protein kinase C activator, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) stimulated choline incorporation into two CHO cell lines, a wild-type cell line, WTB, and a mutant cell line, DTG 1-5-4. DTG 1-5-4 is a mutant defective in receptor-mediated endocytosis. A 3-h phospholipase C treatment resulted in the activation and translocation of CTP:phosphocholine cytidylyltransferase in both cell lines. TPA treatment, however, resulted in only a slight (20%) translocation of cytidylyltransferase in WTB; no detectable translocation of cytidylyltransferase was observed in DTG 1-5-4. A decrease in the phosphocholine pools was observed in response to TPA treatment in both cell lines, which indicated that the cytidylyltransferase step was being activated. Phospholipase C stimulated choline incorporation into PC even when protein kinase C had been down-regulated in both cell lines. It was concluded that phospholipase C does not activate PC synthesis by activating protein kinase C. © 1991.