Possible regulation by lysophosphatidylcholine of protein kinase C in rat basophilic leukemia (RBL-2H3) cells

• Published in: Japanese Journal of Pharmacology 1989, Vol.49 (suppl), p.180-180
• Main Authors: Masaalsu K. Uchida, Kazuhiko Oishi, J.F. Kuo
• Format: Article
• Language: Japanese
• ISSN: 0021-5198

Unsaturated free fatty acids such as oleic and arachidonic acid are able to stimulate protein kinase C (PKC). We have recently shown that certain lysophospholipids, lysophosphatidylcholine (lyso-PC), in particular, stimulated pig brain PKC activated by phosphatidylserine (PS) in the presence of Ca2+ , but conversely, inhibited it at higher concentrations (.>30μM). These findings are of special interest, because they suggested the existence of yet another signal transduction pathway involved in PKC activation, in addition to the well-recognized diacylglycerol system. The present study was performed to clarify whether PKC purified from RBL-2H3 cells is also responsible for the biphasic effect by lyso-PC. Lyso-PC stimulated further and at higher concentrations inhibited the RBL-2H3 enzyme activity activated by PS (2.5 μg/ml) in the presence of CaCl2 (200 μM), similar to the effects on the pig enzyme. This biphasic effect was also noted for PKC activated by diolein (3 μg/ml) in the presence of PS (2.5 μg/ml) and a low concentration of CaCl2 (1 μM). Considering that receptor-mediated activation of phospholipae A2 (PLA2 ) has been reported in RBL-2H3 cells, these results suggest that lyso-PC, presumably generated by the hydrolysis of phosphatidylcholine by PLA2 , can regulate PKC singly or in a concerted manner with diacylglycerol and/or fatty acid in RBL-2H3 cells.