Increased concentrations of phosphatidate, diacylglycerol and ceramide in ras- and tyrosine kinase (fps)-transformed fibroblasts

Concentrations of the bioactive lipids, phosphatidate and diacylglycerol, increased with time in culture in ras- and tyrosine kinase (fps)-transformed fibroblasts but not in control fibroblasts, On Day 3, diacylglycerol and phosphatidate concentrations were about 3.3- and 5.5-fold higher respectively in the Pas-transformed compared to control fibroblasts. These concentrations in fps-transformed fibroblasts were increased about twofold. The changes in phosphatidate and diacylglycerol resulted from enhanced phospholipid turnover rather than from synthesis de novo, The increased ratio of phosphatidate to diacylglycerol is explained by decreased activities of two distinct phosphatidate phosphohydrolases and increased diacylglycerol kinase in Pas-transformed fibroblasts. Ceramide concentrations were about 2.5- and threefold higher in the fps- and ras-transformed cells respectively on Day 3 compared to the controls, Incubating control fibroblasts from Days 1 to 3 with phosphatidylcholine-specific phospholipase C increased diacylglycerol, phosphatidate and ceramide concentrations, and decreased Mg2+-independent-phosphatidate phosphohydrolase activity, 8-(4-chlorophenylthio)-cAMP had a cytostatic effect in Pas-transformed cells, it decreased the concentrations of phosphatidate and diacylglycerol, but increased that of ceramide, The consequences of increased ceramide and phosphatidate concentrations in Pas-transformed cells are discussed in relation to signal transduction, cell division and the transformed phenotype.