Signal transduction in EJ-H-ras-transformed cells: de novo synthesis of diacylglycerol and subversion of agonist-stimulated inositol lipid metabolism.

Abstract We examined the level of 1,2-diacylglycerol and inositol phosphates in normal and EJ-H- ras -transformed BALB/3T3 fibroblasts by prelabelling the cells with [ 3 H]glycerol, [ 3 H]inositol, [ 14C ]glucose, [ 14 C]arachidonic acid, and [ 14 ]palmitic acid. Steady-state level of diacylglycerol was increased in ras -transformed cells prelabelled with radioactive glycerol, glucose and palmitic acid. Steady-state level of inositol phosphates, however, was the same in control and transformed cells. Diacylglycerol labelling by [ 14 C]arachidonic acid was the same in control and transformed cells. Insulin dramatically increased diacylglycerol labelling by [ 14 C]glucose in normal cells, wheras it did not affect ras -transformed fibroblasts. Neurotransmitter-induced inositol lipid turnover was greatly enhanced in ras -transformed cells; conversely, platelet-derived growth factor and thrombin-stimulated normal cells to a greater extent than transformed fibroblasts. Taken together these results suggest that ras transformation may induce multifarious effects on signal transduction: it may cause de novo synthesis of diacylglycerol and subversion of neurotransmitter and growth factor receptor coupling to inositol lipid metabolism.