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

Abstract

Concentrations of the bioactive lipids, phosphatidate and diacylglycerol, increased with time in culture in ras-and tyrosine kinase (fps)-transformed ®broblasts but not in control ®broblasts. On Day 3, diacylglycerol and phosphatidate concentrations were about 3.3-and 5.5-fold higher respectively in the ras-transformed compared to control ®broblasts. These concentrations in fpstransformed ®broblasts 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 ras-transformed ®bro-blasts. 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 ®broblasts from Days 1 to 3 with phosphatidylcholine-speci®c phospholipase C increased diacylglycerol, phosphatidate and ceramide concentrations, and decreased Mg 2+ -independent-phosphatidate phosphohydrolase activity. 8-(4-chlorophenylthio)-cAMP had a cytostatic e ect in ras-transformed cells, it decreased the concentrations of phosphatidate and diacylglycerol, but increased that of ceramide. The consequences of increased ceramide and phosphatidate concentrations in ras-transformed cells are discussed in relation to signal transduction, cell division and the transformed phenotype.

Pulmonary phosphatidic acid phosphatase and lipid phosphate phosphohydrolase

“…Caveolin-1 levels and caveolae are decreased in a variety of ras and src oncogene-transformed cell lines (198). Rastransformed Rat 2 cells have decreased LPP activity and higher PA/DAG ratios than standard Rat 2 fibroblasts (151). Caveolin levels are also decreased in some bronchiolar epithelial cell lines (198) but are increased in lung tissue from old rats and in cultured cell lines undergoing senescence (188).…”

Lipid Phosphate Phosphatase-1 Regulates Lysophosphatidate-induced Fibroblast Migration by Controlling Phospholipase D2-dependent Phosphatidate Generation

“…They were then turned upside down, and developed in the reverse direction with chloroform/methanol/ acetic acid/acetone/water (50:10:12:20:5, by volume). The mass of DAG in the cells was determined by converting it to PA in the presence of [␥-32 P]ATP and DAG kinase (42). The concentration of DAG was determined by using a standard curve prepared with sn-1,2-dioleoylglycerol.…”

“…The concentration of DAG was determined by using a standard curve prepared with sn-1,2-dioleoylglycerol. The mass of DAG was expressed relative to the total phospholipid content of the cells (42).…”

Activation of phospholipase D activity in transforming growth factor-beta-induced cell growth inhibition

“…Many growth factors for receptor tyrosine kinases, including the epidermal growth factor (EGF), platelet-derived growth factor (PDGF), v-Src, fibroblast growth factor (FGF), and insulin-like growth factor (IGF), have been shown to activate PLD activity [9][10][11][12][13][14]. Activation of non-receptor tyrosine kinase v-Src has also been shown to activate PLD activity [15].…”