Molecular species of phosphatidylinositol, phosphatidic acid and diacylglycerol in a phytohemagglutinin-stimulated T-cell leukemia line

Abstract

Addition of phytohemagglutinin to JURKAT cells, a human T-cell leukemia line, induced a rapid breakdown of phosphatidylinositol 4,5-bisphosphate (and may also be phosphatidylinositol 4-phosphate) and an accumlation of phosphatidic acid. The accumulation and disappearance of the various molecular species of phosphatidic acid, diacylglycerol and phosphatidylinositol (PtdIns) in response to phytohemagglutinin was studied in JURKAT cells. The cells were prelabeled with [2- 3H]glycerol for 2 days and 3H-labeled lipids were isolated from the cells after incubation for 2 min at 37°C in the absence or in the presence of phytohemagglutinin. The isolated 3H-labeled lipids were separated into individual molecular species by reverse-phase HPLC after conversion to their 1,2-[ 3H]diacylglycerol acetate derivatives by acetolysis or by acetylation. Stimulation with phytohemagglutinin induced a 2-fold increase In [ 3H]phosphatidic acid. The molecular species of the accumulated [ 3H]phosphatidic acid consisted of polyenoic species, which were almost absent in the [ 3H]phosphatidic acid of the unstimulated cells. Stearoylarachidonoyl species of [ 3H]phosphatidic acid accumulated most prominently. Although an accumulation of [ 3H]diacylglycerol was hardly measurable in the phytohemagglutinin-stimulated cells, the HPLC analysis of the molecular species of [ 3H]diacylglycerol showed a 2-fold increase in the stearoylarachidudonoyl species in the stimulated cells. Stimulation with phytohemagglutinin had almost no effect on the composition of molecular species of [ 3H]PtdIns. The stearoylarachidonyl species is the most abundant molecular species of PtdIns in JURKAT cells. These results suggest that the [ 3H]diacylglycerol moiety of [ 3H]phosphatidic acid originates from inositol lipid(s). The results also suggest a rapid and preferential phosphorylation of the diacylglycerol formed by receptor-stimulated hydrolysis of inositol lipid(s).