Inhibition of phosphatidylserine synthesis by phosphatidic acid in the Jurkat T cell line: role of calcium ions released from intracellular stores.

Phosphatidic acid exogenously added to Jurkat T-cells, provokes a marked inhibition of phosphatidylserine (PS) synthesis. Comparison of the efficiency of synthetic phosphatidic acids, differing in their fatty acid content, to induce inhibition of PS-synthesis have shown that short chain saturated and long chain unsaturated fatty acid-containing phosphatidic acids were the best inhibitors. Treatment of Jurkat cells with phosphatidic acid, induced a mobilization of calcium ions arising exclusively from intracellular stores, suggesting that Ca2+ from intracellular compartments might play a key role in the inhibition of PS synthesis. In activated cells, the use of R59022, a diacylglycerolkinase inhibitor, suggests that PA and probably calcium ions released by PA are the messengers responsible for the inhibition of PS synthesis in Jurkat T cells.