Phosphatidylserine has been implicated both in the regulation of protein kinase C activity and in the regulation of T lymphocyte activation. Taking into account the fact that some serine analogues modify the activity of the base exchange enzyme system responsible for the synthesis of phosphatidylserine and to a lesser extent the synthesis of phosphatidylcholine and phosphatidylethanolamine, in vitro, we have tested the ability of both isoserine and serinol to modify phospholipid synthesis in the T cell line Jurkat. It was found that serinol was able to decrease by 75% the amount of phosphatidylserine synthesized by the cells and also to decrease the synthesis of phosphatidylcholine and phosphatidylethanolamine, while phosphatidylinositol synthesis was not affected. Concomitantly, in serinol-treated Jurkat cells, interleukin-2 production was markedly inhibited. Monitoring the production of second messengers generated by T cell activators showed that in serinol-treated cells the production of diacylglycerol was impaired while Ca2+ mobilization remained unaffected. Serinol thus appeared to be a potential immunoregulatory molecule active at the level of protein kinase C regulation either through its interaction with phosphatidylserine or through diacylglycerol production.
