Regulation of phospholipid metabolism by K+ channel blockers and inhibitors of choline transport in the Jurkat T cell line. Relationships with cell proliferation and interleukin-2 production.

In the human T cell line Jurkat, three drugs generally used as effectors of K+ channels, i.e., quinine, 4-aminopyridine and tetraethylammonium, modify phospholipid metabolism. The drugs inhibited the synthesis of both phosphatidylcholine and phosphatidylethanolamine. The mechanism of such inhibition involves a decreased uptake of choline and ethanolamine by the cells, since the three K+ channel blockers were found to be able to competitively inhibit the high-affinity choline/ethanolamine transport system at the membrane level. In contrast, choline transport-inhibitors such as hemicholinium-3, decamethonium and dodecyltrimethylammonium do not inhibit interleukin-2 synthesis and proliferation of the Jurkat T cell line. This indicates that the inhibition of either phosphatidylcholine and/or phosphatidylethanolamine synthesis is not directly implicated in these processes. The inhibition of interleukin-2 synthesis appeared to be mediated through the inhibition of diacylglycerol production induced by T cell activators. A major role for phosphatidylserine in the regulation of T cell activation emerged, since we demonstrated that a panel of K+ channel blockers enhanced the synthesis of this phospholipid mimicking the previously described effect of exogenously added phosphatidylserine in Jurkat cells, i.e., a blockade of interleukin-2 synthesis probably due to a defect in diacylglycerol production.