Lysophosphatidylcholine is a regulator of tyrosine kinase activity and intracellular Ca2+ level in Jurkat T cell line

Lysophospholipids, particularly lysophosphatidylcholine (lyso-PC), have been implicated in modulating T cell functions at the sites of inflammation and atherosclerosis. Although the chemotactic and immunomodulatory effects are well documented, the exact signaling pathway of lyso-PC action is poorly defined. In this work, we studied the earliest biochemical events in T cells triggered by lyso-PC. A marked and immediate tyrosine phosphorylation was induced in the leukemic T cell line, Jurkat. Phosphorylation of cellular substrates included src family kinase, p56(lck) and syk family kinase, ZAP70. The lyso-PC induced tyrosine phosphorylation was largely dependent on the presence of functional p56(lck). Tyrosine phosphorylation was followed by the elevation of intracellular Ca2+ concentration. The magnitude of the mobilization of the intracellular Ca2+ was similar in the absence of the p56(lck) activity in JCaM1.6 cells as in Jurkat cells, however, it was slightly but reproducibly delayed compared to that in the wild type cells. Inhibition of the Ser/Thr kinases and tyrosine kinases with staurosporine and genistein, respectively, decreased the rise in the intracellular Ca2+ content. Moreover, pertussis toxin completely blocked the Ca2+ signal supporting the role of the G-protein coupled LPC receptor in this event. (C) 2003 Elsevier B.V. All rights reserved.