Concanavalin A modulates tyrosine phosphorylation and activation of a typeII phosphatidylinositol 4-kinase in rat splenic lymphocytes

Activation of rat splenic lymphocytes by concanavalin A resulted in two-fol d increase in PtdIns 4-kinase activity and rapid tyrosine phosphorylation o f the enzyme. The activation kinetics showed a strong correlation with tyro sine phosphorylation state of the enzyme. Characterization of the enzyme ac tivity suggests that it is a type II PtdIns 4-kinase. Kinetic analysis of t he enzyme reaction showed three-fold decrease in K-m for PtdIns and two-fol d increase in V-max in Con A stimulated cells. These results suggest that a type II PtdIns 4-kinase is an integral component of the early signal trans duction machinery during T-cell activation by concanavalin A and is activel y regulated by protein tyrosine phosphorylation-dephosphorylation. (C) 1998 Elsevier Science Ltd. All rights reserved.