Involvement of Tyrosine Phosphorylation in IgE Receptor-mediated Phospholipase D Activation in Rat Basophilic Leukemia (RBL-2H3) Cells

The effect of protein tyrosine phosphorylation on phospholipase D (PLD) activation measured by the formation of radiolabeled phosphatidylbutanol (PBut) was examined in rat basophilic leukemia (RBL-2H3) cells stimulated with antigen. The PLD activation elicited by antigen was attenuated dose-dependently by pretreatment with protein tyrosine kinase inhibitors, genistein and ST638. In parallel, tyrosine phosphorylation of 72 kDa protein was inhibited by the same pretreatment. These results, taken together with little effect of genistein on phosphoinositide hydrolysis, suggest that tyrosine kinase may be implicated in the IgE-mediated PLD activation which is regulated by a protein kinase C-independent process.