PLD2 complexes with the EGF receptor and undergoes tyrosine phosphorylation at a single site upon agonist stimulation

Mammalian phospholipase D (PLD) activity becomes upregulated when cells are stimulated by a variety of hormones, growth factors, and other extracellul ar signals. Two distinct PLDs, PLD1 and PLD2, have been identified. The mec hanism through which each PLD is activated, however, is poorly understood. Using transiently transfected human embryonic kidney fibroblasts (HEK293), we demonstrate here that PLD1 activity, and to a lesser extent PLD2 activit y, is stimulated in response to epidermal growth factor (EGF), PLD2, but no t PLD1, associates with the EGF receptor in a ligand-independent manner and becomes tyrosine-phosphorylated upon EGF receptor activation. Tyrosine 11 (Tyr-11) of PLD2 was identified as the specific phosphorylation site. Mutat ion of this residue to phenylalanine enhanced basal activity almost a-fold, but did not alter the magnitude of the EGF-mediated increase in PLD2 activ ity. In conclusion, we show here for the first time agonist-stimulated acti vation of both PLD1 and PLD2 in vivo and provide evidence of a distinct typ e of interaction for each iso form with the EGF receptor, Moreover, our res ults suggest that agonist-induced tyrosine phosphorylation plays a role in PLD2 regulation.