Bf. Tate et Se. Rittenhouse, THROMBIN ACTIVATION OF HUMAN PLATELETS CAUSES TYROSINE PHOSPHORYLATION OF PLC-GAMMA(2), Biochimica et biophysica acta, 1178(3), 1993, pp. 281-285
Human platelets contain phospholipase C (PLC)-gamma2, a distinct isofo
rm closely related to PLC-gamma1. Both inositol phospholipid-specific
phospholipases C contain the src-related SH2 regions. Stimulation of p
latelets with the potent agonist, thrombin, led to a rapid and transie
nt phosphorylation of PLC-gamma2 on tyrosine residues. Activated plate
lets lysed in the absence of sodium orthovanadate had levels of tyrosi
ne-phosphorylated PLC-gamma2 paralleling those seen in unstimulated pl
atelets. Previously, it had been shown that PLC-gamma1 was phosphoryla
ted on tyrosine residues by the agonist-occupied platelet-derived grow
th factor (PDGF) receptor and epidermal growth factor (EGF) receptor i
n cells other than platelets. In addition, more recent data have indic
ated that PLC-gamma2 is also capable of being tyrosine-phosphorylated
in cells of hematopoietic origin, such as B cells and natural killer (
NK) cells. Here we report that PLC-gamma2 expressed in a terminally-di
fferentiated hematopoietic cell is also tyrosine-phosphorylated in res
ponse to an agonist.