ADP is not significantly involved in FcγRIIA-mediated protein tyrosine phosphorylation.

Platelets were preincubated in the absence or in the presence of A3P5PS, CP-CPK, and CP-CPK and 1 μmol/L epinephrine and stimulated by FcγRIIA cross-linking. The effect of 1-μmol/L epinephrine alone was also assessed. (A) Immunoblotting of platelet total protein extracts with the antiphosphotyrosine antibody 4G10. PLCγ2 (B), FcγRIIA (C), and LAT (D) were immunoprecipitated and submitted to immunoblotting with 4G10 antibody. As a loading control, the nitrocellulose membranes were stripped and reprobed with anti-PLCγ2 antibody and anti-LAT antibody (lower panels). (C) Immunoprecipitations performed with nonimmune serum as a control (C,D). Con, control. Data are representative of 3 to 4 independent experiments.