Alboaggregin-A and pvWF induce association of tyrosine phosphorylated FcR γ-chain with GST-Syk-SH2. Platelets were stimulated with either alboaggregin-A (3.5 μg/mL), pvWF (10 μg/mL), and ristocetin (1 mg/mL) or with collagen (100 μg/mL) for the indicated times, and proteins were precipitated from cell lysates using 10 μg of GST-Syk SH2 per lane. Precipitated proteins were separated by SDS-PAGE and immunoblotted with 4G10 [A(i) and B(i)] and anti-FcR γ-chain [A(ii) and B(ii)]. For (A), lane 1 is resting platelets and lanes 2 through 4 were stimulated with alboaggregin-A for the times indicated. For (B), lanes 1 and 7 were resting platelets, lanes 2 through 6 were stimulated with pvWF in the presence of ristocetin for the times indicated, and in lane 8, platelets were stimulated with collagen. Results shown are representative of at least 3 separate experiments.