Interaction of JAM-A with the integrin α_IIbβ₃is dependent upon tyrosine phosphorylation of JAM-A. (A) Representative immunoblots of antiphosphotyrosine (4G10) of proteins immunoprecipitated with anti-α_IIb from lysates of resting- or thrombin-activated human platelets. Blots were reprobed with anti–JAM-A, and anti-α_IIb to ensure equal loading. (B) Quantitation of normalized optical density of “A” from 3 independent experiments (P = .004). (C) Representative 4G10 immunoblots of immunoprecipitated proteins with anti–JAM-A from lysates of human platelets exposed to immobilized Fg or BSA for 60 minutes. (D) Quantitation of normalized optical density of “C” from 3 independent experiments (P = .03).