Csk binds tyrosine phosphorylated JAM-A through its SH2 domain. (A) Representative anti-Csk immunoblots of proteins immunoprecipitated with anti–JAM-A or control IgG1 from lysates of Dami cells transfected with mock or JAM-A–WT or JAM-A–Y²⁸⁰F constructs. (B) Quantitation of normalized optical density of “A” from 3 independent experiments (P = .01). (C) Representative anti-α_IIb immunoblots of proteins immunoprecipitated with anti–JAM-A or control IgG1 from lysates of Dami cells transfected with mock or JAM-A–WT or JAM-A–Y²⁸⁰F constructs. In (A,C), blots were reprobed with anti–JAM-A to ensure equal loading. (D) Quantitation of normalized optical density of “C” from 3 independent experiments (P = .03). (E) Representative anti–JAM-A immunoblots of GST-SH2-Csk pull-down proteins from lysates of resting or AYPGKY (100 μM) activated human platelets. (F) Quantitation of normalized optical density of “E” from 3 independent experiments (P = .02). (G) Representative anti–JAM-A immunoblots of GST-SH2-Csk pull-down proteins from lysates of human platelets exposed to immobilized BSA or Fg for 60 minutes. In (E and G), blots were reprobed with anti-GST to ensure equal loading. (H) Quantitation of normalized optical density of “G” from 3 independent experiments (P = .05).