Activation of platelets with thrombin increases GRK5 and PAR-1 binding in human platelets. (A) Resting human platelets or thrombin (1 U/mL)-activated platelets were prepared and lysed. Proteins were precipitated with an anti–PAR-1 (ATAP-2) antibody or control immunoglobulin (Ig) and then probed with anti-GRK5 antibody and reprobed with an anti–PAR-1 antibody (n = 6). (B) Lysates from resting or activated platelets were precipitated with an anti-GRK5 antibody or Ig and probed with anti–PAR-1 before reprobing with anti-GRK5 (n = 3). IB, immunoblotting; IP, immunoprecipitation; ns, not significant.