MPαC specifically inhibits VWF- and GPIb-IX-dependent platelet agglutination. (A,B) PRP was preincubated with myristoylated peptides MPαC, MαC, MPαCsc, or MαCsc, or vehicle (DMSO) together with 1 mM of the integrin inhibitor RGDS. Ristocetin (1.25 mg/mL) was added to induce GPIb-IX-specific platelet agglutination. Typical agglutination traces are shown in panel A, and quantitative data from 4 experiments are shown in panel B (mean ± SD). (C-E) PRP was preincubated with MPαC; MαC or MαCsc; or DMSO, then stimulated with ADP (C), collagen (D), or the thromboxane A2 analog, U46619 (E) to induce platelet aggregation.