Effects of PKG and PKA inhibitors on glyco-SNAP1–induced phosphorylation of VASP at Ser²³⁹. Washed platelets were preincubated with (A) KT5823 (5-10 μM) or H89 (25-50 μM), (B) Rp-pCPT-cGMPS (0.2 mM) or PKI (50 μM) for 10 minutes. Platelets also were preincubated with buffer or DMSO as controls. Platelets were then treated with glyco-SNAP1 (1 μM) at 37°C in the platelet aggregometer for 5 minutes. VASP phosphorylation was then detected by immunoblotting as described in Figure 1. Data shown are representative of at least 3 independent experiments.