Fig. 3.

NO-dependent inhibition of Rap1b activation is not impaired in VASP-null platelets. a Platelets (2 × 10⁸) from WT mice (left panel) or VASP KO mice (right panel) were pretreated for 2 min with SNP (1–5 μM) and then stimulated with thrombin (0.01 U/ml, 30s). Cells were lysed and the levels of Rap1b-GTP/total Rap1b were measured as described in the legend to Fig. 1. PKG-mediated phosphorylation of VASP at serine 235 (pS235-VASP) and levels of CalDAG-GEFI in whole lysates were measured using VASP phospho-specific or anti-CalDAG-GEFI Abs, respectively. The Western blots show the results of one representative experiment (out of three). b Quantification of the percent inhibition by SNP (1–5 μM) of thrombin-induced activation of Rap1b in both WT and VASP KO platelets. Please note that the blot in panel A (right) was more exposed than the blot in panel A (left)