FVIIa cleavage of PAR1 on HUVECs is dependent on EPCR. (A) HUVECs were treated with varying concentrations of FVIIa in the absence (●) or presence of polyclonal anti-EPCR antibody (50 μg/mL; ■) or APCi (1μM; ▴) for 1 hour. (B) HUVECs transfected with control scrambled siRNA (200nM, dark bar) or EPCR siRNA (200nM, gray bar) were treated with FVIIa (10nM) for 1 hour. Residual uncleaved intact PAR1 was measured in a cell-surface ELISA using ATAP2 (n = 3).