Activated protein C promotes endothelial barrier protection through biased PAR1 signaling mediated by β‐arrestin and dishevelled‐2 scaffolds

Abstract

Thrombin, a coagulant protease contributes to inflammatory responses associated with vascular injury and thrombosis. Activated protein C (APC), an anti‐coagulant protease reduces thrombin generation and promotes anti‐inflammatory signaling in endothelial cells. Thrombin and APC signal through the G‐protein coupled protease‐activated receptor1 (PAR1) but elicit opposite effects on endothelial barrier function. The mechanism of APC‐activated PAR1 signaling in endothelial barrier protection is poorly understood. In human endothelial cells, APC activates caveolar PAR1 populations to promote barrier protective responses independent of Gαi signaling. PAR1 is precoupled to β‐arrestins and co‐segregate in caveolin‐1 enriched fractions. APC‐activated PAR1 promotes β‐arrestin‐dependent recruitment and activation of dishevelled‐2 (Dvl‐2), a key mediator of the Wnt/Frizzled signaling pathways. Depletion of β‐arrestins or Dvl‐2 resulted in the loss of APC‐induced Rac1 activation and protection against thrombin‐activated endothelial barrier permeability but not thrombin‐induced RhoA signaling. These findings indicate that PAR1 utilizes β‐arrestins to promote biased signaling and unveils a distinct pathway where β‐arrestins and Dvl‐2 scaffolds promote APC effects on endothelial barrier protection. Funded by R01 HL073328, UC TRDRP 20FT‐0074.