Nitration of p190RhoGAP secondary to caveolae‐mediated endocytosis increases endothelial junctional permeability

Abstract

Depletion of caveolin‐1, which increases endothelial nitric oxide synthase (eNOS) activity, may influence the function of endothelial adherens junctions (AJs), thereby increases the junctional permeability. We showed that stimulation of caveolae‐mediated endocytosis increased the activity of eNOS (Miniatis et al., Circ Res. 2006; 99:870‐7). We now show that activation caveolae‐mediated endocytosis augments the increase in endothelial permeability in response to activation of protease activated receptor‐1 (PAR‐1) suggesting a relationship between signals emanating from caveolae and disruption of the junctional barrier. Following endocytosis, eNOS was translocated to AJs, resulting in augmented NO production after PAR‐1 activation. Thus, we addressed the possibility that protein nitration of p190RhoGAP (which constitutively associated with the AJ protein p120‐catenin) occurring secondary to the NO production p190RhoGAP nitration might interfere with the GAP activity, and hence RhoA activation. We observed nitration of p190RhoGAP that led to inhibition of its GAP activity resulting in sustained activation of RhoA. We conclude that signals initiated by caveolae internalization regulate junctional endothelial permeability by activating eNOS and through NO‐mediated inhibition of p190RhoGAP activity.