Fluid shear stress activates proline-rich tyrosine kinase via reactive oxygen species-dependent pathway

Objective - Fluid shear stress (flow) modulates endothelial cell (EC) function via specific signal transduction events. Previously, we showed that flow-mediated tyrosine phosphorylation of p130 Crk-associated substrate (Cas) required calcium-dependent c-Src activation. Because flow increases reactive oxygen species (ROS) production in ECs and because H₂O₂ increases tyrosine phosphorylation of proline-rich tyrosine kinase (PYK2), we hypothesized that flow may activate PYK2 via ROS. Methods and Results - Exposure of bovine aortic ECs to flow stimulated PYK2 phosphorylation rapidly, with a peak at 2 minutes. The activation of PYK2 and phosphorylation of Cas induced by flow were inhibited by pretreatment with the antioxidant N-acetylcysteine. Flow-induced PYK2 phosphorylation was inhibited by BAPTA-AM, an intracellular calcium chelator. Bovine aortic ECs transfected with kinase-inactive PYK2 showed attenuated flow-stimulated Cas tyrosine phosphorylation. Although flow-induced Cas phosphorylation was inhibited by kinase-inactive Src, PYK2 activation induced by flow was not inhibited by overexpression of kinase-inactive Src. Conclusions - These results show a redox-sensitive pathway for flow-mediated activation of nonreceptor tyrosine kinase activity that requires ROS and intracellular calcium, but not Src kinase.