Zyxin is involved in thrombin signaling via interaction with PAR‐1 receptor

Protease‐activated receptor 1 (PAR‐1) mediates thrombin signaling in human endothelial cells. As a G‐protein‐coupled receptor, PAR‐1 transmits thrombin signal through activation of the heterotrimeric G proteins, Gi, Gq, and G12/13. In this study, we demonstrated that zyxin, a LIM‐domain‐containing protein, is involved in thrombin‐mediated actin cytoskeleton remodeling and serum response element (SRE)‐ dependent gene transcription. We determined that zyxin binds to the C‐terminal domain of PAR‐1, providing a possible mechanism of involvement of zyxin as a signal transducer in PAR‐1 signaling. Data showing that disruption of PAR‐1‐zyxin interaction inhibited thrombin‐induced stress fiber formation and SRE activation supports this hypothesis. Similarly, depletion of zyxin using siRNA inhibited thrombin‐induced actin stress fiber formation and SRE‐dependent gene transcription. In addition, depletion of zyxin resulted in delay of endothelial barrier restoration after thrombin treatment. Notably, down‐regulation of zyxin did not affect thrombin‐induced activation of RhoA or Gi, Gq, and G12/13 heterotrimeric G proteins, implicating a novel signaling pathway regulated by PAR‐1 that is not mediated by G‐proteins. The observation that zyxin targets VASP, a partner of zyxin in regulation of actin assembly and dynamics, to focal adhesions and along stress fibers on thrombin stimulation suggests that zyxin may participate in thrombin‐induced cytoskeletal remodeling through recruitment of VASP. In summary, this study establishes a crucial role of zyxin in thrombin signaling in endothelial cells and provides evidence for a novel PAR‐1 signaling pathway mediated by zyxin.—Han, J., Liu, G., Profirovic, J., Niu. J., Voyno‐Yasenetskaya, T. Zyxin is involved in thrombin signaling via interaction with PAR‐1 receptor. FASEB J. 23, 4193‐4206 (2009). www.fasebj.org