Modulation of Rho GTPase activity in endothelial cells by selective proteinase-activated receptor (PAR) agonists

J Thromb Haemost. 2003 May;1(5):1103-11. doi: 10.1046/j.1538-7836.2003.00238.x.


The proteinase-activated receptors (PAR) PAR1 and PAR2 mediate responses to thrombin and trypsin-like proteases, respectively. Both receptors are expressed on endothelial cells where they have been reported to transduce a similar set of intracellular responses. In cultured human umbilical vein endothelial cells (HUVEC), we observed a marked difference in shape changes induced by PAR-activating peptides (PAR-APs); unlike PAR1-AP, PAR2-AP failed to stimulate cell rounding. Objectives were to shed light on the mechanisms underlying PAR-mediated cytoskeletal responses. We examined the activation of the Rho family GTPases in HUVEC using highly selective PAR1- and PAR2-APs to do this. Both peptides induced a robust and transient activation of RhoA, with the time course of activation being more sustained for the PAR1-AP. Interestingly, divergent effects on Rac activity were observed. Addition of PAR1-AP inhibited basal Rac activity as well as the phosphorylation of the Rac effector, p21-activated kinase (PAK). In contrast, PAR2-AP induced a modest activation of Rac, phosphorylation of PAK and translocation of cortactin from the cytosol to membrane ruffles, a Rac-dependent event. In vivo, only PAR1-AP rapidly enhanced vascular permeability in a mouse skin assay. We conclude that the differential regulation of the Rac/PAK pathway by PAR1 and PAR2 agonists in endothelial cells points toward distinct roles for these receptors in the control of vascular permeability and blood vessel remodeling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Capillary Permeability / drug effects
  • Endothelium, Vascular / cytology*
  • Endothelium, Vascular / metabolism
  • Mice
  • Oligopeptides / pharmacology
  • Phosphorylation / drug effects
  • Protein-Serine-Threonine Kinases / metabolism
  • Receptor, PAR-1 / agonists*
  • Receptor, PAR-2 / agonists
  • Skin / blood supply
  • p21-Activated Kinases
  • rho GTP-Binding Proteins / metabolism*
  • rhoA GTP-Binding Protein / drug effects
  • rhoA GTP-Binding Protein / metabolism


  • Oligopeptides
  • PAR-1-activating peptide
  • Receptor, PAR-1
  • Receptor, PAR-2
  • Protein-Serine-Threonine Kinases
  • p21-Activated Kinases
  • rho GTP-Binding Proteins
  • rhoA GTP-Binding Protein