This is amino acids 1 to 6 fragment of the protease-activated receptor 3 (PAR-3). This synthetic peptide induces ERK activation in human carcinoma cells endogeneously expressing PAR-1 and PAR-3. This effect is completely abolished by single alanine substitution at positions 3, 4 and 6 in the peptide. PAR-3 allosterically regulates PAR-1 signaling by receptor dimerization governing increased endothelial permeability. Targeting of PAR-3 may mitigate the effects of PAR-1 in activating endothelial responses such as vascular inflammation. However this peptide does not affect VEGF release or expression.