Proteolytically activated receptor-3: A member of an emerging gene family of protease receptors expressed on vascular endothelial cells and platelets

Macromolecular assembly and generation of serine proteases on cellular surfaces is critically involved in regulation of hemostatic, inflammatory, or fibrinolytic pathways. The concept that a number of these serine proteases may effect cellular activation and proliferative responses has engendered an emerging paradigm focusing on the molecular mechanisms regulating cellular/protease interactions. Previous data suggest that some of these cellular responses are mediated by a novel class of G protein-coupled proteolytically activated receptors. Proteolytically activated receptor-3 (PAR-3) is the third member of this rapidly emerging gene family, all three of which (PAR-1, PAR-2, PAR-3) are known to co-cluster in the human genome, and are expressed on vascular endothelial cells, cells which critically regulate the hemostatic repertoire. This review will focus on the genetics of these receptors (emphasizing recent advances in the identification and characterization of PAR-3), review known structure/function similarities, and outline potential links in regulation of the hemostatic response by protease generation on the endothelial cell surface.