Protease-activated Receptors in the Cardiovascular System

The coagulation protease thrombin regulates plateletaggregation and a host of responses in endothelial cellsand other cell types. How does thrombin, a protease, elicitcellular responses like a traditional hormone? Proteaseactivated receptors (PARs) provide an answer. PARs areG-protein-coupled receptors that have evolved a mechanism to convert an extracellular proteolytic event into atransmembrane signal. In essence, PARs are peptide receptors that carry their own ligands, which remain silentuntil activated by receptor cleavage. Overall, it appearsthat PARs, together with the coagulation cascade, serveto link tissue injury to appropriate cellular responses, butPARs also appear to serve important functions in othercontexts...