Proteinase-activated receptors in the lower urinary tract

Proteinase-activated receptors (PARs) are G-protein-coupled receptors that convert specific extracellular proteolytic activity into intracellular signals, and have been suggested to play diverse roles in the body. In this review, evidence for the roles of PARs in bladder contractility and inflammation are presented. The role of PARs in prostate cancer is also reviewed. The existing literature in this area can be difficult to interpret due to the many nonspecific actions of the pharmacological tools employed. Although there are reports that PAR activators can cause contraction of bladder smooth muscle, further pharmacological and molecular studies are required to define roles for these receptors in bladder contractility. While structural studies suggest that roles for PARs in bladder inflammation are likely, few functional investigations have been performed. The significance of the expression of PARs on sensory nerves innervating the bladder and changes in receptor expression in inflammatory disease models are fascinating areas for future research. Finally, it seems probable that PARs, particularly PAR1, may play important roles in the growth and metastasis of prostate cancers.