Getting the message across: Pathophysiology and signaling via receptors for polypeptide hormones and proteinases

This article provides a personalized overview of the role of proteinases in generating hormone-like cell signals. Also outlined is the unexpected route of discovery that led one investigator over a four-decade time span, from early studies of the interactions of oxytocin and vasopressin with their neurophysin binding proteins to current studies of the tethered ligand activation mechanism that is unique for the G-protein-coupled family of proteinase-activated receptors (PARs). The focus is not only on the intriguing PAR receptor family, but also on alternative mechanisms whereby proteinases activate signal transduction pathways. Also summarized are the potential physiological and pathophysiological roles that PARs may play in the setting of inflammatory disorders ranging from arthritis to colitis. The therapeutic implications of considering PARs as drug targets are also discussed.