Trypsin activates pancreatic duct epithelial cell ion channels through proteinase-activated receptor-2

Proteinase-activated receptor-2 (PAR-2) is a G protein-coupled receptor tha t is cleaved by trypsin within the NH2-terminus, exposing a tethered ligand that binds and activates the receptor. We examined the secretory effects o f trypsin, mediated through PAR-2, on well-differentiated nontransformed do g pancreatic duct epithelial cells (PDEC). Trypsin and activating peptide ( AP or SLIGRL-NH2, corresponding to the PAR-2 tethered ligand) stimulated bo th an I-125(-) efflux inhibited by Ca2+-activated Cl- channel inhibitors an d a Rb-86(+) efflux inhibited by a Ca2+-activated Kt channel inhibitor. The reverse peptide (LRGILS-NH2) and inhibited trypsin were inactive. Thrombin had no effect, suggesting absence of PAR-1, PAR-3, or PAR-4. In Ussing cha mbers, trypsin and AP stimulated a short-circuit current from the basolater al, but not apical, surface of PDEC monolayers. In monolayers permeabilized basolaterally or apically with nystatin, AP activated apical Cl- and basol ateral K+ conductances. PAR-2 agonists increased [Ca2+](i) in PDEC, and the calcium chelator BAPTA inhibited the secretory effects of AP. PAR-2 expres sion on dog pancreatic ducts and PDEC was verified by immunofluorescence. T hus, trypsin interacts with basolateral PAR-2 to increase [Ca2+](i) and act ivate ion channels in PDEC. In pancreatitis, when trypsinogen is prematurel y activated, PAR-2-mediated ductal secretion may promote clearance of toxin s and debris.