Functional selectivity of G protein signaling by agonist peptides and thrombin for the protease-activated receptor-1

摘要: Thrombin activates protease-activated receptor-1 (PAR-1) by cleavage of the amino terminus to unmask a tethered ligand. Although peptide analogs can activate PAR-1, we show that functional responses mediated via PAR-1 differ between agonists. caused endothelial monolayer permeability and mobilized intracellular calcium with EC(50) values 0.1 1.7 nm, respectively. The opposite order activation was observed for agonist (SFLLRN-CONH(2) or TFLLRNKPDK) activation. addition inactivated thrombin did not affect signaling, suggesting differences in mechanisms are intramolecular origin. PAR-2 peptides induced mobilization, only affected barrier function. Induced is likely be Galpha(12/13)-mediated as chelation Galpha(q)-mediated BAPTA-AM, pertussis toxin inhibition Galpha(i/o), GM6001 matrix metalloproteinase had no effect, whereas Y-27632 Rho kinase abrogated response. Similarly, mobilization independent Galpha(i/o) Galpha(12/13) because U-73122 phospholipase C-beta blocked It therefore changes reflect activation, Galpha(q) implying pharmacological agonists ability receptor Galpha(q). This selectivity characterized quantitatively mathematical model describing each step leading and/or mobilization. provides an estimate alters receptor/G protein binding favor over approximately 800-fold.