title: The protease-activated receptor-2-specific agonists 2-aminothiazol-4-yl-LIGRL-NH2 and 6-aminonicotinyl-LIGRL-NH2 stimulate multiple signaling pathways to induce physiological responses in vitro and in vivo.
abstract: Protease-activated receptor-2 (PAR(2)) is one of four protease-activated G-protein-coupled receptors. PAR(2) is expressed on multiple cell types where it contributes to cellular responses to endogenous and exogenous proteases. Proteolytic cleavage of PAR(2) reveals a tethered ligand that activates PAR(2) and two major downstream signaling pathways: mitogen-activated protein kinase (MAPK) and intracellular Ca(2+) signaling. Peptides or peptidomimetics can mimic binding of the tethered ligand to stimulate signaling without the nonspecific effects of proteases. The most commonly used peptide activators of PAR(2) (e.g. SLIGRL-NH(2) and SLIGKV-NH(2)) lack potency at the receptor. However, although the potency of 2-furoyl-LIGRLO-NH(2) (2-f-LIGRLO-NH(2)) underscores the use of peptidomimetic PAR(2) ligands as a mechanism to enhance pharmacological action at PAR(2), 2-f-LIGRLO-NH(2) has not been thoroughly evaluated. We evaluated the known agonist 2-f-LIGRLO-NH(2) and two recently described pentapeptidomimetic PAR(2)-specific agonists, 2-aminothiazol-4-yl-LIGRL-NH(2) (2-at-LIGRL-NH(2)) and 6-aminonicotinyl-LIGRL-NH(2) (6-an-LIGRL-NH(2)). All peptidomimetic agonists stimulated PAR(2)-dependent in vitro physiological responses, MAPK signaling, and Ca(2+) signaling with an overall rank order of potency of 2-f-LIGRLO-NH(2) ≈ 2-at-LIGRL-NH(2) > 6-an-LIGRL-NH(2) ≫ SLIGRL-NH(2). Because PAR(2) plays a major role in pathological pain conditions and to test potency of the peptidomimetic agonists in vivo, we evaluated these agonists in models relevant to nociception. All three agonists activated Ca(2+) signaling in nociceptors in vitro, and both 2-at-LIGRL-NH(2) and 2-f-LIGRLO-NH(2) stimulated PAR(2)-dependent thermal hyperalgesia in vivo. We have characterized three high potency ligands that can be used to explore the physiological role of PAR(2) in a variety of systems and pathologies.
authors.affiliation: Department of Physiology, Bio5 Collaborative Research Institute, Arizona Respiratory Center, Arizona Health Sciences Center, Tucson, Arizona 85724, USA.
authors.forename: Andrea N
authors.initials: AN
authors.lastname: Flynn
authors.forename: Dipti V
authors.initials: DV
authors.lastname: Tillu
authors.forename: Marina N
authors.initials: MN
authors.lastname: Asiedu
authors.forename: Justin
authors.initials: J
authors.lastname: Hoffman
authors.forename: Josef
authors.initials: J
authors.lastname: Vagner
authors.forename: Theodore J
authors.initials: TJ
authors.lastname: Price
authors.forename: Scott
authors.initials: S
authors.lastname: Boitano
mesh_terms: D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects* / Q000235:genetics; D002461:Cell Line, Transformed; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D008024:Ligands; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000235:genetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D057786:Peptidomimetics / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D044464:Receptor, PAR-2 / Q000819:agonists* / Q000235:genetics / Q000378:metabolism
chemical_list: D008024:Ligands; D057786:Peptidomimetics; D044464:Receptor, PAR-2; D020929:Mitogen-Activated Protein Kinase Kinases; D002118:Calcium