Novel Agonists and Antagonists for Human Protease Activated Receptor 2

Abstract

Human protease activated receptor 2 (PAR2) is a G protein-coupled receptor that is associated with inflammatory diseases and cancers. PAR2 is activated by serine proteases that cleave its N-terminus and by synthetic peptides corresponding to the new N-terminus. Peptide agonists are widely used to characterize physiological roles for PAR2 but typically have low potency (e.g., SLIGKV-NH2, SLIGRL-NH2), uncertain target selectivity, and poor bioavailability, limiting their usefulness for specifically interrogating PAR2 in vivo. Structure−activity relationships were used to derive new PAR2 agonists and antagonists containing nonpeptidic moieties. Agonist GB110 (19, EC50 0.28 μM) selectively induced PAR2-, but not PAR1-, mediated intracellular Ca2+ release in HT29 human colorectal carcinoma cells. Antagonist GB83 (36, IC50 2 μM) is the first compound at micromolar concentrations to reversibly inhibit PAR2 activation by both proteases and other PAR2 agonists (e.g., trypsin, 2f-furoyl-LIGRLO-NH2, 19). The new compounds are selective for PAR2 over PAR1, serum stable, and suitable for modulating PAR2 in disease models.

Proteinase-activated receptor 2 is involved in the behavioural changes associated with sickness behaviour

“…Several selective PAR-activating peptides have been developed to probe the distinct functions of each receptor, although evidence suggests diligence is required when using such agonists and their use for CNS investigations in vivo is limited due to poor bioavailability . To overcome these issues, novel non-peptidic agonists, including AC-264613 and GB110, with high potency and good stability have been developed (Gardell et al, 2008;Barry et al, 2010).…”

“…The "tethered-ligand" binds to the second extracellular loop . To overcome these issues, novel non-peptidic agonists, including AC-264613 and GB110, with high potency and good stability have been developed (Gardell et al, 2008;Barry et al, 2010).…”

Novel agonists & antagonists for protease-activated receptor 2 and C3a receptor

“…180 This peptide remains one of the most potent PAR2 agonists reported to date for cells (EC 50 0.2 μM), as measured by iCa 2+ mobilization. 171,180,181 It has also been reported that addition of a seventh residue, such as isoleucine (3), to the C-terminus of SLIGRL-NH 2 increased potency by ∼6-fold 182,183 and that replacing the sixth residue leucine with aromatic groups, such as tyrosine (4), 4-nitrophenylalanine (5), or 3,4-dichlorophenylalanine (6), increased potency further (Table 3). 182 Therefore, it was expected that substituting the sixth residue leucine of 2f-LIGRLI-NH 2 peptide (7) with a 4-nitrophenylalanine group (8) could also improve agonist potency.…”

“…171 From the furoyldipeptide, optimization of the second and third residues led to L-phenylalanine (13) or L-cyclohexylalanine (14) at position 2 and L-isoleucine at position 3 with the greatest PAR2 agonist potencies. However, compound 13 with Phe at position 2 was not selective for PAR2 over PAR1, whereas 14 did retain PAR2 selectivity.…”

“…171,187 Compounds 21 and 22 were novel PAR2 antagonists that shared an N-terminal structural component (5-isoxazoyl-Cha-Ile) with the PAR2 agonist 16, differing only in the C-terminal spiropiperidine. 171,187 It was concluded that the C-terminal fragment dictated ligand function. Unlike previously reported PAR2 antagonists, 22 was the first potent, nonpeptidic PAR2 antagonist that inhibited PAR2-induced iCa 2+ release by all known agonists, including synthetic peptides (SLIGKV-NH 2 , SLIGRL-NH 2 , 2f-LIGRLO-NH 2 ), nonpeptidic agonist (16), and endogenous agonists like trypsin and tryptase.…”