Designing biased ligands for Protease Activated Receptor 2

JY Suen, Y Jiang, MK Yau, J Lim, WM Kok, W Xu and DP Fairlie

Institute for Molecular Bioscience, The University of Queensland, St. Lucia, QLD, Australia

Protease Activated Receptor 2 (PAR2) has been implicated in inflammation, cancer and metabolic disorders. The receptor mediates communication between extracellular proteases and intracellular signaling pathways. Increasing numbers of proteases have been reported to activate PAR2 with different signaling profiles, suggesting different physiological portfolios. Such ‘biased’ signaling could bring benefits to the cell while modulating other disease-associated pathways. However, to date there has not been a systemic approach to understanding and developing biased ligands for this receptor. We have performed a structure-function relationship study on peptides related to the PAR2 tethered ligand, SLIGRL-NH2, with greatly improved functional potencies. We show here quantitative data for receptor binding, intracellular calcium mobilization and ERK1/2 phosphorylation for peptide agonists with single or double alanine substitutions, with the objective to understand key ligand-receptor interactions required for PAR2 biased signaling. Other chemical modifications were also explored with compounds showing single digit nM potencies. In summary, we have identified key residue crucial for agonist affinity, and a separate residue as key for dictating receptor biased signaling. We also report a few PAR2 agonists with pathway selective properties, and application of these ligands have demonstrated the importance of ERK1/2 in PAR2-induced migration, prevention of cell death and wound healing. These findings highlight the potential of potent, pathway-selective ligand of PAR2 in human diseases. Reference: Hollenberg et al. (2014) Br J Pharmacol 171:1180 Suen et al. (2014) Br J Pharmacol 171:4112 Funding: We thank the ARC and NHMRC for research funding.