A biased ligand for OXE-R uncouples G alpha and G beta gamma signaling within a heterotrimer

Differential targeting of heterotrimeric G protein versus beta-arrestin signaling are emerging concepts in G protein-coupled receptor (GPCR) research and drug discovery, and biased engagement by GPCR ligands of either beta-arrestin or G protein pathways has been disclosed. Herein we report on a new mechanism of ligand bias to titrate the signaling specificity of a cell-surface GPCR. Using a combination of biomolecular and virtual screening, we identified the small-molecule modulator Gue1654, which inhibits G beta gamma but not G alpha signaling triggered upon activation of G alpha(1)-beta gamma by the chemoattractant receptor OXE-R in both recombinant and human primary cells. Gue1654 does not interfere nonspecifically with signaling directly at or downstream of G beta gamma. This hitherto unappreciated mechanism of ligand bias at a GPCR highlights both a new paradigm for functional selectivity and a potentially new strategy to develop pathway-specific therapeutics.