G-Protein coupled receptors (GPCRs) are the largest group of small-molecule drug targets in the body. However, only 16%–20% of the 800 known GPCRs are currently targeted by approved therapeutics, creating a gap in disease treatments. Orphan GPCRs (oGPCRs), which lack known endogenous ligands and are poorly characterized, make up approximately 15% of GPCRs. Efforts to identify natural or synthetic small molecules or peptides to activate these oGPCRs present an intriguing therapeutic opportunity. Here, we develop a mammalian cell-based assay that detects changes in GPCR-G-protein interaction upon ligand binding using the NanoBiT protein-protein interaction system, allowing in-context evaluation of ligand effects. This platform was applied to four oGPCRs predominantly expressed in brain tissue: GPR26, GPR173, GPR171, and GPR83. We demonstrate that this bioluminescent assay offers advantages in cases of low affinity or where other coupling assays have shown limited success. We confirm recently identified ligands and discover novel G-protein coupling profiles that have not been previously reported. Additionally, the assay platform provides greater sensitivity and temporal resolution than traditional signaling assays and can be adapted for high-throughput drug screening.
Sonbati et al. (Sun,) studied this question.