Nanoluciferase-Based Complementation Assay to Detect GPCR-G Protein Interaction.

G protein-coupled receptors (GPCR) are one of the principal class of membrane proteins and around 30% of the currently marketed drugs act on one of them. The efficacious detection of ligands with the desired pharmacological profile remains a challenge of paramount importance in the GPCR drug discovery and pharmacological research. Recent evidences demonstrate that GPCR ligands can stabilize distinct receptor conformation and trigger various signaling pathways with different efficacies and/or potencies. This phenomenon called functional selectivity or biased signaling may lead to improved drugs with fewer side effects. Most receptors are promiscuous and can couple to more than one G protein family. To enable the discovery of biased ligands able to selectively trigger one G protein pathway over another, simple and efficient screening procedures are needed. The traditional assays aiming at detecting G protein activation monitor the generation of second messengers ([Ca], cAMP, IP) or active G proteins (with GTP-g-S for instance). While these approaches have proven sensitive and robust, they are not suited for the detection of a single GPCR-G protein interaction. Here, we present in detail a method to assess directly the interaction between the receptor and the G protein. It permits the profiling of a receptor or a ligand toward G protein interactions and is compatible with high-throughput screening.