Ligand binding to G protein-coupled receptors (GPCRs) drives transitions between distinct conformational states, transducing extracellular chemical signals into intracellular responses. The specific conformations stabilized by a ligand determine both the nature and magnitude of the resulting pharmacological response. Notably, distinct pharmacological responses can emerge from chemically similar ligands acting on the same receptor, while similar responses can sometimes result from structurally diverse compounds. However, the precise molecular mechanisms governing how ligands produce varied activation profiles remain incompletely understood. To address this knowledge gap, we will conduct a residue-level investigation into ligand-dependent GPCR activation. We have generated a library of over 12,000 single-point mutants of the α2AAR receptor, and using deep mutational scanning (DMS), we will assess their responses with a cAMP signaling reporter assay to a series of analogues. This integrated chemicogenetic approach is designed to enable a comprehensive analysis of the broad spectrum of receptor activation, offering a deeper understanding of how chemical diversity modulates GPCR behavior. The successful completion of this work is expected to establish the molecular determinants governing how specific ligand-receptor interactions translate into distinct levels of activation, thereby advancing our understanding of the chemical principles underlying GPCR activation.
Shin et al. (Sun,) studied this question.