Structure-based virtual screening identifies potential endogenous ligands of the human bitter taste receptor TAS2R46

The sensing of bitter taste mediated by TAS2Rs serves as a defense mechanism against potentially harmful substances. The expression of TAS2Rs in extra-oral tissues, which are not directly exposed to the external environment, suggests the presence of endogenous ligands and points to TAS2Rs having novel roles as chemical sensors of the internal environment. Here, we performed structure-based screening to identify potential endogenous ligands of TAS2R46, whose structure has recently been determined. Our strategy combined ensemble docking of diverse conformations generated by molecular dynamics simulations of the TAS2R46-strychnine complex with machine learning-based integration of the docking results. This approach improved evaluation metrics compared with single-conformation docking. Screening compounds from the Human Metabolome Database identified nine steroid hormones (including their derivatives) as candidate ligands. Functional assays revealed that eight of these steroids-17-hydroxyprogesterone, testosterone, dihydrotestosterone, dehydroepiandrosterone, androstenedione, corticosterone, deoxycorticosterone, and cortexolone-activated TAS2R46, whereas estrone did not. Boltz-2-based predictions of TAS2R46-steroid complexes and mutational analysis revealed key residues that contribute to both stable steroid binding and subsequent receptor activation. Together, these findings provide new insights into the physiological roles of TAS2R46 in extra-oral tissues and its mechanism of activation, and they establish a broadly applicable framework for ligand prediction across G protein-coupled receptors, including taste receptors.