Molecular interactions between glutathione and Umami taste receptor TAS1R1/TAS1R3

International audience

English. Glutathione (γ-L-glutamyl-L-cysteinyl-glycine, GSH) is known for its kokumi properties, able to confer mouthfullness, richness, complexity and intensity to umami, salty, and sweet taste perception. In addition to activating the calcium-sensing receptor, GSH has also been shown to activate the heterodimeric G-protein coupled receptor, TAS1R1/TAS1R3. The TAS1R1 and TAS1R3 subunits are characterized by a large extracellular N-terminal domain, composed of the Venus Fly Trap (VFT) domain followed by a cysteine-rich domain (CRD), which connects to the transmembrane domain (TMD).Previous studies combining molecular docking and site-directed mutagenesis studies combined to cellular assays have shown that L-Glutamate (L-Glu) and 5’-inosine monophosphate (IMP) interact within the VFT of TAS1R1. This stabilizes the closed state and drives the synergism between L-Glu and IMP.In this study we investigated the GSH binding site in the TAS1R1/TAS1R3 receptor and demonstrated its synergism with L-Glu. Using molecular docking, we identified key amino acid residues involved in GSH binding. We further validate the role of these amino acids on GSH-induced activation or synergism by performing cell-based functional assays using human HEK293T cells expressing point mutants of the TAS1R1/TAS1R3 receptor. Cellular responses were measured using a fluorescent protein calcium biosensor after cell stimulation with umami molecules using an automated fluorometric imaging plate reader. Our results demonstrate that GSH interacts at a binding site overlapping with those of L-Glu and IMP within the VFT of TAS1R1.