Inhibiting a promiscuous GPCR: iterative discovery of bitter taste receptor ligands

Abstract

The human GPCR family comprises circa 800 members, activated by hundreds of thousands of compounds. Bitter taste receptors, TAS2Rs, constitute a large and distinct subfamily, expressed orally and extra-orally and involved in physiological and pathological conditions. TAS2R14 is the most promiscuous member, with over 150 agonists and 3 antagonists known prior to this study. Due to the scarcity of TAS2R14 inhibitors and to the importance of chemical probes for exploring TAS2R14 functions, we aimed to discover new ligands for TAS2R14, with emphasis on antagonists. To cope with the lack of experimental structure of the receptor, we used a mixed experimental/computational methodology which iteratively improved the performance of the predicted structure. The increasing number of active compounds, obtained through experimental screening of FDA-approved drug library, and through chemical synthesis of flufenamic acid derivatives, enabled the refinement of the binding pocket, which in turn improved the structure-based virtual screening reliability. This mixed approach led to the identification of 207 new agonists and 10 new antagonists of TAS2R14, illustrating the untapped potential of rigorous medicinal chemistry for TAS2Rs. The iterative framework suggested residues involved in the activation process, is suitable for expanding bitter and bitter-masking chemical space, and is applicable to other promiscuous GPCRs lacking experimental structures.

Machine Learning-based Modeling of Olfactory Receptors in their Inactive State: Human OR51E2 as a Case Study

“…In particular, the AF in and AF/OF structures have almost the same TM7 residues involved in the interhelical contacts (Y279 7.40 , I286 7.48 , I290 7.52 ), while for TM6 the only residue identified as interacting in both models is V246 6.43 . From a practical point of view, TM6 appears to be shifted by 1-2 residues in the structural alignment of the two models, similarly to what was observed in a recent work on another chemosensory receptor, TAS2R14, 32 when comparing two models built with AlphaFold and I-TASSER, respectively. 33…”

“…In particular, the AF in and OF structures have almost the same TM7 residues involved in the interhelical contacts (Y279 7.40 , I286 7.48 , I290 7.52 ), while for TM6 the only residue identified as interacting in both models is V246 6.43 . From a practical point of view, TM6 appears to be shifted by 1-2 residues in the structural alignment of the two models, similarly to what was observed in a recent work on another chemosensory receptor, TAS2R14, 32 when comparing two models built with AlphaFold and I-TASSER, respectively. 33 This observation exemplifies that, although the global differences between structures generated with different predictors might seem minimal, small local differences can still result in significant changes and thus misleading predictions regarding structure-function relationships.…”

Intracellular binding pocket revealed in the human bitter taste receptor TAS2R14

“…TAS2R14 is activated by a large array of chemically diverse ligands ( 4, 22, 33 ). FFA is among the most potent reported TAS2R14 agonists, and activates the receptor at micromolar concentrations ( Fig.…”

Lidocaine Induces Apoptosis in Head and Neck Squamous Cell Carcinoma Through Activation of Bitter Taste Receptor T2R14

“…6-MF did not alter Ca 2+ responses with denatonium benzoate, a non-T2R14 agonist (Fig 4E ). A recent preprint also identified several other structurally-distinct T2R14 inhibitors [58]. We purchased and tested two of these inhibitors, LF1 and LF22, and found that they both also blocked the Ca 2+ responses to both lidocaine and flufenamic acid (Fig 4F ).…”

“…Compounds were dissolved in DMSO at 500 mM and used at 1:1000 as indicated. Stock solutions were stored at -20° C [58].…”