Puckering astringent compounds target Gαq-coupled receptors and induce store-operated calcium entry via Orai channels in the human tongue cell line HSC-3

Astringency is a poorly understood rough sensation in the mouth often experienced in conjunction with bitterness. Despite various theories, the signaling pathways underlying astringency perception remain unclear. We hypothesize that Gα q -coupled GPCRs are involved in astringency, and store-operated calcium entry (SOCE) may contribute to the lingering perception of astringency by enhancing transient GPCR-mediated Ca 2+ signals via Ca 2+ influx. Using the human tongue cell line HSC-3 in Ca 2+ and cAMP assays (n = 3), we could demonstrate that (I) by applying the Gα q -specific antagonist FR900359, the astringent compounds epigallocatechin gallate (EGCG) (-104 ± 0.5%, p ≤ 0.0001), tannic acid (TA) (-100 ± 0.4%, p ≤ 0.0001), and rutin (-53 ± 4.0%, ≤ 0.001) but not the bitter compound quinine (+21 ± 10.0%, ns) activate Gα q -dependent signaling, and (II) the puckering and lingering astringent EGCG and TA involve SOCE, but not the velvety astringent rutin, suggesting a mechanistic basis for differences in astringent subqualities and their persistence as supported by a sensory study (n = 12 trained panelist). Additionally (III), we showed that the astringent compounds and the bitter quinine target Gα i -coupled GPCRs, like TAS2Rs, a result aligning with sensory studies, as most astringent compounds are perceived as bitter as well. However, the identity of the Gα q -coupled receptor(s) remains to be determined and represents an important focus for future investigations. • HSC-3 cells express GPCR effectors, TAS2Rs, TRP, and Orai channels on mRNA level • Astringent compounds target Gα q -coupled GPCRs (Ca 2+ ↑), but not bitter quinine • Puckering and lingering astringent EGCG and tannic acid involve SOCE via Orais • Velvety astringent rutin does not involve SOCE • Gα i -coupled GPCRs (cAMP↓) are activated by the astringent and bitter compounds