Presentation Details
| Gαq Protein-coupled Receptors and Store-operated Calcium Entry via Orai Channels Might Be Involved in the Lingering Perception of Astringency Alina U.Müller1, 2, Gaby Andersen2, Veronika Somoza2, 3. 1TUM School of Life Sciences Weihenstephan, Technical University of Munich, Freising, Germany.2Leibniz Institute for Food Systems Biology at the Technical University of Munich, Freising, Germany.3Physiological Chemistry at the Faculty of Chemistry, University of Vienna, Vienna, Austria |
Abstract
The mechanism behind the dry and lingering sensation, known as astringency, that occurs after consuming foods rich in polyphenols is not yet fully understood. Although various theories on how astringency might be perceived mechanistically have been proposed, it is still unclear whether, and if so, which GPCRs, and/or ion channels, are involved in astringency. Our hypothesis is that GPCRs coupled to Gαq are activated by astringent compounds to induce a Ca2+ mobilization and that store-operated calcium entry (SOCE) via Orai channels, inducing a longer-lasting Ca2+ influx, results in the lingering effect of astringency. To address this, we performed Ca2+ imaging experiments, using the puckering astringent compounds epigallocatechin gallate (EGCG) and tannic acid (TA), the velvety astringent rutin, and the non-astringent and bitter-tasting quinine in the human tongue cell line HSC-3, a widely used surrogate model for investigating astringency. By applying the Gαq inhibitor FR900359, the Ca2+-signal was reduced only for EGCG, TA, and rutin, but not for quinine. Furthermore, the lasting Ca2+-signal of EGCG and TA was blocked by the Orai channel inhibitor Synta66, whereas no reduction was detected for rutin and quinine, as confirmed by knock-down experiments. This indicates that SOCE might be involved in the puckering and lingering perception of astringency but not in the short-lasting and velvety astringency, as further evidenced by sensory studies showing that EGCG and TA are perceived more lingering than rutin (p <0.05) at perception thresholds. To summarize, these results provide evidence that astringency may be perceived through Gαq protein-coupled receptors and that the lingering effect can be attributed to the involvement of SOCE via Orai channels.
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