Expression and functional activity of the bitter taste receptors TAS2R1 and TAS2R38 in human keratinocytes

Recent studies have shown that human bitter taste receptors (TAS2Rs) are not only expressed in mucous epithelial cells of the tongue but also in epithelial cells of the colon and stomach and upper respiratory tract [1]. These cell types come in close contact with external bitter compounds by ingestion or breathing. In the present work we addressed the question if bitter taste receptors might also be expressed in cornified epithelial cells of the skin. Here, we show for the first time the expression of TAS2R1 and TAS2R38 (the best characterized TAS2R) in human skin in situ. Double staining of the keratinocyte cell line HaCaT demonstrated the co-localization of TAS2R1 and TAS2R38 with the adaptor protein α-gustucin that is essential for signal transduction upon ligand binding. To test if TAS2Rs in the skin are functional we stimulated HaCaT cells with diphenidol, a clinically used bitter tasting antiemetic or amarogentin, the bitterest plant substance, that binds TAS2Rs, including TAS2R1 and TAS2R38. Diphenidol and amarogentin induced calcium influx. Furthermore, diphenidol and amarogentin stimulated in HaCaT cells the expression of the differentiation marker keratin 10, involucrin and transglutaminase. Therefore, apart from the known role in mucous membranes of the gastrointestinal tract, TAS2Rs are expressed in the epidermis and might play a role in keratinocyte differentiation.

Keywords: Bitter taste receptors, calcium influx, skin, amarogentin

References:

[1] Finger T E, Kinnamon S C. Taste isn't just for taste buds anymore. F1000 Biol Rep 2011: 3: 20.