The bitter truth about bitter taste receptors: beyond sensing bitter in the oral cavity

Abstract

The bitter taste receptor (TAS2R)-family of G-protein-coupled receptors has been identified on the tongue as detectors of bitter taste over a decade ago. In the last few years, they have been discovered in an ever growing number of extra-oral tissues, including the airways, the gut, the brain and even the testis. In tissues that contact the exterior, protective functions for TAS2Rs have been proposed, in analogy to their function on the tongue as toxicity detector. However, TAS2Rs have also been found in internal organs, suggesting other roles for these receptors, perhaps involving as yet unidentified endogenous ligands. The current review gives an overview of the different proposed functions for TAS2Rs in tissues other than the oral cavity; from appetite regulation to the treatment of asthma, regulation of gastrointestinal motility and control of airway innate immunity.

Anti-cancer stemness and anti-invasive activity of bitter taste receptors, TAS2R8 and TAS2R10, in human neuroblastoma cells

“…There are 25 types of bitter taste receptors in humans, and it has recently been discovered that they are expressed in tissues other than the tongue [67]. In the present study, the levels of TAS2R8 and TAS2R10 expression were distinct in different tissues, including liver, tongue, cerebellum, and hypothalamus tissues.…”

Taste buds: cells, signals and synapses

“…Instead, members of the large taste receptor type 2 (T2R) family, and the smaller T1R family, are found in several tissues and organs throughout the body 95, 193, 194 (see the table). The function of many of these extraoral taste GPCRs remains incompletely explored.…”

Obesity alters adrenergic and chemosensory signaling pathways that regulate ghrelin secretion in the human gut

“…After overnight culture, human fundic cells were fixed in 4% (w/v) paraformaldehyde for 30 min and underwent antigen retrieval by incubation in 10 mM sodium citrate solution (pH 6) for 30 min at 80°C, followed by preincubation with PBS containing 10% (v/v) donkey serum and 0.3% (v/v) Triton X-100 for 2 h. Afterward, samples were incubated overnight at 4°C with the following primary antibodies: rabbit anti-octanoyl ghrelin [1][2][3][4][5][6][7][8] (1:250; Ab5004, in-house developed), rabbit antia-transducin (1:100, sc-390; Santa Cruz Biotechnology, Dallas, TX, USA), rabbit anti-TAS2R10 (1:100, PA5-39708; Thermo Fisher Scientific), rabbit anti-TAS1R3 (1:100, OST00398W; Osenses, Keswick, Australia), rabbit anti-sodium-dependent glucose cotransporter (SGLT1; 1:50, ab14686; Abcam, Cambridge, MA, USA), rabbit anti-somatostatin (1:1000, A0566; Dako, Glostrup, Denmark), or goat anti-total ghrelin (1:250, sc-10368; Santa Cruz Biotechnology). After washing, samples were incubated with donkey anti-rabbit Cy5 (1:800) or donkey anti-goat Cy3 (1:800; Jackson Immunoresearch Laboratories, West Grove, PA, USA) for 2 h at room temperature.…”