TMC4 is a novel chloride channel involved in high-concentration salt taste sensation

Taste substances are received by taste receptors expressed in taste cells. “Salty taste” sensation is evoked when sodium and chloride ions are present together in the oral cavity. The presence of an epithelial cation channel that receives Na+ has previously been reported. However, no molecular entity involving Cl- receptors has been elucidated. We report the strong expression of transmembrane channel-like 4 (TMC4) in the circumvallate and foliate papillae projected to the glossopharyngeal nerve, mediating a high-concentration of NaCl. Electrophysiological analysis using HEK293T cells revealed that TMC4 was a voltage-dependent Cl- channel and the consequent currents were completely inhibited by NPPB, an anion channel blocker. This channel could be activated without an increase in intracellular calcium ion. TMC4 allowed permeation of organic anions including gluconate, but their current amplitudes at positive potentials were less than that of Cl-. Tmc4-deficient mice showed significantly weaker glossopharyngeal nerve response to high-concentration of NaCl than the wild-type littermates. These results indicated that TMC4 is a novel chloride channel that responds to high-concentration of NaCl. Overall design: The number of RNA sequence trials was once per tissue. Total RNA was extracted from the circumvallate papillae or the epithelium without papillae of tongue using C57BL/6J mice (n = 20 or more) and pooled for each.