Host: The Japanese Society of Toxicology
Name : The 50th Annual Meeting of the Japanese Society of Toxicology
Date : June 19, 2023 - June 21, 2023
In mammals, toxic compounds in diet are detected by bitter taste, an unpleasant sense. At the molecular level, bitter taste is mediated by bitter taste receptors expressed in the oral cavity especially on the papilla of tongue. Bitter taste receptors are encoded by TAS2R genes. For example, human has 26 TAS2R genes. They construct the different structures of a ligand-binding pocket; therefore, a broad range of toxic agonists is detectable in the oral cavity. The number of TAS2R genes are very variable among mammalian species. Many mammalian species have less than 20 TAS2R genes. Extremely whales have no TAS2R genes. In contrast, chimpanzee and koala has 28 and 24 TAS2R genes, respectively, which reflects their reliance on leaf eating habits in their arboreal life. 26 human TAS2R genes are also as a result of arboreal evolution in our primate ancestor. Primate species and koala also have a number of antitoxic factors such as CYP genes. What is the origin of bitter taste in mammals? Our distant cousin, platypus has only 7 TAS2R genes, but the conserved bitter taste receptors among all mammalian lineages are sensitive to glucosides such as cyanide compounds. Early mammals may be evolved in a strong selective pressure by the cyanide in their environments.
