Molecular mechanisms of taste reception and taste cell differentiation

Recently, there has been significant advance in understanding of the molecular mechanisms of taste reception. Taste receptors for sweet, umami and bitter have been cloned, and studies on the ligand specificity and functional domain of the receptor have been performed by Ca^<2+> imaging in HEK293 cells in the past few years. However, the cellular basis for taste perception still remains elusive Taste receptors are specifically expressed in the taste buds that are distributed on the tongue and soft palate. In mammals, taste buds are maintained under the continuous cell renewal and the life span of taste bud cell is estimated about 10 days. Taste buds are trophically supported by taste nerve, and denervation causes the disappearance of taste buds in about 10 days. We have investigated on the molecular basis for the taste bud maintenance and the taste cell differentiation. In the first part of this review, recent progress in understanding the taste receptor functions is described. In the second part, the molecular mechanisms of taste bud maintenance are discussed mainly based on our recent studies