Sci. STKE, 4 November 2003
SENSORY PERCEPTION Mice with Engineered Sweet Tooth
Tastes are detected, at least in part, by receptors on the surface of cells in the taste buds of the tongue. A family of G protein-coupled receptors called T1Rs have been implicated in detecting sweetness and umami (a taste associated with amino acids, particularly monosodium glutamate in humans). Zhao et al. analyzed knockout mice lacking each of the three types of T1R receptors (T1R1, T1R2, or T1R3) to clarify several fundamental aspects of mammalian taste sensation. They monitored taste responses by recording action potentials in a nerve connected to taste receptor cells or by a behavioral test that monitored licking or intake preference. Umami taste was mediated by heteromeric receptors composed of T1R1 and T1R3, and loss of either receptor dramatically reduced physiological or behavioral responses to amino acids. Similarly, T1R2 and T1R3 were shown to combine to confer perception of sweet tastes. In fact, swapping a human T1R2 receptor into the mouse made the mice attracted to sweet-tasting compounds that are normally detected by humans but not rodents. Finally, the authors showed that when cells that express T1R2 were acutely induced to express a modified opioid receptor that generates signals like those of T1R2 but responds instead to a synthetic ligand, the mice now behaved as though the opioid ligand evoked a sweet taste. Thus taste sensation appears to result from hard-wired signaling from dedicated cells on the tongue rather than complicated integration of signals produced by receptors distributed in multiple taste cell types.
G. Q. Zhao, Y. Zhang, M. A. Hoon, J. Chandrashekar, I. Erlenbach, N. J. P. Ryba, C. S. Zuker, The receptors for mammalian sweet and umami taste. Cell 115, 255-266 (2003). [Online Journal]
Citation: Mice with Engineered Sweet Tooth. Sci. STKE 2003, tw426 (2003).
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