小橋 昭彦 2005年12月20日

Heat activation of TRPM5 underlies thermal sensitivity of sweet taste : Nature
TRPM5, a cation channel of the TRP superfamily, is highly expressed in taste buds of the tongue, where it has a key role in the perception of sweet, umami and bitter tastes1, 2. Activation of TRPM5 occurs downstream of the activation of G-protein-coupled taste receptors and is proposed to generate a depolarizing potential in the taste receptor cells2. Factors that modulate TRPM5 activity are therefore expected to influence taste. Here we show that TRPM5 is a highly temperature-sensitive, heat-activated channel: inward TRPM5 currents increase steeply at temperatures between 15 and 35 ?C. TRPM4, a close homologue of TRPM5, shows similar temperature sensitivity. Heat activation is due to a temperature-dependent shift of the activation curve, in analogy to other thermosensitive TRP channels3. Moreover, we show that increasing temperature between 15 and 35 ?C markedly enhances the gustatory nerve response to sweet compounds in wild-type but not in Trpm5 knockout mice. The strong temperature sensitivity of TRPM5 may underlie known effects of temperature on perceived taste in humans4, 5, 6, including enhanced sweetness perception at high temperatures and ‘thermal taste’, the phenomenon whereby heating or cooling of the tongue evoke sensations of taste in the absence of tastants7
九州大の二ノ宮裕三教授ら。

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