title: Heat activation of TRPM5 underlies thermal sensitivity of sweet taste.
abstract: 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 tastes. 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 cells. 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 degrees 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 channels. Moreover, we show that increasing temperature between 15 and 35 degrees 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 humans, 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 tastants.
authors.affiliation: Laboratorium voor Fysiologie, Campus Gasthuisberg, KU Leuven, B-3000 Leuven, Belgium. Karel.talavera@med.kuleuven.be
authors.forename: Karel
authors.initials: K
authors.lastname: Talavera
authors.forename: Keiko
authors.initials: K
authors.lastname: Yasumatsu
authors.forename: Thomas
authors.initials: T
authors.lastname: Voets
authors.forename: Guy
authors.initials: G
authors.lastname: Droogmans
authors.forename: Noriatsu
authors.initials: N
authors.lastname: Shigemura
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Ninomiya
authors.forename: Robert F
authors.initials: RF
authors.lastname: Margolskee
authors.forename: Bernd
authors.initials: B
authors.lastname: Nilius
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D017353:Gene Deletion; D006358:Hot Temperature; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques; D013549:Sweetening Agents / Q000494:pharmacology*; D050053:TRPM Cation Channels / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000378:metabolism; D013649:Taste / Q000187:drug effects* / Q000502:physiology*; D013816:Thermodynamics
chemical_list: D013549:Sweetening Agents; D050053:TRPM Cation Channels; C476766:TRPM4 protein, mouse; C492297:TRPM8 protein, mouse; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C498617:Trpm5 protein, mouse; D002118:Calcium