title: Extracellular zinc ion regulates transient receptor potential melastatin 5 (TRPM5) channel activation through its interaction with a pore loop domain.
abstract: The transient receptor potential melastatin 5 (TRPM5) channel is a monovalent cation channel activated by intracellular Ca(2+). Expression of this channel is restricted to taste cells, the pancreas and brainstem, and is thought to be involved in controlling membrane potentials. Its endogenous ligands are not well characterized. Here, we show that extracellular application of Zn(2+) inhibits TRPM5 activity. In whole-cell patch-clamp recordings, extracellular application of ZnCl2 inhibited step-pulse-induced TRPM5 currents with 500 nM free intracellular Ca(2+) in a dose-dependent manner (IC50 = 4.3 μM at -80 mV). ZnSO4 also inhibited TRPM5 activity. Extracellular application of ZnCl2 inhibited TRPM5 activation at several temperatures. Furthermore, inhibition by 30 μM ZnCl2 was impaired in TRPM5 mutants in which His at 896, and Glu at 926 and/or Glu at 939 in the outer pore loop were replaced with Gln. From these results, we conclude that extracellular Zn(2+) inhibits TRPM5 channels, and the residues in the outer pore loop of TRPM5 are critically involved in the inhibition.
authors.affiliation: From the Division of Cell Signaling, National Institute for Physiological Sciences (Okazaki Institutes for Integrative Bioscience), National Institutes of Natural Sciences, Okazaki 444-8787, Japan and; the Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan. Electronic address: kuchida@nips.ac.jp.
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Uchida
authors.affiliation: From the Division of Cell Signaling, National Institute for Physiological Sciences (Okazaki Institutes for Integrative Bioscience), National Institutes of Natural Sciences, Okazaki 444-8787, Japan and; the Department of Physiological Sciences, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan. Electronic address: kuchida@nips.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Tominaga
mesh_terms: D019943:Amino Acid Substitution; D002413:Cations, Divalent / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects*; D009067:Mouthwashes / Q000494:pharmacology*; D020125:Mutation, Missense; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology; D017967:Zinc Compounds / Q000494:pharmacology*
chemical_list: D002413:Cations, Divalent; D002712:Chlorides; D009067:Mouthwashes; D050053:TRPM Cation Channels; C404409:TRPM5 protein, human; D017967:Zinc Compounds; C016837:zinc chloride; D015032:Zinc
keywords: Calcium; Ion Channels; Patch Clamp Electrophysiology; TRP Channels; Zinc