title: Identification and functional characterization of a voltage-gated chloride channel and its novel splice variant in taste bud cells.
abstract: Taste bud cells are epithelial cells with neuronal properties. Voltage-dependent ion channels have been physiologically described in these cells. Here, we report the molecular identification and functional characterization of a voltage-gated chloride channel (ClC-4) and its novel splice variant (ClC-4A) from taste bud cells. ClC-4A skipped an exon near its 5'-end, incurring the loss of 60 amino acids at the N terminus. In situ hybridization and immunohistochemistry localized these two channels' transcripts and proteins to a subset of taste bud cells. Electrophysiological recordings of the heterologously expressed channels in Xenopus oocytes showed that ClC-4 and ClC-4A have opposite sensitivity to pH and unique ion selectivity. The chloride channel blockers niflumic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid had a slight or no inhibitory effect on the conductance of ClC-4, but both blockers inhibited ClC-4A, suggesting that ClC-4A is a candidate channel for an acid-induced 5-nitro-2-(3-phenylpropylamino)benzoic acid-sensitive current. Furthermore, these two channels may play a role in bitter-, sweet-, and umami-mediated taste transmission by regulating transmitter uptake into synaptic vesicles.
authors.affiliation: Monell Chemical Senses Center, Philadelphia, Pennsylvania 19104-3308, USA. lhuang@monell.org
authors.forename: Liquan
authors.initials: L
authors.lastname: Huang
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.forename: Lynn A
authors.initials: LA
authors.lastname: Vo
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Brand
mesh_terms: D017398:Alternative Splicing; D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D018118:Chloride Channels / Q000235:genetics* / Q000502:physiology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004594:Electrophysiology; D005091:Exons; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007477:Ions; D051379:Mice; D008969:Molecular Sequence Data; D009544:Niflumic Acid / Q000378:metabolism / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D009693:Nucleic Acid Hybridization; D009865:Oocytes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D013572:Synaptic Vesicles / Q000378:metabolism; D013650:Taste Buds / Q000473:pathology*; D014981:Xenopus
chemical_list: D020533:Angiogenesis Inhibitors; C097503:CLC-5 chloride channel; C496604:CLCA4 protein, human; D018118:Chloride Channels; D016861:Cyclooxygenase Inhibitors; D018076:DNA, Complementary; D007477:Ions; D009579:Nitrobenzoates; D012333:RNA, Messenger; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D009544:Niflumic Acid