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Proc Natl Acad Sci U S A. 2016 Jan 12;113(2):E229-38. doi: 10.1073/pnas.1514282112. Epub 2015 Dec 1.

The K+ channel KIR2.1 functions in tandem with proton influx to mediate sour taste transduction.

Author information

1
Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089;
2
Department of Otolaryngology, University of Colorado Medical School, Aurora, CO 80045; Rocky Mountain Taste and Smell Center, University of Colorado Medical School, Aurora, CO 80045;
3
Department of Cell and Developmental Biology, University of Colorado Medical School, Aurora, CO 80045;
4
Department of Pharmacology, University of Vermont, Burlington, VT 05405;
5
Department of Pharmacology, University of Vermont, Burlington, VT 05405; Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9PT, United Kingdom.
6
Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089; liman@USC.edu.

Abstract

Sour taste is detected by a subset of taste cells on the tongue and palate epithelium that respond to acids with trains of action potentials. Entry of protons through a Zn(2+)-sensitive proton conductance that is specific to sour taste cells has been shown to be the initial event in sour taste transduction. Whether this conductance acts in concert with other channels sensitive to changes in intracellular pH, however, is not known. Here, we show that intracellular acidification generates excitatory responses in sour taste cells, which can be attributed to block of a resting K(+) current. We identify KIR2.1 as the acid-sensitive K(+) channel in sour taste cells using pharmacological and RNA expression profiling and confirm its contribution to sour taste with tissue-specific knockout of the Kcnj2 gene. Surprisingly, acid sensitivity is not conferred on sour taste cells by the specific expression of Kir2.1, but by the relatively small magnitude of the current, which makes the cells exquisitely sensitive to changes in intracellular pH. Consistent with a role of the K(+) current in amplifying the sensory response, entry of protons through the Zn(2+)-sensitive conductance produces a transient block of the KIR2.1 current. The identification in sour taste cells of an acid-sensitive K(+) channel suggests a mechanism for amplification of sour taste and may explain why weak acids that produce intracellular acidification, such as acetic acid, taste more sour than strong acids.

KEYWORDS:

gustatory; inward rectifier; potassium channel; proton channel; taste cell

Comment in

PMID:
26627720
PMCID:
PMC4720319
DOI:
10.1073/pnas.1514282112
[Indexed for MEDLINE]
Free PMC Article

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