The K+ channel KIR2.1 functions in tandem with proton influx to mediate sour taste transduction.
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.
['Ye|Wenlei|W|', 'Chang|Rui B|RB|', 'Bushman|Jeremy D|JD|', 'Tu|Yu-Hsiang|YH|', 'Mulhall|Eric M|EM|', 'Wilson|Courtney E|CE|', 'Cooper|Alexander J|AJ|', 'Chick|Wallace S|WS|', 'Hill-Eubanks|David C|DC|', 'Nelson|Mark T|MT|', 'Kinnamon|Sue C|SC|', 'Liman|Emily R|ER|']
D000143:Acids D000200:Action Potentials D000818:Animals D015220:Calcium Channels D057809:HEK293 Cells D006801:Humans D006863:Hydrogen-Ion Concentration D019426:Integrases D042541:Intracellular Space D015640:Ion Channel Gating D018345:Mice, Knockout D008954:Models, Biological D009928:Organ Specificity D024661:Potassium Channels, Inwardly Rectifying D011522:Protons D011956:Receptors, Cell Surface D015398:Signal Transduction D050053:TRPM Cation Channels D013649:Taste D013650:Taste Buds D015032:Zinc
taste cell gustatory inward rectifier potassium channel proton channel