抄録
An acid-activated ion channel complex PKD1L3/PKD2L1 has been reported as a candidate of sour taste receptor molecules. In mouse tongue, PKD1L3 and PKD2L1 are co-expressed in a subset of taste receptor cells. PKD1L3 and PKD2L1 proteins can interact with each other, and co-expression of the PKD1L3 and PKD2L1 is necessary for their functional cell surface expression. Large currents are evoked by both citric acid and HCl in the PKD1L3/PKD2L1 expressed HEK293 cells. These results suggest that PKD1L3/PKD2L1 channel complex may function as sour taste receptors. Here, we report a unique property of PKD1L3/PKD2L1 channel complex, named as an off-response, which implies that the channel is activated upon the removal of acid stimulus. Acid-induced responses were observed only after the removal of an acidic solution with a pH lower than 3.0. A small increase in pH as low as 1.5 unit appears to be sufficient to activate the PKD1L3/PKD2L1 channels once exposed to the acidic solution with pH 2.5. These results indicate that the PKD1L3/PKD2L1 channel belongs to a novel type of ion channels, named as off-channels, activated by the removal of stimulus. The off-response property of PKD1L3/PKD2L1 channel may explain the physiological phenomena observed in sour taste sensation. [J Physiol Sci. 2008;58 Suppl:S79]
