Electrophysiological analysis of a novel acid sensing channel complex PKD1L3/PKD2L1

Abstract

Acid sensation is a critical cue to avoid spoiled foods or harmful solutions in animals. It has been reported that several ion channels activated by proton such as ASIC and HCN channels are involved in sour taste sensation. However, molecular mechanisms underlying sour taste sensation remain largely unclear. Here, we report a novel class of acid-activated ion channel complex PKD1L3/PKD2L1, as a candidate of sour taste receptor molecules. PKD1L3 and PKD2L1 are similar to members of polycistin family polycystin-1 and -2, whose defects are thought to cause autosomal dominant polycystic kidney diseases. TRP2L1 also belongs to transient receptor potential (TRP) channel family. In mouse tongue, PKD1L3 and PKD2L1 are co-expressed in a subset of taste receptor cells, which are distinct from taste cells having receptors for bitter, sweet, or umami tastants. 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 weak and strong acids (citric acid and HCl, respectively) in the PKD1L3/PKD2L1 expressed HEK293 cells. EC₅₀ is pH 2.9 for citric acid and pH 2.7 for HCl, respectively. These results suggest that PKD1L3/PKD2L1 may function as sour taste receptors. [J Physiol Sci. 2007;57 Suppl:S227]