Sour Taste Responses in Mice Lacking PKD Channels

Nao Horio,Keiko Yasumatsu,Hiroaki Matsunami,Yuzo Ninomiya,Yuchio Yanagawa,Ryusuke Yoshida,Yoshiro Ishimaru,Wolfgang Meyerhof

doi:10.1371/journal.pone.0020007

Abstract

BackgroundThe polycystic kidney disease-like ion channel PKD2L1 and its associated partner PKD1L3 are potential candidates for sour taste receptors. PKD2L1 is expressed in type III taste cells that respond to sour stimuli and genetic elimination of cells expressing PKD2L1 substantially reduces chorda tympani nerve responses to sour taste stimuli. However, the contribution of PKD2L1 and PKD1L3 to sour taste responses remains unclear.Methodology/Principal FindingsWe made mice lacking PKD2L1 and/or PKD1L3 gene and investigated whole nerve responses to taste stimuli in the chorda tympani or the glossopharyngeal nerve and taste responses in type III taste cells. In mice lacking PKD2L1 gene, chorda tympani nerve responses to sour, but not sweet, salty, bitter, and umami tastants were reduced by 25–45% compared with those in wild type mice. In contrast, chorda tympani nerve responses in PKD1L3 knock-out mice and glossopharyngeal nerve responses in single- and double-knock-out mice were similar to those in wild type mice. Sour taste responses of type III fungiform taste cells (GAD67-expressing taste cells) were also reduced by 25–45% by elimination of PKD2L1.Conclusions/SignificanceThese findings suggest that PKD2L1 partly contributes to sour taste responses in mice and that receptors other than PKDs would be involved in sour detection.

Highlights

Sour taste serves to detect acids in foods and drinks to deter the animals from ingesting spoiled and unripe food sources [1]
PKD2L1 is expressed both in the fungiform papillae (FP) on the anterior part of the tongue and in the circumvallate papillae (CV) on the posterior part of the tongue, expression of PKD1L3 was only observed in the CV [7,8], indicating that PKD1L3 may not function in the anterior tongue
Previous studies using in situ hybridization demonstrated that PKD2L1 expression was observed in both FP and CV, whereas PKD1L3 expression was detected in the CV but not in the FP [7,8]

Summary

Introduction

Sour taste serves to detect acids in foods and drinks to deter the animals from ingesting spoiled and unripe food sources [1]. Though many candidate sour taste receptors have been implicated in detection, such as acid sensing ion channels (ASICs; [2]), hyperpolarization activated cyclic nucleotide gated potassium channels (HCNs; [3]), potassium channels [4,5], NPPB sensitive Cl2 channels [6], and polycystic kidney disease 1L3 and 2L1 heteromers (PKD1L3+PKD2L1, [7,8]), none of them has a demonstrated role in sour taste sensation in loss of function animals. PKD2L1 is a potential candidate because genetic elimination of cells expressing PKD2L1 substantially reduces gustatory nerve responses to sour taste stimuli [8]. The polycystic kidney disease-like ion channel PKD2L1 and its associated partner PKD1L3 are potential candidates for sour taste receptors. The contribution of PKD2L1 and PKD1L3 to sour taste responses remains unclear

Methods

Results

Conclusion