title: A proton current associated with sour taste: distribution and functional properties.
abstract: Sour taste is detected by taste receptor cells that respond to acids through yet poorly understood mechanisms. The cells that detect sour express the protein PKD2L1, which is not the sour receptor but nonetheless serves as a useful marker for sour cells. By use of mice in which the PKD2L1 promoter drives expression of yellow fluorescent protein, we previously reported that sour taste cells from circumvallate papillae in the posterior tongue express a proton current. To establish a correlation between this current and sour transduction, we examined its distribution by patch-clamp recording. We find that the current is present in PKD2L1-expressing taste cells from mouse circumvallate, foliate, and fungiform papillae but not in a variety of other cells, including spinal cord neurons that express PKD2L1. We describe biophysical properties of the current, including pH-dependent Zn(2+) inhibition, lack of voltage-dependent gating, and activation at modest pH values (6.5) that elicit action potentials in isolated cells. Consistent with a channel that is constitutively open, the cytosol of sour taste cells is acidified. These data define a functional signature for the taste cell proton current and indicate that its expression is mostly restricted to the subset of taste cells that detect sour.
authors: Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA.
authors: Jeremy D
authors: JD
authors: Bushman
authors: Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA.
authors: Wenlei
authors: W
authors: Ye
authors: Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA liman@usc.edu.
authors: Emily R
authors: ER
authors: Liman
mesh_terms: D000200:Action Potentials; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D055592:Biophysical Phenomena; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic; D011522:Protons; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013649:Taste / Q000235:genetics / Q000502:physiology*; D013650:Taste Buds / Q000166:cytology* / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D015220:Calcium Channels; D008164:Luminescent Proteins; C117185:PKD2L1 protein, human; C486487:Pkd2l1 protein, mouse; D011522:Protons; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; C054562:yellow fluorescent protein, Bacteria
keywords: PKD2L1; acid; ion channel; pH; sensory transduction