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This Article Full Text Full Text (PDF) Supplemental Figures All Versions of this Article: 102/3/1591    most recent 91301.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lyall, V. Articles by DeSimone, J. A. PubMed PubMed Citation Articles by Lyall, V. Articles by DeSimone, J. A.

Regulation of the Benzamil-Insensitive Salt Taste Receptor by Intracellular Ca²⁺, Protein Kinase C, and Calcineurin

Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia

Submitted 9 December 2008; accepted in final form 22 June 2009

Abstract

The regulation of the benzamil (Bz)-insensitive salt taste receptor was investigated by intracellular Ca²⁺ ([Ca²⁺]_i), protein kinase C (PKC), and the Ca²⁺-dependent serine-threonine phosphatase, calcineurin (PP2B), by monitoring chorda tympani taste nerve responses to 0.1 M NaCl solutions containing Bz (5 x 10^–6 M) and resiniferatoxin (RTX; 0–10 x 10^–6 M) in Sprague–Dawley rats and in wild-type (WT) and transient receptor potential vanilloid-1 knockout (TRPV1 KO) mice. In rats and WT mice, RTX increased the NaCl + Bz chorda tympani responses between 0.25 x 10^–6 and 1 x 10^–6 M and inhibited the responses above 1 x 10^–6 M. Decreasing taste receptor cell (TRC) [Ca²⁺]_i with BAPTA loading, activation of PKC with 4-phorbol-12,13-didecanoate (PMA), or inhibition of PP2B by cyclosporin A or FK-506, enhanced the magnitude of the Bz-insensitive NaCl chorda tympani responses in the presence of RTX and either minimized or completely eliminated the decrease in the chorda tympani response >1 x 10^–6 M RTX. In contrast, increasing TRC [Ca²⁺]_i with ionomycin inhibited Bz-insensitive NaCl chorda tympani responses in the presence of RTX. No effect of the cited modulators was observed on the chorda tympani responses in WT mice and rats in the presence of TRPV1 blocker SB-366791 (1 x 10^–6 M) or in TRPV1 KO mice. ³²P-labeling demonstrated direct phosphorylation of TRPV1 or TRPV1t in anterior lingual epithelium by PMA, cyclosporin A, or FK-506. PMA also enhanced the RTX-sensitive unilateral apical Na⁺ flux in polarized fungiform TRC in vitro. We conclude that TRPV1 or its variant TRPV1t is phosphorylated and dephosphorylated by PKC and PP2B, respectively, and either sensitizes or desensitizes the Bz-insensitive NaCl chorda tympani responses to RTX stimulation.