Identification of a phospholipase C beta subtype in rat taste cells

From rat circumvallate papillae a novel phospholipase C (PLC) subtype has b een cloned and identified as most closely related to human PLC beta(2). The corresponding mRNA was only detected in sensory lingual tissue but not in non-taste lingual tissue or any other tissues examined by Northern blot ana lysis. In situ hybridization revealed that a subset of taste receptor cells of circumvallate papillae was specifically labeled. A functional involveme nt of this PLC beta subtype in taste signal transduction emerged from bioch emical analysis monitoring the second messenger response in circumvallate p reparations induced by denatonium benzoate. This bitter agent elicited a ra pid and transient increase of the inositol 1,4,5-trisphosphate level; this response was blocked by U73122, a potent inhibitor of PLC, and by PLC beta( 2)-specific antibodies. These data indicate that a phospholipase C beta(2) isoform mediates a denatonium benzoate-induced second messenger response of taste sensory cells in the circumvallate papillae.