Co-expression of calcium signaling components in vertebrate taste bud cells

In order to investigate the molecular mechanism of calcium signaling pathways common to the vertebrate gustatory systems, we have analyzed the expression of their molecular components. We first identified a phospholipase C (PLC) beta subtype expressed in the taste buds of pond leach (Misgurnus anguillicaudatus), designated DPLC beta S, which is closely related to mammalian PLC beta 2 shown recently to be expressed in rat taste buds. The taste bud-specific expression of PLC beta 2 in a fish species as well as rat strongly suggests that PLC beta 2 mediates the tastant-induced second messenger response in taste buds, which is common to vertebrates. Next, we examined the correlation of gene expression of the candidate components leading to PLC beta 2 activation in rat circumvallate papillae, including G proteins, G(12) and gustducin, and a G protein-coupled receptor, TR2. As a result, it was shown that the mRNAs for PLC beta 2 and G(12) co-exist in the same cells, and PLC beta 2- and G(12)-positive cells include both gustducin-positive cells and TR2-positive cells. However, no correlation was found between the expressions of TR2 and gustducin as reported previously. Our results thus indicate that a taste transduction pathway comprising TR2, G(12) and PLC beta 2 occurs in a subset of taste cells. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.