IP3 receptor type 3 and PLCβ2 are co-expressed with taste receptors T1R and T2R in rat taste bud cells

The Ca2+ signaling cascade has been reported to be activated by many tastants in vertebrate taste systems. Recently we have shown that G(i2) and phospholipase C beta2 (PLC beta2) are co-expressed in a subset of taste bud cells and are possibly involved in Ca2+ triggering of taste signaling in rats. We report here that, as a component downstream of PLC beta2, the type 3 isoform of the inositol 1,4,5-trisphosphate (IP3) receptor (IP(3)R3) is specifically expressed in the same cells as PLC beta2 in rat taste buds. We also show that cells expressing rT2R9, a probable cycloheximide receptor, are included among PLC beta2- and IP(3)R3-positive cells, as in the case of rT1R2, a different type of taste receptor. Our findings indicate that PLC beta2 and IP(3)R3 co-localize together with G(i2) as downstream components of two different types of taste receptors, T1R and T2R, in taste bud cells.