Fig. 5.

A model for taste transduction. Binding of taste stimuli to G protein-coupled taste receptors (R) leads to dissociation of the heterotrimeric G protein. βγ subunits of the G protein activate PLCβ2, which in turn hydrolyzes PIP₂ into DAG and IP₃. IP₃ activates IP₃ receptors, which release Ca²⁺ from intracellular stores. Intracellular Ca²⁺ opens TRPM5 channels, leading to an influx of Na⁺ and depolarization of the cell. Note that TRPM5 is not permeable to Ca²⁺ and, therefore, there is no positive feedback loop.