Characterization of umami receptor and coupling G protein in mouse taste cells

Taste receptor cells (TRCs) express multiple umami receptors. We performed physiological investigations to determine whether umami-responding cells in taste buds possess G protein-coupled receptors and to determine what type of G proteins exist if any. To clarify the components that participate in intracellular umami signal transduction in mouse, we recorded the activation of TRCs. TRCs treated with the G protein inhibitor GDP-β-S lost umami-induced inward currents. Treatment with the Gαi inhibitor, pertussis toxin, did not increase the intracellular Ca2+ level in many TRCs. Immunohistochemical analysis revealed that a subset of TRCs responding to umami stimuli expressed α-gustducin. Thus, we demonstrated that umami stimuli were received by G protein-coupled receptors that function together with some of the Gαi family members.