Tonic activity of Gα-gustducin regulates taste cell responsivity

The taste-selective G protein, α-gustducin (α-gus) is homologous to α-transducin and activates phosphodiesterase (PDE) in vitro. α-Gus-knockout mice are compromized to bitter, sweet and umami taste stimuli, suggesting a central role in taste transduction. Here, we suggest a different role for Gα-gus. In taste buds of α-gus-knockout mice, basal (unstimulated) cAMP levels are high compared to those of wild-type mice. Further, H-89, a cAMP-dependent protein kinase inhibitor, dramatically unmasks responses to the bitter tastant denatonium in gus-lineage cells of knockout mice. We propose that an important role of α-gus is to maintain cAMP levels tonically low to ensure adequate Ca2+ signaling.