GUSTDUCIN AND ITS ROLE IN TASTE

The mechanisms responsible for taste signal transductions are very com plex. A key molecule, alpha-gustducin, a primarily taste-specific G pr otein alpha-subunit, was discovered in 1992 and was later found to be involved in both bitter and sweet taste transduction. A proposed mecha nism for alpha-gustducin involves coupling specific cell-surface recep tors with a cyclic nucleotide phosphodiesterase which would open a cyc lic nucleotide-suppressible cation channel leading to influx of calciu m, and ultimately leading to release of neurotransmitter. Although ''k nock-out'' animals deficient in the alpha-gustducin gene clearly demon strate that gustducin is an essential molecule for tasting certain bit ter and sweet compounds, the precise role of alpha-gustducin in bitter and sweet taste is presently unclear. Indeed, there are several other signaling mechanisms in sweet and bitter taste, apparently unrelated to alpha-gustducin, that increase cyclic AMP or inositol 1,4,5 trispho sphate. Thus, proposed models for alpha-gustducin and those found by o ther laboratories may be parallel and interdependent.