Gustducin

Gustducin is a taste-cell-specific G protein closely related to the transducins 827... 

McLaughlin, S. K., McKinnon, P. J. and Margolskee, R. F. Gustducin is a taste-cell-specific G protein closely related to the transducins. Nature 357 563-569,1992. 

Huang, L. et al. Ggammal3 colocalizes with gustducin in taste receptor cells and mediates IP3 responses to bitter denatonium. Nat. Neurosci. 2 1055-1062,1999. 

He, W. et al. Umami taste responses are mediated by alpha-transducin and alpha-gustducin. /. Neurosci. 24 7674—7680, 2004. 

Wong, G. T. and Gannon K. S. (1996). Transduction ofbitter and sweet taste by gustducin. Nature 381,796-800. 

Perception of bitter taste can take place via G-proteins the a-subrmit of these G-proteins is know as gustducin and is highly homologous with transducin. The corresponding receptors are just beginning to be characterized (Hohn, 1999). A phosphodiesterase with specificity for cyclic nucleotides and a cyclic nucleotide-gated ion charmel... 

Sweet-tasting molecule (S) binds to sweet-taste receptor (SR), activating the G protein gustducin (Ggust). 

Gustducin a subunit activates adenylyl cyclase (AC) of the apical membrane, raising [cAMP]. 

An experimental difficulty lies in the fact that there are only a few thousand taste buds in the tongue, with only 50-100 cells in a bud. They age rapidly, having a lifespan of only about ten days.924 There may be only 30,000-50,000 hard-to-isolate taste receptor cells on the tongue s surface.923 However, very recently published reports describe a large family of bitter and sweet receptors in mice and humans924-928 and in Drosophila.929 930 The sweet-sour receptors are thought to activate a G protein called gustducin,931/932 which plays a role similar to that of transducin in vision and... 

There are some hundred different 7TM receptors involved in perception of bitter tastants. The bitter taste receptors also couple through the G protein gustducin yielding the activated Gag-GTP which can thence activate C.AMP/C.GMP phosphodiesterase, thus lowering cAMP and cGMP concentration. Bitter tastant receptors can also act via pertussis... 

Merigo F, Benati D, Tizzano M, Osculati F, Sbarbati A. alpha-Gustducin immunoreactivity in the airways. Cell Tissue Res. 2005 319 211-219. 

Zancanaro C, Caretta CM, Merigo F, Cavaggioni A, Osculati F. alpha-Gustducin expression in the vomeronasal organ of the mouse. Fur. J. Neurosci. 1999 11 4473-4475. 

Hofer D, Puschel B, Drenckhahn, D. Taste receptor-hke cells in the rat gut identified by expression of alpha-gustducin. Proc. Natl. Acad. Sci. U. S. A. 1996 93 6631-6634. 

Hofer D, Drenckhahn D. Identification of the taste cell G-protein, alpha-gustducin, in brush cells of the rat pancreatic duct system. Histochem. Cell. Biol. 1998 110 303-309. 

Fehr J, Meyer D, Widmayer P, Borth HC, Ackermann F, Wilhelm B, Gudermann T, Boekhoff I. Expression of the G-protein alpha-subunit gustducin in mammalian spermatozoa. J. Comp. Physiol. A Neuroethol. Sens Neural Behav. Physiol. 2007 193 21-34. 

Just as in olfaction, a number of clues pointed to the involvement of G proteins and, hence, 7TM receptors in the detection of bitter and sweet tastes. The evidence included the isolation of a specific G protein a subunit termed gustducin, which is expressed primarily in taste buds (Figure 32.13). How could the 7TM receptors be identified The ability to detect some compounds depends on specific genetic loci in both human beings and mice. For instance, the ability to taste the bitter compound 6- -propyl-2-thiouracil (PROP) was mapped to a region on human chromosome 5 by comparing DNA markers of persons who vary in sensitivity to this compound. 

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