Gα-gustducin is extensively coexpressed with sweet and bitter taste receptors in both the soft palate and fungiform papillae but has a different functional significance.
To clarify the regional differences in the expression and functional significance of Gα-gustducin in soft palate (SP) and fungiform (FF) taste buds, we examined the coexpression of Gα-gustducin with taste receptors and the impact of Gα-gustducin knockout (gKO) on neural responses to several sweet and bitter compounds. Sweet responses from both the greater superficial petrosal (GSP) and chorda tympani (CT) nerves in gKO mice were markedly depleted, reflecting overlapping expression of Gα-gustducin and Tas1r2. However, although Gα-gustducin was expressed in 87% and 88% of Tas2rs cells in the SP and FF, respectively, there were no statistically significant differences in the CT responses to quinine-HCl (QHCl) and denatonium (Den) between gKO and wild-type (WT) mice. In contrast, GSP responses to these compounds were markedly reduced in gKO mice with an apparent elevation of thresholds (>10-fold). These results suggest that 1) Gα-gustducin plays a critical role in sweet transduction in both the SP and the FF, 2) other Gα subunits coexpressed with Gα-gustducin in the FF are sufficient for responses to QHCl and Den, and 3) robust GSP responses to QHCl and Den occur in the SP by a Gα-gustducin-dependent mechanism, which is absent in the FF.
Department of Oral Physiology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima-shi, Kagoshima Japan.
Hiroshi
H
Tomonari
Hirohito
H
Miura
Ayumi
A
Nakayama
Eriko
E
Matsumura
Makoto
M
Ooki
Yuzo
Y
Ninomiya
Shuitsu
S
Harada
D000818:Animals; D002814:Chorda Tympani Nerve / Q000187:drug effects / Q000502:physiology; D005154:Facial Nerve / Q000187:drug effects / Q000502:physiology; D015870:Gene Expression; D008297:Male; D051379:Mice; D020320:Oligoribonucleotides, Antisense; D010160:Palate, Soft / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D050053:TRPM Cation Channels / Q000235:genetics / Q000378:metabolism; D013650:Taste Buds / Q000378:metabolism*; D013652:Taste Threshold; D015293:Transducin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D020320:Oligoribonucleotides, Antisense; D000644:Quaternary Ammonium Compounds; D011803:Quinine; D043562:Receptors, G-Protein-Coupled; D050053:TRPM Cation Channels; D015293:Transducin; C431926:taste receptors, type 1; C043414:denatonium; C075192:gustducin