In rat and mouse T2R/TRB receptors are expressed in15–
20% of TRCs in taste buds of the circumvallate and foliate
papillae and the palate but in very few TRCs in fungiform
papillae (1). Based onin situ hybridization with mixedversus
individual T2R/TRB probes it was concluded that most T2R/
TRB receptors are expressed in the same TRCs (1, 2). T2R/TRB
receptors are only found in TRCs positive for expression of
gustducin (a G protein implicated in bitter taste) (see Fig. 2)
(1).
One murine T2R/TRB receptor (mT2R5), when expressed in
heterologous cells, responded to bitter cycloheximide at a concentration comparable with the murine threshold for aversion
(6). mT2R5 was found to couple selectively to-gustducinversusother G protein-subunits. Taste responses were obtained
from only one other T2R/TRB-transfected cell; a human/mouse
orthologous pair, hT2R4/mT2R8, apparently encodes a receptor
responsive to denatonium and 6-n-propyl-2-thiouracil. However, the concentration of denatonium required to stimulate
this receptor was more than 3 orders of magnitude higher than
the human threshold for detection, suggesting that another
GPCR is likely to be the “denatonium” receptor.
G Proteins and Effector Enzymes—-Gust
đang được dịch, vui lòng đợi..
