Taste receptor type 1 member 3is aproteinthat in humans is encoded by theTAS1R3gene.[5][6]TheTAS1R3gene encodes the human homolog of mouse Sactaste receptor,a major determinant of differences between sweet-sensitive and -insensitive mouse strains in their responsiveness to sucrose, saccharin, and other sweeteners.[6][7]
The protein encoded by theTAS1R3gene is aG protein-coupled receptorwith seven trans-membrane domains and is a component of the heterodimericamino acidtaste receptorTAS1R1+3 andsweettaste receptorTAS1R2+3. This receptor is formed as aprotein dimerwith eitherTAS1R1orTAS1R2.[8]
Experiments have also shown that a homo-dimer of TAS1R3 is also sensitive to naturalsugarsubstances. This has been hypothesized as the mechanism by whichsugar substitutesdo not have the same taste qualities as natural sugars.[9]
TAS1R2andTAS1R1receptors have been shown to bind toG proteins,most often thegustducin Gα subunit,although agustducinknock-outhas shown small residual activity. TAS1R2 and TAS1R1 have also been shown to activate Gαo and Gαi protein subunits.[11]This suggests that TAS1R1 and TAS1R2 areG protein-coupled receptorsthat inhibitadenylyl cyclasesto decreasecyclic guanosine monophosphate(cGMP) levels intaste receptors.[12]The TAS1R3 protein, however, has been shown in vitro to couple with Gα subunits at a much lower rate than the other TAS1R proteins. While the protein structures of the TAS1R proteins are similar, this experiment shows that the G protein-coupling properties of TAS1R3 may be less important in the transduction of taste signals than the TAS1R1 and TAS1R2 proteins.[11]
TAS1R1+3 expressing cells are found infungiform papillaeat the tip and edges of the tongue and palate taste receptor cells in the roof of the mouth.[8]These cells are shown to synapse upon thechorda tympaninerves to send their signals to the brain.[10]TAS1R2+3 expressing cells are found incircumvallate papillaeandfoliate papillaenear the back of the tongue and palate taste receptor cells in the roof of the mouth.[8]These cells are shown to synapse upon theglossopharyngeal nervesto send their signals to the brain.[13][14]TAS1R and TAS2R (bitter) channels are not expressed together in any taste buds.[8]
^abSainz E, Cavenagh MM, LopezJimenez ND, Gutierrez JC, Battey JF, Northup JK, Sullivan SL (2007). "The G-protein coupling properties of the human sweet and amino acid taste receptors".Developmental Neurobiology.67(7): 948–959.doi:10.1002/dneu.20403.PMID17506496.S2CID29736077.
^Abaffy T, Trubey KR, Chaudhari N (2003). "Adenylyl cyclase expression and modulation of cAMP in rat taste cells".American Journal of Physiology. Cell Physiology.284(6): C1420–C1428.doi:10.1152/ajpcell.00556.2002.PMID12606315.S2CID2704640.
Max M, Shanker YG, Huang L, Rong M, Liu Z, Campagne F, Weinstein H, Damak S, Margolskee RF (2001). "Tas1r3, encoding a new candidate taste receptor, is allelic to the sweet responsiveness locus Sac".Nat. Genet.28(1): 58–63.doi:10.1038/88270.PMID11326277.
Spadaccini R, Trabucco F, Saviano G, Picone D, Crescenzi O, Tancredi T, Temussi PA (2003). "The mechanism of interaction of sweet proteins with the T1R2-T1R3 receptor: evidence from the solution structure of G16A-MNEI".J. Mol. Biol.328(3): 683–92.doi:10.1016/S0022-2836(03)00346-2.PMID12706725.
Ariyasu T, Matsumoto S, Kyono F, Hanaya T, Arai S, Ikeda M, Kurimoto M (2004). "Taste receptor T1R3 is an essential molecule for the cellular recognition of the disaccharide trehalose".In Vitro Cell. Dev. Biol. Anim.39(1–2): 80–8.doi:10.1290/1543-706X(2003)039<0080:TRTIAE>2.0.CO;2.PMID12892531.S2CID13071416.
Koizumi A, Nakajima K, Asakura T, Morita Y, Ito K, Shmizu-Ibuka A, Misaka T, Abe K (2007). "Taste-modifying sweet protein, neoculin, is received at human T1R3 amino terminal domain".Biochem. Biophys. Res. Commun.358(2): 585–9.doi:10.1016/j.bbrc.2007.04.171.PMID17499612.
