TAS1R2
Taste receptor type 1 member 2 is a protein that in humans is encoded by the TAS1R2 gene.[5]
The sweet taste receptor is predominantly formed as a dimer of T1R2 and T1R3 by which different organisms sense this taste. In songbirds, however, the T1R2 monomer does not exist, and they sense the sweet taste through the umami taste receptor (T1R1 and T1R3) as a result of an evolutionary change that it has undergone.[6]
Structure[]
The protein encoded by the TAS1R2 gene is a G protein-coupled receptor with seven trans-membrane domains and is a component of the heterodimeric amino acid taste receptor T1R2+3. This receptor is formed as a dimer of the TAS1R2 and TAS1R3 proteins. Moreover, the TAS1R2 protein is not functional without formation of the 2+3 heterodimer.[7] Another interesting quality of these receptors expressed by TAS1R2 and TAS1R1 genes, is their spontaneous activity in the absence of the extracellular domains and binding ligands.[8] This may mean that the extracellular domain regulates function of the receptor by preventing spontaneous action as well as binding to activating ligands such as sucrose.
Ligands[]
The TAS1R2+3 receptor has been shown to respond to natural sugars sucrose and fructose, and to the artificial sweeteners saccharin, acesulfame potassium, dulcin, and guanidinoacetic acid. Research initially suggested that rat receptors did not respond to many other natural and artificial sugars, such as glucose and aspartame, leading to the conclusion that there must be more than one type of sweet taste receptor.[7] Contradictory evidence, however, suggested that cells expressing the human TAS1R2+3 receptor showed sensitivity to both aspartame and glucose but cells expressing the rat TAS1R2+3 receptor were only slightly activated by glucose and showed no aspartame activation.[9] These results are inconclusive about the existence of another sweet taste receptor, but show that the TAS1R2+3 receptors are responsible for a wide variety of different sweet tastes.
Signal transduction[]
TAS1R2 and TAS1R1 receptors have been shown to bind to G proteins, most often the gustducin Gα subunit, although a gusducin knock-out has shown small residual activity. TAS1R2 and TAS1R1 have also been shown to activate Gαo and Gαi protein subunits.[8] This suggests that TAS1R1 and TAS1R2 are G protein-coupled receptors that inhibit adenylyl cyclases to decrease cyclic guanosine monophosphate (cGMP) levels in taste receptors.[10] Research done by creating knock-outs of common channels activated by sensory G-protein second messenger systems has also shown a connection between sweet taste perception and the phosphatidylinositol (PIP2) pathway. The nonselective cation Transient Receptor Potential channel TRPM5 has been shown to correlate with both umami and sweet taste. Also, the phospholipase PLCβ2 was shown to similarly correlate with umami and sweet taste. This suggests that activation of the G-protein pathway and subsequent activation of PLC β2 and the TRPM5 channel in these taste cells functions to activate the cell.[11]
Location and innervation[]
TAS1R2+3 expressing cells are found in circumvallate papillae and foliate papillae near the back of the tongue and palate taste receptor cells in the roof of the mouth.[7] These cells are shown to synapse upon the chorda tympani and glossopharyngeal nerves to send their signals to the brain.[12][13] TAS1R and TAS2R (bitter) channels are not expressed together in taste buds.[7]
See also[]
- Taste receptor
- TAS1R1
- TAS1R3
References[]
- ^ a b c GRCh38: Ensembl release 89: ENSG00000179002 - Ensembl, May 2017
- ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000028738 - Ensembl, May 2017
- ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
- ^ "Entrez Gene: TAS1R2 taste receptor, type 1, member 2".
- ^ Toda Y, Ko MC, Liang Q, Miller ET, Rico-Guevara A, Nakagita T, et al. (July 2021). "Early origin of sweet perception in the songbird radiation". Science. 373 (6551): 226–231. Bibcode:2021Sci...373..226T. doi:10.1126/science.abf6505. PMID 34244416. S2CID 235769720.
- ^ a b c d Nelson G, Hoon MA, Chandrashekar J, Zhang Y, Ryba NJ, Zuker CS (2001). "Mammalian sweet taste receptors". Cell. 106 (3): 381–390. doi:10.1016/S0092-8674(01)00451-2. PMID 11509186. S2CID 11886074.
- ^ a b Sainz 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. PMID 17506496. S2CID 29736077.
- ^ Li X, Staszewski L, Xu H, Durick K, Zoller M, Adler E (2002). "Human receptors for sweet and umami taste". Proceedings of the National Academy of Sciences. 99 (7): 4692–4696. Bibcode:2002PNAS...99.4692L. doi:10.1073/pnas.072090199. PMC 123709. PMID 11917125.
- ^ 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. PMID 12606315.
- ^ Zhang Y, Hoon MA, Chandrashekar J, Mueller KL, Cook B, Wu D, Zuker CS, Ryba NJ (2003). "Coding of sweet, bitter, and umami tastes: Different receptor cells sharing similar signaling pathways". Cell. 112 (3): 293–301. doi:10.1016/S0092-8674(03)00071-0. PMID 12581520. S2CID 718601.
- ^ Beamis JF, Shapshay SM, Setzer S, Dumon JF (1989). "Teaching models for Nd:YAG laser bronchoscopy". Chest. 95 (6): 1316–1318. doi:10.1378/chest.95.6.1316. PMID 2721271.
- ^ Danilova V, Hellekant G (2003). "Comparison of the responses of the chorda tympani and glossopharyngeal nerves to taste stimuli in C57BL/6J mice". BMC Neuroscience. 4: 5–6. doi:10.1186/1471-2202-4-5. PMC 153500. PMID 12617752.
Further reading[]
- Chandrashekar J, Hoon MA, Ryba NJ, Zuker CS (2007). "The receptors and cells for mammalian taste". Nature. 444 (7117): 288–94. doi:10.1038/nature05401. PMID 17108952. S2CID 4431221.
- Hoon MA, Adler E, Lindemeier J, Battey JF, Ryba NJ, Zuker CS (1999). "Putative mammalian taste receptors: a class of taste-specific GPCRs with distinct topographic selectivity". Cell. 96 (4): 541–51. doi:10.1016/S0092-8674(00)80658-3. PMID 10052456. S2CID 14773710.
- Li X, Staszewski L, Xu H, Durick K, Zoller M, Adler E (2002). "Human receptors for sweet and umami taste". Proc. Natl. Acad. Sci. U.S.A. 99 (7): 4692–6. Bibcode:2002PNAS...99.4692L. doi:10.1073/pnas.072090199. PMC 123709. PMID 11917125.
- 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. PMID 12706725.
- Liao J, Schultz PG (2003). "Three sweet receptor genes are clustered in human chromosome 1". Mamm. Genome. 14 (5): 291–301. doi:10.1007/s00335-002-2233-0. PMID 12856281. S2CID 30665284.
- Zhao GQ, Zhang Y, Hoon MA, Chandrashekar J, Erlenbach I, Ryba NJ, Zuker CS (2004). "The receptors for mammalian sweet and umami taste". Cell. 115 (3): 255–66. doi:10.1016/S0092-8674(03)00844-4. PMID 14636554. S2CID 11773362.
- Galindo-Cuspinera V, Winnig M, Bufe B, Meyerhof W, Breslin PA (2006). "A TAS1R receptor-based explanation of sweet 'water-taste'". Nature. 441 (7091): 354–7. Bibcode:2006Natur.441..354G. doi:10.1038/nature04765. PMID 16633339. S2CID 291228.
- Behrens M, Bartelt J, Reichling C, Winnig M, Kuhn C, Meyerhof W (2006). "Members of RTP and REEP gene families influence functional bitter taste receptor expression". J. Biol. Chem. 281 (29): 20650–9. doi:10.1074/jbc.M513637200. PMID 16720576.
External links[]
This article incorporates text from the United States National Library of Medicine, which is in the public domain.
- Genes on human chromosome 1
- Human taste receptors