TAS1R3

Taste receptor, type 1, member 3
Identifiers
Symbols TAS1R3 ; T1R3
External IDs OMIM: 605865 MGI: 1933547 HomoloGene: 12890 IUPHAR: 658 ChEMBL: 1613742 GeneCards: TAS1R3 Gene
Orthologs
Species Human Mouse
Entrez 83756 83771
Ensembl ENSG00000169962 ENSMUSG00000029072
UniProt Q7RTX0 Q925D8
RefSeq (mRNA) NM_152228 NM_031872
RefSeq (protein) NP_689414 NP_114078
Location (UCSC) Chr 1:
1.33 – 1.34 Mb		 Chr 4:
155.86 – 155.86 Mb
PubMed search

Taste receptor type 1 member 3 is a protein that in humans is encoded by the TAS1R3 gene.[1][2] The TAS1R3 gene encodes the human homolog of mouse Sac taste receptor, a major determinant of differences between sweet-sensitive and -insensitive mouse strains in their responsiveness to sucrose, saccharin, and other sweeteners.[2]

Structure

The protein encoded by the TAS1R3 gene is a G protein-coupled receptor with seven trans-membrane domains and is a component of the heterodimeric amino acid taste receptor TAS1R1+3 and sweet taste receptor TAS1R2+3. This receptor is formed as a protein dimer with either TAS1R1 or TAS1R2.[3] Experiments have also shown that a homo-dimer of TAS1R3 is also sensitive to natural sugar substances. This has been hypothesized as the mechanism by which sugar substitutes do not have the same taste qualities as natural sugars.[4]

Ligands

The G protein-coupled receptors for sweet and umami taste are formed by dimers of the TAS1R proteins. The TAS1R1+3 taste receptor is sensitive to the glutamate in MSG as well as the synergistic taste-enhancer molecules inosine monophosphate (IMP) and guanosine monophosphate (GMP). These taste-enhancer molecules are unable to activate the receptor alone, but are rather used to enhance receptor responses many to L-amino acids.[5] The TAS1R2+3 receptor has been shown to respond to natural sugars sucrose and fructose, and to artificial sweeteners saccharin, acesulfame potassium, dulcin, guanidinoacetic acid.[3]

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.[6] 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.[7] 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.[6]

Location and innervation

TAS1R1+3 expressing cells are found in fungiform papillae at the tip and edges of the tongue and palate taste receptor cells in the roof of the mouth.[3] These cells are shown to synapse upon the chorda tympani nerves to send their signals to the brain.[5] 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.[3] These cells are shown to synapse upon the glossopharyngeal nerves to send their signals to the brain.[8][9] TAS1R and TAS2R (bitter) channels are not expressed together in any taste buds.[3]

See also

References

  1. ↑ Montmayeur JP, Liberles SD, Matsunami H, Buck LB (Apr 2001). "A candidate taste receptor gene near a sweet taste locus". Nat Neurosci 4 (5): 492–8. doi:10.1038/87440. PMID 11319557.
  2. 1 2 "Entrez Gene: TAS1R3 taste receptor, type 1, member 3".
  3. 1 2 3 4 5 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.
  4. ↑ Zhao GQ, Zhang Y, Hoon MA, Chandrashekar J, Erlenbach I, Ryba NJ, Zuker CS (2003). "The receptors for mammalian sweet and umami taste". Cell 115 (3): 255–266. doi:10.1016/S0092-8674(03)00844-4. PMID 14636554.
  5. 1 2 Nelson G, Chandrashekar J, Hoon MA, Feng L, Zhao G, Ryba NJ, Zuker CS (2002). "An amino-acid taste receptor". Nature 416 (6877): 199–202. doi:10.1038/nature726. PMID 11894099.
  6. 1 2 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.
  7. ↑ 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.
  8. ↑ 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.
  9. ↑ 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

External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.

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