TAS1R2

Taste receptor, type 1, member 2
Identifiers
Symbols TAS1R2 ; GPR71; T1R2; TR2
External IDs OMIM: 606226 MGI: 1933546 HomoloGene: 75323 IUPHAR: 657 ChEMBL: 1613741 GeneCards: TAS1R2 Gene
RNA expression pattern
More reference expression data
Orthologs
Species Human Mouse
Entrez 80834 83770
Ensembl ENSG00000179002 ENSMUSG00000028738
UniProt Q8TE23 Q925I4
RefSeq (mRNA) NM_152232 NM_031873
RefSeq (protein) NP_689418 NP_114079
Location (UCSC) Chr 1:
18.84 – 18.86 Mb		 Chr 4:
139.65 – 139.67 Mb
PubMed search

Taste receptor type 1 member 2 is a protein that in humans is encoded by the TAS1R2 gene.[1]

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.[2] Another interesting quality of the TAS1R2 and TAS1R1 genes is their spontaneous activity in the absence of the extracellular domains and binding ligands.[3] 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.[2] 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.[4] 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.[3] 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.[5] 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 nonselecive 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.[6]

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.[2] These cells are shown to synapse upon the chorda tympani and glossopharyngeal nerves to send their signals to the brain.[7][8] TAS1R and TAS2R (bitter) channels are not expressed together in taste buds.[2]

See also

References

  1. ↑ "Entrez Gene: TAS1R2 taste receptor, type 1, member 2".
  2. 1 2 3 4 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.
  3. 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.
  4. ↑ 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. doi:10.1073/pnas.072090199. PMC 123709. PMID 11917125.
  5. ↑ 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.
  6. ↑ 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.
  7. ↑ 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.
  8. ↑ 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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