TAS1R1

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Taste receptor, type 1, member 1
Identifiers
Symbols TAS1R1 ; GPR70; T1R1; TR1
External IDs OMIM606225 MGI1927505 HomoloGene12888 IUPHAR: TAS1R1 GeneCards: TAS1R1 Gene
Orthologs
Species Human Mouse
Entrez 80835 110326
Ensembl ENSG00000173662 ENSMUSG00000028950
UniProt Q7RTX1 Q99PG6
RefSeq (mRNA) NM_138697 NM_031867
RefSeq (protein) NP_619642 NP_114073
Location (UCSC) Chr 1:
6.62 – 6.64 Mb
Chr 4:
152.03 – 152.04 Mb
PubMed search [1] [2]

Taste receptor type 1 member 1 is a protein that in humans is encoded by the TAS1R1 gene.[1]


Protein composition

The protein encoded by the TAS1R1 gene is a G protein-coupled receptor with seven trans-membrane domains and is a component of the heterodimeric amino acid taste receptor T1R1+3. This receptor is formed as a dimer of the TAS1R1 and TAS1R3 proteins. Moreover, the TAS1R1 protein is not functional outside of formation of the 1+3 heterodimer.[2] The TAS1R1+3 receptor has been shown to respond to L-amino acids but not to their D-enantiomers or other compounds. This ability to bind L-amino acids, specifically L-glutamine, enables the body to sense the umami, or savory, taste.[3] Multiple transcript variants encoding several different isoforms have been found for this gene, which may account for differing taste thresholds among individuals for the umami taste.[1][4] Another interesting quality of the TAS1R1 and TAS1R2 proteins is their spontaneous activity in the absence of the extracellular domains and binding ligands.[5] 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 L-glutamine.

Binding molecules

The umami taste is distinctly related to the compound monosodium glutamate(MSG). Synthesized in 1908 by Japanese chemist Kikunae Ikeda, this flavor-enhancing compound led to the naming of a new flavor quality that was named “umami”, the Japanese word for “tasty”.[6] 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 to many L-amino acids.[3][7]

G-Proteins and TAS1R1

TAS1R1 and TAS1R2 receptors have been shown to bind to G proteins, most often the gustducin Gα subunit, although a gustducin knock-out has shown small residual activity. TAS1R1 and TAS1R2 have also been shown to activate Gαo and Gαi.[5] 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.[8] Research done by creating knock-outs of common channels activated by sensory G-protein second messenger systems has also shown a connection between umami 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.[9]

Location and Innervation

TAS1R1+3 expressing cells are found mostly in the fungiform papillae at the tip and edges 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 nerves to send their signals to the brain, although some activation of the glossopharyngeal nerve has been found.[3][10] TAS1R and TAS2R (bitter) channels are not expressed together in taste buds.[2]

See also[edit]

References[edit]

  1. ^ a b "Entrez Gene: TAS1R1 taste receptor, type 1, member 1". 
  2. ^ a b c Nelson g, H. M. (2001). "Mammalian sweet taste receptors". Cell 106 (3): 381–390. doi:10.1016/S0092-8674(01)00451-2. PMID 11509186.  edit
  3. ^ a b c Nelson g, C. J.; Chandrashekar, J.; Hoon, M. A.; Feng, L.; Zhao, G.; Ryba, N. J. P.; Zuker, C. S. (2002). "An amino-acid taste receptor". Nature 416 (6877): 199–202. doi:10.1038/nature726. PMID 11894099.  edit
  4. ^ White, B. D.; Corll, C. B.; Porter, J. R. (1989). "The metabolic clearance rate of corticosterone in lean and obese male Zucker rats". Metabolism: clinical and experimental 38 (6): 530–536. PMID 2725291.  edit
  5. ^ 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.  edit
  6. ^ Sand, Jordan (2005). "A Short History of MSG: Good Science, Bad Science, and Taste Cultures". Gastronomica: The Journal of Food and Culture (University of California Press) 5 (4): 38–49. doi:10.1525/gfc.2005.5.4.38. 
  7. ^ Delay Er, B. A.; Beaver, A. J.; Wagner, K. A.; Stapleton, J. R.; Harbaugh, J. O.; Catron, K. D.; Roper, S. D. (2000). "Taste preference synergy between glutamate receptor agonists and inosine monophosphate in rats". Chemical senses 25 (5): 507–515. doi:10.1093/chemse/25.5.507. PMID 11015322.  edit
  8. ^ Abaffy, T.; Trubey, K. R.; 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.  edit
  9. ^ 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.  edit
  10. ^ Danilova v, H. 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.  edit

Further reading[edit]

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

External links[edit]