TAS1R1

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

TAS1R1
Identifiers
Aliases	TAS1R1, GPR70, T1R1, TR1, GM148, taste 1 receptor member 1
External IDs	OMIM: 606225; MGI: 1927505; HomoloGene: 12888; GeneCards: TAS1R1; OMA:TAS1R1 - orthologs
Gene location (Human) Chr. Chromosome 1 (human) Band 1p36.31 Start 6,555,307 bp End 6,579,755 bp
Gene location (Mouse) Chr. Chromosome 4 (mouse) Band 4 E2|4 82.83 cM Start 152,112,371 bp End 152,123,025 bp
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in gonad testicle left testis right testis muscle of thigh right adrenal cortex gallbladder gastrocnemius muscle olfactory zone of nasal mucosa Descending thoracic aorta Top expressed in yolk sac spermatid morula seminiferous tubule blastocyst embryo spermatocyte muscle of thigh dentate gyrus of hippocampal formation granule cell primary visual cortex More reference expression data BioGPS n/a
Gene ontology Molecular function G protein-coupled receptor activity signal transducer activity taste receptor activity protein heterodimerization activity signaling receptor activity Cellular component integral component of membrane plasma membrane membrane integral component of plasma membrane Biological process sensory perception of umami taste signal transduction response to stimulus sensory perception of taste G protein-coupled receptor signaling pathway detection of chemical stimulus involved in sensory perception of taste Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 80835 110326 Ensembl ENSG00000173662 ENSMUSG00000028950 UniProt Q7RTX1 Q99PG6 RefSeq (mRNA) NM_138697 NM_177539 NM_177540 NM_177541 NM_031867 RefSeq (protein) NP_619642 NP_803884 NP_114073 Location (UCSC) Chr 1: 6.56 – 6.58 Mb Chr 4: 152.11 – 152.12 Mb PubMed search
Wikidata
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Structure

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. 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. 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. Another interesting quality of the TAS1R1 and TAS1R2 proteins is their spontaneous activity in the absence of the extracellular domains and binding ligands. 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.

Ligands

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”. 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.

Signal transduction

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. 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.

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 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.

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. 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. TAS1R and TAS2R (bitter) channels are not expressed together in taste buds.

See also

• Taste receptor
• TAS1R2
• TAS1R3

Further reading

• Chandrashekar J, Hoon MA, Ryba NJ, Zuker CS (2007). "The receptors and cells for mammalian taste". Nature. 444 (7117): 288–94. Bibcode:2006Natur.444..288C. 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.
• Makalowska I, Sood R, Faruque MU, Hu P, Robbins CM, Eddings EM, Mestre JD, Baxevanis AD, Carpten JD (2002). "Identification of six novel genes by experimental validation of GeneMachine predicted genes". Gene. 284 (1–2): 203–13. doi:10.1016/S0378-1119(01)00897-6. PMID 11891061.
• 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. Bibcode:2002Natur.416..199N. doi:10.1038/nature726. PMID 11894099. S2CID 1730089.
• 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.
• 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.
• Xu H, Staszewski L, Tang H, Adler E, Zoller M, Li X (2005). "Different functional roles of T1R subunits in the heteromeric taste receptors". Proc. Natl. Acad. Sci. U.S.A. 101 (39): 14258–63. Bibcode:2004PNAS..10114258X. doi:10.1073/pnas.0404384101. PMC 521102. PMID 15353592.
• 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". Dev Neurobiol. 67 (7): 948–59. doi:10.1002/dneu.20403. PMID 17506496. S2CID 29736077.

External links

• TAS1R1 Gene
• TASTE RECEPTOR TYPE 1, MEMBER 1; TAS1R1

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