View source for TAS1R1

{{Infobox_gene}}
'''Taste receptor type 1 member 1''' is a [[protein]] that in humans is encoded by the ''TAS1R1'' [[gene]].<ref name="entrez">{{cite web | title = Entrez Gene: TAS1R1 taste receptor, type 1, member 1| url = https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=80835| accessdate = }}</ref>

== 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.<ref name="Nelson2001">{{cite journal | vauthors = Nelson G, Hoon MA, Chandrashekar J, Zhang Y, Ryba NJ, Zuker CS | title = Mammalian sweet taste receptors | journal = Cell | volume = 106 | issue = 3 | pages = 381–390 | year = 2001 | pmid = 11509186 | doi = 10.1016/S0092-8674(01)00451-2 }}</ref> 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 acid]]s, specifically L-[[glutamine]], enables the body to sense the [[umami]], or savory, taste.<ref name="Nelson2002">{{cite journal | vauthors = Nelson G, Chandrashekar J, Hoon MA, Feng L, Zhao G, Ryba NJ, Zuker CS | title = An amino-acid taste receptor | journal = Nature | volume = 416 | issue = 6877 | pages = 199–202 | year = 2002 | pmid = 11894099 | doi = 10.1038/nature726 }}</ref> 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.<ref name="entrez" /><ref name="Shigemura">{{cite journal | vauthors = White BD, Corll CB, Porter JR | title = The metabolic clearance rate of corticosterone in lean and obese male Zucker rats | journal = Metabolism: clinical and experimental | volume = 38 | issue = 6 | pages = 530–536 | year = 1989 | pmid = 2725291 | doi=10.1016/0026-0495(89)90212-6}}</ref> Another interesting quality of the TAS1R1 and [[TAS1R2]] proteins is their spontaneous activity in the absence of the extracellular domains and binding ligands.<ref name="sainz">{{cite journal | vauthors = Sainz E, Cavenagh MM, LopezJimenez ND, Gutierrez JC, Battey JF, Northup JK, Sullivan SL | title = The G-protein coupling properties of the human sweet and amino acid taste receptors | journal = Developmental Neurobiology | volume = 67 | issue = 7 | pages = 948–959 | year = 2007 | pmid = 17506496 | doi = 10.1002/dneu.20403 }}</ref> 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”.<ref>{{cite journal |last=Sand |first=Jordan |year=2005 |title= A Short History of MSG: Good Science, Bad Science, and Taste Cultures |journal= Gastronomica: The Journal of Food and Culture|volume=5 |issue=4 |pages=38–49 |publisher=University of California Press |doi= 10.1525/gfc.2005.5.4.38}}</ref> 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.<ref name="Nelson2002"/><ref name="Delay">{{cite journal | vauthors = Delay ER, Beaver AJ, Wagner KA, Stapleton JR, Harbaugh JO, Catron KD, Roper SD | title = Taste preference synergy between glutamate receptor agonists and inosine monophosphate in rats | journal = Chemical senses | volume = 25 | issue = 5 | pages = 507–515 | year = 2000 | pmid = 11015322 | doi = 10.1093/chemse/25.5.507 }}</ref>

== Signal transduction ==

TAS1R1 and [[TAS1R2]] receptors have been shown to bind to [[G protein]]s, 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.<ref name="sainz"/> This suggests that TAS1R1 and [[TAS1R2]] are [[G protein-coupled receptors]] that inhibit [[adenylyl cyclase]]s to decrease [[cyclic guanosine monophosphate]] (cGMP) levels in [[taste receptor]]s.<ref name="Abaffy">{{cite journal | vauthors = Abaffy T, Trubey KR, Chaudhari N | title = Adenylyl cyclase expression and modulation of cAMP in rat taste cells | journal = American Journal of Physiology. Cell Physiology | volume = 284 | issue = 6 | pages = C1420–C1428 | year = 2003 | pmid = 12606315 | doi = 10.1152/ajpcell.00556.2002 }}</ref>

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.<ref name="Zhang">{{cite journal | vauthors = Zhang Y, Hoon MA, Chandrashekar J, Mueller KL, Cook B, Wu D, Zuker CS, Ryba NJ | title = Coding of sweet, bitter, and umami tastes: Different receptor cells sharing similar signaling pathways | journal = Cell | volume = 112 | issue = 3 | pages = 293–301 | year = 2003 | pmid = 12581520 | doi = 10.1016/S0092-8674(03)00071-0 }}</ref>

== Location and innervation ==

TAS1R1+3 expressing cells are found mostly in the [[fungiform papilla]]e at the tip and edges of the tongue and palate taste receptor cells in the roof of the mouth.<ref name="Nelson2001"/>  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.<ref name="Nelson2002"/><ref name="Danilova">{{cite journal | vauthors = Danilova V, Hellekant G | title = Comparison of the responses of the chorda tympani and glossopharyngeal nerves to taste stimuli in C57BL/6J mice | journal = BMC Neuroscience | volume = 4 | pages = 5–6 | year = 2003 | pmid = 12617752 | pmc = 153500 | doi = 10.1186/1471-2202-4-5 }}</ref> TAS1R and TAS2R (bitter) channels are not expressed together in taste buds.<ref name="Nelson2001"/>

==See also==
* [[Taste receptor]]
* [[TAS1R2]]
* [[TAS1R3]]

==References==
{{reflist|35em}}

==Further reading==
{{refbegin|35em}}
*{{cite journal | vauthors = Chandrashekar J, Hoon MA, Ryba NJ, Zuker CS | title = The receptors and cells for mammalian taste. | journal = Nature | volume = 444 | issue = 7117 | pages = 288–94 | year = 2007 | pmid = 17108952 | doi = 10.1038/nature05401 }}
*{{cite journal | vauthors = Hoon MA, Adler E, Lindemeier J, Battey JF, Ryba NJ, Zuker CS | title = Putative mammalian taste receptors: a class of taste-specific GPCRs with distinct topographic selectivity. | journal = Cell | volume = 96 | issue = 4 | pages = 541–51 | year = 1999 | pmid = 10052456 | doi = 10.1016/S0092-8674(00)80658-3 }}
*{{cite journal | vauthors = Makalowska I, Sood R, Faruque MU, Hu P, Robbins CM, Eddings EM, Mestre JD, Baxevanis AD, Carpten JD | title = Identification of six novel genes by experimental validation of GeneMachine predicted genes. | journal = Gene | volume = 284 | issue = 1-2 | pages = 203–13 | year = 2002 | pmid = 11891061 | doi = 10.1016/S0378-1119(01)00897-6 }}
*{{cite journal | vauthors = Nelson G, Chandrashekar J, Hoon MA, Feng L, Zhao G, Ryba NJ, Zuker CS | title = An amino-acid taste receptor. | journal = Nature | volume = 416 | issue = 6877 | pages = 199–202 | year = 2002 | pmid = 11894099 | doi = 10.1038/nature726 }}
*{{cite journal | vauthors = Li X, Staszewski L, Xu H, Durick K, Zoller M, Adler E | title = Human receptors for sweet and umami taste. | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 99 | issue = 7 | pages = 4692–6 | year = 2002 | pmid = 11917125 | pmc = 123709 | doi = 10.1073/pnas.072090199 }}
*{{cite journal | vauthors = Liao J, Schultz PG | title = Three sweet receptor genes are clustered in human chromosome 1. | journal = Mamm. Genome | volume = 14 | issue = 5 | pages = 291–301 | year = 2003 | pmid = 12856281 | doi = 10.1007/s00335-002-2233-0 }}
*{{cite journal | vauthors = Xu H, Staszewski L, Tang H, Adler E, Zoller M, Li X | title = Different functional roles of T1R subunits in the heteromeric taste receptors. | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 101 | issue = 39 | pages = 14258–63 | year = 2005 | pmid = 15353592 | pmc = 521102 | doi = 10.1073/pnas.0404384101 }}
*{{cite journal | vauthors = Sainz E, Cavenagh MM, LopezJimenez ND, Gutierrez JC, Battey JF, Northup JK, Sullivan SL | title = The G-protein coupling properties of the human sweet and amino acid taste receptors. | journal = Dev Neurobiol | volume = 67 | issue = 7 | pages = 948–59 | year = 2007 | pmid = 17506496 | doi = 10.1002/dneu.20403 }}
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==External links==
* [http://www.genecards.org/cgi-bin/carddisp.pl?gene=TAS1R1 TAS1R1 Gene]
* [http://omim.org/entry/606225 TASTE RECEPTOR TYPE 1, MEMBER 1; TAS1R1]

{{G protein-coupled receptors|g3}}
{{NLM content}}

[[Category:G protein coupled receptors]]