TAS1R1

Taste receptor, type 1, member 1

Identifiers

TAS1R1 ; GM148; GPR70; T1R1; TR1

External IDs

OMIM: 606225 MGI: 1927505 HomoloGene: 12888 IUPHAR: 656 GeneCards: TAS1R1 Gene

Gene ontology
Molecular function	• taste receptor activity • protein heterodimerization activity
Cellular component	• plasma membrane • integral component of membrane
Biological process	• G-protein coupled receptor signaling pathway • detection of chemical stimulus involved in sensory perception of taste • sensory perception of umami taste
Sources: Amigo / QuickGO

Orthologs

Species

Human

Mouse

RefSeq (mRNA)

RefSeq (protein)

Location (UCSC)

Chr 1:
6.56 – 6.58 Mb

Chr 4:
152.03 – 152.04 Mb

PubMed search

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

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.^[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.

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”.^[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]

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.^[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]

References

1 2 "Entrez Gene: TAS1R1 taste receptor, type 1, member 1".
1 2 3 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.
1 2 3 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.
↑ White BD, Corll CB, Porter JR (1989). "The metabolic clearance rate of corticosterone in lean and obese male Zucker rats". Metabolism: clinical and experimental 38 (6): 530–536. doi:10.1016/0026-0495(89)90212-6. PMID 2725291.
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.
↑ 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.
↑ Delay ER, Beaver AJ, Wagner KA, Stapleton JR, Harbaugh JO, Catron KD, Roper SD (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.
↑ 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.
↑ 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.
↑ 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.

External links

Cell surface receptor: G protein-coupled receptors

Class A: Rhodopsin like

Neurotransmitter

Adrenergic	α1 (A B D) α2 (A B C) β1 β2 β3

Purinergic	Adenosine (A1 A2A A2B A3) P2Y (1 2 4 5 6 8 9 10 11 12 13 14)

Serotonin	(all but 5-HT3) 5-HT1 (A B D E F) 5-HT2 (A B C) 5-HT (4 5A 6 7)

Other	Acetylcholine (M1 M2 M3 M4 M5) Dopamine (D1 D2 D3 D4 D5) Histamine (H1 H2 H3 H4) Melatonin (1A 1B 1C) TAAR (1 2 3 5 6 8 9)

Metabolites and
signaling molecules

Eicosanoid	CysLT (1 2) LTB4 (1 2) FPRL1 OXE Prostaglandin (DP (1 2), EP (1 2 3 4), FP) Prostacyclin Thromboxane

Other	Bile acid Cannabinoid (CB1 CB2, GPR (18 55 119)) EBI2 Estrogen Free fatty acid (1 2 3 4) Lactate Lysophosphatidic acid (1 2 3 4 5 6) Lysophospholipid (1 2 3 4 5 6 7 8) Niacin (1 2) Oxoglutarate PAF Sphingosine-1-phosphate (1 2 3 4 5) Succinate

Peptide

Neuropeptide	B/W (1 2) FF (1 2) S Y (1 2 4 5) Neuromedin (B U (1 2)) Neurotensin (1 2)

Other	Anaphylatoxin (C3a C5a) Angiotensin (1 2) Apelin Bombesin (BRS3 GRPR NMBR) Bradykinin (B1 B2) Chemokine Cholecystokinin (A B) Endothelin (A B) Formyl peptide (1 2 3) FSH Galanin (1 2 3) GHB receptor Gonadotropin-releasing hormone (1 2) Ghrelin Kisspeptin Luteinizing hormone/choriogonadotropin MAS (1 1L D E F G X1 X2 X3 X4) Melanocortin (1 2 3 4 5) MCHR (1 2) Motilin Opioid (Delta Kappa Mu Nociceptin & Zeta, but not Sigma) Orexin (1 2) Oxytocin Prokineticin (1 2) Prolactin-releasing peptide Relaxin (1 2 3 4) Somatostatin (1 2 3 4 5) Tachykinin (1 2 3) Thyrotropin Thyrotropin-releasing hormone Urotensin-II Vasopressin (1A 1B 2)

Miscellaneous

Orphan	GPR (1 3 4 6 12 15 17 18 19 20 21 22 23 25 26 27 31 32 33 34 35 37 39 42 44 45 50 52 55 61 62 63 65 68 75 77 78 81 82 83 84 85 87 88 92 101 103 109A 109B 119 120 132 135 137B 139 141 142 146 148 149 150 151 152 153 160 161 162 171 173 174 176 177 182 183)

Other	Adrenomedullin Olfactory Opsin (3 4 5 1LW 1MW 1SW RGR RRH) Protease-activated (1 2 3 4) SREB (1 2 3)

Class B: Secretin like

Adhesion	ADGRG (1 2 3 4 5 6 7)

Orphan	GPR (56 64 97 98 110 111 112 113 114 115 116 123 124 125 126 128 133 143 144 155 157)

Other	Brain-specific angiogenesis inhibitor (1 2 3) Cadherin (1 2 3) Calcitonin CALCRL CD97 Corticotropin-releasing hormone (1 2) EMR (1 2 3) Glucagon (GR GIPR GLP1R GLP2R) Growth hormone releasing hormone PACAPR1 GPR Latrophilin (1 2 3 ELTD1) Methuselah-like proteins Parathyroid hormone (1 2) Secretin Vasoactive intestinal peptide (1 2)

Class C: Metabotropic glutamate / pheromone

Taste	TAS1R (1 2 3) TAS2R (1 3 4 5 7 8 9 10 13 14 16 19 20 30 31 38 39 40 41 42 43 45 46 50 60)

Other	Calcium-sensing receptor GABA B (1 2) Glutamate receptor (Metabotropic glutamate (1 2 3 4 5 6 7 8)) GPRC6A GPR (156 158 179) RAIG (1 2 3 4)

Class F: Frizzled / Smoothened

Frizzled	Frizzled (1 2 3 4 5 6 7 8 9 10)

Smoothened	Smoothened

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

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