World Library  
Flag as Inappropriate
Email this Article

Tas1r1

Article Id: WHEBN0014567218
Reproduction Date:

Title: Tas1r1  
Author: World Heritage Encyclopedia
Language: English
Subject: TR1, Taste receptor, Taste
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Tas1r1

Taste receptor, type 1, member 1
Identifiers
TAS1R1 Gene
Orthologs
SpeciesHumanMouse

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

References

Further reading

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

External links

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


This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.