Biology:TAS2R1

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A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

Taste receptor type 2 member 1 (TAS2R1/T2R1) is a protein that in humans is encoded by the TAS2R1 gene.[1][2][3] It belongs to the G protein-coupled receptor (GPCR) family and is related to class A-like GPCRs, they contain 7 transmembrane helix bundles and short N-terminus loop.[4] Furthermore, TAS2R1 is member of the 25 known human bitter taste receptors, which enable the perception of bitter taste in the mouth cavity. Increasing evidence indicates a functional role of TAS2Rs in extra-oral tissues.[5]

Expression and function

Extra-oral roles of TAS2Rs

Bitter taste receptors are expressed in taste receptor cells, which organized into taste buds on the papillae of the tongue and palate epithelium.

In addition, TAS2Rs were found to be expressed in extra-oral tissues, e.g. brain, lungs, gastrointestinal tract, etc.[5] So far, less is known about their function however, for example it was shown that:

  • TAS2Rs mediate relaxation of airway smooth muscles.[6]
  • TAS2R43 is involved in secretion of gastric acid in the stomach.[7]

Extra-oral roles of TAS2R1

  • TAS2R1, TAS2R4, TAS2R10, TAS2R38 and TAS2R49 were found to be down-regulated in breast cancer cells[8].
  • TAS2R1, causes vasoconstrictor responses in the pulmonary circuit and relaxation in the airways[9].

Structure of TAS2R1 receptor

Based on a recent homology model from BitterDB[10][11] several conserved motifs, which are counterparts to Class A GPCRs[4] were found:

  • Transmembrane helix 1: N1.50xxI1.53
  • Transmembrane helix 2: L2.46xxxR2.50
  • Transmembrane helix 3: F3.49Y3.50xxK3.53
  • Transmembrane helix 5: P5.50
  • Transmembrane helix 6: F6.44xxxY6.46
  • Transmembrane helix 7: H7.49S7.50xxL7.53

Numbering is according to the Balleros-Weinstein[12] system.

Unlike in Class A GPCRs, in transmembrane helix 4 no DRY[13] motif was found as well as position 6.50 is not conserved.

TAS2R1 gene

This gene encodes a member of a family of candidate taste receptors that are members of the G protein-coupled receptor superfamily and that are specifically expressed by taste receptor cells of the tongue and palate epithelia. This intronless taste receptor gene encodes a 7-transmembrane receptor protein, functioning as a bitter taste receptor.

SNPs

In T2R1 two SNPs are known in R111H and R206W (dbSNP).

Transcription Factors

So far, AML1a, AP-1, AREB6, FOXL1, IRF-7A, Lmo2, NF-E2, NF-E2 p45 were found as the top transcription factor binding sites by QIAGEN in the TAS2R1 gene promoter.

Mutagenesis data

Several mutations have been shown to influence binding of a ligand to TAS2R1 (based on BitterDB):

Receptor region BW number Residue Reference
TM1 1.5 N24 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM1 1.53 I27 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM2 2.5 R55 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM2 2.56 F61 doi: 10.1074/jbc.M111.246983
TM2 2.61 N66 doi: 10.3389/fmolb.2017.00063 doi: 10.1021/acs.jctc.5b00472 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.1074/jbc.M111.246983
ECL1 E74 doi: 10.3389/fmolb.2017.00063
TM3 3.32 L85 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.3109/10799893.2011.578141
TM3 3.33 L86 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.3109/10799893.2011.578141
TM3 3.36 N89 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.1074/jbc.M111.246983 doi: doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM3 3.37 E90 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.3109/10799893.2011.578141
TM3 3.41 W94 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM3 3.46 L99 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM5 5.46 E182 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.3109/10799893.2011.578141
TM5 5.61 L197 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM5 5.64 S200 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM5 5.65 L201 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM7 7.39 I263 doi: 10.1016/bs.mcb.2015.10.005 doi: 10.3109/10799893.2011.578141
TM7 7.49 H273 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM7 7.53 L277 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983
TM7 7.54 I278 doi: 10.1021/acs.jctc.5b00472 doi: 10.1074/jbc.M111.246983

Ligands

Up to now, 39 ligands for T2R1 were identified (BitterDB), among them L-amino acids, peptides, humulones, small molecules etc.

See also

References

  1. "A novel family of mammalian taste receptors". Cell 100 (6): 693–702. Apr 2000. doi:10.1016/S0092-8674(00)80705-9. PMID 10761934. 
  2. "A family of candidate taste receptors in human and mouse". Nature 404 (6778): 601–4. Apr 2000. doi:10.1038/35007072. PMID 10766242. Bibcode2000Natur.404..601M. 
  3. "Entrez Gene: TAS2R1 taste receptor, type 2, member 1". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=50834. 
  4. 4.0 4.1 Di Pizio, Antonella; Levit, Anat; Slutzki, Michal; Behrens, Maik; Karaman, Rafik; Niv, Masha Y. (2016), "Comparing Class A GPCRs to bitter taste receptors", Methods in Cell Biology (Elsevier) 132: 401–427, doi:10.1016/bs.mcb.2015.10.005, ISBN 9780128035955, PMID 26928553 
  5. 5.0 5.1 Lu, Ping; Zhang, Cheng-Hai; Lifshitz, Lawrence M.; ZhuGe, Ronghua (2017-01-04). "Extraoral bitter taste receptors in health and disease". The Journal of General Physiology 149 (2): 181–197. doi:10.1085/jgp.201611637. ISSN 0022-1295. PMID 28053191. 
  6. Deshpande, Deepak A; Wang, Wayne C H; McIlmoyle, Elizabeth L; Robinett, Kathryn S; Schillinger, Rachel M; An, Steven S; Sham, James S K; Liggett, Stephen B (2010-10-24). "Bitter taste receptors on airway smooth muscle bronchodilate by localized calcium signaling and reverse obstruction". Nature Medicine 16 (11): 1299–1304. doi:10.1038/nm.2237. ISSN 1078-8956. PMID 20972434. 
  7. Liszt, Kathrin Ingrid; Ley, Jakob Peter; Lieder, Barbara; Behrens, Maik; Stöger, Verena; Reiner, Angelika; Hochkogler, Christina Maria; Köck, Elke et al. (2017-07-10). "Caffeine induces gastric acid secretion via bitter taste signaling in gastric parietal cells". Proceedings of the National Academy of Sciences 114 (30): E6260–E6269. doi:10.1073/pnas.1703728114. ISSN 0027-8424. PMID 28696284. 
  8. Singh, Nisha; Chakraborty, Raja; Bhullar, Rajinder Pal; Chelikani, Prashen (April 2014). "Differential expression of bitter taste receptors in non-cancerous breast epithelial and breast cancer cells". Biochemical and Biophysical Research Communications 446 (2): 499–503. doi:10.1016/j.bbrc.2014.02.140. ISSN 0006-291X. PMID 24613843. 
  9. Upadhyaya, Jasbir D.; Singh, Nisha; Sikarwar, Anurag S.; Chakraborty, Raja; Pydi, Sai P.; Bhullar, Rajinder P.; Dakshinamurti, Shyamala; Chelikani, Prashen (2014-10-23). "Dextromethorphan Mediated Bitter Taste Receptor Activation in the Pulmonary Circuit Causes Vasoconstriction". PLoS ONE 9 (10): e110373. doi:10.1371/journal.pone.0110373. ISSN 1932-6203. PMID 25340739. Bibcode2014PLoSO...9k0373U. 
  10. Wiener, Ayana; Shudler, Marina; Levit, Anat; Niv, Masha Y. (2011-09-22). "BitterDB: a database of bitter compounds". Nucleic Acids Research 40 (D1): D413–D419. doi:10.1093/nar/gkr755. ISSN 1362-4962. PMID 21940398. 
  11. Dagan-Wiener, Ayana; Di Pizio, Antonella; Nissim, Ido; Bahia, Malkeet S; Dubovski, Nitzan; Margulis, Eitan; Niv, Masha Y (2018-10-24). "BitterDB: taste ligands and receptors database in 2019". Nucleic Acids Research 47 (D1): D1179–D1185. doi:10.1093/nar/gky974. ISSN 0305-1048. PMID 30357384. 
  12. Ballesteros, Juan A.; Weinstein, Harel (1995), "[19] Integrated methods for the construction of three-dimensional models and computational probing of structure-function relations in G protein-coupled receptors", Methods in Neurosciences (Elsevier): pp. 366–428, doi:10.1016/s1043-9471(05)80049-7, ISBN 9780121852955 
  13. Rovati, G. E.; Capra, V.; Neubig, R. R. (2007-01-12). "The Highly Conserved DRY Motif of Class A G Protein-Coupled Receptors: Beyond the Ground State". Molecular Pharmacology 71 (4): 959–964. doi:10.1124/mol.106.029470. ISSN 0026-895X. PMID 17192495. https://semanticscholar.org/paper/a8d7aa739bb8c4825095ccbf2dd850d4077a664a. 

Further reading

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