Extracellular loop 2 of the free fatty acid receptor 2 mediates allosterism of a phenylacetamide ago-allosteric modulator

Smith, N.J. et al. (2011) Extracellular loop 2 of the free fatty acid receptor 2 mediates allosterism of a phenylacetamide ago-allosteric modulator. Molecular Pharmacology, 80(1), pp. 163-173. (doi: 10.1124/mol.110.070789)

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Abstract

Allosteric agonists are powerful tools for exploring the pharmacology of closely related G protein-coupled receptors that have non-selective endogenous ligands, such as the short chain fatty acids at Free Fatty Acid receptors 2 and 3 (FFA2/GPR43 and FFA3/GPR41, respectively). We explored the molecular mechanisms mediating the activity of 4-CMTB, a recently described phenylacetamide allosteric agonist and allosteric modulator of endogenous ligand function at human FFA2, by combining our previous knowledge of the orthosteric binding site with targeted examination of 4-CMTB structure-activity relationships and mutagenesis and chimeric receptor generation. Here we show that 4-CMTB is a selective agonist for FFA2 that binds to a site distinct from the orthosteric site of the receptor. Ligand structure-activity relationship studies indicated that the N-thiazolyl amide likely provides hydrogen bond donor/acceptor interactions with the receptor. Substitution at Leu173 and the exchange of the entire extracellular loop 2 of FFA2 with that of FFA3 was sufficient to respectively reduce, or ablate, allosteric communication between the endogenous and allosteric agonists. Thus, we conclude that extracellular loop 2 of human FFA2 is required for transduction of co-operative signaling between the orthosteric and an as yet undefined allosteric binding site of the FFA2 receptor that is occupied by 4-CMTB.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Ward, Dr Richard and Hudson, Dr Brian and Milligan, Professor Graeme and Smith, Dr Nicola
Authors: Smith, N.J., Ward, R.J., Stoddart, L.A., Hudson, B.D., Kostenis, E., Ulven, T., Morris, J.C., Trankle, C., Tikhonova, I.G., Adams, D.R., and Milligan, G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
College of Medical Veterinary and Life Sciences > School of Life Sciences
Journal Name:Molecular Pharmacology
ISSN:0026-895X
Published Online:15 April 2011

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
519861Developing selective ligands for Free Fatty Acid Receptor 2 with novel pharmacological propertiesGraeme MilliganWellcome Trust (WELLCOME)089600/Z/09/ZInstitute of Neuroscience and Psychology