title: Non-equivalence of Key Positively Charged Residues of the Free Fatty Acid 2 Receptor in the Recognition and Function of Agonist Versus Antagonist Ligands.
abstract: Short chain fatty acids (SCFAs) are produced in the gut by bacterial fermentation of poorly digested carbohydrates. A key mediator of their actions is the G protein-coupled free fatty acid 2 (FFA2) receptor, and this has been suggested as a therapeutic target for the treatment of both metabolic and inflammatory diseases. However, a lack of understanding of the molecular determinants dictating how ligands bind to this receptor has hindered development. We have developed a novel radiolabeled FFA2 antagonist to probe ligand binding to FFA2, and in combination with mutagenesis and molecular modeling studies, we define how agonist and antagonist ligands interact with the receptor. Although both agonist and antagonist ligands contain negatively charged carboxylates that interact with two key positively charged arginine residues in transmembrane domains V and VII of FFA2, there are clear differences in how these interactions occur. Specifically, although agonists require interaction with both arginine residues to bind the receptor, antagonists require an interaction with only one of the two. Moreover, different chemical series of antagonist interact preferentially with different arginine residues. A homology model capable of rationalizing these observations was developed and provides a tool that will be invaluable for identifying improved FFA2 agonists and antagonists to further define function and therapeutic opportunities of this receptor.
authors.affiliation: From the Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom and.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Sergeev
authors.affiliation: the Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Anders Højgaard
authors.initials: AH
authors.lastname: Hansen
authors.affiliation: the Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Pandey
authors.affiliation: From the Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom and.
authors.forename: Amanda E
authors.initials: AE
authors.lastname: MacKenzie
authors.affiliation: From the Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom and.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Hudson
authors.affiliation: the Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark ulven@sdu.dk.
authors.forename: Trond
authors.initials: T
authors.lastname: Ulven
authors.affiliation: From the Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom and Graeme.Milligan@glasgow.ac.uk.
authors.forename: Graeme
authors.identifier: http://orcid.org/0000-0002-6946-3519
authors.initials: G
authors.lastname: Milligan
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D002087:Butyrates / Q000737:chemistry / Q000494:pharmacology; D020148:Butyric Acid / Q000494:pharmacology; D004952:Esters / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000737:chemistry; D013876:Thiophenes / Q000737:chemistry / Q000494:pharmacology; D014316:Tritium / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled
chemical_list: D000596:Amino Acids; D002087:Butyrates; D020148:Butyric Acid; D004952:Esters; D008024:Ligands; D050505:Mutant Proteins; D011956:Receptors, Cell Surface; D013876:Thiophenes; D014316:Tritium; C000595478:4-(((R)-1-(benzo(b)thiophene-3-carbonyl)-2-methyl-azetidine-2-carbonyl)-(3-chloro-benzyl)-amino)-butyric acid; C473103:FFAR2 protein, human; D043562:Receptors, G-Protein-Coupled
keywords: 7 transmembrane domain receptor; G protein-coupled receptor (GPCR); fatty acid; free fatty acid; homology modeling; intestinal metabolism; medicinal chemistry