title: Distinct roles of metabotropic glutamate receptor dimerization in agonist activation and G-protein coupling.
abstract: The eight metabotropic glutamate receptors (mGluRs) are key modulators of synaptic transmission and are considered promising targets for the treatment of various brain disorders. Whereas glutamate acts at a large extracellular domain, allosteric modulators have been identified that bind to the seven transmembrane domain (7TM) of these dimeric G-protein-coupled receptors (GPCRs). We show here that the dimeric organization of mGluRs is required for the modulation of active and inactive states of the 7TM by agonists, but is not necessary for G-protein activation. Monomeric mGlu2, either as an isolated 7TM or in full-length, purified and reconstituted into nanodiscs, couples to G proteins upon direct activation by a positive allosteric modulator. However, only a reconstituted full-length dimeric mGlu2 activates G protein upon glutamate binding, suggesting that dimerization is required for glutamate induced activation. These data show that, even for such well characterized GPCR dimers like mGluR2, a single 7TM is sufficient for G-protein coupling. Despite this observation, the necessity of dimeric architecture for signaling induced by the endogenous ligand glutamate confirms that the central core of signaling complex is dimeric.
authors.affiliation: Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5203, Institut de Génomique Fonctionnelle, Université Montpellier 1 et 2, 34094 Montpellier cedex 05, France.
authors.forename: Driss
authors.initials: D
authors.lastname: El Moustaine
authors.forename: Sébastien
authors.initials: S
authors.lastname: Granier
authors.forename: Etienne
authors.initials: E
authors.lastname: Doumazane
authors.forename: Pauline
authors.initials: P
authors.lastname: Scholler
authors.forename: Rita
authors.initials: R
authors.lastname: Rahmeh
authors.forename: Patrick
authors.initials: P
authors.lastname: Bron
authors.forename: Bernard
authors.initials: B
authors.lastname: Mouillac
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Banères
authors.forename: Philippe
authors.initials: P
authors.lastname: Rondard
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pin
mesh_terms: D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D019204:GTP-Binding Proteins / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000648:ultrastructure; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D007295:Inositol Phosphates; D043562:Receptors, G-Protein-Coupled; D018094:Receptors, Metabotropic Glutamate; C450520:seven-transmembrane G-protein-coupled receptor; D018698:Glutamic Acid; D019204:GTP-Binding Proteins