title: Overlapping binding sites drive allosteric agonism and positive cooperativity in type 4 metabotropic glutamate receptors.
abstract: Type 4 metabotropic glutamate (mGlu4) receptors are emerging targets for the treatment of various disorders. Accordingly, numerous mGlu4-positive allosteric modulators (PAMs) have been identified, some of which also display agonist activity. To identify the structural bases for their allosteric action, we explored the relationship between the binding pockets of mGlu4 PAMs with different chemical scaffolds and their functional properties. By use of innovative mGlu4 biosensors and second-messenger assays, we show that all PAMs enhance agonist action on the receptor through different degrees of allosteric agonism and positive cooperativity. For example, whereas VU0155041 and VU0415374 display equivalent efficacies [log(τ(B)) = 1.15 ± 0.38 and 1.25 ± 0.44, respectively], they increase the ability of L-AP4 to stabilize the active conformation of the receptor by 4 and 39 times, respectively. Modeling and docking studies identify 2 overlapping binding pockets as follows: a first site homologous to the pocket of natural agonists of class A GPCRs linked to allosteric agonism and a second one pointing toward a site topographically homologous to the Na(+) binding pocket of class A GPCRs, occupied by PAMs exhibiting the strongest cooperativity. These results reveal that intrinsic efficacy and cooperativity of mGlu4 PAMs are correlated with their binding mode, and vice versa, integrating structural and functional knowledge from different GPCR classes.
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS UMR 5203, Université de Montpellier, Montpellier, France; INSERM, U661, Montpellier, France;
authors.forename: Xavier
authors.initials: X
authors.lastname: Rovira
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS UMR 5203, Université de Montpellier, Montpellier, France; INSERM, U661, Montpellier, France;
authors.forename: Fanny
authors.initials: F
authors.lastname: Malhaire
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS UMR 5203, Université de Montpellier, Montpellier, France; INSERM, U661, Montpellier, France;
authors.forename: Pauline
authors.initials: P
authors.lastname: Scholler
authors.affiliation: Laboratoire de Chimie Thérapeutique, BioCIS UMR-CNRS 8076, LabEx LERMIT, Faculté de Pharmacie, Université Paris-Sud, Châtenay-Malabry, Paris, France;
authors.forename: Jordi
authors.initials: J
authors.lastname: Rodrigo
authors.affiliation: Laboratory of Medicinal Chemistry, Departament of Biomedicinal Chemistry, Institute of Advanced Chemistry of Catalonia IQAC-CSIC, Barcelona, Spain; and.
authors.forename: Patricia
authors.initials: P
authors.lastname: Gonzalez-Bulnes
authors.affiliation: Laboratory of Medicinal Chemistry, Departament of Biomedicinal Chemistry, Institute of Advanced Chemistry of Catalonia IQAC-CSIC, Barcelona, Spain; and.
authors.forename: Amadeu
authors.initials: A
authors.lastname: Llebaria
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS UMR 5203, Université de Montpellier, Montpellier, France; INSERM, U661, Montpellier, France;
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pin
authors.affiliation: Laboratory of Molecular Neuropharmacology and Bioinformatics, Institut de Neurociències and Unitat de Bioestadística, Universitat Autònoma de Barcelona, Bellaterra, Spain cyril.goudet@igf.cnrs.fr jesus.giraldo@uab.es.
authors.forename: Jesús
authors.initials: J
authors.lastname: Giraldo
authors.affiliation: Institut de Génomique Fonctionnelle, CNRS UMR 5203, Université de Montpellier, Montpellier, France; INSERM, U661, Montpellier, France; cyril.goudet@igf.cnrs.fr jesus.giraldo@uab.es.
authors.forename: Cyril
authors.initials: C
authors.lastname: Goudet
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site; D000813:Anilides / Q000494:pharmacology; D015374:Biosensing Techniques; D003509:Cyclohexanecarboxylic Acids / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists* / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems
chemical_list: D000813:Anilides; D003509:Cyclohexanecarboxylic Acids; D008024:Ligands; D018094:Receptors, Metabotropic Glutamate; D011994:Recombinant Proteins; C544970:VU 0155041; C108823:metabotropic glutamate receptor 4
keywords: allostery; sodium