title: Probing the existence of G protein-coupled receptor dimers by positive and negative ligand-dependent cooperative binding.
abstract: An increasing amount of ligand binding data on G protein-coupled receptors (GPCRs) is not compatible with the prediction of the simple mass action law. This may be related to the propensity of most GPCRs, if not all, to oligomerize. Indeed, one of the consequences of receptor oligomerization could be a possible cross-talk between the protomers, which in turn could lead to negative or positive cooperative ligand binding. We prove here that this can be demonstrated experimentally. Saturation, dissociation, and competition binding experiments were performed on vasopressin and oxytocin receptors expressed in Chinese hamster ovary or COS-7 cells. Linear, concave, and convex Scatchard plots were then obtained, depending on the ligand used. Moreover, some competition curves exhibited an increase of the radiotracer binding for low concentrations of competitors, suggesting a cooperative binding process. These data demonstrate that various vasopressin analogs display either positive or negative cooperative binding. Because positive cooperative binding cannot be explained without considering receptor as multivalent, these binding data support the concept of GPCR dimerization process. The results, which are in good accordance with the predictions of previous mathematical models, suggest that binding experiments can be used to probe the existence of receptor dimers.
authors.affiliation: Institut de Génomique Fonctionnelle, Centre National de la Recherche Scientifique Unité Mixte Recherche 5203, 141 rue de la Cardonille, 34094 Montpellier CEDEX 5, France.
authors.forename: Laura
authors.initials: L
authors.lastname: Albizu
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Balestre
authors.forename: Christophe
authors.initials: C
authors.lastname: Breton
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pin
authors.forename: Maurice
authors.initials: M
authors.lastname: Manning
authors.forename: Bernard
authors.initials: B
authors.lastname: Mouillac
authors.forename: Claude
authors.initials: C
authors.lastname: Barberis
authors.forename: Thierry
authors.initials: T
authors.lastname: Durroux
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D001667:Binding, Competitive; D016466:CHO Cells; D019556:COS Cells; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008962:Models, Theoretical; D010121:Oxytocin / Q000378:metabolism; D011485:Protein Binding; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D017483:Receptors, Vasopressin / Q000378:metabolism; D013997:Time Factors
chemical_list: D008024:Ligands; D043562:Receptors, G-Protein-Coupled; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010121:Oxytocin