title: Role of stoichiometry in the dimer-stabilizing effect of AMPA receptor allosteric modulators.
abstract: Protein dimerization provides a mechanism for the modulation of cellular signaling events. In α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, the rapidly desensitizing, activated state has been correlated with a weakly dimeric, glutamate-binding domain conformation. Allosteric modulators can form bridging interactions that stabilize the dimer interface. While most modulators can only bind to one position with a one modulator per dimer ratio, some thiazide-based modulators can bind to the interface in two symmetrical positions with a two modulator per dimer ratio. Based on small-angle X-ray scattering (SAXS) experiments, dimerization curves for the isolated glutamate-binding domain show that a second modulator binding site produces both an increase in positive cooperativity and a decrease in the EC50 for dimerization. Four body binding equilibrium models that incorporate a second dimer-stabilizing ligand were developed to fit the experimental data. The work illustrates why stoichiometry should be an important consideration during the rational design of dimerizing modulators.
authors.affiliation: Department of Molecular Medicine and ‡Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Ptak
authors.forename: Ching-Lin
authors.initials: CL
authors.lastname: Hsieh
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Weiland
authors.forename: Robert E
authors.initials: RE
authors.lastname: Oswald
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects*; D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D005973:Glutamine / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D055503:Protein Multimerization / Q000187:drug effects*; D017434:Protein Structure, Tertiary / Q000187:drug effects; D051381:Rats; D018091:Receptors, AMPA / Q000737:chemistry / Q000378:metabolism*; D053838:Scattering, Small Angle; D049971:Thiazides / Q000737:chemistry / Q000494:pharmacology*; D014961:X-Ray Diffraction
chemical_list: D008024:Ligands; D018091:Receptors, AMPA; D049971:Thiazides; D005973:Glutamine