title: Thermodynamics and structural analysis of positive allosteric modulation of the ionotropic glutamate receptor GluA2.
abstract: Positive allosteric modulators of the ionotropic glutamate receptor-2 (GluA2) are promising compounds for the treatment of cognitive disorders, e.g. Alzheimer's disease. These modulators bind within the dimer interface of the LBD (ligand-binding domain) and stabilize the agonist-bound conformation slowing receptor desensitization and/or deactivation. In the present study, we employ isothermal titration calorimetry to determine binding affinities and thermodynamic details of binding of modulators of GluA2. A mutant of the LBD of GluA2 (LBD-L483Y-N754S) that forms a stable dimer in solution was used. The potent GluA2 modulator BPAM-97 was used as a reference compound. Evidence that BPAM-97 binds in the same pocket as the well-known GluA2 modulator cyclothiazide was obtained from X-ray structures. The LBD-L483Y-N754S:BPAM-97 complex has a Kd of 5.6 μM (ΔH=-4.9 kcal/mol, -TΔS=-2.3 kcal/mol; where 1 kcal≈4.187 kJ). BPAM-97 was used in a displacement assay to determine a Kd of 0.46 mM (ΔH=-1.2 kcal/mol, -TΔS=-3.3 kcal/mol) for the LBD-L483Y-N754S:IDRA-21 complex. The major structural factors increasing the potency of BPAM-97 over IDRA-21 are the increased van der Waals contacts to, primarily, Met496 in GluA2 imposed by the ethyl substituent of BPAM-97. These results add important information on binding affinities and thermodynamic details, and provide a new tool in the development of drugs against cognitive disorders.
authors: Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors: Christian
authors: C
authors: Krintel
authors: Karla
authors: K
authors: Frydenvang
authors: Lars
authors: L
authors: Olsen
authors: Maria T
authors: MT
authors: Kristensen
authors: Oriol
authors: O
authors: de Barrios
authors: Peter
authors: P
authors: Naur
authors: Pierre
authors: P
authors: Francotte
authors: Bernard
authors: B
authors: Pirotte
authors: Michael
authors: M
authors: Gajhede
authors: Jette S
authors: JS
authors: Kastrup
mesh_terms: D001581:Benzothiadiazines / Q000494:pharmacology; D002151:Calorimetry / Q000379:methods; D003460:Crystallization; D003499:Cyclic S-Oxides / Q000494:pharmacology; D004232:Diuretics / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology*; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism*; D058468:Receptors, Ionotropic Glutamate / Q000235:genetics / Q000378:metabolism*; D013816:Thermodynamics; D013829:Thiadiazines / Q000494:pharmacology
chemical_list: C531043:4-ethyl-7-fluoro-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide; D001581:Benzothiadiazines; D003499:Cyclic S-Oxides; D004232:Diuretics; D018091:Receptors, AMPA; D058468:Receptors, Ionotropic Glutamate; D013829:Thiadiazines; C091420:IDRA 21; C104722:glutamate receptor ionotropic, AMPA 2; C004639:cyclothiazide