title: Thermodynamic characterization of new positive allosteric modulators binding to the glutamate receptor A2 ligand-binding domain: combining experimental and computational methods unravels differences in driving forces.
abstract: Positive allosteric modulation of the ionotropic glutamate receptor GluA2 presents a potential treatment of cognitive disorders, for example, Alzheimer's disease. In the present study, we describe the synthesis, pharmacology, and thermodynamic studies of a series of monofluoro-substituted 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides. Measurements of ligand binding by isothermal titration calorimetry (ITC) showed similar binding affinities for the modulator series at the GluA2 LBD but differences in the thermodynamic driving forces. Binding of 5c (7-F) and 6 (no-F) is enthalpy driven, and 5a (5-F) and 5b (6-F) are entropy driven. For 5d (8-F), both quantities were equal in size. Thermodynamic integration (TI) and one-step perturbation (OSP) were used to calculate the relative binding affinity of the modulators. The OSP calculations had a higher predictive power than those from TI, and combined with the shorter total simulation time, we found the OSP method to be more effective for this setup. Furthermore, from the molecular dynamics simulations, we extracted the enthalpies and entropies, and along with the ITC data, this suggested that the differences in binding free energies are largely explained by the direct ligand-surrounding enthalpies. Furthermore, we used the OSP setup to predict binding affinities for a series of polysubstituted fluorine compounds and monosubstituted methyl compounds and used these predictions to characterize the modulator binding pocket for this scaffold of positive allosteric modulators.
authors.affiliation: Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen , Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors.forename: Ann-Beth
authors.initials: AB
authors.lastname: Nørholm
authors.forename: Pierre
authors.initials: P
authors.lastname: Francotte
authors.forename: Eric
authors.initials: E
authors.lastname: Goffin
authors.forename: Iuliana
authors.initials: I
authors.lastname: Botez
authors.forename: Laurence
authors.initials: L
authors.lastname: Danober
authors.forename: Pierre
authors.initials: P
authors.lastname: Lestage
authors.forename: Bernard
authors.initials: B
authors.lastname: Pirotte
authors.forename: Jette S
authors.initials: JS
authors.lastname: Kastrup
authors.forename: Lars
authors.initials: L
authors.lastname: Olsen
authors.forename: Chris
authors.initials: C
authors.lastname: Oostenbrink
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D001581:Benzothiadiazines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D019277:Entropy; D008024:Ligands; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018091:Receptors, AMPA / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D001581:Benzothiadiazines; D008024:Ligands; D018091:Receptors, AMPA