Thermodynamics and structural analysis of positive allosteric modulation of the ionotropic glutamate receptor GluA2

TY - JOUR

T1 - Thermodynamics and structural analysis of positive allosteric modulation of the ionotropic glutamate receptor GluA2

AU - Krintel, Christian

AU - Frydenvang, Karla

AU - Olsen, Lars

AU - Kristensen, Maria T

AU - de Barrios, Oriol

AU - Naur, Peter

AU - Francotte, Pierre

AU - Pirotte, Bernard

AU - Gajhede, Michael

AU - Kastrup, Jette Sandholm

N1 - Keywords: ionotropic glutamate receptors, positive allosteric modulators, isothermal titration calorimetry, crystal structure, binding affinity

PY - 2012/1/1

Y1 - 2012/1/1

N2 - 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 wellknown GluA2 modulator cyclothiazide was obtained from Xray structures. The LBD-L483Y-N754S:BPAM-97 complex has a K d 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 K d 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, Met 496 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.

AB - 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 wellknown GluA2 modulator cyclothiazide was obtained from Xray structures. The LBD-L483Y-N754S:BPAM-97 complex has a K d 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 K d 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, Met 496 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.

KW - Former Faculty of Pharmaceutical Sciences

U2 - 10.1042/bj20111221

DO - 10.1042/bj20111221

M3 - Journal article

C2 - 21895609

SN - 0264-6021

VL - 441

SP - 173

EP - 178

JO - Biochemical Journal

JF - Biochemical Journal

IS - 1

ER -