5elv

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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Positive allosteric modulators of ionotropic glutamate receptors are potential compounds for treatment of cognitive disorders, e.g., Alzheimer's disease. The modulators bind within the dimer interface of the ligand-binding domain (LBD) and stabilize the agonist-bound conformation, thereby slowing receptor desensitization and/or deactivation. Here we describe the synthesis and pharmacological testing at GluA2 of a new generation of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides. The most potent modulator 3 in complex with GluA2-LBD-L483Y-N754S was subjected to structural analysis by X-ray crystallography, and the thermodynamics of binding was studied by isothermal titration calorimetry. Compound 3 binds to GluA2-LBD-L483Y-N754S with a Kd of 0.35 muM (DeltaH = -7.5 kcal/mol and -TDeltaS = -1.3 kcal/mol). This is the first time that submicromolar binding affinity has been achieved for this type of positive allosteric modulator. The major structural factor increasing the binding affinity of 3 seems to be interactions between the cyclopropyl group of 3 and the backbone of Phe495 and Met496.
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The 1,2,4-benzothiadiazine 1,1-dioxide type of positive allosteric modulators of the ionotropic glutamate receptor A2 (GluA2) are promising lead compounds for the treatment of cognitive disorders, e.g., Alzheimer's disease. The modulators bind in a cleft formed by the interface of two neighboring ligand binding domains and act by stabilizing the agonist-bound open-channel conformation. The driving forces behind the binding of these modulators can be significantly altered with only minor substitutions to the parent molecules. In this study, we show that changing the 7-fluorine substituent of modulators BPAM97 (2) and BPAM344 (3) into a hydroxyl group (BPAM557 (4) and BPAM521 (5), respectively), leads to a more favorable binding enthalpy (DeltaH, kcal/mol) from -4.9 (2) and -7.5 (3) to -6.2 (4) and -14.5 (5), but also a less favorable binding entropy (-TDeltaS, kcal/mol) from -2.3 (2) and -1.3 (3) to -0.5 (4) and 4.8 (5). Thus, the dissociation constants (Kd, muM) of 4 (11.2) and 5 (0.16) are similar to those of 2 (5.6) and 3 (0.35). Functionally, 4 and 5 potentiated responses of 10 muM L-glutamate at homomeric rat GluA2(Q)i receptors with EC50 values of 67.3 and 2.45 muM, respectively. The binding mode of 5 was examined with x-ray crystallography, showing that the only change compared to that of earlier compounds was the orientation of Ser-497 pointing toward the hydroxyl group of 5. The favorable enthalpy can be explained by the formation of a hydrogen bond from the side-chain hydroxyl group of Ser-497 to the hydroxyl group of 5, whereas the unfavorable entropy might be due to desolvation effects combined with a conformational restriction of Ser-497 and 5. In summary, this study shows a remarkable example of enthalpy-entropy compensation in drug development accompanied with a likely explanation of the underlying structural mechanism.
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Synthesis, Pharmacological and Structural Characterization, and Thermodynamic Aspects of GluA2-Positive Allosteric Modulators with a 3,4-Dihydro-2H-1,2,4-benzothiadiazine 1,1-Dioxide Scaffold.,Norholm AB, Francotte P, Olsen L, Krintel C, Frydenvang K, Goffin E, Challal S, Danober L, Botez-Pop I, Lestage P, Pirotte B, Kastrup JS J Med Chem. 2013 Nov 5. PMID:24131202<ref>PMID:24131202</ref>
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Enthalpy-Entropy Compensation in the Binding of Modulators at Ionotropic Glutamate Receptor GluA2.,Krintel C, Francotte P, Pickering DS, Juknaite L, Pohlsgaard J, Olsen L, Frydenvang K, Goffin E, Pirotte B, Kastrup JS Biophys J. 2016 Jun 7;110(11):2397-406. doi: 10.1016/j.bpj.2016.04.032. PMID:27276258<ref>PMID:27276258</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 15:43, 23 June 2016

Crystal structure of the GluA2 ligand-binding domain (S1S2J-L504-N775) in complex with glutamate and BPAM-521 at 1.92 A resolution

5elv, resolution 1.92Å

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