RT Journal Article
SR Electronic
T1 Docking of 1,4-Benzodiazepines in the α<sub>1</sub>/γ<sub>2</sub> GABA<sub>A</sub> Receptor Modulator Site
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 440
OP 450
DO 10.1124/mol.109.054650
VO 76
IS 2
A1 Berezhnoy, D.
A1 Gibbs, T. T.
A1 Farb, D. H.
YR 2009
UL http://molpharm.aspetjournals.org/content/76/2/440.abstract
AB Positive allosteric modulation of the GABAA receptor (GABAAR) via the benzodiazepine recognition site is the mechanism whereby diverse chemical classes of therapeutic agents act to reduce anxiety, induce and maintain sleep, reduce seizures, and induce conscious sedation. The binding of such therapeutic agents to this allosteric modulatory site increases the affinity of GABA for the agonist recognition site. A major unanswered question, however, relates to how positive allosteric modulators dock in the 1,4-benzodiazepine (BZD) recognition site. In the present study, the X-ray structure of an acetylcholine binding protein from the snail Lymnea stagnalis and the results from site-directed affinity-labeling studies were used as the basis for modeling of the BZD binding pocket at the α1/γ2 subunit interface. A tethered BZD was introduced into the binding pocket, and molecular simulations were carried out to yield a set of candidate orientations of the BZD ligand in the binding pocket. Candidate orientations were refined based on known structure-activity and stereospecificity characteristics of BZDs and the impact of the α1H101R mutation. Results favor a model in which the BZD molecule is oriented such that the C5-phenyl substituent extends approximately parallel to the plane of the membrane rather than parallel to the ion channel. Application of this computational modeling strategy, which integrates site-directed affinity labeling with structure-activity knowledge to create a molecular model of the docking of active ligands in the binding pocket, may provide a basis for the design of more selective GABAAR modulators with enhanced therapeutic potential.