Abstract
GABAA receptors play a crucial role in the actions of general anesthetics. The recently published crystal structure of the general anesthetic propofol bound to Gloeobacter violaceus ligand-gated ion channel (GLIC), a bacterial homolog of GABAA receptors, provided an opportunity to explore structure-based ligand discovery for pentameric ligand-gated ion channels (pLGICs). We used molecular docking of 153,000 commercially available compounds to identify molecules that interact with the propofol binding site in GLIC. In total, 29 compounds were selected for functional testing on recombinant GLIC, and 16 of these compounds modulated GLIC function. Active compounds were also tested on recombinant GABAA receptors, and point mutations around the presumed binding pocket were introduced into GLIC and GABAA receptors to test for binding specificity. The potency of active compounds was only weakly correlated with properties such as lipophilicity or molecular weight. One compound was found to mimic the actions of propofol on GLIC and GABAA, and to be sensitive to mutations that reduce the action of propofol in both receptors. Mutant receptors also provided insight about the position of the binding sites and the relevance of the receptor’s conformation for anesthetic actions. Overall, the findings support the feasibility of the use of virtual screening to discover allosteric modulators of pLGICs, and suggest that GLIC is a valid model system to identify novel GABAA receptor ligands.
Footnotes
- Received June 5, 2013.
- Accepted August 15, 2013.
↵1 Current affiliation: Chemistry Department, Skidmore College, Saratoga Springs, New York.
This work was supported by the National Institutes of Health National Institute on Alcohol Abuse and Alcoholism [Grants AA06399 and AA19875]; the Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology; the Swedish Foundation for Strategic Research and the Swedish e-Science Research Center; and the Knut and Alice Wallenberg Foundation. Computational resources were provided by the Swedish National Infrastructure for Computing.
Part of this work was presented as follows: Heusser SA (2012) Functional Validation of Rationally Designed Allosteric Ion Channel Modulators. Master’s thesis, Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, Zurich, Switzerland.
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This article has supplemental material available at molpharm.aspetjournals.org.
- Copyright © 2013 by The American Society for Pharmacology and Experimental Therapeutics
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