SAR-Guided Scoring Function and Mutational Validation Reveal the Binding Mode of CGS-8216 at the α1+/γ2- Benzodiazepine Site

J Chem Inf Model. 2018 Aug 27;58(8):1682-1696. doi: 10.1021/acs.jcim.8b00199. Epub 2018 Aug 8.

Abstract

The structural resolution of a bound ligand-receptor complex is a key asset to efficiently drive lead optimization in drug design. However, structural resolution of many drug targets still remains a challenging endeavor. In the absence of structural knowledge, scientists resort to structure-activity relationships (SARs) to promote compound development. In this study, we incorporated ligand-based knowledge to formulate a docking scoring function that evaluates binding poses for their agreement with a known SAR. We showcased this protocol by identifying the binding mode of the pyrazoloquinolinone (PQ) CGS-8216 at the benzodiazepine binding site of the GABAA receptor. Further evaluation of the final pose by molecular dynamics and free energy simulations revealed a close proximity between the pendent phenyl ring of the PQ and γ2D56, congruent with the low potency of carboxyphenyl analogues. Ultimately, we introduced the γ2D56A mutation and in fact observed a 10-fold potency increase in the carboxyphenyl analogue, providing experimental evidence in favor of our binding hypothesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzodiazepines / metabolism
  • Binding Sites
  • Humans
  • Ligands
  • Molecular Docking Simulation
  • Protein Subunits / chemistry
  • Protein Subunits / metabolism
  • Pyrazoles / chemistry
  • Pyrazoles / pharmacology*
  • Receptors, GABA-A / chemistry
  • Receptors, GABA-A / metabolism*
  • Software
  • Structure-Activity Relationship

Substances

  • Ligands
  • Protein Subunits
  • Pyrazoles
  • Receptors, GABA-A
  • Benzodiazepines
  • 2-phenylpyrazolo(4,3-c)quinolin-3(5H)-one