The GABAA receptor alpha+beta- interface: a novel target for subtype selective drugs

J Neurosci. 2011 Jan 19;31(3):870-7. doi: 10.1523/JNEUROSCI.5012-10.2011.


GABA(A) receptors mediate the action of many clinically important drugs interacting with different binding sites. For some potential binding sites, no interacting drugs have yet been identified. Here, we established a steric hindrance procedure for the identification of drugs acting at the extracellular α1+β3- interface, which is homologous to the benzodiazepine binding site at the α1+γ2- interface. On screening of >100 benzodiazepine site ligands, the anxiolytic pyrazoloquinoline 2-p-methoxyphenylpyrazolo[4,3-c]quinolin-3(5H)-one (CGS 9895) was able to enhance GABA-induced currents at α1β3 receptors from rat. CGS 9895 acts as an antagonist at the benzodiazepine binding site at nanomolar concentrations, but enhances GABA-induced currents via a different site present at α1β3γ2 and α1β3 receptors. By mutating pocket-forming amino acid residues at the α1+ and the β3- side to cysteines, we demonstrated that covalent labeling of these cysteines by the methanethiosulfonate ethylamine reagent MTSEA-biotin was able to inhibit the effect of CGS 9895. The inhibition was not caused by a general inactivation of GABA(A) receptors, because the GABA-enhancing effect of ROD 188 or the steroid α-tetrahydrodeoxycorticosterone was not influenced by MTSEA-biotin. Other experiments indicated that the CGS 9895 effect was dependent on the α and β subunit types forming the interface. CGS 9895 thus represents the first prototype of drugs mediating benzodiazepine-like modulatory effects via the α+β- interface of GABA(A) receptors. Since such binding sites are present at αβ, αβγ, and αβδ receptors, such drugs will have a much broader action than benzodiazepines and might become clinical important for the treatment of epilepsy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Binding Sites / physiology
  • Dose-Response Relationship, Drug
  • Electrophysiology
  • Flumazenil / pharmacology
  • GABA-A Receptor Agonists / pharmacology*
  • Protein Subunits / physiology*
  • Pyrazoles / pharmacology
  • Receptors, GABA-A / physiology*
  • Xenopus laevis
  • gamma-Aminobutyric Acid / pharmacology


  • GABA-A Receptor Agonists
  • Protein Subunits
  • Pyrazoles
  • Receptors, GABA-A
  • Flumazenil
  • gamma-Aminobutyric Acid
  • 2,5-dihydro-2-(4-methoxyphenyl)-3H-pyrazolo(4,3-c)quinolin-3-one