Mechanism of alpha-subunit selectivity of benzodiazepine pharmacology at gamma-aminobutyric acid type A receptors.

Peter B Wingrove, Patrick Safo, Lola Wheat, Sally A Thompson, Keith A Wafford, Paul J Whiting

Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, Eastwick Road, Essex CM20 2QR, Harlow, UK. Peter_Wingrove@Merck.com

European journal of pharmacology 2002 Feb 15

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Benzodiazepine pharmacology at the GABA(A) receptor is dependent on the alpha and gamma subunit isoforms present. Ligands with higher affinity for certain isoforms--selective compounds--have been classified into benzodiazepine type I and II and into diazepam-sensitive and diazepam-insensitive receptors. A single amino acid position (alpha1G201/alpha3E225) has been identified which discriminates BZI and BZII receptors. The role of this residue has been explored by mutagenesis of alpha1 position 201 and the pharmacology of recombinant receptors examined using BZI receptor agonists. Ligand affinity is reduced by increasing side chain volume at alpha1G201 suggesting that steric inhibition underlies alpha-subunit selectivity. A second amino acid (alpha1H102/alpha6R100) determines diazepam sensitivity. The nature of the amino acid at this position was also examined by mutagenesis. Flumazenil and Ro15-4513 (ethyl 8-azido-6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a]-[1,4]benzodiazepine-3-carboxylate) binding affinity correlated weakly with the amino acid hydrophobicity suggesting a weak hydrophobic interaction between the ligand and alpha1H102.

Citation

Peter B Wingrove, Patrick Safo, Lola Wheat, Sally A Thompson, Keith A Wafford, Paul J Whiting. Mechanism of alpha-subunit selectivity of benzodiazepine pharmacology at gamma-aminobutyric acid type A receptors. European journal of pharmacology. 2002 Feb 15;437(1-2):31-9