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The role of loops B and C in determining the potentiation of GABA_A receptors by midazolam.

ABSTRACT: Many benzodiazepines are positive allosteric modulators (PAMs) of GABA_A receptors that cause sedation, hypnosis, and anxiolysis. Benzodiazepines bind GABA_A receptors at the extracellular interface of the ? and ? subunits. Within the ? subunit, the benzodiazepine binding site is defined by three highly conserved structural loops, loops A-C. Although previous mutagenesis studies have identified His102 in Loop A as important for benzodiazepine modulation of GABA_A receptors, the functional roles of many of the other conserved residues in loops A-C remain incompletely understood. In this study, we made single mutations in loops A-C of the benzodiazepine binding-site across all six ? subunits. We used whole-cell patch clamp recording to measure the functional effects of these mutations on midazolam potentiation. The results showed that mutating the threonine in loop B and serine in loop C (Thr163 and S206 in human ?1) did not abolish the receptors' responsiveness to midazolam, as the ?1(H102R) mutation did. The loop C mutations exhibited a novel array of ?-isoform specific effects on midazolam potentiation. The ?3(S230I) and ?5(S209I) mutations had the largest effect on midazolam potentiation, increasing the efficacy of midazolam. Novel benzodiazepines targeting loop C may represent a future direction for designing new drugs that specifically alter the activity of ?3- and ?5-containing GABA_A receptors.

SUBMITTER: Moody OA

PROVIDER: S-EPMC6234229 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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The role of loops B and C in determining the potentiation of GABAA receptors by midazolam.

Moody Olivia A OA Jenkins Andrew A

Pharmacology research & perspectives 20181113 6

Many benzodiazepines are positive allosteric modulators (PAMs) of GABAA receptors that cause sedation, hypnosis, and anxiolysis. Benzodiazepines bind GABAA receptors at the extracellular interface of the α and γ subunits. Within the α subunit, the benzodiazepine binding site is defined by three highly conserved structural loops, loops A-C. Although previous mutagenesis studies have identified His102 in Loop A as important for benzodiazepine modulation of GABAA re ...[more]

PMID: 30459951

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Dataset Information

The role of loops B and C in determining the potentiation of GABA_A receptors by midazolam.

Publications

The role of loops B and C in determining the potentiation of GABA<sub>A</sub> receptors by midazolam.

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