Probing the molecular basis for affinity/potency- and efficacy-based subtype-selectivity exhibited by benzodiazepine-site modulators at GABAA receptors

2区 · 医学

Article

作者: Söderhielm, Pella Cecilia ; Hansen, Karoline M ; Jensen, Anders A ; Balle, Thomas ; Ahring, Philip K ; Bak-Nyhus, Søren ; Zhang, Michael

The extracellular α⁽⁺⁾/γ₂^(-) interface in the α_1,2,3,5βγ₂ GABA_A receptor harbours the allosteric binding site targeted by benzodiazepines and newer generations of subtype-selective modulators. We have probed the molecular determinants for the affinity/potency-based α₁-preference exhibited by the hypnotic zolpidem (Ambien®, Stilnox®) and the efficacy-based α₃-over-α₁ selectivity displayed by the analgesic NS11394. Binding affinities and functional properties of the modulators were characterized at wild-type, concatenated, mutant and chimeric α_1,3β₂γ_2S receptors expressed in tsA201 cells and Xenopus oocytes by [³H]flumazenil binding and two-electrode voltage clamp electrophysiology. Substitution of Gly²⁰¹ in α₁ with the corresponding Glu in α₃ completely eliminated the α₁-over-α₃ preference exhibited by zolpidem. In contrast, the reverse α₃-E225G mutation did not yield corresponding increases in the binding affinity or modulatory potency of zolpidem at α₃β₂γ_2S, and two additional molecular elements in the extracellular domain of the α-subunit were found also to contribute to its α₁-preference. Interestingly, the α₁-Gly²⁰¹/α₃-Glu²²⁵ residue was also a key determinant of the efficacy-based α₃-over-α₁ selectivity exhibited by NS11394, and a pronounced correlation existed between the side-chain bulkiness of this residue and the modulatory efficacy of NS11394 at the receptor. The subtype-selectivity determinants identified for zolpidem and NS11394 were found also to apply in different degrees to the α₁-preferring modulator indiplon and the α₃-over-α₁ selective modulator L-838,417, respectively. In conclusion, the molecular origins of subtype-selectivity exhibited by benzodiazepine-site modulators at the α_1,2,3,5βγ₂ GABA_A receptor seem more complex than previously appreciated, and the importance of the α₁-Gly²⁰¹/α₃-Glu²²⁵ residue for both potency- and efficacy-based subtype-selective modulation through this site is likely to be rooted in different molecular mechanisms.

2016-11-01·European Journal of Pharmacology3区 · 医学

The α2β3γ2 GABAA receptor preferring agonist NS11394 aggravates dystonia in the phenotypic dt model

3区 · 医学

Article

作者: Bauer, Anne ; Richter, Angelika ; Gerstenberger, Julia ; Richter, Franziska ; Spröte, Christine

Dystonia is a movement disorder, characterized by involuntary muscle contractions resulting in abnormal movements and/or postures. Antidystonic effects of benzodiazepines in patients with different types of dystonia could be replicated in the dt^sz mutant hamster, a phenotypic model of paroxysmal dystonia. Compounds with preferred binding at specific subunits of the gamma aminobutyric acid type A (GABA_A) receptor may provide a more beneficial spectrum of effects in comparison with benzodiazepines. We therefore examined the effects of the α1β3γ2 GABA_A receptor preferring compound zolpidem (2.0-10.0mg/kg i.p.) and of the α2β3γ2 GABA_A receptor preferring compound NS11394 (3.0-30mg/kg i.p.) on the severity of dystonia in the dt^sz mutant in comparison with the benzodiazepine clonazepam (0.5-1.0mg/kg i.p.). As expected, clonazepam exerted pronounced antidystonic effects. While zolpidem showed moderate beneficial effects, NS11394 significantly increased the severity of dystonia. The present results indicate for the first time that positive GABA_A receptor modulators show contrary effects on dystonia dependent on their preference for alpha-subunits. The potential link between alterations in GABA_A receptor subunits and GABAergic disinhibition in dystonia deserves further attention in research on the pathophysiology and therapeutic targets.

2015-07-01·Neuroscience3区 · 医学

GABAA receptor α2 subtype activation suppresses retinal spreading depression

3区 · 医学

Article

作者: Wang, M ; Lin, Y ; Li, Y

Cortical spreading depression (SD) is a transient propagating neuronal excitation followed by depression, which is generally accepted as the underlying cause of migraine. The inhibitory γ-aminobutyric acid type A (GABAA) receptor activation not only reduces cortical SD frequency and propagation, but also relieves migraine headache. This study aims to determine the role of major α subtypes of GABAA receptor in mediating SD genesis and propagation using an efficient in vitro chick retinal model. We firstly demonstrated that abundant α2, and to a lesser extent, α5 of GABAA receptor expression in the chick retina, enabled the tissue useful for studying GABAA receptor pharmacology and SD. Marked suppression of SD by SL651498 and TPA023 was observed at 10 μmol L(-1) and 50 μmol L(-1), respectively, suggesting a critical role of GABAA receptor α subtypes, in particular α2, in modulating retinal SD elicitation and propagation. The negative data on NS11394 at 3 μmol L(-1) on SD and the little positive selectivity of TPA023 for α5 did not support that α5 subtype is involved in SD genesis and propagation. Our data provide strong evidence that α2, but not α5 is involved in the early stage of migraine, indicating that α2 subtype is a possible drug target related to migraine with aura.

100 项与 NS11394 相关的药物交易

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