Department of Anesthesiology, Washington University in St. Louis, St. Louis, United States.
Taylor Family Institute for Innovative Psychiatric Research, Washington University in St. Louis, St. Louis, United States.
Elife. 2020 Sep 21;9:e55331. doi: 10.7554/eLife.55331.
This study examines how site-specific binding to three identified neurosteroid-binding sites in the αβ GABA receptor (GABAR) contributes to neurosteroid allosteric modulation. We found that the potentiating neurosteroid, allopregnanolone, but not its inhibitory 3β-epimer epi-allopregnanolone, binds to the canonical β(+)-α(-) intersubunit site that mediates receptor activation by neurosteroids. In contrast, both allopregnanolone and epi-allopregnanolone bind to intrasubunit sites in the β subunit, promoting receptor desensitization and the α subunit promoting effects that vary between neurosteroids. Two neurosteroid analogues with diazirine moieties replacing the 3-hydroxyl (KK148 and KK150) bind to all three sites, but do not potentiate GABAR currents. KK148 is a desensitizing agent, whereas KK150 is devoid of allosteric activity. These compounds provide potential chemical scaffolds for neurosteroid antagonists. Collectively, these data show that differential occupancy and efficacy at three discrete neurosteroid-binding sites determine whether a neurosteroid has potentiating, inhibitory, or competitive antagonist activity on GABARs.
这项研究考察了特定于三个已鉴定的神经甾体结合位点在 αβ GABA 受体 (GABAR) 中的结合如何导致神经甾体变构调节。我们发现，增强型神经甾体，别孕烯醇酮，但不是其抑制性 3β-差向异构体 epi-别孕烯醇酮，结合到经典的 β(+)-α(-)亚基间位点，该位点介导神经甾体对受体的激活。相比之下，别孕烯醇酮和 epi-别孕烯醇酮都结合到 β 亚基的亚基内位点，促进受体脱敏和 α 亚基促进作用，这些作用在神经甾体之间有所不同。两种具有叠氮化物部分取代 3-羟基的神经甾体类似物 (KK148 和 KK150) 结合到所有三个位点，但不能增强 GABAR 电流。KK148 是一种脱敏剂，而 KK150 没有变构活性。这些化合物为神经甾体拮抗剂提供了潜在的化学支架。总的来说，这些数据表明，在三个离散的神经甾体结合位点的差异占据和效力决定了神经甾体对 GABAR 是具有增强、抑制还是竞争性拮抗剂活性。
