The Brain's Valium: Investigating the Role of DBI in Regulating GABA-mediated Inhibition

项目总结： 苯二氮卓类药物(BZD)于20世纪50年代首次合成，是一种广泛使用的处方药，它能发挥其 通过与GABA-A受体(GABAARs)结合，具有抗焦虑、肌肉松弛、镇静和抗惊厥作用； 大脑中主要的抑制性配体门控离子通道。自从它们的合成以来，许多科学家已经从理论上 大脑中存在一种内源性BZD，或称Endozepine。1983年，一种候选多肽 GABAAR结合试验中移位的BZD是从脑匀浆中分离出来的。然而，证据表明这一点 1 被称为安定结合抑制物(DBI)的多肽在大脑中具有功能作用，目前尚缺乏。 最近，使用DBI击倒实验证明了它在侧脑室下区 DBI及其多肽片段ODN抑制GABA诱导的电流并促进 神经发生，表明DBI和ODN在体内作为GABAARs的负变构调节器发挥作用。 2. 然而，在丘脑网状核(在控制癫痫方面发挥重要作用的核)中 癫痫发作)、DBI和/或DBI衍生的多肽被发现增强GABA电流并抑制癫痫 活动。因此，根据大脑区域的不同，DBI可以增强或抑制GABAAR的活性。然而，几乎没有什么是 3. 了解DBI如何执行这些操作。 单一蛋白质的产物是如何对GABAAR电流产生正面或负面影响的？做DBI- ODN等衍生多肽具有与DBI？相同的功能效应。不同的细胞类型是否会使 加工不同的DBI多肽(S)？DBI是否在翻译后进行修改(例如，磷酸化、酰化)，并且可以 这些修改会改变DBI的生理效应吗？拟议的实验将解决这些问题 基本问题和将1)确定特定的GABAAR亚基组合是否中介积极和 DBI和ODN的负作用；2)决定星形胶质细胞和神经元是否释放不同的DBI多肽和/或 翻译后对DBI的处理不同，这影响了它的功能效应，3)决定了星形胶质细胞 神经元表达不同的DBI转录变体。这些实验的成功完成将验证 DBI作为内源性BZD的作用，将为理解DBI如何调节GABA奠定基础。 调节大脑中的抑制作用。

Project Summary: First synthesized in the 1950s, benzodiazepines (BZDs) are widely prescribed drugs that exert their anxiolytic, muscle relaxant, sedative, and anticonvulsant actions by binding to GABA-A receptors (GABAARs), the main inhibitory ligand-gated ion channel in the brain. Since their synthesis, many scientists have theorized that there exists an endogenous BZD, or endozepine, in the brain. In 1983, a candidate polypeptide that displaced BZDs in a GABAAR binding assay was isolated from brain homogenates . However, proof that this 1 peptide called diazepam-binding inhibitor (DBI) had functional effects in the brain was lacking. Recently, using DBI knock-down experiments it was demonstrated in the subventricular zone of the lateral ventricles that DBI and one of its peptide fragments, ODN, inhibit GABA-induced currents and promote neurogenesis , indicating that DBI and ODN work as negative allosteric modulators of GABAARs in vivo. 2 However, in the thalamic reticular nucleus (a nucleus that plays an important role in controlling epileptic seizures), DBI and/or a DBI-derived peptide was found to enhance GABAAR currents and suppress epileptic activity . Thus, depending on the brain region, DBI can potentiate or inhibit GABAAR activity. Little, however, is 3 known about how DBI exerts these actions. How do products from a single protein elicit positive versus negative effects on GABAAR currents? Do DBI- derived peptides such as ODN elicit the same functional effects as DBI? Do different cell types make and process distinct DBI peptide(s)? Is DBI modified post-translationally (e.g. phosphorylated, acylated) and can these modifications alter DBI's physiological effects? The proposed experiments will address these fundamental questions and will 1) determine if specific GABAAR subunit combinations mediate the positive and negative actions of DBI and ODN; 2) determine if astrocytes and neurons release different DBI peptides and/or post-translationally process DBI differently, which impact its functional effects and 3) determine if astrocytes and neurons express different DBI transcript variants. Successful completion of these experiments will validate DBI's role as an endogenous BZD and will lay the foundation for understanding how DBI regulates GABA- mediated inhibition in the brain.