Benzodiazepines modulate GABAA receptor surface levels and synaptic inhibition

描述（由申请人提供）：苯二氮卓类药物广泛用于治疗焦虑、失眠和癫痫发作。此外，它们是精神分裂症，抑郁症和酒精解毒的关键辅助治疗。然而，由于耐受性的发展，这些安全有效的化合物的使用受到严重限制。苯二氮卓类可增强3-氨基丁酸（GABAA）受体的活性，GABAA受体是中枢神经系统中的主要抑制性神经递质受体。耐受性发展的分子机制尚未确定。越来越明显的是，苯并二氮卓类药物优先增强GABAA受体亚型的活性，这些受体亚型主要由？一比三，？然后呢？2个亚单位。相反，大多数突触外GABAA受体（GABAARs），介导紧张性抑制，其结构不同于它们的突触对应物，并且对苯二氮卓类药物的功能调节不敏感。然而，尚未证实苯二氮卓类药物治疗神经元与GABAAR亚型表面水平变化和神经元抑制疗效之间的联系机制。这些现象与我们的初步研究一起产生了驱动本提案中描述的实验的中心假设：暴露于苯二氮卓类药物的神经元促进去除？2亚单位的GABAAR从质膜和其随后的降解，导致抑制性突触的大小和数量的减少沿着突触抑制的功效降低。我们的研究主要集中在以下三个方面：（1）研究苯二氮卓类药物（benzodiazepine，BZ）对GABAAR膜运输和降解的影响;（2）研究BZ对突触抑制的影响，并确定其影响突触效应的机制;和（3）我们将测量BZ处理调节野生型小鼠和？2 H101 R突变小鼠表达？2-对BZ不敏感的GABAAR。 公共卫生相关性：苯二氮卓类药物被广泛用于治疗焦虑、失眠和癫痫发作，但由于耐受性的发展，其临床应用受到严重限制。苯二氮卓类药物的治疗作用主要通过增强？-氨基丁酸（GABA）A型受体，中枢神经系统中的主要抑制性神经递质受体。我们将研究苯二氮卓类药物对GABA A型受体的影响，以确定苯二氮卓类药物耐受性的分子机制，促进新治疗药物的开发，以改善患者的生活质量。

DESCRIPTION (provided by applicant): Benzodiazepines are widely used to treat anxiety, insomnia and seizure disorders. Furthermore they are key adjunct treatments in schizophrenia, depression and alcohol detoxification. However, the use of these safe and efficacious compounds is severely limited due to the development of tolerance. Benzodiazepines potentiate the activity of 3-aminobutyric acid (GABAA) receptors, the major inhibitory neurotransmitter receptors in the central nervous system. The molecular mechanism underlying the development of tolerance has not yet been determined. It is increasingly evident that benzodiazepines preferentially enhance the activity of GABAA receptor subtypes present at synaptic sites that are largely composed of ?1-3, ? and ?2 subunits. In contrast, the majority of extrasynaptic GABAA receptors (GABAARs), which mediate tonic inhibition, have structures different from those of their synaptic counterparts and are insensitive to functional modulation by benzodiazepines. However, a mechanism linking benzodiazepine treatment of neurons to changes in surface levels of GABAAR subtypes and the efficacy of neuronal inhibition has not been demonstrated. These phenomena together with our preliminary studies generated the central hypothesis driving the experiments described in this proposal: Exposure of neurons to benzodiazepines promotes the removal of ?2 subunit-containing GABAARs from the plasma membrane and their subsequent degradation, leading to a reduction in inhibitory synapse size and number along with a decrease in the efficacy of synaptic inhibition. Our proposal centers on three specific aims: (1) We will characterize the effects of benzodiazepine (BZ) treatment on GABAAR membrane trafficking and degradation; (2) We will measure the effects of BZ treatment on synaptic inhibition and identify the mechanism altering synaptic efficacy; and (3) We will measure the ability of BZ treatment to modulate cell surface accumulation of GABAARs and synaptic inhibition in wild type mice and ?2H101R mutant mice that express ?2-containing GABAAR that are BZ insensitive. PUBLIC HEALTH RELEVANCE: Benzodiazepines are widely used to treat anxiety, insomnia and seizure disorders, but their clinical use is severely limited due to the development of tolerance. The therapeutic actions of benzodiazepines are primarily exerted by potentiating the activity of ?-aminobutyric acid (GABA) type A receptors, the major inhibitory neurotransmitter receptors in the central nervous system. We will investigate the effects of benzodiazepines on GABA type A receptors to define a molecular mechanism underlying benzodiazepine tolerance, facilitating the development of new therapeutic agents to improve patient quality of life.