Molecular mechanisms of the synaptic organizer alpha-neurexin

描述（由申请人提供）：α-neurexins和它们招募的许多蛋白质与神经精神疾病有关，包括精神分裂症、自闭症谱系障碍和精神发育迟滞-这些疾病迫切需要更好的药物治疗。α-神经毒素是参与神经元通信的突触组织者，并且通过称为剪接插入物的小段氨基酸而多样化。尚不清楚α-神经毒素如何利用其分子特征结合突触间隙中的多种配偶体，包括神经配蛋白、富含亮氨酸的重复跨膜蛋白（LRRTMs）、neurexophilins、GABAA受体以及可能尚未鉴定的蛋白质。了解使α-神经毒素与其不同伴侣结合的分子机制非常重要，因为当这些相互作用被破坏时，基本的生物过程就会改变，而这些过程被认为会导致许多严重精神障碍的病理。我们实验室的长期目标是在分子水平上了解突触间隙中的蛋白质如何整合到形成和维持功能性突触的高度组织化的蛋白质相互作用网络中。这个特殊应用的目的是揭示α-神经毒素家族如何作为突触组织者在不同的突触上将不同的蛋白质组装成不同的蛋白质复合物。中心假设是，α-neurexins利用其独特的分子特征，以产生独特的和塑料结合位点的投资组合。首先，我们假设α-neurexins使用其特有的9个结构域的胞外区，以创建一个分子支架，空间组织蛋白质在突触间隙。其次，我们假设α-neurexins产生不同的结合表面使用剪接插入依赖和剪接插入独立的分子框架。该假设得到了申请人提供的强有力的初步数据的支持，这些数据包括结构研究、蛋白质组学数据、使用新方法研究分子相互作用的生物物理数据以及生物化学和基于细胞的技术。将通过追求三个具体目标来检验该假设：1）描绘使蛋白质伴侣能够以剪接插入物依赖性、α-neurexin依赖性方式结合的分子特征; 2）描绘使蛋白质伴侣能够以剪接插入物非依赖性、α-neurexin依赖性方式结合的分子特征;以及最后3）建立我们已经鉴定的对α-神经毒素特异的新配偶体的结合模式。这一建议的基本原理是，结果将揭示α-神经毒素如何组织突触间隙中的不同分子组装体，这些分子组装体参与严重神经精神疾病的生物学过程。该提案是创新的，因为它提供了一个起点，设计策略，使用小分子化合物或生物制剂操纵突触间隙中的α-neurexin相互作用。这一信息非常重要，因为它可以揭示全新的药物靶点，以逆转神经精神疾病的病理影响，并创造治疗这些毁灭性疾病的全新策略。

DESCRIPTION (provided by applicant): Alpha-neurexins and many of the proteins they recruit are implicated in neuropsychiatric diseases including schizophrenia, autism spectrum disorder, and mental retardation - diseases that are in desperate need of better medications. Alpha-neurexins are synaptic organizers involved in neuronal communication, and are diversified though small stretches of amino acids called splice inserts. It is not known how alpha-neurexins utilize their molecular features to bind a diverse array of partners in the synaptic cleft includin neuroligins, leucine rich repeat transmembrane proteins (LRRTMs), neurexophilins, GABAA-receptors, and likely as yet unidentified proteins as well. It is important to understand the molecular mechanisms that enable alpha-neurexins to bind their diverse partners, because when these interactions are disrupted, fundamental biological processes are altered that are thought to contribute to the pathology of many severe mental disorders. The long term goal of our laboratory is to understand on a molecular level how proteins in the synaptic cleft integrate into highly organized protein interaction networks that form and maintain functional synapses. The objective of this particular application is to reveal how the family of alpha-neurexins works as synaptic organizers to assemble diverse proteins into distinct protein complexes at different synapses. The central hypothesis is that alpha-neurexins exploit their unique molecular features to generate a portfolio of distinct and plastic binding sites. Firstly, we hypothesize that alpha-neurexins use their characteristic nine domain extracellular region to create a molecular scaffold that spatially organizes proteins in the synaptic cleft. Secondly, we hypothesize that alpha-neurexins generate distinct binding surfaces using splice insert-dependent and splice insert-independent molecular frameworks. This hypothesis is supported by strong preliminary data presented by the applicant entailing structural studies, proteomic data, biophysical data using a new method to study molecular interactions, as well as biochemical and cell-based techniques. The hypothesis will be tested by pursuing three specific aims: 1) delineate the molecular features that enable protein partners to bind in a splice insert-dependent, alpha-neurexin-dependent manner; 2) delineate the molecular features that enable protein partners to bind in a splice insert-independent, alpha-neurexin- dependent manner; and finally 3) establish the binding mode of a new partner that we have identified specific for alpha-neurexins. The rationale for this proposal is that the results will reveal how alpha-neurexins organize different molecular assemblies in the synaptic cleft which take part in biological processes involved in severe neuropsychiatric diseases. The proposal is innovative because it provides a starting point to design strategies to manipulate alpha-neurexin interactions in the synaptic cleft using small molecule compounds or biologics. This information is very significant because it could reveal completely new drug targets to reverse pathological effects of neuropsychiatric disorders and create completely new strategies to treat these devastating disorders.