Molecular mechanisms of the synaptic organizer alpha-neurexin

描述(申请人提供)：α-neurexins和他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缓-这些疾病迫切需要更好的药物。Alpha-Neurexins是参与神经元交流的突触组织者，通过称为拼接插入的小段氨基酸而多样化。目前尚不清楚α-Neurexins如何利用其分子特征与突触裂隙中的一系列合作伙伴结合，包括神经连接蛋白、富含亮氨酸重复序列的跨膜蛋白(LRRTM)、Neurexophilins、GABAA受体，以及可能尚未确定的蛋白质。重要的是要了解使α-neurexins结合不同伴侣的分子机制，因为当这些相互作用被破坏时，基本的生物过程就会改变，这些过程被认为是导致许多严重精神障碍的病理因素。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高度有组织的蛋白质相互作用网络中，形成并维持功能性突触。这一特殊应用的目的是揭示α-Neurexins家族如何作为突触组织者在不同的突触将不同的蛋白质组装成不同的蛋白质复合体。中心假设是，α-Neurexins利用其独特的分子特征来产生一系列不同的可塑性结合位点。首先，我们假设α-Neurexins使用其特有的九个结构域胞外区来创建一个分子支架，在突触裂隙中空间组织蛋白质。其次，我们假设α-Neurexins使用剪接插入依赖和剪接插入非依赖的分子框架产生不同的结合表面。这一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化和基于细胞的技术。这一假说将通过追求三个具体目标来检验：1)描述使蛋白质伙伴能够以剪接插入依赖、α-neurexin的方式结合的分子特征；2)描述使蛋白质伙伴能够以剪接插入非依赖的、α-neuresin依赖的方式结合的分子特征；以及最后3)建立我们已经确定的α-neurexins特异的新伙伴的结合模式。这一提议的基本原理是，研究结果将揭示阿尔法-纽氨酸是如何在突触裂隙中组织不同的分子组装的，这些组装参与了与严重的神经精神疾病有关的生物过程。这项提议是创新的，因为它为设计策略提供了一个起点，以使用小分子化合物或生物制剂来操纵突触间隙中的阿尔法-纽瑞新相互作用。这一信息非常重要，因为它可以揭示全新的药物靶点，以逆转神经精神障碍的病理效应，并创建全新的策略来治疗这些毁灭性的疾病。

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.