Formation and Function of Prefibrillar ABeta Assemblies

描述（由申请人提供）：我们假设淀粉样蛋白β蛋白（Abeta）组装是阿尔茨海默病（AD）和脑淀粉样血管病（CAA）的一个种子神经发病过程。如果是这样，控制β组装可能具有治疗价值。在过去的十年中，我们一直致力于阐明体外β自结合的途径，鉴定组装中间体，并评估这些结构的神经毒性活性。这项工作导致淀粉样蛋白原纤维的发现，后来在体外和体内被发现具有神经毒性，并与“北极”形式的阿尔茨海默病有关。最近，新的化学交联研究表明，存在较小的寡聚结构（副核），这些结构由Abeta（1-42）快速形成，而不是由Abeta（1-40）。因此，Abeta（1-42）与AD的强关联可能是由于Abeta（1-42）特异性组装事件发生在自结合的最早阶段，即寡聚化。我们还描述了一种新的富含螺旋的低聚体组装中间体。我们预测Asp23- b> Asn氨基酸的替换会影响该中间体和原纤维的形成速度。有趣的是，这个位点的重要性已经在人类身上得到了证明，通过发现爱荷华州的一个亲属患有由这种替代引起的早发性CAA。在这一建议中，我们将研究早期Abeta组装反应的热力学和结构生物学，以了解控制这些反应的基本因素并表征形成的结构。在同时进行的实验中，我们将检查Abeta组装的神经毒性活动，以确定哪些可能是最相关的病理生物学。我们的研究将为更好地理解Abeta组装的形成机制和生物活性以及淀粉样蛋白形成和蛋白质错误折叠的一般原理提供帮助。我们的实验计划包括四个具体目标。

DESCRIPTION (provided by applicant): We hypothesize that amyloid Beta-protein (Abeta) assembly is a seminal neuropathogenetic process in Alzheimer's disease (AD) and in cerebral amyloid angiopathy (CAA). If so, controlling Abeta assembly could be of therapeutic value. Over the last decade, we have worked to elucidate the pathways of Abeta self-association in vitro, to identify assembly intermediates, and to evaluate the neurotoxic activities of these structures. This work led to the discovery of the amyloid protofibril, later found to be neurotoxic in vitro and in vivo, and to be linked to an "Arctic" form of AD. Recently, novel chemical cross-linking studies have revealed the existence of smaller oligomeric structures (paranuclei), which are formed rapidly by Abeta (1-42) but not by Abeta (1-40). The strong association of Abeta (1-42) with AD thus may result from Abeta (1-42)-specific assembly events occurring at the earliest stage of self-association, oligomerization. We also have described a novel helix-rich oligomeric assembly intermediate. We predicted that an Asp23->Asn amino acid replacement would affect the rate of formation of this intermediate and of fibrils. Interestingly, the importance of this site has been proven in humans through the discovery of an Iowa kindred suffering from an early onset form of CAA caused by this exact substitution. In this proposal, we will examine the thermodynamics and structural biology of early Abeta assembly reactions in order to understand the fundamental factors controlling these reactions and to characterize the structures formed. In concurrent experiments, we will examine the neurotoxic activities of the Abeta assemblies to establish which may be of most relevance pathobiologically. Our studies will provide a better understanding of the mechanisms of formation and the biological activities of Abeta assemblies and of general principles of amyloid formation and protein misfolding. Our experimental plan comprises four specific aims. Aim 1. To elucidate the thermodynamics of early Abeta assemblies and Abeta fibril formation. Aim 2. To determine the structural features of early Abeta assemblies. Aim 3. To determine the structure and mechanism of action of oligomeric Abeta fibrillogenesis inhibitors. Aim 4. To determine the biological activity of early intermediates.