Formation and Function of Prefibrillar ABeta Assemblies

描述(申请人提供)：我们假设淀粉样β蛋白(Abeta)组装是阿尔茨海默病(AD)和脑淀粉样血管病(CAA)的原始神经病理过程。如果是这样的话，控制Abeta组装可能具有治疗价值。在过去的十年里，我们一直致力于阐明Abeta在体外的自结合途径，识别组装中间体，并评估这些结构的神经毒性活性。这项工作导致了淀粉样原纤维的发现，后来发现在体外和体内都有神经毒性，并与一种“北极”形式的阿尔茨海默病有关。最近，新的化学交联研究揭示了较小的寡聚结构(核旁)的存在，这些结构由Abeta(1-42)迅速形成，但不由Abeta(1-40)形成。因此，Abeta(1-42)与AD的强烈结合可能是由于Abeta(1-42)特异的组装事件发生在自结合、寡聚的最早阶段。我们还描述了一种新型的富含螺旋的寡聚组装中间体。我们预测，Asp23-&GT；Asn氨基酸的替代将影响这种中间体和纤维的形成速度。有趣的是，这个位点的重要性已经在人类身上得到了证实，因为发现了一个爱荷华州的家庭，由于这种精确的替换而导致了一种早发性CAA。在这个提案中，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组件的神经毒性活性，以确定哪些组件可能与病理生物学最相关。我们的研究将更好地了解Abeta组件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。我们的实验计划包括四个具体目标。 目的1.阐明早期Abeta组装和Abeta原纤维形成的热力学。 目的2.确定早期Abeta组件的结构特征。 目的3.确定寡聚体Aβ纤维蛋白生成抑制剂的结构和作用机制。 目的4.测定早期中间体的生物活性。

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.