The prion protein as a probe for identifying neurotoxic protein oligomers

 阿尔茨海默病（AD）是一种影响数百万美国人的破坏性神经退行性疾病，是当今生物医学科学中最紧迫和最具挑战性的谜团之一。多方面的研究旨在实现早期诊断和治疗的方法以及对所涉及的生物学的基本了解。关于该疾病的早期阶段的一个有希望的假设起源于关于淀粉样蛋白β（Aβ）斑块形成的观察，这是AD的独特病理学标志。最近的研究表明，在斑块形成之前成核的Aβ小聚集体实际上可能对细胞直接有毒。这些相对 小的聚集体（寡聚体和原纤维）已经显示出干扰突触信号传导，并且可以在体内产生毒性作用。在解决这些低聚物的毒性作用，阿尔茨海默病和哺乳动物朊蛋白（PrPc）之间的一个有趣的连接已经曝光，为我们提供了什么可能是一个关键的环节，在理解的初始过程导致进行性痴呆和神经元损失。PrPc是一种细胞表面蛋白，其功能尚不清楚。然而，现在有相当多的证据表明，合成Aβ的聚集体特异性结合PrPc，产生下游效应，包括突触改变和细胞死亡。这种联系开辟了一个新的研究领域，有可能影响我们对AD的理解，从而改进跟踪和靶向疾病早期阶段的方法。一个关键的联系，增加了兴趣，这一机制在于，PrPc本身，在一个错误的折叠状态（表示PrPSc），作为传染性海绵状脑病（TSE）的传染性aget，通过大脑传播，并产生进行性痴呆和神经变性。这就提出了一个问题，即PrPc是否通过与毒性聚集体的相互作用，在AD和TSE的早期阶段促进细胞的神经退行性变化。本提案中提出的项目旨在描述PrPc与毒性形式Aβ之间的相互作用，使用特定的生物物理方法将蛋白质和肽聚集体作为一个单一单元分离在一起，然后表征Aβ聚集体的大小和构象。我们希望这将导致 更好地了解哪些Aβ聚集体对神经元健康构成最大威胁，哪些聚集体可能作为早期诊断的标志物或提供治疗靶点。此外，我们试图阐明的毒性机制PrPSc使用一种新的方法，旨在捕捉和表征早期结合事件。由于PrPSc和神经元之间的详细毒性相互作用尚未被表征，这种方法有可能为TSE的药物靶向和预防性治疗开辟一个新的领域。

 DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is a devastating neurodegenerative disease that affects millions of Americans, and presents one of the most pressing and challenging mysteries in biomedical science today. Multiple lines of research are aimed at achieving methods for early diagnosis and treatment as well as a basic understanding of the biology involved. One promising hypothesis regarding the early stages of the disease originates in observations regarding the formation of amyloid beta (Aβ) plaques, which are a unique pathological hallmark of AD. Recent research indicates that small aggregates of Aβ that nucleate prior to the formation of plaques may in fact be directly toxic to cells. These relatively small aggregates (oligomers and protofibrils) have been shown to interfere in synaptic signaling, and can produce toxic effects in vivo. In addressing the toxic effect of these oligomers, an interesting connection between Alzheimer's disease and the mammalian prion protein (PrPc) has come to light, providing us with what might be a crucial link in understanding the initial processes leading to progressive dementia and neuronal loss. PrPc is a cell-surface protein with an as-yet unknown function. However, there is now considerable evidence that aggregates of synthetic Aβ bind specifically to PrPc, producing downstream effects including synaptic alteration and cell death. This connection opens up a new area of research, one with the potential to impact our understanding of AD, leading to improved methods for following and targeting the early stages of the disease. A crucial linkage that adds interest to this mechanism lies in the fact that PrPc itself, in a misfolded state (denoted PrPSc), acts as the infectious aget in transmissible spongiform encephalopathies (TSEs), spreading through the brain and producing progressive dementia and neurodegeneration. This raises questions about whether PrPc acts to promote neurodegenerative changes in cells in the early stages of both AD and TSEs through interactions with toxic aggregates. The project put forth in this proposal aims to describe the interaction between PrPc and toxic forms of Aβ using specific biophysical methods for isolating the protein and the peptide aggregates together as a single unit, and then characterizing the size and conformation of the Aβ aggregates. Our hope is that this will lead to a better understanding of which Aβ aggregates present the greatest threat to neuronal health, and which aggregates might serve as markers for early diagnosis or provide targets for treatment. Additionally, we seek to shed light on the mechanism of toxicity for PrPSc using a novel approach designed to capture and characterize early binding events. Because the detailed toxic interactions between PrPSc and neurons have not yet been characterized, this approach holds potential for opening a new field of drug targeting and preventative treatment for TSEs.