The prion protein as a probe for identifying neurotoxic protein oligomers

 描述(申请人提供)：阿尔茨海默病(AD)是一种毁灭性的神经退行性疾病，影响着数百万美国人，是当今生物医学科学中最紧迫和最具挑战性的谜团之一。多项研究的目标是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。关于疾病早期阶段的一个有希望的假说源于对淀粉样β蛋白(Aβ)斑块形成的观察，这是AD的一个独特的病理标志。最近的研究表明，在斑块形成之前形成的Aβ的小聚集体实际上可能对细胞直接有毒。这些相对来说 小聚集体(寡聚体和原纤维)已被证明干扰突触信号，并可在体内产生毒性效应。在解决这些寡聚体的毒性效应时，阿尔茨海默氏病和哺乳动物PrPC之间的一个有趣的联系被揭开了，这为我们提供了一个可能是理解导致进行性痴呆和神经元丧失的初始过程的关键环节。PrPC是一种功能未知的细胞表面蛋白。然而，现在有相当多的证据表明，合成的Aβ聚集体与PrPC特异性结合，产生包括突触改变和细胞死亡在内的下游效应。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，导致改进跟踪和针对疾病早期阶段的方法。增加这一机制的一个关键联系在于PrPc本身处于错误折叠状态(表示为PrPSc)，在可传播的海绵状脑病(TSE)中充当感染性抗原，通过大脑传播并产生进行性痴呆和神经变性。这引发了人们的疑问：PrPc是否通过与有毒聚集体的相互作用，在AD和TSE的早期阶段促进了细胞的神经退行性变化。这项建议中提出的项目旨在利用特定的生物物理方法来描述PrPC与Aβ毒性形式之间的相互作用，以将蛋白质和多肽聚集体分离为一个单一单元，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，以及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，我们试图通过一种新的方法来阐明PrPSc的毒性机制，该方法旨在捕获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，该方法具有打开TSE药物靶向和预防性治疗的新领域的潜力。

 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.