The suprastructure-function relationship between amyloid assemblies and their toxic and infectious potentials

许多人类疾病，例如阿尔茨海默病（AD）、帕金森病（PD）和传染性海绵状脑病（TSE），与蛋白质的异常折叠和组装有关。这种错误折叠的最终结果是形成大的不溶性蛋白质沉积物以及称为淀粉样蛋白的有毒和可传播的蛋白质颗粒。并非所有的淀粉样蛋白都与疾病有关，因为有些淀粉样蛋白可以被细胞耐受，甚至对其宿主生物体发挥有益的功能。为什么有些淀粉样蛋白是疾病相关的和有毒的，而另一些则不是，这是一个根本性的重要生物学问题，我们目前确实有答案。我们知识上的这一差距不仅阻碍了研究人员充分理解淀粉样蛋白生命周期中的基本生物学，而且也阻碍了制药行业靶向正确的分子结构并开发针对毁灭性淀粉样蛋白相关疾病的有效疗法。在这个项目中，我们将通过调查新的想法来解决这个知识缺口，即淀粉样蛋白是否与病理学有关，这与单个淀粉样蛋白丝作为构建块如何组织形成尺寸在百万分之一到十亿分之一米范围内的大结构有关，我们称之为淀粉样蛋白超结构。详细的原子分辨率结构模型，用于几种疾病相关的淀粉样蛋白原纤维解决使用固体，国家核磁共振光谱和透射电子显微镜的方法，使洞察到如何个别原子是组织在淀粉样结构使用这些方法已经解决了淀粉样蛋白结构中单个蛋白质链的详细组织，但这些结构如何与生物学相互作用，以及为什么一些淀粉样蛋白与疾病相关，即使所有淀粉样蛋白共享相同类型的蛋白质链组织，尚未被理解。在这里，我们提出，我们对淀粉样蛋白结构的了解与它们如何与生物学和/或疾病相互作用之间的“缺失环节”是编码在单个淀粉样蛋白丝将组装成的超结构类型中，即这些淀粉样蛋白构建块是否可以形成直束，扭曲的绳索或管，大的开放网络或紧密堆积的簇等。如果我们能收集关于淀粉样蛋白构建的超结构类型的数据-块可以形成并遵循这些结构中的每一个如何影响淀粉样蛋白如何与细胞相互作用并在疾病背景下传播，那么我们就能够解决淀粉样蛋白结构和它们的生物学之间缺失的联系。这正是我们现在所能做的，因为我们将使用原子力显微镜（AFM）成像方法，使我们能够可视化大量的单个淀粉样蛋白超结构，其尺寸在百万分之一米到十亿分之一米之间，所谓的介观尺寸范围。在原子大小到细胞大小之间的这些中间长度尺度中的淀粉样蛋白结构的原子力显微镜成像给出了低噪声和高分辨率图像，其对于由不同组装体的混合物组成的样品（例如淀粉样蛋白样品）中的单个淀粉样蛋白超结构的精确定量测量非常理想。这与相同的淀粉样蛋白结构如何在细胞中表现的生物学测量相结合，我们将独特地发现淀粉样蛋白结构与其细胞功能之间的缺失联系。我们的研究结果将揭示为什么淀粉样蛋白结构可以在某些但不是所有情况下赋予哺乳动物和人类细胞毒性和感染性，并且还将为我们提供制药行业在寻找有效治疗方法时应该瞄准的线索。

A number of human disorders, for example Alzheimer's disease (AD), Parkinson's disease (PD), and transmissible spongiform encephalopathies (TSEs), are associated with the abnormal folding and assembly of proteins. The net result of this misfolding is the formation of large insoluble protein deposits as well as toxic and transmissible protein particles in a state called amyloid. Not all amyloids are associated with disease, as some are tolerated by the cells or even perform beneficial functions for their host organisms. Why some amyloid are disease-associated and toxic while others are not is a fundamentally important biological question that we currently do have answer to. This gap in our knowledge not only prevents researchers from fully understanding the fundamental biology in the amyloid life-cycle, but also prevent pharmaceutical industries from targeting the correct molecular structures and developing effective therapeutics against the devastating amyloid associated diseases. In this project, we will address this knowledge gap by investigating the new idea that whether amyloid is associated with pathology or not is linked to how individual amyloid filaments, as building blocks, are organised to form large structures in the range of a millionth to a billionth of metre in size, which we call the amyloid suprastructure.Recently, detailed atomic-resolution structural models for several disease-associated amyloid fibrils resolved using solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy methods have allowed insight into how individual atoms are organised in the amyloid structures. Using these methodologies have resolved the detailed organisation of individual protein chains in amyloid structures, yet how these structures interact with biology and why some amyloid are associated with disease even though all amyloid share the same type of organisation of the protein chains has not been understood. Here, we propose that the "missing-link" between our knowledge on amyloid structures and how they interact with biology and/or associated with disease is encoded in the type of suprastructure individual amyloid filaments will assembly into, that is whether these amyloid building-blocks may form straight bundles, twisted ropes or tubes, large open networks or tightly packed clusters etc. If we can gather data on the types of suprastructures amyloid building-blocks can form and follow how each of these structures may influence how amyloid interact with cells and propagate in a disease context, then we will be able to resolve the missing-link between amyloid structure and their biology. This is exactly what we can now do, as we will use atomic force microscopy (AFM) imaging method that enable us to visualise large number of individual amyloid superstructures that are between millionths of metre in size to billionths of metre in size, so called mesoscopic size range. Atomic force microscopy imaging of amyloid structures in these intermediate length scales between the sizes of atoms to the size of cells gives low-noise and high resolution images that are very much ideal for the precise quantitative measurement of individual amyloid suprastructures in sample that are composed of mixtures of diverse assemblies such as amyloid samples. This combined with biological measurements of how the same amyloid structures behave with/in cells, we will be uniquely placed to discover the missing-link between structure of amyloid and their cellular functions. Our findings will shed new light on the why amyloid structures can confers cytotoxicity and infectivity in mammals and humans in some but not all cases, and will also give us clues as to what pharmaceutical industries should target in the search for effective therapies against the devastating diseases some amyloid structures are associated with.