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

许多人类疾病，如阿尔茨海默病（AD）、帕金森病（PD）和传染性海绵状脑病（tse），都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一种称为淀粉样蛋白的有毒和可传播的蛋白质颗粒。并不是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，甚至对宿主生物有有益的功能。为什么有些淀粉样蛋白与疾病相关且有毒，而另一些则没有，这是一个非常重要的生物学问题，我们目前确实有答案。这一知识上的差距不仅阻碍了研究人员对淀粉样蛋白生命周期的基础生物学的充分理解，也阻碍了制药行业针对正确的分子结构和开发有效的治疗方法来对抗破坏性的淀粉样蛋白相关疾病。在这个项目中，我们将通过研究淀粉样蛋白是否与病理相关的新观点来解决这一知识差距，这与作为构建块的单个淀粉样蛋白细丝如何组织形成百万分之一到十亿分之一米大小的大型结构有关，我们称之为淀粉样蛋白上层结构。最近，使用固态核磁共振波谱和透射电子显微镜方法，对几种疾病相关的淀粉样蛋白原纤维进行了详细的原子分辨率结构模型，使人们能够深入了解淀粉样蛋白结构中单个原子的组织方式。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，然而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有关，尽管所有淀粉样蛋白都具有相同类型的蛋白质链组织，但仍未被理解。在这里，我们提出，我们关于淀粉样蛋白结构的知识与它们如何与生物学相互作用和/或与疾病相关之间的“缺失环节”是编码在个体淀粉样蛋白细丝将组装成的上层结构类型中，即这些淀粉样蛋白构建块是否可能形成直束，扭曲的绳索或管，大型开放网络或紧密排列的簇等。如果我们能够收集有关淀粉样蛋白构建块可以形成的上层结构类型的数据，并跟踪这些结构如何影响淀粉样蛋白如何与细胞相互作用并在疾病环境中繁殖，那么我们将能够解决淀粉样蛋白结构与其生物学之间缺失的联系。这正是我们现在可以做的，因为我们将使用原子力显微镜（AFM）成像方法，使我们能够看到大量的单个淀粉样蛋白超结构，它们的大小在百万分之一米到十亿分之一米之间，也就是所谓的介观尺寸范围。原子力显微镜成像的淀粉样蛋白结构在这些中间长度尺度之间的原子的大小和细胞的大小，提供低噪声和高分辨率的图像，是非常理想的精确定量测量单个淀粉样蛋白上结构的样品，由不同的组件，如淀粉样蛋白样品的混合物组成。结合对相同淀粉样蛋白结构在细胞内的行为的生物学测量，我们将以独特的方式发现淀粉样蛋白结构与其细胞功能之间缺失的联系。我们的发现将揭示为什么淀粉样蛋白结构在某些但不是所有的情况下会赋予哺乳动物和人类细胞毒性和传染性，也将为我们提供线索，告诉制药行业在寻找有效治疗淀粉样蛋白结构相关的毁灭性疾病时应该瞄准哪些目标。

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.