Assembly of recombinant tau into filaments identical to those of Alzheimer's disease and chronic traumatic encephalopathy.
Assembly of recombinant tau into filaments identical to those of Alzheimer's disease and chronic traumatic encephalopathy.
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DOI：
10.7554/elife.76494
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发表时间：
2022-03-04
期刊：
影响因子：
7.7
通讯作者：
Scheres SHW
中科院分区：
文献类型：
--
作者：
Lövestam S;Koh FA;van Knippenberg B;Kotecha A;Murzin AG;Goedert M;Scheres SHW
tau蛋白的大量丝状包涵体是超过20种神经退行性疾病的特征，这些疾病统称为tau蛋白病。来自人脑的tau淀粉样蛋白丝的电子冷冻显微镜（cryo-EM）结构揭示了不同的tau折叠与许多不同的疾病有关。缺乏基于实验室的模型系统来生成这些结构，阻碍了揭示tau蛋白病背后的分子机制的努力。在这里，我们报告在体外组装条件与重组tau复制丝的结构，从阿尔茨海默氏病（AD）和慢性创伤性脑病（CTE），确定由冷冻EM。我们的研究结果表明，tau蛋白的翻译后修饰调节细丝组装，并且先前观察到的AD和CTE细丝中的额外密度可能来自无机盐的存在，如磷酸盐和氯化钠。在体外将tau组装成疾病相关的细丝将有助于研究确定它们在不同疾病中的作用，以及开发特异性结合这些结构或防止其形成的化合物。许多神经退行性疾病，包括阿尔茨海默病，最常见的痴呆症，其特征是一种称为tau的蛋白质的打结团块。在这些疾病中，tau蛋白错误折叠，堆叠在一起并形成异常的细丝，这些细丝具有结构化的核心和模糊的外壳。这些粘性、错误折叠的蛋白质被认为对脑细胞有毒，脑细胞的丢失最终会导致人们的移动、思考、感觉或行为出现问题。使用称为电子冷冻显微镜或cryo-EM的原子级成像技术重建tau细丝的形状，研究人员发现某些疾病中存在不同类型的tau细丝。例如，在阿尔茨海默病中，发现了成对的螺旋和直丝的混合物。在慢性创伤性脑病（CTE）中再次看到不同的tau丝，这是一种与重复性脑创伤相关的疾病。然而，目前尚不清楚tau如何折叠成这些不同的形状，以及在什么条件下形成某些类型的细丝。不同的tau折叠在不同疾病中的作用也知之甚少。这在很大程度上是因为在实验室中制造tau蛋白的研究人员还没有复制出在患病脑组织中发现的tau细丝的确切结构。Löveillance等人描述了在实验室中制造tau纤维的条件，这些条件与从死于阿尔茨海默病和CTE的人的大脑中分离出来的条件相同。Löveillance等人指导细菌制造tau蛋白，优化了细丝组装条件，包括振荡时间和速度，并发现真正的细丝由缩短的tau蛋白形成。在冷冻电镜成像中，实验室产生的细丝具有与阿尔茨海默病特征细丝相同的左旋扭曲和螺旋对称性。然而，添加盐改变了tau纤维的形状。在氯化钠（也称为厨房盐）的存在下，tau形成在核心处具有填充空腔的细丝，与CTE中观察到的tau细丝相同。同样，该结构在冷冻EM成像上得到证实。能够制造与人类tau蛋白病中发现的tau蛋白丝相同的tau蛋白丝，将使科学家能够研究这些丝是如何形成的，并阐明它们在疾病中发挥的作用。最终，更好地了解tau蛋白丝的形成可能会改善涉及tau蛋白的神经退行性疾病的诊断和治疗。
Abundant filamentous inclusions of tau are characteristic of more than 20 neurodegenerative diseases that are collectively termed tauopathies. Electron cryo-microscopy (cryo-EM) structures of tau amyloid filaments from human brain revealed that distinct tau folds characterise many different diseases. A lack of laboratory-based model systems to generate these structures has hampered efforts to uncover the molecular mechanisms that underlie tauopathies. Here, we report in vitro assembly conditions with recombinant tau that replicate the structures of filaments from both Alzheimer’s disease (AD) and chronic traumatic encephalopathy (CTE), as determined by cryo-EM. Our results suggest that post-translational modifications of tau modulate filament assembly, and that previously observed additional densities in AD and CTE filaments may arise from the presence of inorganic salts, like phosphates and sodium chloride. In vitro assembly of tau into disease-relevant filaments will facilitate studies to determine their roles in different diseases, as well as the development of compounds that specifically bind to these structures or prevent their formation. Many neurodegenerative diseases, including Alzheimer’s disease, the most common form of dementia, are characterised by knotted clumps of a protein called tau. In these diseases, tau misfolds, stacks together and forms abnormal filaments, which have a structured core and fuzzy coat. These sticky, misfolded proteins are thought to be toxic to brain cells, the loss of which ultimately causes problems with how people move, think, feel or behave. Reconstructing the shape of tau filaments using an atomic-level imaging technique called electron cryo-microscopy, or cryo-EM, researchers have found distinct types of tau filaments present in certain diseases. In Alzheimer’s disease, for example, a mixture of paired helical and straight filaments is found. Different tau filaments are seen again in chronic traumatic encephalopathy (CTE), a condition associated with repetitive brain trauma. It remains unclear, however, how tau folds into these distinct shapes and under what conditions it forms certain types of filaments. The role that distinct tau folds play in different diseases is also poorly understood. This is largely because researchers making tau proteins in the lab have yet to replicate the exact structure of tau filaments found in diseased brain tissue. Lövestam et al. describe the conditions for making tau filaments in the lab identical to those isolated from the brains of people who died from Alzheimer’s disease and CTE. Lövestam et al. instructed bacteria to make tau protein, optimised filament assembly conditions, including shaking time and speed, and found that bona fide filaments formed from shortened versions of tau. On cryo-EM imaging, the lab-produced filaments had the same left-handed twist and helical symmetry as filaments characteristic of Alzheimer’s disease. Adding salts, however, changed the shape of tau filaments. In the presence of sodium chloride, otherwise known as kitchen salt, tau formed filaments with a filled cavity at the core, identical to tau filaments observed in CTE. Again, this structure was confirmed on cryo-EM imaging. Being able to make tau filaments identical to those found in human tauopathies will allow scientists to study how these filaments form and elucidate what role they play in disease. Ultimately, a better understanding of tau filament formation could lead to improved diagnostics and treatments for neurodegenerative diseases involving tau.