Liquid liquid phase separation and tau biology

液体液体相分离和tau生物学Tau是阿尔茨海默病中神经原纤维缠结的一种成分，也是与之密切相关的神经退行性疾病中类似聚集体的一种成分，称为tau病。目前尚不清楚是什么启动了从一种非常易溶的微管相关蛋白到聚集体的变化。目前的应用是基于最近的一系列实验，这些实验可能会给几十年来对tau的观察带来新的转折。在第一个目标中，我们进一步 探索tau(如果被磷酸化、突变或暴露于多阴离子，如RNA)可以 进行液液相分离，形成凝聚的、高度集中的可逆液滴。 有趣的是，液-液相分离目前被认为与FUS、TDP43、 在肌萎缩侧索硬化症中的hnRNP和C9orf72蛋白；根据我们关于tau、阿尔茨海默氏症和额颞叶痴呆的新数据， 液液相变是神经退行性变某些方面的基础，这一类比令人信服 探索。这些液滴的结构令人着迷，随着时间的推移，它们会经历胶凝，最后 重塑以具有一些Beta折叠的片状结构，可能在通往高度有序的道路上 神经原纤维缠结的结构。第二个目的是研究这些液滴的功能，当 “新鲜”，能够与微管蛋白相互作用并使微管结构成核，“润湿”微管表面 微管聚集在一起，然后沿着它流动，稳定了延伸的结构。鉴于……的悠久历史 研究结果表明，tau稳定微管，液滴的形成似乎是不可避免的 与tau的这一基本生理作用有关。第三个目标是使这些观察结果完整地循环，从 用重组蛋白对存在于脑中的tau进行体外观察-在两种动物模型中 Tau诱导的神经变性和人类阿尔茨海默病、额颞叶痴呆(tau阳性或TDP43阳性) 阳性)，并控制大脑。我们的初步数据显示，从阿尔茨海默病大脑中分离出来的可溶性tau 生化分离技术富集高分子量过磷酸化低聚物和AN 免疫亲和柱，保留形成LLP的能力。我们提议的研究将进一步研究这一比例。 将它的性质与其他分数进行比较，并(与目标1和2一起)允许我们探索如何 研究tau的简化系统与人类疾病中存在的tau有关。我们建议新的 所描述的tau的液液相分离性质是连接结构和 Tau-、磷酸化和突变形式的功能--与疾病相关的聚集的启动。

Liquid liquid phase separation and tau biology Tau is a component of neurofibrillary tangles in Alzheimer disease and of analogous aggregates in closely related neurodegenerative diseases called tauopathies. What initiates a change from a very soluble, microtubule associated protein to an aggregate is unknown. The current application is based on a series of very recent experiments that may put a new twist on decades of observations of tau. In the first aim we further explore the new observation that tau (if phosphorylated, mutant, or exposed to polyanions like RNA) can undergo liquid liquid phase separation forming a coherent highly concentrated and reversible droplet. Intriguingly, liquid-liquid phase separation has currently been implicated in the pathobiology of Fus, TDP43, hnRNP, and C9orf72 proteins in ALS; with our new data on tau and Alzheimer's and frontotemporal dementia, the analogy that liquid liquid phase transitions underlie some aspects of neurodegeneration is compelling to explore. The structure of these droplets is fascinating, and over time they undergo a gelation and finally remodel to have some beta pleated sheet structure, potentially on the pathway towards the highly ordered structure of neurofibrillary tangles. The second aim examines the function of these droplets which, when “fresh”, have the ability to interact with tubulin and to nucleate microtubule structures, “wetting” the surface of the microtubule bundle and then flowing along it, stabilizing the extending structure. Given the long history of studies showing conclusively that tau stabilizes microtubules, it seems inescapable that droplet formation is linked to this fundamental physiological role of tau. The third aim is to bring these observations full circle, from in vitro observations with recombinant proteins to the tau that is present in the brain – both in animal models of tau induced neurodegeneration and in human Alzheimer, Frontotemporal dementia (tau positive or TDP43 positive), and control brain. Our preliminary data show that soluble tau isolated from Alzheimer brain – using biochemical separation techniques to enrich for high molecular weight hyperphosphorylated oligomers and an immunoaffinity column, retains the ability to form LLPS. Our proposed studies will further examine this fraction of tau, compare its properties to other fractions, and (together with aims 1 and 2) allow us to explore how reduced systems studying tau relate to the tau present in human disease. We suggest that the newly described liquid liquid phase separation properties of tau are an important clue that connects the structure and function of tau – and phosphorylated and mutant forms - with the disease relevant initiation of aggregation.