Ambadipudi Susmitha, Biernat Jacek, Riedel Dietmar, Mandelkow Eckhard, Zweckstetter Markus
Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), von-Siebold-Str. 3a, 37075, Göttingen, Germany.
Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE), Ludwig-Erhard-Allee 2, 53175, Bonn, Germany.
Nat Commun. 2017 Aug 17;8(1):275. doi: 10.1038/s41467-017-00480-0.
The protein Tau aggregates into tangles in the brain of patients with Alzheimer's disease. In solution, however, Tau is intrinsically disordered, highly soluble, and binds to microtubules. It is still unclear what initiates the conversion from an innocuous phase of high solubility and functionality to solid-like neurotoxic deposits. Here, we show that the microtubule-binding repeats of Tau, which are lysine-rich, undergo liquid-liquid phase separation in solution. Liquid-liquid demixing causes molecular crowding of amyloid-promoting elements of Tau and drives electrostatic coacervation. Furthermore, we demonstrate that three-repeat and four-repeat isoforms of Tau differ in their ability for demixing. Alternative splicing of Tau can thus regulate the formation of Tau-containing membrane-less compartments. In addition, phosphorylation of Tau repeats promotes liquid-liquid phase separation at cellular protein conditions. The combined data propose a mechanism in which liquid droplets formed by the positively charged microtubule-binding domain of Tau undergo coacervation with negatively charged molecules to promote amyloid formation.Tau forms aggregates in the brains of Alzheimer patients. Here, the authors identify conditions, where the microtubule-binding repeats of Tau undergo a phosphorylation-dependent liquid-liquid phase separation, leading to molecular crowding in the formed Tau liquid droplets and characterize them by NMR and other biophysical methods.
在阿尔茨海默病患者的大脑中，蛋白质Tau会聚集成缠结。然而，在溶液中，Tau本质上是无序的、高度可溶的，并且能与微管结合。目前仍不清楚是什么引发了从高溶解性和功能性的无害阶段到类似固体的神经毒性沉积物的转变。在此，我们表明，富含赖氨酸的Tau的微管结合重复序列在溶液中会发生液-液相分离。液-液分层导致Tau的淀粉样蛋白促进元件分子聚集，并驱动静电凝聚。此外，我们证明Tau的三重复和四重复亚型在分层能力上存在差异。因此，Tau的可变剪接可以调节含Tau的无膜区室的形成。此外，Tau重复序列的磷酸化在细胞蛋白质条件下促进液-液相分离。综合数据提出了一种机制，即由Tau带正电荷的微管结合结构域形成的液滴与带负电荷的分子发生凝聚以促进淀粉样蛋白的形成。Tau在阿尔茨海默病患者的大脑中形成聚集体。在此，作者确定了Tau的微管结合重复序列发生磷酸化依赖性液-液相分离的条件，导致在形成的Tau液滴中分子聚集，并通过核磁共振和其他生物物理方法对其进行了表征。
