In vitro 0N4R tau fibrils contain a monomorphic β-sheet core enclosed by dynamically heterogeneous fuzzy coat segments
In vitro 0N4R tau fibrils contain a monomorphic β-sheet core enclosed by dynamically heterogeneous fuzzy coat segments
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DOI：
10.1073/pnas.1906839116
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发表时间：
2019-08-13
影响因子：
11.1
通讯作者：
Hong, Mei
中科院分区：
文献类型：
--
作者：
Dregni, Aurelio J.;Mandala, Venkata S.;Hong, Mei
微管结合蛋白tau错误折叠成丝状聚集体是许多神经退行性疾病如阿尔茨海默病和进行性核上性麻痹的特征。确定这些tau纤维的结构和动力学对于设计针对tau聚集的抑制剂是重要的。已经通过冷冻电子显微镜发现从患者脑获得的Tau原纤维采用疾病特异性分子构象。然而，最近发现，在体外肝素fiphilized 2N 4 R tau，其中包含所有四个微管结合重复序列（4 R），采用多态性结构。在这里，我们使用固态核磁共振光谱研究肝素化的0 N4 R tau蛋白的全局折叠和动力学。在四个重复序列中的残基观察到一组C-13和N-15化学位移，表明原纤维核心的单一β-折叠构象。该刚性核心跨越R2和R3重复，并采用发夹样折叠，其与任何多态性2N 4 R折叠具有相似性但也具有明显差异。获得均匀的原纤维样品需要仔细纯化蛋白质和去除任何蛋白水解片段。水和移动的侧链的各种实验和极化转移表明，0 N4 R tau原纤维表现出不均匀的动力学：刚性R2-R3核心外，R1和R4重复是半刚性的，即使它们表现出β-链特征，富含脯氨酸的结构域经历大幅度的各向异性运动，而两个末端几乎是各向同性的柔性。这些结果对体内4 R tau纤维的结构和动力学具有重要意义。
Misfolding of the microtubule-binding protein tau into filamentous aggregates is characteristic of many neurodegenerative diseases such as Alzheimer's disease and progressive supranuclear palsy. Determining the structures and dynamics of these tau fibrils is important for designing inhibitors against tau aggregation. Tau fibrils obtained from patient brains have been found by cryo-electron microscopy to adopt disease-specific molecular conformations. However, in vitro heparin-fibrillized 2N4R tau, which contains all four microtubule-binding repeats (4R), was recently found to adopt polymorphic structures. Here we use solid-state NMR spectroscopy to investigate the global fold and dynamics of heparin-fibrillized 0N4R tau. A single set of C-13 and N-15 chemical shifts was observed for residues in the four repeats, indicating a single beta-sheet conformation for the fibril core. This rigid core spans the R2 and R3 repeats and adopts a hairpin-like fold that has similarities to but also clear differences from any of the polymorphic 2N4R folds. Obtaining a homogeneous fibril sample required careful purification of the protein and removal of any proteolytic fragments. A variety of experiments and polarization transfer from water and mobile side chains indicate that 0N4R tau fibrils exhibit heterogeneous dynamics: Outside the rigid R2-R3 core, the R1 and R4 repeats are semirigid even though they exhibit beta-strand character and the proline-rich domains undergo large-amplitude anisotropic motions, whereas the two termini are nearly isotropically flexible. These results have significant implications for the structure and dynamics of 4R tau fibrils in vivo.