Tracking the Structural Development of Amyloid Precursors in the Insulin B Chain and the Inhibition Effect by Fibrinogen
Tracking the Structural Development of Amyloid Precursors in the Insulin B Chain and the Inhibition Effect by Fibrinogen
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DOI：
10.1021/acs.jpcb.2c05136
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发表时间：
2022-12-19
影响因子：
3.3
通讯作者：
Chatani，Eri
中科院分区：
文献类型：
--
作者：
Yamamoto，Naoki;Inoue，Rintaro;Chatani，Eri
淀粉样原纤维是与几种淀粉样变性和神经退行性疾病相关的异常蛋白质聚集体。在淀粉样纤维形成之前出现的前纤维中间体在结构形成中起重要作用。因此，为了防止原纤维的形成，必须阐明支持结构发展的前原纤维中间体的机制。胰岛素衍生肽，胰岛素B链，已知其稳定积累的前原纤维中间体。在这项研究中，B链预纤维中间体的结构发展和纤维蛋白原（Fg）的抑制作用进行了监测，通过透射电子显微镜（TEM）和小角X射线散射（SAXS）结合固态核磁共振谱（NMR）和尺寸排阻色谱。在延时的方式获得的TEM图像表明，prefibrillar中间体是波浪形的棒状结构出现从初始的非棒状聚集体，和他们的捆绑是负责原丝的形成。时间分辨小角X射线散射表明，作为时间的函数，prefibrillar中间体变得更厚，更长。固态NMR测量表明，Ala 14残基周围的β-折叠的形成对于前纤维中间体向淀粉样纤维的结构转化至关重要。这些观察结果表明，prefibrillar中间体作为反应领域的淀粉样蛋白成核和其结构的传播。时间分辨SAXS还表明，Fg防止伸长的prefibrillar中间体形成特定的复合物在一起，这意味着，调节的prefibrillar中间体的长度后Fg结合的因素抑制prefibrillar中间体伸长。本研究发现的纤维形成机制和抑制策略将有助于寻找合适的方法来治疗淀粉样蛋白相关疾病。
Amyloid fibrils are abnormal protein aggregates associated with several amyloidoses and neurodegenerative diseases. Prefibrillar intermediates, which emerge before amyloid fibril formation, play an important role in structure formation. Therefore, to prevent fibril formation, the mechanisms underpinning the structural development of prefibrillar intermediates must be elucidated. An insulin-derived peptide, the insulin B chain, is known for its stable accumulation of prefibrillar intermediates. In this study, the structural development of B chain prefibrillar intermediates and their inhibition by fibrinogen (Fg) were monitored by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) combined with solid-state nuclear magnetic resonance spectroscopy (NMR) and size exclusion chromatography. TEM images obtained in a time-lapse manner demonstrated that prefibrillar intermediates were wavy rod-like structures emerging from initial non-rod-like aggregates, and their bundling was responsible for protofilament formation. Time-resolved SAXS revealed that the prefibrillar intermediates became thicker and longer as a function of time. Solid-state NMR measurement suggested a β-sheet formation around Ala14 residue was crucial for the structural conversion from prefibrillar intermediates to amyloid fibril. These observations suggested that prefibrillar intermediates serve as reaction fields for amyloid nucleation and its structural propagation. Time-resolved SAXS also demonstrated that Fg prevented elongation of the prefibrillar intermediates by forming specific complexes together, which implied that regulation of the length of prefibrillar intermediates upon Fg binding was the factor suppressing the prefibrillar intermediate elongation. The fibril formation mechanism and the inhibition strategy found in this study will be helpful in seeking appropriate methods against amyloid-related diseases.