S100A6 Amyloid Fibril Formation Is Calcium-modulated and Enhances Superoxide Dismutase-1 (SOD1) Aggregation
S100A6 Amyloid Fibril Formation Is Calcium-modulated and Enhances Superoxide Dismutase-1 (SOD1) Aggregation
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DOI：
10.1074/jbc.m112.396416
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发表时间：
2012-12-07
影响因子：
4.8
通讯作者：
Gomes, Claudio M.
中科院分区：
文献类型：
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作者：
Botelho, Hugo M.;Leal, Sonia S.;Gomes, Claudio M.
S100A6 是一种小型 EF-hand 钙锌结合蛋白，参与细胞增殖和细胞骨架动力学的调节。它在神经退行性疾病中过度表达，并被提议作为肌萎缩侧索硬化症 (ALS) 的标志物。根据最近 S100 蛋白形成淀粉样蛋白的报道，我们研究了 S100A6 的聚集特性。使用聚集预测因子 Waltz 和 Zyggregator 进行的计算分析揭示了 S100A6 螺旋 HI 和 HIV 内的倾向增加。随后对酸性条件下硫磺素-T 结合动力学的分析引发了一个非常快的过程，没有滞后期，并且如电子显微镜观察到的那样，大量形成了聚集体和堆叠原纤维。 Ca2+ 对聚集动力学产生抑制作用，但螯合后可以恢复。对这些条件下发生的早期构象变化的 FT-IR 研究表明，Ca2+ 促进抑制纤维颤动的反平行 β-折叠构象。 pH 值为 7 时，Ca2+ 使原纤维形成动力学减慢：时间分辨成像显示原纤维形成受到高度抑制，反而形成聚集体。在没有金属的情况下，形成广泛的原纤维网络。研究发现，S100A6 寡聚体（而非原纤维）具有细胞毒性，可降低细胞活力高达 40%。当在 Ca2+ 存在下形成聚集体时，没有观察到这种效应。有趣的是，天然 S1006 引发 SOD1 聚集，缩短其成核过程。这表明这两种参与 ALS 的蛋白质之间存在交叉对话。总体而言，这些结果提出了 S100 蛋白的新作用，其金属调节的聚集倾向可能是其生理学和功能的一个关键方面。
S100A6 is a small EF-hand calcium- and zinc-binding protein involved in the regulation of cell proliferation and cytoskeletal dynamics. It is overexpressed in neurodegenerative disorders and a proposed marker for Amyotrophic Lateral Sclerosis (ALS). Following recent reports of amyloid formation by S100 proteins, we investigated the aggregation properties of S100A6. Computational analysis using aggregation predictors Waltz and Zyggregator revealed increased propensity within S100A6 helices HI and HIV. Subsequent analysis of Thioflavin-T binding kinetics under acidic conditions elicited a very fast process with no lag phase and extensive formation of aggregates and stacked fibrils as observed by electron microscopy. Ca2+ exerted an inhibitory effect on the aggregation kinetics, which could be reverted upon chelation. An FT-IR investigation of the early conformational changes occurring under these conditions showed that Ca2+ promotes anti-parallel beta-sheet conformations that repress fibrillation. At pH 7, Ca2+ rendered the fibril formation kinetics slower: time-resolved imaging showed that fibril formation is highly suppressed, with aggregates forming instead. In the absence of metals an extensive network of fibrils is formed. S100A6 oligomers, but not fibrils, were found to be cytotoxic, decreasing cell viability by up to 40%. This effect was not observed when the aggregates were formed in the presence of Ca2+. Interestingly, native S1006 seeds SOD1 aggregation, shortening its nucleation process. This suggests a cross-talk between these two proteins involved in ALS. Overall, these results put forward novel roles for S100 proteins, whose metalmodulated aggregation propensity may be a key aspect in their physiology and function.