State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan 430072, China.
J Biol Chem. 2009 Dec 11;284(50):34648-57. doi: 10.1074/jbc.M109.058883. Epub 2009 Oct 13.
A hallmark of a group of neurodegenerative diseases such as Alzheimer disease is the formation of neurofibrillary tangles, which are principally composed of bundles of filaments formed by microtubule-associated protein Tau. Clarifying how natively unstructured Tau protein forms abnormal aggregates is of central importance for elucidating the etiology of these diseases. There is considerable evidence showing that zinc, as an essential element that is highly concentrated in brain, is linked to the development or progression of these diseases. Herein, by using recombinant human Tau fragment Tau(244-372) and its mutants, we have investigated the effect of zinc on the aggregation of Tau. Low micromolar concentrations of Zn(2+) dramatically accelerate fibril formation of wild-type Tau(244-372) under reducing conditions, compared with no Zn(2+). Higher concentrations of Zn(2+), however, induce wild-type Tau(244-372) to form granular aggregates in reducing conditions. Moreover, these non-fibrillar aggregates assemble into mature Tau filaments when Zn(2+) has been chelated by EDTA. Unlike wild-type Tau(244-372), low micromolar concentrations of Zn(2+) have no obvious effects on fibrillization kinetics of single mutants C291A and C322A and double mutant C291A/C322A under reducing conditions. The results from isothermal titration calorimetry show that one Zn(2+) binds to one Tau molecule via tetrahedral coordination to Cys-291 and Cys-322 as well as two histidines, with moderate, micromolar affinity. Our data demonstrate that low micromolar zinc accelerates the fibrillization of human Tau protein via bridging Cys-291 and Cys-322 in physiological reducing conditions, providing clues to understanding the relationship between zinc dyshomeostasis and the etiology of neurodegenerative diseases.
一组神经退行性疾病（如阿尔茨海默病）的标志是神经纤维缠结的形成，其主要由微管相关蛋白 Tau 形成的纤维束组成。阐明天然无规 Tau 蛋白如何形成异常聚集体对于阐明这些疾病的病因至关重要。有相当多的证据表明，锌作为一种在大脑中高度集中的必需元素，与这些疾病的发展或进展有关。在此，我们使用重组人 Tau 片段 Tau(244-372)及其突变体，研究了锌对 Tau 聚集的影响。与没有锌（2+）相比，低微摩尔浓度的 Zn(2+)在还原条件下可显著加速野生型 Tau(244-372)的纤维形成。然而，较高浓度的 Zn(2+)在还原条件下诱导野生型 Tau(244-372)形成颗粒状聚集体。此外，当 EDTA 螯合 Zn(2+)时，这些无纤维的聚集体组装成成熟的 Tau 纤维。与野生型 Tau(244-372)不同，低微摩尔浓度的 Zn(2+)对还原条件下单突变体 C291A 和 C322A 以及双突变体 C291A/C322A 的纤维形成动力学没有明显影响。等温滴定量热法的结果表明，一个 Zn(2+)通过四面体配位与 Cys-291 和 Cys-322 以及两个组氨酸结合，以中等、微摩尔亲和力结合到一个 Tau 分子上。我们的数据表明，低微摩尔锌通过在生理还原条件下桥接 Cys-291 和 Cys-322 加速人 Tau 蛋白的纤维化，为理解锌代谢失衡与神经退行性疾病病因之间的关系提供了线索。
