人类 tau 纤维形成可通过与 His-330 和 His-362 的相互作用加速暴露于铅。
Fibrillization of human tau is accelerated by exposure to lead via interaction with His-330 and His-362.
机构信息
State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China.
出版信息
PLoS One. 2011;6(9):e25020. doi: 10.1371/journal.pone.0025020. Epub 2011 Sep 26.
BACKGROUND
Neurofibrillary tangles, mainly consisted of bundles of filaments formed by the microtubule-associated protein Tau, are a hallmark of Alzheimer disease. Lead is a potent neurotoxin for human being especially for the developing children, and Pb(2+) at high concentrations is found in the brains of patients with Alzheimer disease. However, it has not been reported so far whether Pb(2+) plays a role in the pathology of Alzheimer disease through interaction with human Tau protein and thereby mediates Tau filament formation. In this study, we have investigated the effect of Pb(2+) on fibril formation of recombinant human Tau fragment Tau(244-372) and its mutants at physiological pH.
METHODOLOGY/PRINCIPAL FINDINGS: As revealed by thioflavin T and 8-anilino-1-naphthalene sulfonic acid fluorescence, the addition of 5-40 µM Pb(2+) significantly accelerates the exposure of hydrophobic region and filament formation of wild-type Tau(244-372) on the investigated time scale. As evidenced by circular dichroism and Fourier transform infrared spectroscopy, fibrils formed by wild-type Tau(244-372) in the presence of 5-40 µM Pb(2+) contain more β-sheet structure than the same amount of fibrils formed by the protein in the absence of Pb(2+). However, unlike wild-type Tau(244-372), the presence of 5-40 µM Pb(2+) has no obvious effects on fibrillization kinetics of single mutants H330A and H362A and double mutant H330A/H362A, and fibrils formed by such mutants in the absence and in the presence of Pb(2+) contain similar amounts of β-sheet structure. The results from isothermal titration calorimetry show that one Pb(2+) binds to one Tau monomer via interaction with His-330 and His-362, with sub-micromolar affinity.
CONCLUSIONS/SIGNIFICANCE: We demonstrate for the first time that the fibrillization of human Tau protein is accelerated by exposure to lead via interaction with His-330 and His-362. Our results suggest the possible involvement of Pb(2+) in the pathogenesis of Alzheimer disease and provide critical insights into the mechanism of lead toxicity.
背景
神经原纤维缠结，主要由微管相关蛋白 Tau 形成的纤维束组成，是阿尔茨海默病的一个标志。铅是人类的一种强有力的神经毒素，尤其是对发育中的儿童，而在阿尔茨海默病患者的大脑中发现高浓度的 Pb(2+)。然而，迄今为止，还没有报道 Pb(2+)是否通过与人类 Tau 蛋白相互作用在阿尔茨海默病的病理学中发挥作用，从而介导 Tau 纤维的形成。在这项研究中，我们研究了 Pb(2+)对生理 pH 下重组人 Tau 片段 Tau(244-372)及其突变体的纤维形成的影响。
方法/主要发现：如硫黄素 T 和 8-苯胺-1-萘磺酸荧光所揭示的，在研究的时间范围内，加入 5-40 μM 的 Pb(2+)可显著加速野生型 Tau(244-372)暴露于疏水区和纤维形成。如圆二色性和傅里叶变换红外光谱所示，在 5-40 μM 的 Pb(2+)存在下形成的野生型 Tau(244-372)纤维比相同量的蛋白质在没有 Pb(2+)存在下形成的纤维含有更多的β-折叠结构。然而，与野生型 Tau(244-372)不同，存在 5-40 μM 的 Pb(2+)对单突变体 H330A 和 H362A 以及双突变体 H330A/H362A 的纤化动力学没有明显影响，并且在没有和存在 Pb(2+)的情况下形成的突变体的纤维含有相似量的β-折叠结构。等温滴定量热法的结果表明，一个 Pb(2+)通过与 His-330 和 His-362 相互作用与一个 Tau 单体结合，亲和力为亚微摩尔。
结论/意义：我们首次证明，通过与 His-330 和 His-362 相互作用，暴露于铅可加速人类 Tau 蛋白的纤维化。我们的结果表明 Pb(2+)可能参与阿尔茨海默病的发病机制，并为铅毒性的机制提供了重要的见解。
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