Metal-free superoxide dismutase forms soluble oligomers under physiological conditions: A possible general mechanism for familial ALS
Metal-free superoxide dismutase forms soluble oligomers under physiological conditions: A possible general mechanism for familial ALS
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DOI：
10.1073/pnas.0704307104
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发表时间：
2007-07-03
影响因子：
11.1
通讯作者：
Whitelegge, Julian P.
中科院分区：
文献类型：
--
作者：
Banci, Lucia;Bertini, Ivano;Whitelegge, Julian P.
肌萎缩侧索硬化症（ALS）是一种选择性影响运动神经元的进行性神经退行性疾病; 90%的病例是散发性的，但2%与编码抗氧化酶铜锌超氧化物歧化酶（SOD 1）的基因突变有关。ALS中运动神经元死亡的原因通常知之甚少，但对于SOD 1相关的家族性ALS，SOD 1突变蛋白的异常寡聚化已被强烈牵连。在这项工作中，我们表明，野生型人SOD 1，当缺乏它的两个金属离子，形成大的，稳定的，可溶性蛋白质寡聚体的平均分子量约为650 kDa的生理条件下，即，37 ℃，pH7.0和100 μ M蛋白质浓度。这里进一步表明，在寡聚化过程中形成分子间二硫键，并且Cys-6和Cys-111涉及该键合。可溶性低聚物的形成通过其增强硫磺素T（一种苯并噻唑染料，其在与淀粉样蛋白纤维结合后荧光强度增加）的荧光的能力以及通过在加入离液剂盐酸胍后破坏这种结合来监测。我们的研究结果表明，当野生型或突变型SOD 1蛋白缺乏金属离子时，SOD 1聚集可以起作用。虽然我们不能排除SOD 1相关的家族性ALS的其他机制，但这里提出的一个机制具有解释大量不同的SOD 1突变蛋白如何通过相同的机制导致疾病的优势。
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder selectively affecting motor neurons; 90% of the total cases are sporadic, but 2% are associated with mutations in the gene coding for the antioxidant enzyme copper-zinc superoxide dismutase (SOD1). The causes of motor neuron death in ALS are poorly understood in general, but for SOD1-linked familial ALS, aberrant oligomerization of SOD1 mutant proteins has been strongly implicated. In this work, we show that wild-type human SOD1, when lacking both its metal ions, forms large, stable, soluble protein oligomers with an average molecular mass of approximate to 650 kDa under physiological conditions, i.e., 37 degrees C, pH 7.0, and 100 mu M protein concentration. It further is shown here that intermolecular disulfide bonds are formed during oligomerization and that Cys-6 and Cys-111 are implicated in this bonding. The formation of the soluble oligomers was monitored by their ability to enhance the fluorescence of thioflavin T, a benzothiazole dye that increases in fluorescence intensity upon binding to amyloid fibers, and by disruption of this binding upon addition of the chaotropic agent guanidine hydrochloride. Our results suggest a general, unifying picture of SOD1 aggregation that could operate when wild-type or mutant SOD1 proteins lack their metal ions. Although we cannot exclude other mechanisms in SOD1-linked familial ALS, the one proposed here has the strength of explaining how a large and diverse set of SOD1 mutant proteins all could lead to disease through the same mechanism.