Department of Human Anatomy and Cell Science, University of Manitoba, 745 Bannatyne Avenue, Winnipeg, MB R3E 0J9, Canada.
Neurochem Res. 2012 Apr;37(4):835-45. doi: 10.1007/s11064-011-0679-8. Epub 2012 Jan 5.
Converging evidence indicates that SOD1 aggregation is a common feature of mutant SOD1-linked fALS, and seems to be directly related to the gain-of-function toxic property. However, the mechanism inducing the aggregation is not understood. To study the contribution of oxidative modification of cysteine residues in SOD1 aggregation, we systematically examined the redox state of SOD1 cysteine residues in the G37R transgenic mouse model at different stages of the disease and under oxidative stress induced by H₂O₂. Our data suggest that under normal circumstance, cysteine 111 residue in SOD1 is free; however, under oxidative stress, it is prone to oxidative modification by providing the thiolate anion (S-). With the progression of the disease, increased levels of oxidative insults facilitated the oxidation of thiol groups of cysteine residues; human mutant SOD1 could generate an upper shift band in reducing SDS-PAGE, which turned out to be a Cys111-peroxidized SOD1 species. We also detected the formation of SOD1 multimers at different stages of the disease, and found that accumulated oxidative stress facilitated the formation of aggregates, which were not mediated by disulfide bond. This oxidative modification of cysteine 111 therefore promotes the formation of disulfide bond-independent aggregation of SOD1.
越来越多的证据表明，SOD1 聚集是突变型 SOD1 相关肌萎缩侧索硬化症（fALS）的共同特征，并且似乎与获得功能毒性直接相关。然而，诱导聚集的机制尚不清楚。为了研究半胱氨酸残基氧化修饰在 SOD1 聚集中的作用，我们在疾病的不同阶段以及 H₂O₂诱导的氧化应激下，系统地研究了 G37R 转基因小鼠模型中 SOD1 半胱氨酸残基的氧化还原状态。我们的数据表明，在正常情况下，SOD1 中的半胱氨酸 111 残基是游离的；然而，在氧化应激下，它容易被氧化修饰，提供硫醇阴离子（S-）。随着疾病的进展，氧化损伤水平的增加促进了半胱氨酸残基巯基的氧化；人突变型 SOD1 在还原 SDS-PAGE 中可产生一个上移带，结果证明是 Cys111 过氧化物化的 SOD1 物种。我们还在疾病的不同阶段检测到 SOD1 多聚体的形成，并发现积累的氧化应激促进了聚集物的形成，而聚集物的形成不受二硫键的介导。因此，半胱氨酸 111 的这种氧化修饰促进了 SOD1 形成不依赖二硫键的聚集。
