Mechanism of Selective Toxicity of SOD1 Mutants in ALS

描述(由申请人提供)：1993年，首次有报道称 铜锌超氧化物歧化酶(SOD1)编码基因突变 与一种家族性肌萎缩侧索硬化症(ALS)有关。自.以来 当时，已发现70多个单一氨基酸突变为SOD1 因为人类患有肌萎缩侧索硬化症。转多种人SOD1中任何一种的小鼠 突变者发生进行性瘫痪并最终致死性瘫痪 举止让人想起人类的肌萎缩侧索硬化症。对转基因小鼠的研究清楚地表明 SOD1通过获得的功能是有毒的，因为突变会导致疾病 即使在总SOD1酶活性显著增加的情况下。尽管 获得毒性功能的压倒性证据，其确切性质 功能仍然难以捉摸。同样令人费解的是，SOD1 突变体只对运动神经元有毒，尽管它们在所有 单元类型。根据已发表的结果，SOD1的体外特征 突变体，培养运动神经元的研究，以及来自 转基因小鼠，我们已经提出了一个假说，可以解释所有 与肌萎缩侧索硬化症相关的SOD1突变可能通过一种常见的机制有毒，原因是什么？ 毒性只表现在运动神经元上。假设：我们建议 缺锌(含铜)SOD1是猪瘟的常见毒性表型 与肌萎缩侧索硬化症相关的SOD1突变体，缺锌SOD1通过其 能够利用抗坏血酸、氧气和一氧化氮来催化 细胞毒素过氧亚硝酸盐的形成，以及神经丝 蛋白质--与锌紧密结合的蛋白质，在马达中含量非常丰富 神经元--优先参与缺锌大鼠SOD1的形成 运动神经元。本研究提出：具体目标：1)测量缺锌 在应用最广泛的ALS动物模型(G93A转基因小鼠)和 确定导致其积累的因素，具体目标2) 确定SOD1介导的氧化剂产生的条件及其 与有毒蛋白质聚集的潜在关系，以及具体目标3) 两类保护性药物的体内药效评价 培养的运动神经元免受缺锌SOD1的毒性作用 提高G93A小鼠的存活率。

DESCRIPTION (provided by applicant): In 1993, it was first reported that a mutation to the gene coding for Cu,Zn superoxide dismutase (SOD1) was associated with a form of familial amyotrophic lateral sclerosis (ALS). Since that time, more than 70 single amino acid mutations to SOD1 have been found to cause ALS in humans. Mice transgenic for any one of several of the human SOD1 mutants develop progressive and ultimately lethal paralysis in a time-dependent manner reminiscent of human ALS. Studies in transgenic mice clearly indicate that SOD1 is toxic via a gained function because the mutant produces disease even in the presence of marked increases in total SOD1 enzyme activity. Despite the overwhelming evidence for a gained toxic function, the exact nature of that function has remained elusive. Equally puzzling has been the fact that SOD1 mutants are toxic only to motor neurons even though they are expressed in all cell types. Based on published results, in vitro characterizations of SOD1 mutants, studies in cultured motor neurons, and preliminary data from transgenic mice, we have formulated a hypothesis which may explain how all ALS-associated SOD1 mutations can be toxic via a common mechanism and why toxicity is manifested only in motor neurons. HYPOTHESIS: We are proposing that zinc-deficient (copper-containing) SOD1 is the common toxic phenotype of ALS-associated SOD1 mutants, that zinc-deficient SOD1 is injurious via its ability to utilize ascorbate, oxygen, and nitric oxide to catalyze the formation of the cytotoxin peroxynitrite, and that neurofilament proteins--which avidly bind zinc and are very abundant in motor neurons--contribute to the formation of zinc-deficient SOD1 preferentially in motor neurons. This study proposes: Specific Aim 1) to measure zinc-deficient SOD1 in the most widely used animal model of ALS (G93A transgenic mice) and determine the factors responsible for its accumulation, Specific Aim 2) to determine the conditions which lead to SOD1-mediated oxidant generation and its potential relationship to toxic protein aggregation, and Specific Aim 3) to evaluate the in vivo efficacy of two classes of compounds which protect cultured motor neurons from the toxic effects of zinc-deficient SOD1 and which enhance survival in G93A mice.