Depletion of Mitochondrial S-Nitrosothiols in ALS

描述(由申请人提供)：越来越多的证据表明线粒体功能障碍与肌萎缩侧索硬化症(ALS)的发病机制有关。然而，ALS患者线粒体功能障碍的原因尚不清楚。我们假设家族性肌萎缩侧索硬化症相关的SO1突变体异常地消耗线粒体中的S-亚硝硫醇(SNO)，导致线粒体变性和运动神经元死亡。S-亚硝硫醇是半胱氨酸残基上有NO基团的多肽和蛋白质。多肽SNO是有效的抗氧化剂和神经保护物质。蛋白质上关键的半胱氨酸残基的S亚硝化是一种信号转导调节机制。因此，线粒体SNO的异常耗尽很可能是SOD1突变体的一种毒性功能获得。这是在肌萎缩侧索硬化症领域一个几乎未被探索的领域中的一个新的可测试的工作假说。为了支持我们的假设，我们的初步数据表明，多肽和蛋白质SNO主要位于表达野生型SOD1的细胞系的线粒体中。此外，表达SOD1突变体的细胞线粒体中的SNO水平显著降低。在拟议研究的具体目标1中，我们将把我们对细胞系的初步研究扩展到活体动物模型，并确定突变的SOD1转基因小鼠在肌肉无力开始之前或开始时脊髓中线粒体SNO水平是否降低。在特定的目标2中，我们将确定线粒体SNO水平的恢复是否改善了线粒体功能和表达突变SOD1的细胞的活力。如果我们证实了我们的假设，那么在未来的研究中，我们将确定SNO供体化合物是否提高了突变的SOD1转基因小鼠的存活率。我们的长期目标是确定SNO供体化合物(几十年来一直用于治疗毒性有限的冠状动脉疾病)是否对ALS患者具有治疗效果。

DESCRIPTION (provided by applicant): There is increasing evidence that mitochondrial dysfunction contributes to amyotrophic lateral sclerosis (ALS) pathogenesis. However the causes of mitochondrial dysfunction in ALS are not known. We hypothesize that familial ALS-associated SOD1 mutants aberrantly deplete S-nitrosothiols (SNOs) in mitochondria leading to mitochondrial degeneration and motor neuron death. S-nitrosothiols are peptides and proteins that have an NO group attached to a cysteine residue. Peptide SNOs are potent antioxidants and neuroprotective. S-nitrosylation of critical cysteine residues on proteins is emerging as a mechanism of signal transduction regulation. Therefore aberrant depletion of mitochondrial SNOs is likely to be a toxic gain-of-function of SOD1 mutants. This is a novel testable working hypothesis in a virtually unexplored area in the ALS field. In support of our hypothesis, our preliminary data indicate that peptide and protein SNOs are located primarily in the mitochondria of cell lines expressing wild-type SOD1. Moreover, SNO levels are significantly decreased in the mitochondria of cells expressing SOD1 mutants. In specific aim 1 of the proposed studies we will extend our preliminary studies in cell lines to an in vivo animal model and determine if mitochondrial SNO levels are decreased in the spinal cord of mutant SOD1 transgenic mice before or at the time of onset of muscle weakness. In specific aim 2 we will determine if restoration of mitochondrial SNO levels improves mitochondrial function and the viability of cells expressing mutant SOD1. If we confirm our hypothesis, then in future studies we will determine if SNO donor compounds improve the survival of mutant SOD1 transgenic mice. Our long term goal is to determine if SNO donor compounds (which have been used for decades in the treatment of coronary artery disease with limited toxicity) have therapeutic efficacy in patients with ALS.