Ca Signaling in Progression of Amyotrophic Lateral Sclerosis in Skeletal Muscle

描述（由申请人提供）：肌萎缩性侧索硬化症（ALS）是一种进行性神经肌肉疾病，涉及运动神经元变性和骨骼肌萎缩。超氧化物歧化酶（SOD 1）基因的突变与大多数遗传性ALS病例有关，导致线粒体代谢功能受损。目前，缺乏关于功能障碍的线粒体和改变的Ca信号传导如何在ALS进展期间促进肌肉变性的知识。这项新的研究人员发起的研究项目将测试这一假设，即“在ALS的发展过程中，神经肌肉接头（NMJ）的动作电位活动将导致线粒体中的局部钙超载，这是由于突变SOD 1的存在而造成的。这种过载将进一步破坏肌浆网（SR）耦合，并导致改变钙和活性氧（ROS）信号。这种改变反过来会增加局部Ca，加强局部缺陷，从而构成ALS肌肉病理生理学的主要事件。我们研究的中心主题是全面了解导致ALS肌肉钙稳态能力受损的肌钙蛋白-SR偶联逐渐下降的细胞机制。我们预计，从我们的研究中获得的信息将适用于其他神经肌肉疾病，如衰老，糖尿病，帕金森病等，其中改变的钙信号和细胞内氧化应激与肌肉收缩功能障碍和运动神经元通讯改变有关。 在目标1中，我们提出量化线粒体对SR Ca信号传导的局部控制的贡献，并使用该量化来评估缺陷的线粒体-SR偶联如何有助于ALS中肌肉萎缩的进展。通过表征肌萎缩侧索硬化进展不同阶段骨骼肌中钙信号和线粒体功能的变化，我们的研究应该提供一个机制的理解，如何局部控制SR钙信号被线粒体改变，这一过程是如何改变肌萎缩侧索硬化肌肉和什么是轴突撤回的影响破坏SR-线粒体耦合导致肌萎缩侧索硬化肌肉功能的进行性下降。在目的2中，我们建议使用局部线粒体超氧化物（O2-）FLASH信号作为ALS肌肉中线粒体代谢功能的指标，并检查去神经支配对ALS肌肉萎缩过程中控制细胞内Ca释放和局部O2-水平的线粒体SR之间相互作用的影响。这些研究将揭示Ca和O2-产生之间的局部耦合在肌肉生理学中的作用，并建立有助于ALS中NMJ重塑和肌肉病理学进行性发展的细胞机制。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disorder involving degeneration of motor neurons and atrophy of skeletal muscle. Mutations in the superoxide dismutase (SOD1) gene are linked to most cases of inherited ALS, resulting in impaired metabolic function of the mitochondria. Currently, there is a lack of knowledge on how dysfunctional mitochondria and altered Ca signaling contribute to muscle degeneration during ALS progression. This new investigator initiated research project will test the hypothesis that "during the development of ALS, action potential activity at the neuromuscular junction (NMJ) will cause local Ca overload in mitochondria compromised by the presence of mutant SOD1. This overload will further disrupt mitochondria-sarcoplasmic reticulum (SR) coupling and lead to altered Ca and reactive oxygen species (ROS) signaling. The alteration in turn will increase local Ca, reinforcing the local deficit, thus constituting a primary event in the pathophysiology of ALS muscle". The central theme of our studies is to develop a comprehensive understanding of the cellular mechanism that contributes to the progressive decline in mitochondria-SR coupling leading to the compromised Ca homeostatic capacity of ALS muscle. We anticipate that information obtained from our research will apply to other neuromuscular diseases, such as aging, diabetes, Parkinson's disease and others, where altered Ca signaling and intracellular oxidative stress are linked to dysfunctional muscle contractility and altered motor neuron communication. In Aim 1, we propose to quantify the mitochondrial contribution to local control of SR Ca signaling, and use this quantification to evaluate how defective mitochondria-SR coupling contributes to progression of muscle wasting in ALS. By characterizing the changes in Ca signaling and mitochondrial function in skeletal muscle at different stages of ALS progression, our studies should provide a mechanistic understanding of how local control of SR Ca signaling is altered by mitochondria, how this process is altered in ALS muscle and what is the influence of axonal withdrawal in disrupting SR-mitochondria coupling leading to the progressive decline of muscle function in ALS. In Aim 2, we propose to use localized mitochondrial superoxide (O2-) FLASH signal as an index for mitochondrial metabolic function in ALS muscle, and to examine the effect of denervation on the interplay between mitochondria-SR in controlling intracellular Ca release and local O2- levels during the progression of muscle atrophy in ALS. These studies will reveal the role of localized coupling between Ca and O2- production in muscle physiology, and establish the cellular mechanism(s) that contribute to NMJ remodeling and the progressive development of muscle pathology in ALS.