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（SOD1）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，关于线粒体功能障碍和Ca信号改变如何导致ALS进展过程中的肌肉退化的知识缺乏。这个新研究者发起的研究项目将验证这样一个假设：“在ALS的发展过程中，神经肌肉连接处（NMJ）的动作电位活动将导致线粒体中局部钙超载，而线粒体受到突变SOD1的破坏。”这种超载将进一步破坏线粒体-肌浆网（SR）偶联，并导致钙和活性氧（ROS）信号的改变。这种改变反过来会增加局部钙，加强局部缺陷，从而构成肌萎缩侧索硬化症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线粒体- sr偶联逐渐下降导致肌萎缩侧索硬化症肌肉钙稳态能力受损的细胞机制。我们预计从我们的研究中获得的信息将应用于其他神经肌肉疾病，如衰老、糖尿病、帕金森病等，其中Ca信号的改变和细胞内氧化应激与功能失调的肌肉收缩性和运动神经元通讯的改变有关。在Aim 1中，我们建议量化线粒体对SR Ca信号局部控制的贡献，并使用该量化来评估线粒体-SR偶联缺陷如何促进ALS肌肉萎缩的进展。通过表征骨骼肌中Ca信号和线粒体功能在ALS进展不同阶段的变化，我们的研究将为线粒体如何改变SR Ca信号的局部控制提供机制理解，这一过程在ALS肌肉中是如何改变的，以及轴突戒断在破坏SR-线粒体偶联导致ALS肌肉功能进行性下降中的影响。在Aim 2中，我们建议使用线粒体局部超氧化物（O2-） FLASH信号作为ALS肌肉线粒体代谢功能的指标，并研究在ALS肌肉萎缩过程中，去神经支配对线粒体- sr控制细胞内Ca释放和局部O2-水平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中的作用，并建立有助于肌萎缩症NMJ重塑和肌肉病理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.