The Role of PGC-1aplha in the Pathogenesis of Myotonic Dystrophy Type 1

描述（由申请人提供）：1型肌强直性营养不良（DM1）的骨骼肌缺陷的特征是进行性肌肉无力和消瘦，线粒体（Mt）呼吸受损，高血糖和胰岛素抵抗，代谢能力下降和氧化应激升高。DM1的高度复杂和退行性表型表现为染色体19q13.3 DMPK基因3'翻译区CTG三核苷酸重复大量扩增的结果。扩增的CTG重复序列损害Mt功能和DM1代谢调节的机制尚不清楚。PGC-1是一种转录辅激活因子，可调控Mt呼吸、脂肪酸和葡萄糖代谢、活性氧（ROS）以及神经肌肉连接处（NMJ）活性的基因转录。在这个项目中，我们的目标是确定PGC-1活性降低对DM1肌肉发病机制的影响程度：1)目的1将评估PGC-1靶基因在DM1骨骼肌中调节Mt呼吸和神经肌肉连接（NMJ）功能的表达。预期结果将确定PGC-1及其靶基因在DM1骨骼肌病理中的作用；2)目的2将建立突变CUG RNA破坏DM1细胞内氧化还原稳态的机制。这些实验将建立DM1中催化内源性ROS代谢的PGC-1靶基因被破坏的机制，并确定表达突变CUG重复序列的DM1成肌细胞和C2C12细胞中ROS生成酶NADPH氧化酶的活性是否上调；3)目的3将探索扩展的CUG重复序列导致氧化还原依赖性的Ataxia毛细血管扩张突变（ATM）激酶激活、磷酸化和改变DM1中AMPK活性的机制。我们还将测试活化的AMPK是否调节TORC2（受调节CREB活性的传感器）的磷酸化，并调节CREB活性和CREB介导的DM1中PGC-1的转录。我们还将测试扩展的CUG重复序列是否调节torc2介导的CREB活性和DM1中PGC-1的转录。该研究将揭示突变CUG RNA破坏PGC-1活性和损害Mt功能的机制，并可能通过调节DM1中的PGC-1信号传导导致干预的发展。

DESCRIPTION (provided by applicant): Skeletal muscle defects in myotonic dystrophy type 1 (DM1) are characterized by progressive muscle weakness and wasting, impaired mitochondrial (Mt) respiration, hyperglycemia and insulin resistance, diminished metabolic capacity and elevated oxidative stress. Highly complex and degenerative phenotypes in DM1 manifest as the result of massive expansion of a CTG tri-nucleotide repeat in the 3' translated region of DMPK gene in chromosome 19q13.3. The mechanism by which expanded CTG repeats impair Mt function and metabolic regulations in DM1 is unknown. PGC-1 is a transcription co- activator that regulates transcription of genes that regulate Mt respiration, metabolism of fatty acid and glucose and reactive oxygen species (ROS), and activity of the neuromuscular junction (NMJ). In this project our goal is to determine the extent to which diminished PGC-1 activity contributes to muscle pathogenesis in DM1: 1) aim 1 will assess expressions of PGC-1 target genes regulating Mt respiration, and function of neuromuscular junction (NMJ) in DM1 skeletal muscle. The expected outcome will establish the role of decreased PGC-1 and its target genes in skeletal muscle pathology in DM1; 2) aim 2 will establish the mechanism/s by which mutant CUG RNA disrupts intracellular redox homeostasis in DM1. These experiments will establish the mechanism by which PGC-1 target genes catalyzing metabolism of endogenous ROS are disrupted in DM1, and determine whether the activity of the ROS producing enzyme NADPH oxidase is up- regulated in DM1 myoblasts and C2C12 cells expressing mutant CUG repeats; and 3) aim 3 will explore the mechanism by which expanded CUG repeats cause a redox-dependent activation of Ataxia Telangiectasia- Mutated (ATM) kinase, phosphorylates and alters AMPK activity in DM1. We will also test whether activated AMPK modulates phosphorylation of TORC2 (transducer of regulated CREB activity), and regulates CREB activity and CREB-mediated transcription of PGC-1 in DM1. We will also test whether expanded CUG repeats modulate TORC2-mediated CREB activity and transcription of PGC-1 in DM1. The proposed study will provide insight into the mechanism by which mutant CUG RNA disrupts PGC-1 activity and impair Mt function, and might lead to the development of intervention through modulating PGC-1 signaling in DM1.