Understanding the mechanism and role of cell membrane repair in Miyoshi Myopathy

总结 许多肌营养不良症是由蛋白质突变引起的，这些蛋白质突变损害了肌营养不良症的稳定性和完整性。 肌肉肌膜，导致肌酶如肌酸激酶的高血清水平。 了解健康肌纤维维持肌膜完整性的机制将使 为这些肌营养不良症开发新的疗法。Miyoshi肌病（MM）和肢带 由dysferlin基因突变引起的肌营养不良症（LGMD）2B是这样的疾病。我们已经确定 LGMD2B肌纤维中肌膜完整性的丧失是由于溶酶体与肌纤维融合的延迟。 损伤的肌膜这导致损伤触发的溶酶体酶酸分泌延迟 鞘磷脂酶提供细胞外鞘磷脂酶逆转了修复缺陷， 治疗LGMD2B。然而，鞘磷脂和其他细胞膜的改变的机制， 脂质促进损伤的肌细胞膜的修复尚未完全阐明。这项建议旨在 确定脂质和脂质修饰酶如酸性鞘磷脂酶如何促进维持 肌膜完整性和促进受损肌膜的修复。我们将通过可视化和 改变健康肌肉细胞膜的脂质组成，并评估它们对肌膜完整性的影响。 我们还将评估LGMD2B患者和小鼠肌肉细胞中脂质反应如何改变，以确定 潜在的治疗干预来解决这些变化。我们已经建立的一种干预措施是 使用酸性鞘磷脂酶，我们将评估其对LGMD2B的临床前治疗潜力。这些 研究不仅有助于了解脂质在维持肌膜完整性中的作用， 深入了解开发肌营养不良症的新疗法，超越靶向蛋白质， 也针对肌膜脂质。

Summary Many muscular dystrophies are caused by mutation in proteins that compromise the stability and integrity of the muscle sarcolemma, which results in high serum level of muscle enzymes such as Creatine Kinase. Understanding the mechanism by which healthy myofibers maintain their sarcolemmal integrity would enable development of new therapies for these muscular dystrophies. Miyoshi myopathy (MM) and limb girdle muscular dystrophy (LGMD) 2B, caused by mutations in dysferlin gene are such diseases. We have identified that loss of sarcolemmal integrity in LGMD2B muscle fibers is due to the delay in fusion of lysosome with the injured sarcolemma. This causes a delay in injury-triggered secretion of the lysosomal enzyme acid sphingomyelinase. Providing extracellular sphingomyelinase reverses the repair deficit and offers a potential therapy for LGMD2B. However, the mechanism by which alteration in sphingomyelin and other cell membrane lipids facilitates repair of injured muscle cell membranes has not been fully elucidated. This proposal aims to identify how lipids and lipid modifying enzymes such as acid sphingomyelinase facilitate maintenance of sarcolemmal integrity and facilitate repair of injured sarcolemma. We will achieve this by visualizing and modifying lipid composition of healthy muscle cell membrane and assess their effect on sarcolemmal integirty. We will also assess how lipids respond are altered in the LGMD2B patient and mouse muscle cells to identify potential therapeutic interventions to address these alterations. One such intervention we have established is the use of acid sphingomyelinase and we will evaluate its preclinical therapeutic potential for LGMD2B. These studies will not only help understand the role of lipids in maintenance of sarcolemmal integrity, but also provide insight into developing novel therapies for muscular dystrophies that move beyond targeting the proteins to also targeting the sarcolemmal lipids.