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

摘要 许多肌肉营养不良症是由蛋白质突变引起的，这些突变损害了 肌肉肌膜，这会导致血清中肌酸激酶等肌肉酶水平升高。 了解健康的肌纤维维持其肌膜完整性的机制将使 为这些肌营养不良症开发新的治疗方法。Miyoshi肌病(MM)和四肢带 肌营养不良症(LGMD)2B，由deferlin基因突变引起，即为此类疾病。我们已经确定了 LGMD2B肌纤维肌膜完整性的丧失是由于溶酶体与 损伤的肌膜。这会导致损伤触发的溶酶体酶酸分泌的延迟 鞘磷脂酶。提供细胞外鞘磷脂酶可逆转修复缺陷，并提供潜在的 LGMD2B的治疗。然而，鞘磷脂和其他细胞膜的变化机制 脂质促进受损肌肉细胞膜的修复还没有完全阐明。这项建议旨在 确定脂类和脂类修饰酶(如酸性鞘磷脂酶)如何促进 肌膜完整性和促进损伤肌膜的修复。我们将通过可视化和 改善健康肌肉细胞膜的脂质成分，并评估其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的脂质反应是如何改变的，以确定 潜在的治疗干预措施来解决这些变化。我们已经建立的一种这样的干预是 酸性鞘磷脂酶的使用，我们将评估其对LGMD2B的临床前治疗潜力。这些 研究不仅有助于理解脂质在维持肌膜完整性中的作用，而且还提供了 洞察到为肌营养不良症开发新的治疗方法，超越了以蛋白质为目标的治疗 也是针对肌膜脂类。

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.