Structure-Function Analysis of Sarcospan

描述（由申请方提供）：在骨骼肌中，肌营养不良蛋白-糖蛋白复合物位于肌膜处，由外周膜蛋白和整合膜蛋白组成。作为一个整体，这种复合物将细胞外基质连接到细胞内肌动蛋白细胞骨架，并在肌肉收缩期间为肌膜提供结构稳定性。Duchenne肌营养不良症是最常见的营养不良形式，由肌营养不良蛋白基因突变引起，导致肌营养不良蛋白和整个肌营养不良蛋白-糖蛋白复合物的丢失。我的研究小组率先发现了几个与肌节蛋白（肌营养不良蛋白-糖蛋白复合物的组成部分）功能相关的关键发现。我们已经表明，sarcospan在介导蛋白质相互作用中起着重要的作用。Sarcospan影响肌营养不良蛋白-糖蛋白复合物和细胞外基质之间的通讯。重要的是，我们证明，轻度sarcospan过表达mdx小鼠，其中具有突变的鼠肌营养不良蛋白基因，抢救肌营养不良症的稳定表达的蛋白质复合物，功能上类似于肌营养不良蛋白-糖蛋白复合物。我们建议研究SSPN介导的mdx表型改善的分子机制，并揭示可能掩盖SSPN缺失小鼠中潜在的有趣和启发性表型的代偿机制。我们还将通过检查肌肉力学来完成对SSPN的“拯救作用”的表征。我们的假设提供了跨膜/细胞骨架复合物（即整合素和DGC）之间的串扰机制，可以阐明补偿机制是如何调节的。每个目标的结果将提供关于sarcosspan作为肌营养不良蛋白-糖蛋白复合物中重要结构元件的作用的新信息，并揭示sarcosspan在信号传导和疾病中的功能的新信息。我们的提案解决了与肌营养不良蛋白-糖蛋白复合物的破坏如何导致杜氏肌营养不良症有关的问题。在我们之前的资助期间，我们发现肌营养不良蛋白-糖蛋白复合物的组成部分sarcospan能够改善小鼠的肌营养不良蛋白缺陷型肌营养不良症。我们计划测试这些小鼠的生理特性，并研究sarcospan改善的机制。

DESCRIPTION (provided by applicant): In skeletal muscle, the dystrophin-glycoprotein complex is located at the sarcolemma and is composed of peripheral and integral membrane proteins. As a whole, this complex links the extracellular matrix to the intracellular actin cytoskeleton and provides structural stability to the sarcolemma during muscle contraction. Duchenne muscular dystrophy, the most common form of dystrophy, is caused by mutations in the dystrophin gene that result in loss of dystrophin protein and the entire dystrophin-glycoprotein complex. My research group has pioneered several key discoveries related to the function of sarcospan, an integral component of the dystrophin-glycoprotein complex. We have shown that sarcospan plays an important role in mediating protein interactions within this complex. Sarcospan affects communication between the dystrophin-glycoprotein complex and the extracellular matrix. Importantly, we demonstrate that mild sarcospan over-expression in mdx mice, which possess a mutation in the murine dystrophin gene, rescues muscular dystrophy by stabilizing expression of a complex of proteins that is functionally analogous to the dystrophin-glycoprotein complex. We propose to investigate the molecular mechanism(s) of SSPN-mediated amelioration of mdx phenotype and reveal the compensatory mechanisms that may mask a potentially interesting and enlightening phenotype in the SSPN-null mice. We will also complete our characterization of SSPN's `rescue effect' by examining muscle mechanics. Our hypothesis provides a mechanism for cross-talk between transmembrane/cytoskeletal complexes (i.e. integrins and DGC) that may illuminate how compensatory mechanisms are regulated. Results from each of the Aims will provide new information on the role of sarcospan as an important structural element within the dystrophin-glycoprotein complex and uncover new information on sarcospan's function in signaling and disease. PUBLIC HEALTH RELEVANCE Our proposal addresses questions related to how disruption of the dystrophin-glycoprotein complex causes Duchenne muscular dystrophy. During our previous funding period, we discovered that sarcospan, an integral component of the dystrophin-glycoprotein complex, is able to ameliorate dystrophin-deficient muscular dystrophy in mice. We plan to test the physiological properties of these mice and investigate the mechanisms of sarcospan amelioration.