Structure-Function Analysis of Sarcospan

描述（由申请人提供）：在骨骼肌中，肌营养不良蛋白-糖蛋白复合物位于肌膜，由外周蛋白和整体膜蛋白组成。作为一个整体，这种复合物将细胞外基质与细胞内肌动蛋白细胞骨架连接起来，并在肌肉收缩期间为肌膜提供结构稳定性。杜氏肌营养不良是最常见的营养不良形式，是由肌营养不良蛋白基因突变引起的，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萎缩蛋白-糖蛋白复合物的组成部分肌萎缩肌的功能有关的关键发现。我们已经证明，在这个复合体中，肌展在介导蛋白质相互作用中起着重要的作用。肌萎缩影响肌营养不良蛋白-糖蛋白复合物与细胞外基质之间的通讯。重要的是，我们证明了mdx小鼠的轻度肌萎缩过度表达，其具有小鼠肌营养不良蛋白基因突变，通过稳定功能类似于肌营养不良蛋白-糖蛋白复合物的蛋白质复合物的表达来拯救肌肉营养不良。我的研究小组已经开发了使用次要基因，如SSPN和Akt，作为改善营养不良肌肉的策略。这种方法的优势在于，它们有可能针对所有DMD病例，而不考虑特定的肌营养不良蛋白突变。目前的3R01提案建立在第一和第二个资助期的发现基础上，通过询问SSPN改善肌营养不良蛋白缺陷mdx小鼠疾病的特定机制。我们将测试SSPN在人源性DMD肌肉细胞中的功效，并确定具有治疗作用的SSPN的最小结构域。我们的研究将揭示SSPN在确定粘附复合物（DGC， UGC和α7ß1整合素）的细胞表面表达中的伴侣功能，这些粘附复合物已知可改善mdx疾病。我们假设SSPN可能作为“单客户端”伴侣调节肌肉中粘附复合物的细胞表面定位。该结果将改变我们对DMD发病机制的理解，并为开发基于SSPN的治疗提供必要的见解。我们将生成动物模型，这将对该领域的许多未来项目有价值。此外，我们期望我们的结果将阐明分子途径，可以对抗由于细胞外基质接触丧失而引起的广泛的肌肉萎缩疾病。

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. My research group has developed the use of secondary genes, such as SSPN and Akt, as a strategy to ameliorate dystrophic muscle. Such approaches are advantages in that they have the potential to target all DMD cases, regardless of the specific dystrophin mutation. The current 3R01 proposal builds on discoveries made during the first and second funding period by interrogating specific mechanisms by which SSPN ameliorates disease in dystrophin-deficient mdx mice. We will test the efficacy of SSPN in human-derived DMD muscle cells and determine the minimal domains of SSPN that are therapeutic. Our studies will reveal a chaperone function for SSPN in determining the cell surface expression of adhesion complexes (DGC, UGC, and α7ß1 integrin) that are known to ameliorate mdx disease. We hypothesize that SSPN may function as a 'single-client' chaperone to regulate cell surface localization of adhesion complexes in muscle. The outcomes of the proposal will change our understanding of DMD pathogenesis and provide necessary insight for development of SSPN- based therapy. We will generate animal models that will be valuable for many future projects in the field. Furthermore, we expect that our results will illuminate molecular pathways that could counter a broad range of muscle wasting disorders due to loss of extracellular matrix contact.