Mechanisms underlying Paxillin-mediated amelioration of muscle degeneration

描述（由申请人提供）：肌肉肌病和营养不良导致儿童衰弱性疾病，并与几乎所有受影响患者的过早死亡有关。许多肌肉疾病，如Duchenne、Becker和Merosin缺陷型肌营养不良症，是由将肌细胞锚在其周围基底膜（BM）上的粘附复合物突变引起的。尽管在确定许多肌病的遗传基础方面取得了很大进展，但介导BM组装和粘附的机制尚未得到很好的理解。特别地，需要小分子治疗剂和发现用于药物开发的新靶标。我们已经表明，NAD+生物合成是肌肉发育所必需的，足以纠正斑马鱼的营养不良表型。烟酰胺核苷激酶2b（Nrk 2b）介导的NAD+生物合成通过增加BM组织和促进细胞内整合素结合蛋白Paxillin的亚细胞定位来改善肌肉变性。桩蛋白是调节细胞粘附、形态和迁移的重要信号通路。初步数据表明，Paxillin过表达显着改善肌肉结构，减少营养不良斑马鱼的退化，但机制尚不清楚。拟议研究的基本原理是，由于肌纤维及其周围BM之间细胞粘附的机械故障是许多肌病的病因学基础，因此Nrk 2b途径可能对多种先天性肌营养不良症（CMD）具有治疗效用。本申请的目的是阐明该途径中桩蛋白功能的分子基础。我们的中心假设是Nrk 2b介导的NAD+生物合成调节Paxillin的亚细胞定位;导致增加BM微环境的组织和结构的下游信号传导事件。这项研究的贡献预计将是阐明一种新途径的分子机制，该途径可以恢复营养不良斑马鱼的肌肉结构/功能。这一贡献是重要的，因为这是努力根除肌病的新范例。这种方法是创新的，因为它代表了思维的转变。而不是集中在“典型的”肌肉粘附蛋白，重点是在肌肉中的粘附蛋白，传统上研究不足的补偿反应。因此，这种独特的方法侧重于通过加强现有的机制来改善肌肉结构。这项工作的长期目标是利用阐明一种改善营养不良的新途径，以确定治疗肌肉退行性疾病的新药物靶点。

DESCRIPTION (provided by applicant): Muscle myopathies and dystrophies cause debilitating disease in children and are associated with premature death in nearly all patients affected. Many muscle disorders, such as Duchenne, Becker, and Merosin-deficient muscular dystrophies, are caused by mutations in adhesion complexes that anchor muscle cells to their surrounding basement membrane (BM). Despite great strides in identifying the genetic basis of many myopathies, mechanisms that mediate BM assembly and adhesion are not well understood. In particular, there is a need for small molecule therapeutics and discovery of new targets for drug development. We have shown that NAD+ biosynthesis is necessary for muscle development and sufficient to correct dystrophic phenotypes in zebrafish. Nicotinamide Riboside Kinase 2b (Nrk2b)-mediated NAD+ biosynthesis ameliorates muscle degeneration by increasing BM organization and promoting the subcellular localization of an intracellular Integrin-binding protein, Paxillin. Paxillin is an essential signaling nexus that regulates cell adhesion, morphology, and migration. Preliminary data indicate that Paxillin overexpression dramatically improves muscle structure and decreases degeneration in dystrophic zebrafish, but the mechanisms are not known. The rationale of the proposed research is that because mechanical failure in cell adhesion between muscle fibers and their surrounding BM underlies the etiology of many myopathies, the Nrk2b pathway may have therapeutic utility for multiple congenital muscular dystrophies (CMDs). The objectives of this application are to elucidate the molecular underpinnings of Paxillin function in this pathway. Our central hypothesis is that Nrk2b-mediated NAD+ biosynthesis regulates subcellular localization of Paxillin; resulting in downstream signaling events that increase organization and structure of the BM microenvironment. The contribution of the proposed research is expected to be the elucidation of molecular mechanisms underlying a novel pathway that restores muscle structure/function in dystrophic zebrafish. This contribution is significant because this is a new paradigm in the effort to eradicate myopathies. The approach is innovative because it represents a shift in thinking. Instead of focusing on "canonical" muscle adhesion proteins, the focus is on the compensatory response of adhesion proteins that are traditionally understudied in muscle. Thus, this unique approach focuses on improving muscle structure by strengthening existing machinery. The long-term goal of this work is to capitalize on elucidation of a novel pathway that ameliorates dystrophy to identify new drug targets for the treatment of muscle degenerative disorders.