BetaCatenin Regulation of Skeletal Muscle Hypertrophy

描述（申请人提供）：核糖体作为细胞的“建房”大分子，其生物发生对细胞生长至关重要。尽管核糖体在细胞生长中起着核心作用，但我们对核糖体生物发生在成人骨骼肌肥大中的作用的理解仍然存在根本性的差距。我们实验室的研究提供了证据，支持核糖体生物发生增加在骨骼肌肥大中的作用。目前的提案将开始直接检查核糖体生物发生对肌肉肥大的重要性，通过测试-catenin是肌肉肥大所必需的假设，通过c-myc激活核糖体生物发生增加蛋白质合成。为了有条件地操纵-catenin或c-myc基因在成人骨骼肌中的表达，我们制造了HSA-MerCreMer小鼠。目的1将使用catenin基因失活后的足底肌肉机械过载模型来确定-catenin表达是否对骨骼肌肥大是必要的。目的2将确定-catenin表达的增加是否足以刺激骨骼肌肥大。-catenin将在成人骨骼肌中过度表达，使用HSA- MerCreMer菌株产生稳定形式的-catenin。目的3将使用HSA-MerCreMer菌株确定成人骨骼肌c-myc条件失活后，c-myc表达是否对骨骼肌肥大是必要的。基因失活对肥厚反应的影响将通过测量形态学（肌肉重量、纤维CSA）、生化（总蛋白、RNA和DNA）、分子（Western blot、RT-PCR、启动子分析、染色质免疫沉淀（ChIP）和电泳迁移率（EMSA））和代谢（蛋白质合成和降解率）变量来评估。这些研究结果有望通过确定促进骨骼肌蛋白合成和肥厚的新分子靶点而具有重要的临床意义。从长远来看，操纵核糖体生物发生的能力代表了一种有希望的新策略，可以减轻或改善与衰老、卧床休息和恶病质相关的肌肉萎缩。

DESCRIPTION (provided by applicant): As the "house-building" macromolecule of the cell, ribosome biogenesis is essential for cell growth. Despite this central role in cell growth, there remains a fundamental gap in our understanding of the role of ribosome biogenesis in adult skeletal muscle hypertrophy. Studies from our laboratory have provided evidence which supports a role for increased ribosome biogenesis in skeletal muscle hypertrophy. The current proposal will begin to directly examine the importance of ribosome biogenesis to muscle hypertrophy by testing the hypothesis that -catenin is necessary for muscle hypertrophy by increasing protein synthesis through c-myc activation of ribosome biogenesis. To conditionally, manipulate -catenin or c-myc gene expression in adult skeletal muscle we generated the HSA-MerCreMer mouse. Aim 1 will determine if �-catenin expression is necessary for skeletal muscle hypertrophy using a mechanical overload model of the plantaris muscle following catenin gene inactivation. Aim 2 will determine if increased expression of �-catenin is sufficient to stimulate skeletal muscle hypertrophy. �-catenin will be over-expressed in adult skeletal muscle by using the HSA- MerCreMer strain to generate a stabilized form of �-catenin. Aim 3 will determine if c-myc expression is necessary for skeletal muscle hypertrophy following the conditional inactivation of c-myc in adult skeletal muscle using the HSA-MerCreMer strain. The effect of gene inactivation on the hypertrophic response will be assessed by measuring morphometric (muscle weight, fiber CSA), biochemical (total protein, RNA and DNA), molecular (Western blot, RT-PCR, promoter analysis, chromatin immunoprecipitation (ChIP) and electrophorectic mobility shift assay (EMSA)) and metabolic (rates of protein synthesis and degradation) variables. The results of the proposed studies are expected to have important clinical implications by identifying new molecular targets for promoting skeletal muscle protein synthesis and hypertrophy. In the long- term, the ability to manipulate ribosome biogenesis represents a promising novel strategy to attenuate or ameliorate muscle atrophy associated with aging, bed rest and cachexia.