Identifying mechanisms of deregulated mTORC1 activity during skeletal muscle atrophy

项目总结/摘要 骨骼肌萎缩（萎缩）是由许多病理性损伤引起的， 威胁人类健康。mTOR复合物1（mTORC 1）信号通路是细胞生长的主要调节因子， 对营养和运动作出反应而被激活，以促进骨骼肌质量的增加。在萎缩期间， mTORC 1活性受到抑制，这是重要的，因为它反映了该组织从无细胞的转变 （生长）到catenopathy（消瘦）。有趣的是，由于肌肉废用而发生的萎缩会导致肌肉不能运动。 营养素刺激mTORC 1活性和细胞同化（合成代谢抗性）。这一观察结果表明 机械和营养骨骼肌输入之间的复杂相互作用，虽然是分子基础， 这种关系还没有解决。体外模拟肌肉废用和合成代谢抵抗不是一个简单的方法。 任务;骨骼肌中mTORC 1调节的分子理解尚未实现， 当前细胞模型的实验局限性。我已经开发了强大的体外系统和动物模型 这将使细胞，生物化学和遗传策略，揭示串扰的机制， 骨骼肌中mTORC 1的机械和营养输入之间的关系。在此指导阶段， 奖（K99），我将使用这些工具来1）获得如何机械应力（细胞张力）和 神经元输入（膜电位）影响典型mTORC 1信号传导; 2）识别 机械和营养串扰;以及3）生物化学地鉴定mTORC 1调节复合物如何 在萎缩状态下重塑。这些研究将为mTORC 1抑制提供机制基础 在骨骼肌萎缩过程中，揭示了在废用过程中对抗肌肉质量损失的策略。作为 独立研究者（R 00）我将应用细胞系统，动物模型和产生的知识 在指导阶段，研究一个同样重要的问题，即mTORC 1活性如何被破坏， 老化的肌肉，并有助于肌肉减少症（随着年龄的增长，肌肉质量逐渐减少）。肌肉减少 对我们的老年人口构成重大威胁，因为它是脆弱造成的创伤的基础。 这个问题反映了一个合乎逻辑的科学进展，因为废用性萎缩的许多标志是 与衰老相关的萎缩共享，但尚不清楚促进肌肉损失的分子机制 质量在这两种状态下是相同的。根据本提案中提出的策略，我将1）确定， 机械应力影响老年肌肉中的mTORC 1活性，2）鉴定mTORC 1中的生化改变 老年肌肉中的调节蛋白，3）了解生理学，新的mTORC 1调节蛋白 会导致肌肉减少症实现本建议中概述的目标将是一个重大的 我们对肌肉萎缩背后的信号缺陷的理解的进步， 科学问题，追求我建立一个独立的职业生涯在生物医学研究。

Project Summary/Abstract Skeletal muscle wasting (atrophy) results from a number of pathological insults and poses a serious threat to human health. The mTOR Complex 1 (mTORC1) signaling pathway is a major regulator of cell growth, activated in response to nutrients and exercise to promote accretion of skeletal muscle mass. During atrophy, mTORC1 activity is inhibited which is significant because it reflects a shift of this tissue from anabolism (growth) to catabolism (wasting). Interestingly, atrophy occurring from muscle disuse results in an inability of nutrients to stimulate mTORC1 activity and cellular anabolism (anabolic resistance). This observation suggests a complex interplay between mechanical and nutritional skeletal muscle inputs, though a molecular basis for this relationship has not been resolved. Modeling muscle disuse and anabolic resistance in vitro is not a trivial task; a molecular understanding of mTORC1 regulation in skeletal muscle has not been realized due to experimental limitations of current cellular models. I have developed robust in vitro systems and animal models that will enable the cellular, biochemical, and genetic strategies necessary to uncover mechanisms of crosstalk between mechanical and nutrient inputs to mTORC1 in skeletal muscle. During the mentored phase of this award (K99), I will use these tools to 1) gain an understanding of how mechanical stress (cellular tension) and neuronal input (membrane potential) influence canonical mTORC1 signaling; 2) identify molecular-mediators of mechanical and nutritional crosstalk; and 3) identify biochemically how mTORC1 regulatory complexes are remodeled during states of atrophy. These studies will provide a mechanistic basis for mTORC1 inhibition during skeletal muscle atrophy and reveal strategies to combat loss of muscle mass during disuse. As an independent investigator (R00) I will apply the cellular systems, animal models, and knowledge generated during the mentored phase to investigate an equally important question of how mTORC1 activity is disrupted in aged muscle and contributes to sarcopenia (progressive loss of muscle mass with aging). Sarcopenia represents a significant threat to our elderly population as it underlies traumatic injuries resulting from frailty. This question reflects a logical scientific progression since many hallmarks of disuse-associated atrophy are shared with aging-associated atrophy, but it is unknown if the molecular mechanisms promoting loss of muscle mass are the same in these two states. With the strategies developed in this proposal, I will 1) determine if mechanical stress influences mTORC1 activity in aged muscle, 2) identify biochemical alterations in mTORC1 regulatory proteins in aged muscle, and 3) understand physiologically, how novel mTORC1 regulatory proteins contribute to sarcopenia. Achievement of the aims outlined in this proposal will represent a significant advancement in our understanding of signaling defects that underlie muscle atrophy and provide a wealth of scientific questions to pursue as I establish an independent career in biomedical research.