Identifying mechanisms of deregulated mTORC1 activity during skeletal muscle atrophy

项目摘要/摘要 骨骼肌萎缩是由许多病理性的侮辱引起的，并构成严重的 对人类健康的威胁。MTOR复合体1(MTORC1)信号通路是细胞生长的主要调节因子， 对营养和运动的反应被激活，以促进骨骼肌群的增加。在萎缩期间， MTORC1活性受到抑制，这一点很重要，因为它反映了该组织从合成代谢的转变 (生长)到分解代谢(消耗)。有趣的是，由于肌肉停用而导致的萎缩会导致 刺激mTORC1活性和细胞合成代谢(合成代谢抵抗)的营养物质。这一观察结果表明 机械性和营养性骨骼肌输入之间的复杂相互作用，尽管 这种关系还没有得到解决。在体外模拟肌肉废用和合成代谢抵抗并不是一件容易的事 对骨骼肌中mTORC1调控的分子理解还没有实现，原因是 当前细胞模型的实验局限性。我已经开发出了强大的体外系统和动物模型 这将使揭示串扰机制所需的细胞、生化和遗传策略成为可能 骨骼肌中mTORC1的机械输入和营养输入之间的关系。在本课程的指导阶段 奖(K99)，我将使用这些工具来1)了解机械应力(细胞张力)和 神经元输入(膜电位)影响典型的mTORC1信号转导；2)识别mTORC1信号传导的分子介体 机械和营养串扰；以及3)从生化角度确定mTORC1调节复合体 在萎缩状态下重塑。这些研究将为mTORC1的抑制提供一个机制基础 在骨骼肌萎缩的过程中，并揭示了应对停用期间肌肉质量损失的策略。作为一种 独立调查员(R00)我将应用细胞系统、动物模型和产生的知识 在指导阶段，调查一个同样重要的问题，即mTORC1活动是如何在 衰老的肌肉，导致骨质疏松症(随着年龄的增长，肌肉质量逐渐减少)。石棺减少症 对我们的老年人口构成重大威胁，因为它是虚弱造成创伤性伤害的基础。 这个问题反映了一个合乎逻辑的科学进展，因为许多与废用相关的萎缩的特征是 与衰老相关的萎缩相同，但尚不清楚是否促进肌肉丧失的分子机制 在这两种状态下，质量是相同的。根据本提案中制定的战略，我将1)确定 机械应激对老年肌肉mTORC1活性的影响2)确定mTORC1的生化变化 衰老肌肉中的调节蛋白，以及3)从生理上理解mTORC1调节蛋白是如何新颖的 导致骨质疏松症。实现这项提案中概述的目标将是一个重要的 我们对肌肉萎缩背后的信号缺陷的理解取得了进展，并提供了丰富的 当我在生物医学研究中建立独立的职业生涯时，我要追求的科学问题。

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.