Mechanisms of human skeletal muscle protein turnover

骨骼肌是人体内最大的蛋白质储存库。骨骼肌的维持是人类运动和代谢健康的关键。骨骼肌内的蛋白质不断地同时合成和降解。这种恒定的蛋白质周转提供了一种有效的机制，用于去除受损的蛋白质并用新的蛋白质替换以维持蛋白质稳态。在成人骨骼肌中，许多激素、营养和机械刺激整合在它们对肌肉蛋白质合成（MPS）和肌肉蛋白质分解（MPB）过程的调节中。MPS和MPB之间的平衡是净肌肉蛋白质增加的主要决定因素，因此，肌肉纤维扩大（肥大），或净肌肉蛋白质损失和肌肉纤维大小减少（萎缩）。 拟议的研究计划是对骨骼肌在增加负荷和卸载状态下的综合和系统研究，以揭示调节肌肉质量增加和减少的机制。我们广泛使用稳定同位素代谢示踪剂来研究骨骼肌蛋白质周转的调节。我们联合收割机这些复杂的措施，只有少数实验室在世界范围内可以使信号蛋白激活，转录组基因表达和组织化学的措施。因此，我们获得了有助于MPS和MPB的急性调节的因素的综合图片。这些急性调节研究也使我们对骨骼肌的长期表型变化有了深入的了解，我们也将对此进行研究。我们已经开发出一种新的方法，结合动态蛋白质组学分析，产生无与伦比的洞察机制调节肌肉蛋白质周转。我们广泛使用加载和卸载模型，使用自愿阻力锻炼或肢体制动范例，试图确定骨骼肌如何感知负荷并改变MPS和MPB。然而，我们仍然缺乏基本的机械调控知识，如何装卸工作，影响MPS和MPB的变化。 拟议的研究计划旨在试图了解控制急性和慢性MPS和MPB的复杂分子机制，最终决定骨骼肌蛋白质质量的增加或减少。虽然我们已经成功地解开了其中的一些机制，并在挑战某些根深蒂固的范式，更先进的和综合的知识需要建立新的方法，验证和应用于不同的模型。为了解决这些问题，我们将利用质谱法，同位素示踪剂和“组学”技术的新模型，了解响应变化加载卸载刺激的最新进展。我们的持续研究将鼓励在公平，多样和包容的环境中培养和培训下一代加拿大科学家。

Skeletal muscle represents the largest protein reservoir in the human body. Maintenance of skeletal muscle is key for human locomotion and metabolic health. The proteins within skeletal muscle are constantly and simultaneously being synthesized and degraded. This constant protein turnover provides for an efficient mechanism for removal of damaged proteins and replacement with new proteins to maintain proteostasis. In adult skeletal muscle, a number of hormonal, nutritional, and mechanical stimuli are integrated in their regulation of the processes of muscle protein synthesis (MPS) and muscle protein breakdown (MPB). The balance between MPS and MPB is a primary determinant of net muscle protein gain and thus, muscle fibre enlargement (hypertrophy), or net muscle protein loss and a reduction in muscle fibre size (atrophy). The proposed research program is an integrated and systematic study of skeletal muscle in states of increased loading and unloading, to uncover mechanisms regulating muscle mass gain and loss. We make extensive use of stable isotope metabolic tracers to study the regulation of skeletal muscle protein turnover. We combine these complex measures, which only a handful of labs worldwide can make, with measures of signalling protein activation, transcriptomic gene expression, and histochemistry. Thus, we obtain an integrated picture of the factors that contribute to the acute regulation of MPS and MPB. These acute regulatory studies have also given us mechanistic insight into longer-term phenotypic changes in skeletal muscle, which we will also study. We have developed a new method that, combined with dynamic proteomic analysis, yields unparalleled insight into mechanisms regulating muscle protein turnover. We make extensive use of loading and unloading models, using voluntary resistance exercise or limb immobilization paradigms, to try and ascertain how skeletal muscles sense load and alter both MPS and MPB. However, we still lack basic mechanistic regulatory knowledge as to how loading and unloading work to affect changes in MPS and MPB. The proposed program of study is aimed at trying to understand the complex molecular mechanisms that are governing both acute and chronic MPS and MPB, ultimately determining gains or losses in skeletal muscle protein mass. While we have been successful in unravelling some of these mechanisms and in challenging certain entrenched paradigms, a more advanced and integrated knowledge requires that new methods be established, validated and applied to different models. To address these issues, we will make use of recent cutting-edge advances in mass spectrometry, new models of isotopic tracers and `omic' technologies to understand response variation to loading an unloading stimuli. Our continuing studies will encourage the development and training of the next generation of Canadian scientists in an equitable, diverse and inclusive environment.