抑肌素调控泛素化蛋白质降解和体内蛋白质氨基酸稳态的机制研究

Myostatin is the negative regulator of myogenesis in vertebrate which modulate the homeostasis of the protein. In our previous study, the mTOR signaling was repressed in the muscle of adult mystatin deficient zebrafish however at the same time the ubiquitin ligase gene Atrogin-1 and MuRF1 were down-regulated. This is an excellent system to investigate the relationship between proteasome and mTOR signaling. In this system, myostatin deficient zebrafish and gibel carp line were served as model animals. The interaction of FOXOs and Smad3 could be the trigger of activation of atrogin-1 and MuRF1 expression. The mechanisms of the complex formation needed elucidation such as the binding site of the complex on the promoter and which proein serves the activation or the binding function. Whether the proteasome inhibition could change the homeostasis of amino acid was the key point of mTOR signaling. This investigation is not only a fundamental research but also could offer new thinking for rapid growth of muscle mass. Furthemore themyostatin deficient gibel carp linehave decreased nitrogen waste.

抑肌素是脊椎动物肌肉生长的负调控因子，是蛋白质代谢的重要调控因子。敲除抑肌素的成年斑马鱼mTOR信号通路活性被压制，同时泛素连接酶E3的编码基因Atrogin-1和MuRF1表达显著下调。这是很好的研究蛋白酶体抑制和mTOR信号通路关系的模型。为了了解其内在机制，我们利用敲除抑肌素的斑马鱼和异育银鲫为模式动物，通过研究Smad3和FoxOs相互作用导致Atrogin-1和MuRF1启动子激活的机制，以及该模式动物体内氨基酸水平变化和灌喂氨基酸挽救实验，来解释蛋白酶体抑制导致的氨基酸稳态变化进而调控mTOR活性的内在分子机制。本研究的实施可以完善鲤科鱼类抑肌素调控泛素化-蛋白酶体和氨基酸稳态的机制，给完善肌肉快速生长的优良性状提供营养学新思路，同时还可以创建低氮排放的环境友好型潜在养殖品种。

抑肌素是肌肉发生和生长的负调控因子，可以调节脊椎动物肌肉蛋白质的降解和合成的平衡，但是其调控机制还不清楚。在本项目的资助下，我们利用斑马鱼和鲫鱼开展了研究，首先，我们对抑肌素调控蛋白酶体的机制进行了研究，我们发现，在敲除抑肌素的斑马鱼肌肉组织中，泛素化连接酶基因Atrogin-1和trim63的转录表达显著降低，我们利用Atrogin-1的抗体检测了其蛋白表达情况，结果和转录水平结果一致。另一方面，我们研究了抑肌素对蛋白质合成通路调控作用，我们发现，敲除抑肌素可以显著接触随年龄对mTOR信号的抑制。而且该调控作用依赖PI3K的存在。什么分子可以激活PI3K呢？通过转录组分析，我们发现，敲除抑肌素可以显著提高肌肉组织中胰岛素基因的表达。结论：敲除抑肌素一致蛋白质泛素化蛋白酶体降解，通过胰岛素-PI3K-TOR信号通路促进蛋白质合成途径。