Atrogin-1 and Muscle Protein Balance

描述（由申请人提供）：肌肉消耗和负氮平衡是许多疾病状态（包括糖尿病、慢性肾衰竭和癌症）的衰弱特征。 我们最近发现了一个新的基因，atrogin-1，这是在骨骼肌中特异性表达，并强烈诱导肌肉萎缩时，在这些疾病的各种动物模型。 atrogin-1蛋白含有一个F盒，这表明它可能作为一种泛素-蛋白连接酶，催化关键蛋白的泛素化和降解，导致肌肉萎缩。 这项建议是在Alfred Goldberg博士的实验室开始的研究的结果，Lecker博士是那里的博士后研究员，现在将主要在Lecker博士的独立实验室继续进行。 这种新蛋白质的功能和重要性将通过利用遗传和生物化学方法的结合来阐明。 培养中的肌肉细胞将被工程化以诱导表达atrogin-1，从而可以研究其对肌肉生长、分化和萎缩的影响。 小鼠atrogin-1基因将被破坏，产生一个敲除菌株，我们可以测试缺乏atrogin-1的小鼠是否会发生肌肉萎缩。为了了解atrogin-1如何促进肌肉蛋白质分解，我们将尝试通过酵母双杂交方法和atrogin-1相关蛋白的生化分离来确定其靶标和辅因子。最后，我们将开发体外试验来测量atrogin-1结合泛素蛋白质的能力。阐明atrogin-1的功能不仅有助于表征肌肉蛋白分解的机制和生理调节，而且还可以允许开发可以对抗肌肉消耗状况及其相关发病率（例如肾衰竭中的尿毒症）的药理学抑制剂。

DESCRIPTION (provided by applicant): Muscle wasting and negative nitrogen balance are debilitating features of many disease states including diabetes, chronic renal failure and cancer. We have recently identified a new gene, atrogin-1, which is expressed specifically in skeletal muscle and is strongly induced when muscle atrophies in various animal models of these diseases. The atrogin-1 protein contains an F-box, suggesting that it may act as a ubiquitin-protein ligase that catalyzes the ubiquitination and degradation of key proteins, leading to muscle wasting. This proposal is an outgrowth of studies which were initiated in Dr. Alfred Goldberg's laboratory, where Dr. Lecker was a postdoctoral fellow, and will now be continued mainly in the independent laboratory of Dr. Lecker. The functions and importance of this novel protein will be clarified by utilizing a combination of genetic and biochemical approaches. Muscle cells in culture will be engineered to inducibly express atrogin-1, so that its effects on muscle growth, differentiation and atrophy can be studied. The mouse atrogin-1 gene will be disrupted to generate a knockout strain where we can test whether mice lacking atrogin-1 can develop muscle atrophy. In an effort to understand how atrogin-1 might promote muscle protein breakdown, we will attempt to identify its targets and cofactors by the yeast two-hybrid approach and biochemical isolation of atrogin-1-associated proteins. Finally, we will develop in vitro assays to measure the ability of atrogin-1 to conjugate ubiquitin to proteins. Elucidating the functions of atrogin-1 will not only help characterize the mechanisms and physiological regulation of muscle protein breakdown but may also allow the development of pharmacological inhibitors that could combat muscle wasting conditions and its associated morbidity (e.g. the uremia in renal failure).