Biology of nuclear receptor rev-erb alpha in circadian rhythm and metabolism

描述（由申请人提供）： 肥胖和糖尿病在美国已经达到流行病的程度。糖尿病及其相关并发症正在成为该国发病率的主要原因之一。虽然有几种假说将肥胖和胰岛素抵抗联系起来，但昼夜节律在糖尿病发病机制中的作用尚未得到很好的解决。有趣的是，空腹血糖、胰岛素敏感性和葡萄糖耐量存在明显的昼夜节律变化，这在肥胖和糖尿病的情况下会受到严重抑制。 孤儿核受体Rev-erb（作为核心昼夜节律基因出现。通过抑制另一个生物钟基因Bma 1的基因表达，Rev-erb（作为昼夜节律的负调节因子。我们发现GSK 3依赖性磷酸化是维持Rev-erb蛋白稳定性所必需的，并且对于体外同步Bma 1基因的昼夜节律振荡至关重要。为了扩展我们对GSK 3依赖性调节Rev-erb的知识，我们在本申请的第一阶段（K99阶段）提出了两个具体目标，包括：阐明GSK 3上游的信号通路（介导Rev-erb（肝细胞中的降解;和Aim 2.确定Rev-erb（通过GSK 3磷酸化）在昼夜节律和代谢中的体内作用。将建立表达Rev-erb（模拟肝脏中GSK 3（磷酸化）的突变体）的小鼠模型来解决这些问题。这将是第一个分析，以确定Rev-erb的作用（作为一个时钟蛋白在肝脏昼夜节律和葡萄糖代谢。本研究将在宾夕法尼亚大学的Penn糖尿病中心进行，由Mitchell Lazar博士监督。该中心拥有糖尿病和肥胖症研究方面的专业知识，是开展拟议项目的绝佳环境。同时，该项目将为主要研究者Lei Yin博士提供极好的培训，以发展糖尿病和肥胖领域的学术生涯。 泛素-蛋白酶体途径（UPP）在机体代谢和能量平衡过程中的作用尚未得到充分研究。我们最近发现，Cullin 4A为基础的E3连接酶调节Rev-erb的蛋白质稳定性（以及基因表达的重要性，为胚胎发育，表明Cullin 4A是一种新的调节剂，在昼夜节律和代谢功能。因此，在R 00阶段期间提出的具体目标3将集中于阐明Cullin 4A E3泛素连接酶在调节昼夜节律、胰岛素信号传导和葡萄糖代谢中的作用。我们希望这项工作将提供一组证据的功能的重要性，泛素-蛋白酶体系统的调节代谢。此外，这项工作可能为确定治疗胰岛素抵抗和糖尿病的新治疗靶点提供新的思路。

DESCRIPTION (provided by applicant): Obesity and diabetes have reached epidemic levels in the United States. Diabetes and its associated complications are becoming one of the leading causes of morbidity in this country. Although several hypotheses link obesity and insulin resistance, the role of circadian rhythm in the pathogenesis of diabetes has not been well addressed. Interestingly, there is a clear circadian variation in fasting glucose, insulin sensitivity and glucose tolerance, which is severely dampened in the condition of obesity and diabetes. The orphan nuclear receptor Rev-erb( emerged as a core circadian gene. By repressing gene expression of another clock gene, Bma1, Rev-erb( functions as a negative regulator of circadian rhythm. We showed GSK3(-dependent phosphorylation is required for maintaining the protein stability of Rev-erb( and is crucial for synchronizing the circadian oscillation of Bma1 gene in vitro. To extend our knowledge on GSK3(-dependent regulation of Rev-erb(, we propose two specific aims in the first phase of this application (K99 phase), including: Aim 1. Elucidate the signal pathways upstream of GSK3( mediating Rev-erb( degradation in hepatocytes; and Aim 2. Determine in vivo roles of Rev-erb( phosphorylation by GSK3( in circadian rhythm and metabolism. A mouse model expressing Rev-erb( mutant which mimics GSK3( phosphorylation in liver will be created to address these questions. This will be the first analysis to determine the role of Rev-erb( as a clock protein in liver circadian rhythm and glucose metabolism. This study will be carried out in the Penn Diabetes Center at University of Pennsylvania under the supervision of Dr. Mitchell Lazar. The center has expertise in diabetes and obesity research, and is an outstanding environment in which to conduct the proposed project. Meanwhile, the project will provide superb training for the principle investigator, Dr. Lei Yin, to develop an academic career in the field of diabetes and obesity. The role of the ubiquitin-proteasome pathway (UPP) has not been well-studied in the process of metabolism and energy homeostasis. We recently discovered that Cullin 4A-based E3 ligase regulates protein stability of Rev-erb( as well as gene expression important for gluconeogenesis, suggesting Cullin 4A is a novel modulator functioning in both circadian rhythm and metabolism. Therefore, the specific aim 3 proposed during the R00 phase will be focused on unraveling roles of the Cullin 4A E3 ubiquitin ligase in regulating circadian rhythm, insulin signaling and glucose metabolism. We expect this work will provide a panel of evidences for the functional importance of the ubiquitin-proteasome system in the regulation of metabolism. In addition, this work may shed the new light on identifying new therapeutic targets for treating insulin resistance and diabetes.