The Role of KBTBD2 in Lipodystrophy, Insulin Resistance, and Diabetes

项目总结 脂肪组织对全身能量平衡至关重要。肥胖和脂肪营养不良(由 脂肪减少)与糖尿病和胰岛素抵抗有关。我们最近的工作发现了一种新的突变小鼠， 名为Teny，表现出生长迟缓，脂肪营养不良，极端胰岛素抵抗，严重糖尿病 空腹血糖高达600-700 mg/dL，脂肪肝。微小的表型是由基因中的零突变引起的 Kelch Repeat和BTB(POZ)结构域包含2(KBTBD2)，以前没有指定的功能。 我们发现KBTBD2作为一种E3泛素连接酶，通过靶向调节胰岛素信号通路 磷脂酰肌醇3-激酶(PI3K)调节亚基P85α的降解。这项提议将进一步 探索KBTBD2在脂肪营养不良、胰岛素抵抗和糖尿病中的作用，并将寻求确定 糖尿病和肥胖症的机械相关调节器。在指导的K99阶段，将产生小鼠 操纵Kbtbd2在不同组织中的表达，研究其组织特异性功能，并剖析其作用 各组织在幼体表型发育中的作用(目标1)。我发现KBTBD2含有YXXM基序， 它可能被磷酸化，以招募P85α。KBTBD2的磷酸化可以解释为什么P85α 在不同的细胞和组织中被选择性地降解。这反过来又表明KBTDB2.本身可能是 根据组织、发育阶段和/或代谢状态，受到翻译后调节。 目标2的重点将是研究KBTBD2的翻译后修饰。在独立的R00阶段， 我将进一步探索观察到的P85α单一泛素化的生物学后果(目标3)。这个 Kbtbd2在饮食诱导的肥胖中的转录抑制，导致P85α的积累，提示我们 寻找去泛素酶，这种酶可能是抑制剂的靶点，以降低肥胖患者患糖尿病的风险。在……里面 初步研究表明，已鉴定出几种候选的P85α脱泛素酶。以确定新的基因 都与肥胖和糖尿病有关，我们已经在老鼠身上建立了几个正向基因筛查，并发现 有趣的点击量。其中，第二种BTB蛋白(RHOBTB2)可能在我们已有的整体框架内起作用 建好了。在目标4中，我将研究去泛素酶和其他新发现的调节因子在肥胖和 糖尿病。成功完成本提案中概述的目标将提高我们对KBTBD2的理解 并可能为糖尿病的治疗提供新的靶点。为了完成拟议的研究，我将包括Dr。 Philipp Scherer(德克萨斯大学西南医学中心)作为我在导师K99阶段获得的共同导师 在脂肪细胞和糖尿病研究方面进行更多培训。我的导师布鲁斯·比特勒博士建立了一种独特的 具有实时识别致病突变能力的前向遗传主动性。我会继续努力 新发现的肥胖和糖尿病的调节者来自建立的正向基因筛查 独立R00阶段。这次培训将使我能够扩展我的专业知识，并帮助我过渡到 成功的独立学术研究人员。

PROJECT SUMMARY Adipose tissue is critical for whole body energy homeostasis. Both obesity and lipodystrophy (caused by loss of fat) are associated with diabetes and insulin resistance. Our recent work identified a new mutant mouse, termed teeny, that exhibited growth retardation, lipodystrophy, extreme insulin resistance, severe diabetes with fasting glucose as high as 600-700 mg/dL, and fatty liver. The teeny phenotype is caused by a null mutation in the Kelch repeat and BTB (POZ) Domain containing 2 (KBTBD2), which has no previously assigned functions. We found that KBTBD2 operates as an E3 ubiquitin ligase to regulate the insulin signaling pathway by targeting the degradation of the regulatory subunit of phosphatidylinositol 3-kinase (PI3K), p85α. This proposal will further explore the role of KBTBD2 in lipodystrophy, insulin resistance, and diabetes, and will seek to identify mechanistically related regulators of diabetes and obesity. In the mentored K99 phase, mice will be generated to manipulate Kbtbd2 expression in different tissues to study its tissue-specific functions, and to dissect the role of each tissue in the development of teeny phenotype (Aim 1). I found that KBTBD2 harbors a YXXM motif, which may be phosphorylated in order to recruit p85α. The phosphorylation of KBTBD2 could explain why p85α is selectively degraded in different cells and tissues. This, in turn, would suggest that KBTDB2 itself might be subject to post-translational regulation depending upon tissue, developmental stage, and/or metabolic status. The focus of Aim 2 will be to study the post-translational modification of KBTBD2. In the independent R00 phase, I will further explore the biological consequences of the observed p85α mono-ubiquitination (Aim 3). The transcriptional suppression of Kbtbd2 in diet-induced obesity, leading to the accumulation of p85α, prompts us to search for deubiquitinases, which might be targeted by inhibitors to reduce the risk of diabetes in obesity. In preliminary studies, several candidate p85α deubiquitinases have been identified. To identify new genes that are involved in obesity and diabetes, we have established several forward genetic screens in mice and found interesting hits. Among these, a second BTB protein (RHOBTB2) may act within the overall framework we have built. In Aim 4, I will study the mechanism of deubiquitinases and other newly identified regulators in obesity and diabetes. Successful completion of the aims outlined in this proposal will improve our understanding of KBTBD2 and may provide new targets for diabetes treatment. To accomplish the proposed research, I will include Dr. Philipp Scherer (UT Southwestern Medical Center) as my co-mentor during the mentored K99 phase to gain more training in adipocyte and diabetes research. My mentor, Dr. Bruce Beutler, has established a unique forward genetic initiative with the ability to identify causative mutations in real time. I will continue working on newly identified regulators of obesity and diabetes from the established forward genetic screens in the independent R00 phase. This training will allow me to expand my expertise and help my transition into a successful independent academic researcher.