Role of Beta-Catenin Antagonist Chibby in Adipogenesis

描述（由申请人提供）：肥胖是美国和其他西方国家的一个主要健康问题，增加了患糖尿病、心血管疾病和几种癌症的风险。相反，脂肪萎缩，缺乏脂肪组织，也与糖尿病和各种代谢异常有关。因此，了解调节脂肪细胞分化的细胞和分子基础对于制定预防和治疗这些疾病的综合治疗策略是必要的。典型的Wnt/¿-catenin通路通过过表达研究已被证明可以抑制脂肪形成，同时维持分裂的前脂肪型状态。然而，其生理意义仍有待阐明。我们报道了一种新的与连环蛋白相关的拮抗剂，称为Chibby （Cby）。Cby是一种核蛋白，在整个进化过程中都是保守的。我们发现Cby与-catenin的c端激活域相互作用，并通过与Lef-1竞争来抑制-catenin介导的转录激活。我们进一步证明，在果蝇中，Cby功能的丧失会导致该通路的过度激活。为了深入了解Cby在脊椎动物发育和人类疾病中的功能，我们创建了Cby-null （Cby-/-）小鼠。出乎意料的是，这些老鼠的肥胖程度有所降低。使用培养的3T3-L1前脂肪细胞，我们发现Cby蛋白水平在脂肪形成过程中升高。此外，Cby的异位表达引起自发分化，相反，Cby RNAi几乎完全阻断3T3-L1细胞的脂肪生成。这些初步数据有力地证明Cby是一个重要的脂肪形成因素。这项应用的长期目标是阐明Cby在脂肪组织发育中的作用。我们建议分析Cby-/-小鼠的脂肪组织，在体外研究Cby-/-小鼠胚胎成纤维细胞的成脂潜能，并利用前脂肪细胞和多能间充质干细胞表征Cby。我们的研究提供了希望，阻断Cby的活动可能是一种治疗肥胖及其相关疾病的有效方法。

DESCRIPTION (provided by applicant): Obesity is a major health issue in the United States and other Western countries, increasing the risk of diabetes, cardiovascular diseases and several types of cancers. In contrast, lipoatrophy, the lack of adipose tissue, is also associated with diabetes and various metabolic abnormalities. Thus, understanding the cellular and molecular basis that regulates adipocyte differentiation is necessary to develop comprehensive therapeutic strategies for the prevention and treatment of these disorders. The canonical Wnt/¿-catenin pathway has been shown to inhibit adipogenesis while maintaining a dividing preadipoctye state through overexpression studies. However, its physiological importance remains to be elucidated. We reported a novel ¿-catenin-associated antagonist, termed Chibby (Cby). Cby is a nuclear protein that is conserved throughout evolution. We showed that Cby interacts with the C-terminal activation domain of ¿-catenin and represses ¿-catenin-mediated transcriptional activation by competing with Lef-1. We further demonstrated that loss of Cby function leads to hyperactivation of the pathway in Drosophila. To gain insights into the function of Cby during vertebrate development as well as in human disease, we have created Cby-null (Cby-/-) mice. Unexpectedly, these mice exhibit reduced adiposity. Using cultured 3T3-L1 preadipocytes, we found that Cby protein levels increase during adipogenesis. Furthermore, ectopic expression of Cby causes spontaneous differentiation, and conversely, Cby RNAi almost completely blocks adipogenesis of 3T3-L1 cells. These preliminary data strongly argue that Cby is an essential proadipogenic factor. The long-term goal of this application is to elucidate the role of Cby in adipose tissue development. We propose to analyze adipose tissues in Cby-/- mice, investigate adipogenic potential of Cby-/- mouse embryonic fibroblasts in vitro, and characterize Cby using preadipocyte and pluripotent mesenchymal stem cells. Our research offers hope that blocking Cby's activity may be an effective therapy for obesity and its associated disorders.