REGγ影响脂肪肝形成的模式动物研究

Obesity and liver steatosis are increasing threats to human normal life particularly in recently years. There is no efficient way to curb these disorders in lipid metabolism. Ubiquitin-independent protein degradation emerges as a new field in the proteasome mediated protein decays. REGgamma, an 11S proteasome activator, is a major player mediating a ubiquitin-independent shortcut to the destruction of intact mammalian proteins, including the cell cycle regulator p21/Cip, p16, and p19. Accumulating evidence indicates important roles of REGgamma in multiple biological processes. However, it is unclear how REGgamma exerts its distinct biological functions, particularly how the REGgamma-proteasome pathway interplays with other protein degradation processes. In our preliminary studies, we found enhanced autophagy in REGgamma deficient mice, which protects against high-fat-diet induced hepatic steatosis. We found that REGgamma deficiency triggers autophagy in several cell types and in mouse tissues. REGgamma may inhibit autophagy through negative regulation of several factors required for glucose and lipid metabolism. Given that the contribution of autophagy to lipid metabolism has been recently elucidated through the discovery of a process termed macrolipophagy, we hypothesize that inhibition of REGgamma-proteasome activity may be beneficial in hepatic lipid metabolism through activation of lipophagy and may be protective for diabetes-like syndrome. To test this, we propose to further elucidate molecular mechanisms by which REGgamma deficiency enhances autophagy; to carry out tissue specific, proteomic analysis of REGgamm target proteins; and to investigate in vivo roles of REGgamma in lipid metabolism through regulation of autophagy by using different animal models, including liver specific REGgamm transgenic model. Our long term goals are to understand the molecular basis by which ubiquitin-independent proteasome system regulates important molecules during distinct biological processes. Successful execution of this project will provide novel insights into the molecular details by which ubiquitin independent proteasome degradation system regulates energy balance through autophagic process. Knowledge gained in this research, such as enhancing AMPK activity upon inhibition of REGgamma, may provide new venue for the development of pharmacological agents, which would be beneficial for preventing human disorders.

以肥胖、脂肪肝等为核心的脂代谢紊乱近来已成为严重威胁人类健康的代谢性疾病，目前尚无有效防治手段。由REGγ为代表的非泛素依赖的蛋白酶体降解途径途径因其功能的独特性而成为一个备受关注的新兴领域。我们的前期研究发现REGγ敲除小鼠（KO）中自噬功能增强，对高脂后的脂肪肝形成具有保护作用。为阐明REGγ在脂代谢中的作用及其分子调控机制，我们将通过蛋白组学手段挖掘与自噬和脂代谢相关的重要REGγ底物蛋白。并对候选蛋白如AMPK等在介导REGγ调控细胞自噬和脂代谢中的作用机制展开详细的研究，阐明其影响糖和脂代谢的分子机制。我们还将建立肝细胞特异的REGγ转基因模型并研究高脂喂养在该模型中对小鼠糖和脂代谢的影响。最后，我们将通过探索REGγ缺失对ob/ob肥胖小鼠表型及脂肪代谢的影响来确定其在模式动物体内的生物学功能。这项研究将为一些脂质代谢紊乱相关疾病的诊断治疗及药物开发提供新的理论基础及靶点。

REGγ是一种蛋白酶体激活因子，它激活20S蛋白酶体后，能够介导多种细胞周期调控蛋白（如p21,p19,p16）的降解，从而进一步对细胞周期和凋亡进行调控。以肥胖、脂肪肝等为核心的脂代谢紊乱近来已成为严重威胁人类健康的代谢性疾病，目前尚无有效防治手段。由REGγ为代表的非泛素依赖的蛋白酶体降解途径途径因其功能的独特性而成为一个备受关注的新兴领域。在本项目中，我们进一步研究了REGγ对脂质代谢的影响。主要研究内容：1）建立L-REGγ-Cre : REGγ-/-动物模型。2) 深入研究REGγ-/-和REGγ+/+ ob/ob小鼠模型和REGγ转基因动物模型中REGγ对脂代谢的影响。这些研究对进一步认识REGγ在脂质代谢中的调控机制有重要的意义。