USP21去泛素化AMPK调控肿瘤代谢及发生的机制研究

AMPK is a serine/threonine kinase essential for cellular metabolism regulation, where it occurs as heterotrimers comprising catalytic α subunits and regulatory β and γ subunits. Little is known about the regulation mechanism of AMPKγ whereas AMPKα has been well studied. For the first time, we found that AMPKγ subunit could be ubiquitinated. Our mass spectrometry data shows that USP21 is a novel binding partner of AMPK. USP21 could interact with AMPK and deubiquitinate AMPKγ to regulate its kinase activity. Interestingly, our further analysis found conservative phosphorylation site of AMPK on USP21 and we confirm the phosphorylation of this site using MS. Based on the findings, we put forward the hypothesis: USP21-AMPK axis plays a vital role in cellular metabolism and tumorigenesis. This project will further elucidate the molecular mechanism of USP21 deubiquitinating AMPKγ，and AMPK phosphorylating USP21 to regulate its activity. Furthermore, we will make effort to evaluate the feedback regulation between USP21 and AMPK in metabolic reprogramming and tumorigenesis using USP21 knockout mice model we have established. These studies will shed light on the role of AMPK in cell metabolism and tumorigenesis.

AMPK是调控细胞代谢的重要蛋白激酶，由α、β、γ三个亚基组成。相对于α亚基，AMPKγ调控机制研究甚少。本课题组前期发现AMPKγ亚基能发生泛素化修饰，质谱发现去泛素化酶USP21是AMPK结合蛋白。进一步发现USP21能与AMPK相互作用并能对AMPKγ去泛素化，敲除USP21显著增加AMPK的活性。有趣的是，我们发现USP21含有保守的AMPK磷酸化位点，质谱显示该位点能发生磷酸化修饰。基于以上研究，我们提出假说：USP21-AMPK反馈调控轴在细胞代谢及肿瘤发生中起重要作用。本项目将进一步阐明USP21通过去泛素化AMPKγ调控其活性的分子机制，并确证AMPK磷酸化USP21以及对其活性的调节；同时，利用我们构建的USP21基因敲除小鼠解析USP21与AMPK协同调控代谢重编程过程及在肿瘤发生中的作用。这些研究将揭示AMPK在细胞代谢及肿瘤发生中的作用机制。

恶性肿瘤严重危害人类健康，细胞代谢与肿瘤的发生发展密切相关。AMPK作为调控细胞代谢的重要蛋白激酶，由α、β、γ三个亚基组成。相对于α亚基，AMPKγ调控机制研究甚少。我们的研究显示，USP21能够与AMPK各亚基结合，其作为AMPK的去泛素化酶（DUB），通过解离AMPK蛋白的多种类型的泛素化链，从而抑制AMPK活性。此外，我们发现AMPK通过磷酸化修饰反馈调控USP21与AMPK的结合，形成特定的反馈调控的新机制。功能上，我们发现USP21能够通过AMPK调控巨噬细胞极化，抑制肿瘤细胞增殖及迁移过程，因此，靶向USP21-AMPK轴可能不仅从肿瘤代谢上抑制肿瘤，而且可能为肿瘤免疫治疗提供一种潜在的治疗策略。