核膜蛋白Nurim调控细胞自噬的机制及其在肿瘤发生发展中的作用研究

Autophagy has dual roles in tumor initiation and progression, acting as both a tumor suppressor and a tumor promoter. The integral nuclear membrane protein Nurim is expressed in a broad range of cancer types and its expression level is correlated with a higher tumor grade. In our previous study, the ubiquitin protein ligase complex subunit FBXO6 (F-box protein 6) and the autophagosomal marker LC3 （microtubule-associated protein light chain 3） were identified as novel interacting proteins of Nurim using Co-immunoprecipitation (Co-IP) combined with mass spectrometry (MS). In tumor cells expressing Nurim, the nucleus can be specifically degraded by an autophagic process termed nucleophagy that originated from the nuclear envelope. Meanwhile, Nurim knockdown obviously increased macroautophagy and decreased cell proliferation. So we make a hypotheses that when Nurim exists in cancer cells, FBXO6 binds to Nurim and promotes its interaction with LC3 to form the nucleophagy complex, thus contributing to tumor cell survival. On the other hand depletion of Nurim induces increased macroautophagy which leads to cell death. In this project by using Co-IP and Transmission electron microscope we intend to systematically understand the mechanisms of the two different autophagy processes regulated by Nurim and reveal its biological functions in promotion and progression of cancer. The project will provide a potential new target for cancer therapy.

自噬在肿瘤发生发展中有双重作用，即可以作为肿瘤抑制因子，也可以作为肿瘤促进因子。核膜蛋白Nurim在多种类型的肿瘤中过表达，表达量随着肿瘤恶化程度增加。前期实验利用免疫共沉淀技术结合质谱分析，鉴定两个新的Nurim相互作用蛋白:泛素连接酶复合物的亚基FBXO6和自噬标记物LC3。在Nurim内源性表达的肿瘤细胞系，透射电镜观察到两种不同形式的核膜参与的自噬，并且这种细胞核自噬在饥饿状态下增加;而干涉Nurim导致巨自噬增加，细胞增殖减少。因此我们提出假说：Nurim存在情况下，Nurim与FBXO6结合，进而与LC3共同参与细胞核自噬，有利于肿瘤细胞生存；另一方面干涉Nurim诱发巨自噬，有利于肿瘤细胞死亡。本项目拟采用免疫共沉淀、透射电镜等技术，从分子、细胞到个体水平阐明Nurim介导的两种自噬的分子机制，揭示细胞自噬在肿瘤发生发展中的作用，为癌症治疗提供新的靶点和策略。

自噬在肿瘤发生发展中有动态作用，即可以作为肿瘤抑制因子，也可以作为肿瘤促进因子。核膜蛋白Nurim在多种类型的肿瘤中过表达，表达量随着肿瘤恶化程度增加。研究显示，在Nurim内源性表达的肿瘤细胞系， Nurim与组成E3泛素连接酶复合物SCFs的亚基FBXO6互相作用，进而与LC3共同参与细胞核自噬。抑制Nurim可以显著减少细胞核自噬，从而在细胞水平减缓细胞增殖，在个体水平减小肿瘤生成的体积。更重要的是，透射电镜显示在人类的肝癌和胃癌中发现细胞核自噬随着肿瘤恶化增加。上述结果显示，通过敲除/敲低FBXO6以及Nurim可以抑制细胞核自噬，不利于肿瘤细胞生存。FBXO6-Nurim调控的细胞核自噬是肿瘤细胞应对压力和提高生存率的一种方式。FBXO6-Nurim通路介导的细胞核自噬对肿瘤恶化非常重要，我们的工作将为癌症治疗提供新的靶点和策略。