COP1通过PCDH9调控STAT3/Cyclin D1信号通路促进胶质瘤增殖的机制研究

Malignant proliferation of glioma is an important factor leading to the deterioration and even death of the patients. Thus, it is of great significance to elucidate the mechanism underlined malignant proliferation of glioma. Our previous studies found that ubiquitin ligase COP1 was up-regulated in glioma patients, which activated the STAT3 and increased the transcription of Cyclin D1, thereby promoting glioma cell proliferation. To further explore the underlying mechanisms of COP1 promoted glioma cell proliferation, the COP1 was subjected for a interacting protein screen in a human brain cDNA library. The PCDH9 protein was identified to interact with COP1 in the screen experiment and the Co-IP experiment further showed COP1 and PCDH9 could form into a complex. Furthermore, COP1 was found to promote the ubiquitination and degradation of PCDH9. Taken together, these findings suggest that COP1 may promote glioma cell proliferation by regulating the ubiquitination and degradation of PCDH9 thereby activating STAT3/Cyclin D1 signaling. Thus, in this project, we intended to clarify the mechanism that COP1 promoted the proliferation of glioma by regulating substrate PCDH9 using the glioma cells, clinical human glioma tissues and nude mice. Our studies will provide some theoretical basis for molecular targeting therapy of human gliomas.

胶质瘤恶性增殖是造成患者死亡的关键因素，因此深入阐明胶质瘤恶性增殖的分子机制具有非常重要的意义。我们前期研究发现泛素连接酶COP1在胶质瘤患者中表达上调，并可激活STAT3和增强Cyclin D1转录进而促进胶质瘤细胞增殖。为了深入研究COP1调控STAT3/Cyclin D1的分子机制，我们通过酵母双杂交筛选获得了COP1的新相互作用蛋白PCDH9，并通过Co-IP证明两者相互作用。进一步的预实验还发现COP1可以促进PCDH9的泛素化和降解。由此我们推测COP1可能通过调控PCDH9的泛素化和降解而导致STAT3激活和Cyclin D1转录异常，最终促进胶质瘤细胞增殖。因此，本项目拟采用胶质瘤细胞、胶质瘤患者标本和裸鼠原位模型，在分子、细胞与整体水平阐明COP1通过PCDH9调控STAT3/Cyclin D1信号通路而促进胶质瘤增殖的分子机制，为胶质瘤的分子靶向治疗提供理论依据。

胶质瘤是中枢神经系统最常见的原发性肿瘤，占脑肿瘤的 40-50%，其恶性程度高、进展快。尽管应用了手术、放疗和化疗等综合治疗，患者平均生存期仍然只有 15 个月左右，这主要是由于胶质瘤细胞的恶性增殖所致，然而介导这一进程的关键生物学机制目前尚不清楚。因此，探明胶质瘤恶性增殖的分子机制，对于深入了解胶质瘤的发展过程具有重要的意义，同时也可为临床治疗提供理论依据。. 组成型光形态建成蛋白1 (Constitutively photomorphogenic 1，COP1) 是首先在植物中被发现的一个高度保守的泛素连接酶。也是近年发现的一个与肿瘤发生发展密切相关的泛素连接酶。然而，COP1在胶质瘤中的作用和机制尚不清楚。因此，本项目拟采用体外培养的胶质瘤细胞、胶质瘤手术标本和裸鼠原位胶质瘤模型为研究对象，从分子、细胞与整体水平阐明COP1调控胶质瘤恶性增殖的作用和机制。 . 在本项目的资助下，我们主要进行了如下研究：1) COP1和PCDH9相互作用；2) COP1对底物PCDH9泛素化调控； 3) COP1和PCDH9的表达以及相关性；4) COP1泛素化底物PCDH9对下游STAT3/Cyclin D1信号通路和胶质瘤增殖的影响。研究结果表明：1) COP1与PCDH9相互作用；2) COP1依赖其泛素连接酶活性下调PCDH9蛋白水平，COP1可促进PCDH9的K48链接的多聚泛素化和蛋白酶体降解；3) COP1在胶质瘤组织中高表达，而PCDH9在脑胶质瘤组织中低表达，且两者呈负相关；4) COP1下调PCDH9进而激活STAT3/Cyclin D1信号通路。以上研究结果全面阐明了COP1通过PCDH9调控STAT3/Cyclin D1信号通路进而促进胶质瘤增殖的分子机制。