SENP1调控磷酸戊糖途径抑制肿瘤细胞生长及其分子机制

Protein SUMOylation/de-SUMOylation is an important and reversible post-translational modifiction implicated in mutiple cellular processes. Through its ability to alter the substrates' activity and location, etc, SUMOylation/de-SUMOylation participates in diverse physilogical and pathological processes in vivo. De-SUMOylation is carried out by a protein family of SUMO-specific proteases (SENPs), which is responsible for removing the conjugated SUMO protein from the targets. Recently, we observed that compared with Senp1+/+ MEF cells, the growth rate and glucose consumption of Senp1-/- cells were obviously increased. At the molecular level, the expression of key enzymes for PPP and nucleotide de novo synthesis were all upregulated at the transcriptional level . In addition, intermediate metabolites including 6-PG and R-5-P were accumulated in Senp1-/- MEF cells in comparison with in the wildtype ones. In the contrary, when we overexpressed SENP1 in A549 adenocarcinoma cell line, we found that the growth rate, glucose consumption and G6PD expression were all inhibited. Through comparable analysis on samples collected from NSCLC patients, we detected that the expression of SENP1 were decreased in tumor tissues compared with in the corresponding normal cancer adjacent tissues. These data mentioned above prompted us to investigate whether SENP1 can inhibit tumor cell growth through regulating PPP and anabolic metabolism of tumor cells. Hence, in this project, based on the important primary results found above, we will propose to determine, firstly, whether the downregulation of SENP1 in tumors are causative in tumor cell metabolism reprogramming; secondly, through inhibiting anabolism of tumor cells, SENP1 can reduce tumor cell growth and proliferation; lastly, the underlying mechanisms for SENP1 on inhibiting tumor cell anabolic metabolism and growth, e.g. the target proteins modified by SENP1 during the process. The research will help us establish a relationship between SENP1 and tumor cell growth regulation through regulating cell metabolic pathways, as well as providing novel targets for tumor therapy in the clinic.

SUMO修饰通过改变靶蛋白的位置与活性等，参与生理与病理过程的调控。我们前期工作发现， Senp1-/-MEF细胞生长速度较野生型增快，葡萄糖消耗增加，磷酸戊糖途径关键酶G6PD等表达升高，6-磷酸葡萄糖酸酯、5-磷酸核糖等中间代谢产物堆积。在肺腺癌细胞株A549中过表达SENP1，则抑制细胞生长、葡萄糖消耗和G6PD表达。对肺癌患者肿瘤标本和癌旁组织比较分析，发现SENP1在肺癌组织中低表达。上述发现使我们有兴趣进一步探讨SENP1是否通过抑制磷酸戊糖途径抑制了肿瘤细胞生长。本课题将围绕SENP1与肿瘤细胞代谢和生长进行以下研究：1. 肿瘤细胞中SENP1低表达是否改变了细胞的代谢模式；2.SENP1是否通过改变代谢模式抑制肿瘤细胞的生长；3.SENP1调控代谢的分子机制。上述研究，能帮助我们建立SENP1通过调控细胞代谢参与肿瘤生长调控的联系,并将为临床防治肿瘤提供新的作用靶标。

细胞代谢重编程（cell metabolism reprogramming）是肿瘤发生发展的重要原因。具有快速增殖能力的细胞，如胚胎成纤维细胞（mouse embryonic fibroblasts, MEFs）和肿瘤细胞等，与处于静止期的细胞主要以氧化磷酸化获取 ATP 不同，为了满足细胞快速生长的需要，大量的营养物质（如葡萄糖、谷氨酰胺）被细胞摄取后，通过活跃的有氧酵解（aerobic glycolysis）和磷酸戊糖途径（pentose phosphate pathway, PPP），为细胞增殖和分裂提高生物原料，这被称为细胞代谢的重编程。SENP1作为一种去SUMO蛋白酶家族成员，是调控细胞内蛋白SUMO修饰水平的重要因子，从而参与生物体生理和病理过程的调控。开展本项目的前期基础，是基于SENP1缺失后，在MEF细胞中发现了糖酵解和磷酸戊糖途径活跃的数据，提示SENP1参与快速增殖细胞代谢重编程的可能性；另外，我们在人肺癌标本中，发现了SENP1的低表达。在本项目的资助下，我们通过获取临床肺癌患者的肿瘤组织标本、体外构建稳定敲减SENP1的肿瘤细胞系、裸鼠体内成瘤实验，结合一系列分子生物学、细胞生物学和代谢物的分析，获得了如下科学发现：1. 肿瘤细胞中SENP1的低表达促进肿瘤细胞的生长；2.SENP1通过促进肿瘤细胞的糖酵解和磷酸戊糖代谢，促进肿瘤细胞生长；3. SENP1促进磷酸戊糖途径与调控转录因子Nrf2的SUMO化修饰程度有关。本项目的研究结果能够为特定分子和蛋白质翻译后修饰方式，参与代谢过程调控与肿瘤生长之间的联系提供线索，为理解肿瘤生长中代谢动因的普遍性提供证据。