E3泛素连接酶MARCH5通过下调ACC2促进卵巢癌细胞脂肪酸氧化的作用机制研究

脂肪酸氧化增强与卵巢癌恶性进展关系密切，其发生机制仍有待深入阐明。线粒体是调控细胞代谢的主要场所，其膜上分布着众多参与代谢调控的酶。MARCH5是线粒体膜上的E3泛素连接酶，在卵巢癌中表达异常上调，但MARCH5是否会泛素化调控线粒体上脂代谢蛋白表达而参与肿瘤细胞脂代谢重编程尚不清楚。前期预实验发现：下调MARCH5表达后卵巢癌细胞内脂类含量增加，脂肪酸摄取与从头合成均未受影响，而脂肪酸氧化被显著抑制；机制初步探讨发现，MARCH5与脂肪酸氧化调控因子ACC2有相互作用并下调其表达；MARCH5对ACC2表达的调控作用在抑制蛋白酶体降解途径后消失。提示MARCH5可能通过泛素化降解ACC2而促进卵巢癌细胞的脂肪酸氧化。进而，本项目拟基于以往卵巢癌与线粒体代谢相关的基础，创新性的以线粒体E3泛素连接酶MARCH5为切入，系统分析其在卵巢癌脂肪酸氧化中的调控作用与机制，并分析MARCH5调控脂肪酸氧化对卵巢癌生长的影响。本项目开展不但能从线粒体泛素连接酶MARCH5表达异常上调的独特视角，为卵巢癌细胞脂肪酸氧化增强提供新机制，同时也有望为卵巢癌治疗提供新靶标。

Increased fatty acid oxidation is closely related to the progression of ovarian cancer and its underlying mechanism still needs further investigation. Mitochondria play crucial roles in cellular metabolism regulation mainly through membrane located enzymes. MARCH5 is an E3 ubiquitin ligase at mitochondrial membrane. A previous study has reported that MARCH5 is up-regulated in ovarian cancer. However, the involvement of MARCH5 in lipid metabolism reprogramming in cancer cells by regulating lipid metabolism regulators via ubiquitination remains unclear. Our preliminary studies indicated that: Knockdown of MARCH5 in ovarian cancer cells significantly decreased lipid content and fatty acid oxidation, while has no significant effect on fatty acid uptake and de novo synthesis; preliminary mechanistic analysis revealed that MARCH5 interacted with ACC2 (acetyl CoA carboxylase) and down-regulated its expression; after inhibiting the proteasome degradation pathway, The regulation of ACC2 expression by MARCH5 was abolished when proteasome activity was suppressed by treatment with MG132. These results collectively suggest that MARCH5 may promote fatty acid oxidation through ubiquitination of ACC2 in ovarian cancer cells. This project aims to systematically analyze the function and its underlying mechanisms of mitochondrial E3 ubiquitin ligase MARCH5 in the regulation of fatty acid oxidation in ovarian cancer cells. In addition, the contribution of MARCH5-regulated fatty acid oxidation to the growth of ovarian cancer will also be explored. The project will not only provide deep insights into the molecular mechanisms underlying increased mitochondrial oxidation in ovarian cancer cells from a unique perspective of increased mitochondrial ubiquitin ligase MARCH5, but also provide new potential therapeutic targets for the treatment of ovarian cancer.