Zhang Fengwu, Xiong Xiufang, Li Zhijian, Wang Haibo, Wang Weilin, Zhao Yongchao, Sun Yi
Cancer Institute, The Second Affiliated Hospital, Zhejiang University School of Medicine, 310009, Hangzhou, China.
Key Laboratory of Cancer Prevention and Intervention, China National Ministry of Education, 310009, Hangzhou, China.
EMBO J. 2025 Feb;44(4):1185-1219. doi: 10.1038/s44318-024-00353-5. Epub 2025 Jan 6.
Small GTPase RHEB is a well-known mTORC1 activator, whereas neddylation modifies cullins and non-cullin substrates to regulate their activity, subcellular localization and stability. Whether and how RHEB is subjected to neddylation modification remains unknown. Here, we report that RHEB is a substrate of NEDD8-conjugating E2 enzyme UBE2F. In cell culture, UBE2F depletion inactivates mTORC1, inhibiting cell cycle progression, cell growth and inducing autophagy. Mechanistically, UBE2F cooperates with E3 ligase SAG in neddylation of RHEB at K169 to enhance its lysosome localization and GTP-binding affinity. Furthermore, liver-specific Ube2f knockout attenuates steatosis and tumorigenesis induced by Pten loss in an mTORC1-dependent manner, suggesting a causal role of UBE2F in liver tumorigenesis. Finally, UBE2F expression levels and mTORC1 activity correlate with patient survival in hepatocellular carcinoma. Collectively, our study identifies RHEB as neddylation substrate of the UBE2F-SAG axis, and highlights the UBE2F-SAG axis as a potential target for the treatment of non-alcoholic fatty liver disease and hepatocellular carcinoma.
小GTP酶RHEB是一种著名的mTORC1激活剂，而NEDD8化修饰cullins和非cullin底物以调节它们的活性、亚细胞定位和稳定性。RHEB是否以及如何受到NEDD8化修饰仍不清楚。在此，我们报告RHEB是NEDD8结合E2酶UBE2F的底物。在细胞培养中，UBE2F的缺失使mTORC1失活，抑制细胞周期进程、细胞生长并诱导自噬。机制上，UBE2F与E3连接酶SAG协同作用，使RHEB在K169位点发生NEDD8化修饰，以增强其溶酶体定位和GTP结合亲和力。此外，肝脏特异性Ube2f基因敲除以mTORC1依赖的方式减轻了由Pten缺失诱导的脂肪变性和肿瘤发生，表明UBE2F在肝脏肿瘤发生中起因果作用。最后，UBE2F表达水平和mTORC1活性与肝细胞癌患者的生存率相关。总的来说，我们的研究确定RHEB是UBE2F - SAG轴的NEDD8化底物，并强调UBE2F - SAG轴是治疗非酒精性脂肪性肝病和肝细胞癌的潜在靶点。
