Loss of Ufl1/Ufbp1 in hepatocytes promotes liver pathological damage and carcinogenesis through activating mTOR signaling

BACKGROUND: Ufm1-specific ligase 1 (Ufl1) and Ufm1-binding protein 1 (Ufbp1), as putative targets of ubiquitin-fold modifier 1 (Ufm1), have been implicated in several pathogenesis-related signaling pathways. However, little is known about their functional roles in liver disease. METHODS: Hepatocyte-specific Ufl1(Δ/Δhep) and Ufbp1(Δ/Δhep) mice were used to study their role in liver injury. Fatty liver disease and liver cancer were induced by high-fat diet (HFD) and diethylnitrosamine (DEN) administration, respectively. iTRAQ analysis was employed to screen for downstream targets affected by Ufbp1 deletion. Co-immunoprecipitation was used to determine the interactions between the Ufl1/Ufbp1 complex and the mTOR/GβL complex. RESULTS: Ufl1(Δ/Δhep) or Ufbp1(Δ/Δhep) mice exhibited hepatocyte apoptosis and mild steatosis at 2 months of age and hepatocellular ballooning, extensive fibrosis, and steatohepatitis at 6–8 months of age. More than 50% of Ufl1(Δ/Δhep) and Ufbp1(Δ/Δhep) mice developed spontaneous hepatocellular carcinoma (HCC) by 14 months of age. Moreover, Ufl1(Δ/Δhep) and Ufbp1(Δ/Δhep) mice were more susceptible to HFD-induced fatty liver and DEN-induced HCC. Mechanistically, the Ufl1/Ufbp1 complex directly interacts with the mTOR/GβL complex and attenuates mTORC1 activity. Ablation of Ufl1 or Ufbp1 in hepatocytes dissociates them from the mTOR/GβL complex and activates oncogenic mTOR signaling to drive HCC development. CONCLUSIONS: These findings reveal the potential role of Ufl1 and Ufbp1 as gatekeepers to prevent liver fibrosis and subsequent steatohepatitis and HCC development by inhibiting the mTOR pathway. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13046-023-02681-6.