Background & Aims: Metabolic dysfunction-associated steatotic liver disease (MASLD) progresses from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), yet its therapeutic development has been hampered by pathological complexity and heterogeneity. Methods: Bulk RNA-seq and diet-induced MASLD mouse models were employed to explore RNF128 expression patterns in MASLD livers. Hepatic RNF128 expression was characterized in Single-cell RNA sequencing (scRNA-seq) and lipotoxicity-induced hepatocyte models. The impact of hepatocyte-specific RNF128 deletion and overexpression on MASLD progression was evaluated. Furthermore, the molecular mechanisms through which RNF128 exerts its functions were investigated, and both chemical and genetic approaches were employed to assess its potential as a therapeutic target. Results: We found that the E3 ubiquitin ligase RNF128 is upregulated in human MASLD livers and in mice fed a high-fat high-cholesterol diet. Hepatocyte-specific RNF128 knockout ameliorated MASLD, whereas its overexpression exacerbated disease phenotypes. Integrated proteomic and ubiquitinomic analyses identified stearoyl-CoA desaturase 1 (SCD1) as a direct target of RNF128. Mechanistically, RNF128 catalyzes K63-linked ubiquitination of SCD1 at lysine 30, which stabilizes SCD1 by blocking its autophagic-lysosomal degradation, thereby promoting lipid accumulation. Crucially, SCD1 overexpression reversed the effects of RNF128 loss, and SCD1 inhibition rescued RNF128-driven steatosis, both in hepatocytes and in vivo. Therapeutic inhibition of RNF128 with a GalNAc-conjugated antisense oligonucleotide (GalNAc-ASO) and a hepatocyte-specific TBG-promoter-driven shRNA-AAV alleviated MASLD in mice. Conclusions: Our study establishes the RNF128–SCD1 axis as a central mechanism in MASLD and highlights its therapeutic potential.
Cao et al. (Mon,) studied this question.