Palmitoylation-mediated exosomal trafficking of nuclear protein NAT10 potentiates liver fibrosis in MASH

BACKGROUND AND AIMS: Liver fibrosis is the principal histological determinant of mortality in metabolic dysfunction-associated steatohepatitis (MASH), yet the mechanisms driving progression from steatosis to fibrosis remain incompletely defined and effective antifibrotic therapies are limited. Although hepatocyte-derived exosomes under lipotoxic stress promote HSC activation, the pathogenic protein cargos remain undefined. This study sought to identify lipotoxicity-induced hepatocyte-derived exosomal proteins that drive MASH fibrogenesis and to define their mechanistic and therapeutic relevance. APPROACH AND RESULTS: Proteomic analysis of hepatocyte-derived exosomes from murine MASH livers and lipotoxic hepatocyte cultures identified N-acetyltransferase 10 (NAT10) as a stress-enriched exosomal cargo. zinc finger DHHC-type palmitoyltransferase 23 (ZDHHC23)-mediated palmitoylation promoted NAT10 nuclear export and exosomal loading. Functional studies demonstrated that exosomal NAT10 drove fibrogenic signaling in HSCs by enhancing N4-acetylcytidine (ac4C) RNA acetylation and stabilizing Ddr2 mRNA. Hepatocyte-specific Nat10 deletion or administration of NAT10-deficient exosomes attenuated liver fibrosis, whereas hepatocyte Nat10 overexpression exacerbated fibrogenesis in an exosome-dependent manner. In human liver samples, increased NAT10 expression and elevated extranuclear-to-nuclear ratio correlated with fibrosis severity. Finally, hepatocyte-targeted N-acetylgalactosamine-si Nat10 significantly ameliorated fibrosis in murine MASH models. CONCLUSIONS: This study links aberrant nuclear protein localization to subsequent exosome-mediated fibrogenic signaling in MASH and demonstrates that targeting this pathway, either by disrupting palmitoylation-dependent mislocalization or by hepatocyte-specific Nat10 inhibition, ameliorates liver fibrosis with concurrent metabolic benefit.