LC3B Mediated SETDB1‐Accounted Alcoholic Steatohepatitis via Lipidation‐Dependent LAP and Lipidation‐Independent Nuclear Stabilization

Alcohol-associated liver disease (ALD) progresses from steatosis to steatohepatitis, but the underlying mechanisms remain unclear. Here, we investigated SETDB1's role in ALD progression involving LC3B-mediated LC3-associated phagocytosis (LAP). SETDB1 expression was progressively downregulated in livers of alcohol-fed mice and ethanol-treated hepatocytes, correlating with disease severity. Setdb1 HKO mice exhibited accelerated ALD progression, developing severe steatosis, inflammation, and fibrosis even under pair-fed conditions, indicating SETDB1 deficiency enhances disease susceptibility to nutritional stressors. Mechanistically, SETDB1 acted as a transcriptional cofactor for ERG to promote Map1lc3b transcription. SETDB1 deficiency impaired LAP by disrupting Rubicon membrane localization, causing defective lipid droplet clearance and enhanced cGAS-STING activation. The ATG16L1 WD40 domain was essential for this LAP-mediated protection. LC3B restoration in Setdb1 HKO mice ameliorated steatosis, inflammation, and liver injury. Notably, the lipidation-deficient LC3B-G120A mutant failed to rescue steatosis but partially suppressed inflammation, revealing a lipidation-independent LC3B function. We demonstrate lipidated LC3B mediates cytoplasmic LAP-dependent lipid clearance, while non-lipidated LC3B translocates to the nucleus, reducing R-loop accumulation, preserving genomic stability, and restraining cGAS-STING-driven inflammation. Collectively, these findings define a protective SETDB1-ERG-LC3B axis restraining ALD progression and reveal dual LC3B functions, offering mechanistic insight and a potential therapeutic strategy for intercepting steatosis-to-steatohepatitis transition.