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

ABSTRACT 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.