DNA-PKcs promotes alcohol-related liver disease by activating Drp1-related mitochondrial fission and repressing FUNDC1-required mitophagy

DNA-dependent protein kinase catalytic subunit(DNA-PKcs)is a novel housekeeper of hepatic mitochondrial homeostasis outside the DNA repair process.In this study,DNA-PKcs was upregulated in the livers of mice that were exposed to alcohol;the expression of DNA-PKcs positively correlated with hepatic steatosis,fibrosis,apoptosis,and mitochondrial damage.Functional studies revealed that liver-specific DNA-PKcs knockout(DNA-PKcsLKO)mice were protected from chronic ethanol-induced liver injury and mitochondrial damage.Mechanistic investigations established that DNA-PKcs promoted p53 activation,which elevated dynamin-related protein 1(Drp1)-related mitochondrial fission but repressed FUN14 domain containing 1(FUNDC1)-required mitophagy.Excessive fission and defective mitophagy triggered mtDNA damage,mitochondrial respiratory inhibition,mROS overproduction,cardiolipin oxidation,redox imbalance,calcium overload,and hepatic mitochondrial apoptosis.In contrast,the deletion of DNA-PKcs rescued these phenotypic alterations,which alleviated the susceptibility of hepatocytes to alcohol-induced cytotoxicity.Additionally,we also showed that orphan nuclear receptor subfamily 4 group A member 1(NR4A1)was the upstream signal for DNA-PKcs activation and that the genetic ablation of NR4A1 ameliorated the progression of alcohol-related liver disease(ARLD);these results were similar to those obtained in DNA-PKcs knockout mice.Collectively,our results identified the NR4A1/DNA-PKcs/p53 axis as a novel signaling pathway responsible for ARLD pathogenesis that acts by activating Drp1-related mitochondrial fission and restricting FUNDC1-required mitophagy.The findings have potential implications for new approaches for ARLD therapy.