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

Abstract

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.

Role and Mechanisms of Mitophagy in Liver Diseases

“…Interestingly, mitochondrial fission protein Drp1 was activated in primary mouse hepatocytes treated with ethanol for 48 h, leading to mitochondrial fragmentation, which is associated with depressed FUNDC1-mediated mitophagy [122]. However, the causal role of Drp1 in the changes of hepatic mitophagy after alcohol has not been examined in this study [122]. In contrast, increased megamitochondria formation has been identified in patients with ALD and chronic alcohol feeding animal models [123][124][125].…”

“…Impaired mitophagy was reported in the majority of chronic alcohol feeding cases [115,116,122], underscoring its potential critical role in the pathogenesis of ALD. Interestingly, mitochondrial fission protein Drp1 was activated in primary mouse hepatocytes treated with ethanol for 48 h, leading to mitochondrial fragmentation, which is associated with depressed FUNDC1-mediated mitophagy [122]. However, the causal role of Drp1 in the changes of hepatic mitophagy after alcohol has not been examined in this study [122].…”

“…Decompensated mitophagy causes the release of mitochondrial damage-associated molecular patterns (mtDAMPs) that promote inflammatory and profibrogenic response, which in turn impair hepatic mitophagy, contributing to the pathological progression of ALD [121]. Impaired mitophagy was reported in the majority of chronic alcohol feeding cases [115,116,122], underscoring its potential critical role in the pathogenesis of ALD. Interestingly, mitochondrial fission protein Drp1 was activated in primary mouse hepatocytes treated with ethanol for 48 h, leading to mitochondrial fragmentation, which is associated with depressed FUNDC1-mediated mitophagy [122].…”

“…ALD [114,116,119,122] NAFLD [134,140] DILI [155,157,159] HBV/HCV [192] Cancer [216] The expression level of fluorescent proteins varies in different cells/tissues Not robust and easy to be dependent on individuals who are performing the quantification. Also, the half-life of the red puncta in the lysosomes may be dependent on cellular context and conditions, e.g., the activities of the lysosomal proteases NAFLD [86] DILI [159] Cancer [216] 6.…”

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

“…BCL2 and adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) and BNIP3-like (BNIP3L or Nix) are Bcl2 family proteins with an atypical BH3 domain [182]. Fun14 domain-containing protein 1 (Fundc1) is a mitochondrial outer membrane protein containing a conserved LC3 interaction region (LIR) with a W/Y/FxxL/I/V motif [183]. BNIP3 and Nix were initially identified as pro-death proteins and were recently identified as mitophagy activators in specific conditions.…”