Genetic ablation of fas-activated serine/threonine kinase ameliorates alcoholic liver disease through modulating HuR-SIRT1 mRNA complex stability

Chronic alcoholism often causes liver injuries characterized by hepatic steatosis, inflammation as well as oxidative stress and finally leads to advanced cirrhosis and liver cancer. Fas-activated serine/threonine kinase (FASTK) and its homologs are gradually known as multifunctional proteins involved in various biological processes; however, the role of FASTK and its family members in alcoholic liver disease (ALD) is still unexplored. Here we found that, among FASTK family members, the expression of FASTK was specifically induced both in livers of mice received chronic ethanol ingestion and in ethanol-stimulated hepatocytes. Animal studies showed that genetic deletion of FASTK attenuated chronic ethanol ingestion-induced liver damage, steatosis, and inflammation. Moreover, FASTK deficiency was associated with improved oxidative/anti-oxidative system homeostasis and reduced reactive oxygen species (ROS) generation in livers upon chronic ethanol stimulation. Importantly, FASTK ablation preserved hepatic sirtuin-1 (SIRT1) expression/activity upon chronic ethanol ingestion and SIRT1 silencing via adenovirus-mediated small interfering RNA transfer diminished FASTK deletion-elicited beneficial effects on alcohol-associated hepatic steatosis, inflammation, and oxidative stress. Mechanistically, ethanol increased the phosphorylation of human antigen R (HuR, a RNA binding protein that stabilizes SIRT1 mRNA) and triggered the dissociation of HuR-SIRT1 mRNA complex, in turn promoting SIRT1 mRNA decay. Genetic deletion of FASTK diminished ethanol-induced HuR phosphorylation and HuR-SIRT1 mRNA complex dissociation, thereby enhancing SIRT1 mRNA stability. Collectively, these findings for the first time highlight a critical role of FASTK in the pathogenesis of ALD and implicate HuR-SIRT1 mRNA complex involves in this process.