Peli3 ablation ameliorates acetaminophen-induced liver injury through inhibition of GSK3 beta phosphorylation and mitochondrial translocation

Abstract

The signaling pathways governing acetaminophen (APAP)-induced liver injury have been extensively studied. However, little is known about the ubiquitin-modifying enzymes needed for the regulation of APAP-induced liver injury. Here, we examined whether the Pellino3 protein, which has E3 ligase activity, is needed for APAP-induced liver injury and subsequently explored its molecular mechanism. Whole-body Peli3(-/-) knockout (KO) and adenovirus-mediated Peli3 knockdown (KD) mice showed reduced levels of centrilobular cell death, infiltration of immune cells, and biomarkers of liver injury, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), upon APAP treatment compared to wild-type (WT) mice. Peli3 deficiency in primary hepatocytes decreased mitochondrial and lysosomal damage and reduced the mitochondrial reactive oxygen species (ROS) levels. In addition, the levels of phosphorylation at serine 9 in the cytoplasm and mitochondrial translocation of GSK3 beta were decreased in primary hepatocytes obtained from Peli3(-/-) KO mice, and these reductions were accompanied by decreases in JNK phosphorylation and mitochondrial translocation. Pellino3 bound more strongly to GSK3 beta compared with JNK1 and JNK2 and induced the lysine 63 (K63)-mediated polyubiquitination of GSK3 beta. In rescue experiments, the ectopic expression of wild-type Pellino3 in Peli3(-/-) KO hepatocytes restored the mitochondrial translocation of GSK3 beta, but this restoration was not obtained with expression of a catalytically inactive mutant of Pellino3. These findings are the first to suggest a mechanistic link between Pellino3 and APAP-induced liver injury through the modulation of GSK3 beta polyubiquitination. Liver injury: Damage from common painkiller linked to immunity enzymeAn enzyme implicated in innate immunity offers a potential new target for treating liver injury due to acetaminophen, a common painkiller also known as paracetamol in many countries. A team from South Korea led by Seok Hee Park from Sungkyunkwan University in Suwon and Seong-Jin Kim from the GILO Foundation in Seoul showed that an enzyme called Pellino3 plays a critical role in triggering liver damage caused by acetaminophen. The researchers found that mice lacking Pellino3, an enzyme that marks proteins with chemical tags to mediate immune responses, showed reduced liver damage as measured by several indicators of liver stress. Pellino3 usually activates a specific pro-inflammatory protein and drugs directed at such activation could help protect the liver in regular users of this analgesic and anti-fever drug.