Targeting The TRIB3-SQSTM1 Interaction Reduces Liver Fibrosis By Restoring Autophagy

As the elementary pathological change of a variety of chronic liver diseases,including viral hepatitis,biliary obstruction,alcoholic liver and other chronic liver diseases,hepatic fibrosis is characterized by excessive deposition of extracellular matrix(ECM),which destroys the normal structure of liver tissue and affects function.Under the sustained liver injury caused by various internal and external pathogenic factors,liver fibrosis will further develop into cirrhosis,which is an important inducer of liver failure and primary hepatic carcinoma,and also the main cause of death of patients with liver disease.Epidemiological investigation shows that the five-year survival rate of patients with cirrhosis is less than 40%,and with very poor life quality.Therefore,it is urgent to developing effective antifibrotic agents for the treatment of hepatic fibrosis and cirrhosis.Although great progress has been achieved in understanding the pathogenesis of hepatic fibrosis in recent years,there is still no effective therapeutic strategies or drugs for liver fibrosis.It would be of great economic and social meaning to study the pathogenesis and find new drug targets of liver fibrosis.Autophagy is a classic cellular energy metabolism and self-renewal mechanism,which plays an important role in the process of defensing against invading organisms and cellular resistance,as well as in the degradation of intracellular organelles fragments and misfolded proteins.A robust and healthy autophagic flux is essential for body development and maintain homeostasis.However,impaired autophagy is often involved in the pathological process of various diseases,such as neurodegenerative diseases,cancer and liver diseases.When the body is in restricted feeding or at starvation state,liver cells will activate autophagy to provide necessary energy and nutrients by degrading intracellular misfolded proteins and damaged organelles.Accumulated evidence suggests that obstructed autophagy function is involved in the pathogenesis of liver fibrosis,and moderately activated autophagy plays a protective role in the pathogenesis of liver fibrosis.In our study,we found that there were obvious abnormalities of autophagy signals in human liver fibrosis tissues,and that both TRIB3 and selective autophagic receptor SQSTM1(sequestosomel/p62)were highly expressed in fibrosis tissues than that of nonfibrotic liver tissues.Moreover,the elevated expression of TRIB3 and SQSTM1 was positively correlated in the fibrotic tissues.Then,the functional implications of TRIB3 were evaluated in mouse models of hepatic fibrosis induced by bile duct ligation(BDL)or thioacetamide(TAA)injection.Silencing Trib3 protected against experimental hepatic fibrosis,accompanied by restored autophagy activity in fibrotic liver tissues.Furthermore,TRIB3 interacted with SQSTM1 and hindered its binding to MAP1LC3/LC3,which caused the accumulation of SQSTM1 aggregates and obstructed autophagic flux,resulting in a large number of aggregation of degraded autophagosomes and late endosomes.TRIB3 not only inhibited the normal endosome degradation,but also prevented the degradation of the ESCRT(endosomal sorting complexes required for transport)component TSG101 in hepatocytes,the high level of TSG101 promoted the hepatocellular secretion of INHBA/Activin A-enriched exosomes which caused migration,proliferation and activation of HSCs(hepatic stellate cells),the effector cells of liver fibrosis.In addition,HSCs also highly expressed TRIB3 under stress conditions,inhibited the autop hagic degradation of nuclear transcription factors such as SLUG and directly promoted the activation of HSCs.Alpha helical peptide A2 is a piece of polypeptide from the UBA domain of SQSTM1.We link it with the transmembrane peptide Pep2 to form the fusion peptide Pep2-A2.The preliminary research data in the laboratory show that there is high affinity of Pep2-A2 with TRIB3.Disrupting the TRIB3-SQSTM1 interaction with a specific helical peptide Pep2-A2 exerted potent protective effects against hepatic fibrosis by restoring autophagic flux in hepatocytes and HSCs.Together,stress-elevated TRIB3 expression promotes hepatic fibrosis by interacting with SQSTM1 and interfering with its functions in liver-parenchymal cells and activating HSCs.Targeting this interaction is a promising strategy for treating fibroproliferative liver disease.