The hepatitis B virus (HBV) core protein (HBc) functions in multiple steps of the viral life cycle. Heteroaryldihydropyrimidine compounds (HAPs) such as Bay41-4109 are capsid protein allosteric modulators that accelerate HBc degradation and inhibit the virion secretion of HBV, specifically by misleading HBc assembly into aberrant non-capsid polymers. However, the subsequent cellular fates of these HAP-induced aberrant non-capsid polymers are not well understood. Here, we discovered that that the chaperone-binding E3 ubiquitin ligase protein STUB1 is required for the removal of Bay41-4109-induced aberrant non-capsid polymers from HepAD38 cells. Specifically, STUB1 recruits BAG3 to transport Bay41-4109-induced aberrant non-capsid polymers to the perinuclear region of cells, thereby initiating p62-mediated macroautophagy and lysosomal degradation. We also demonstrate that elevating the STUB1 level enhances the inhibitory effect of Bay41-4109 on the production of HBeAg and HBV virions in HepAD38 cells, in HBV-infected HepG2-NTCP cells, and in HBV transgenic mice. STUB1 overexpression also facilitates the inhibition of Bay41-4109 on the cccDNA formation in de novo infection of HBV. Understanding these molecular details paves the way for applying HAPs as a potentially curative regimen (or a component of a combination treatment) for eradicating HBV from hepatocytes of chronic infection patients.
The hepatitis B virus (HBV) core protein (HBc) functions in multiple steps of the viral life cycle. Heteroaryldihydropyrimidine compounds (HAPs) such as Bay41-4109 are capsid protein allosteric modulators that accelerate HBc degradation and inhibit the virion secretion of HBV, specifically by misleading HBc assembly into aberrant non-capsid polymers. However, the subsequent cellular fates of these HAP-induced aberrant non-capsid polymers are not well understood.
One of the most promising viral targets in current hepatitis B virus (HBV) drug development is the core protein due to its multiple roles in the viral life cycle. Here we investigated the differences in the mode of action and antiviral activity of representatives of six different capsid assembly modifier (CAM) scaffolds: three from the well-characterized scaffolds heteroarylpyrimidine (HAP), sulfamoylbenzamide (SBA), and phenylpropenamide (PPA), and three from novel scaffolds glyoxamide-pyrrolamide (GPA), pyrazolyl-thiazole (PT), and dibenzo-thiazepin-2-one (DBT). The target activity and antiviral efficacy of the different CAMs were tested in biochemical and cellular assays.
Hepatitis B Virus core protein (HBc) has multiple roles in the viral lifecycle: viral assembly, compartment for reverse transcription, intracellular trafficking, and nuclear functions. HBc displays assembly polymorphism - it can assemble into icosahedral capsid and aberrant non-capsid structures. It has been hypothesized that the assembly polymorphism is due to allosteric conformational changes of HBc dimer, the smallest assembly unit, however, the mechanism governing the polymorphic assembly of the HBc dimer is still elusive.
