rt269L-Type hepatitis B virus (HBV) in genotype C infection leads to improved mitochondrial dynamics via the PERK-eIF2α-ATF4 axis in an HBx protein-dependent manner

Background: In our previous report, the rt269I type versus the rt269L type in genotype C2 infection led to poor clinical outcomes and enhanced mitochondrial stress in infected hepatocytes. Here, we sought to investigate differences between the rt269L and rt269I types in mitochondrial functionality in hepatitis B virus (HBV) genotype C2 infection, mainly focusing on endoplasmic reticulum (ER) stress-mediated autophagy induction as an upstream signal.

Methods: Mitochondrial functionality, ER stress signaling, autophagy induction, and apoptotic cell death between rt269L-type and rt269I-type groups were investigated via in vitro and in vivo experiments. Serum samples were collected from 187 chronic hepatitis patients who visited Konkuk or Seoul National University Hospital.

Results: Our data revealed that genotype C rt269L versus rt269I infection led to improved mitochondrial dynamics and enhanced autophagic flux, mainly due to the activation of the PERK-eIF2α-ATF4 axis. Furthermore, we demonstrated that the traits found in genotype C rt269L infection were mainly due to increased stability of the HBx protein after deubiquitination. In addition, clinical data using patient sera from two independent Korean cohorts showed that, compared with rt269I, rt269L in infection led to lower 8-OHdG levels, further supporting its improved mitochondrial quality control.

Conclusion: Our data showed that, compared with the rt269I type, the rt269L type, which presented exclusively in HBV genotype C infection, leads to improved mitochondrial dynamics or bioenergetics, mainly due to autophagy induction via activation of the PERK-eIF2α-ATF4 axis in an HBx protein-dependent manner. This suggests that HBx stability and cellular quality control in the rt269L type predominating in genotype C endemic areas could at least partly contribute to some distinctive traits of genotype C infection, such as higher infectivity or longer duration of the hepatitis B e antigen (HBeAg) positive stage.