Background and Aims: Our previous yeast two-hybrid screening data showed the Fibrinogen alpha chain (FGA) as one of the candidate binding proteins of S regional of the HBsAg (HBs). In this study, we aimed to define that FGA is a binding protein of HBs and to determine its function in Hepatocellular carcinoma (HCC) tumorigenesis.
Methods: The binding and co-localization between HBs and FGA were confirmed using co-immunoprecipitation and confocal microscopy was employed flow cytometry to analyze cell apoptosis. The involved mechanisms were investigated using protein array and western blot.
Results: Our results indicated that FGA is a binding protein of HBs and is co-localized in the cytoplasm in vitro. Interaction between HBs and FGA significantly induced apoptosis in HepG2 cells. Moreover, knockdown of the FGA protein decreased the expression levels of the pro-survival factors Bcl-XL and Mcl-1, increased the expression of the proapoptotic proteins, and decreased the phosphorylation levels of Akt in this cell.
Conclusion: FGA is a binding protein of HBs and their interaction induced the apoptotic capacity of HepG2 cells, suggesting the interactions between viral and host cell proteins are involved in the development of virus-related hepatitis or HCC.