ALDOB Acts as a Novel HBsAg-Binding Protein and Its Coexistence Inhibits Cisplatin-Induced HepG2 Cell Apoptosis

Chronic infection with hepatitis B virus is a cause of end-stage liver disease and hepatocellular carcinoma (HCC). We previously screened fructose-bisphosphate aldolase B (ALDOB) as a candidate binding protein of hepatitis B surface antigen (HBsAg) using a yeast 2-hybrid assay. In this study we aimed to confirm ALDOB as a binding protein of the S region of the HbsAg (HBs) and to investigate the function and involved mechanism between its interactions during HCC development. Our results demonstrated that both of exogenous and endogenous ALDOB proteins bind to HBs and colocalize in the cytoplasm in vitro. The coexistence of HBs and ALDOB inhibit apoptosis of cisplatin-induced HepG2 cells. Furthermore, western blot analysis showed the coexistence of HBs and ALDOB enhance the phosphorylations of AKT and its downstream of GSK-3 beta (phosphorylation); decreased expression of the pro-apoptotic proteins Bax, Bid, Bim, and Puma; and increased expression of the prosurvival proteins Bcl-2, Bcl-xl, and Mcl-1 in HepG2 cells. These findings suggest that interaction between HBs and ALDOB might be applied as a potential therapeutic target during the treatment of HBV-related hepatitis or HCC.