Identification of glycogen synthase kinase 3alpha/beta as a host factor required for hepatitis B virus transcription using high-throughput screening

Background & Aims: Hepatitis B virus (HBV) leads to severe liver diseases, such as cirrhosis and hepatocellular carcinoma. Identification of host factors that regulate HBV replication can provide new therapeutic targets. The discovery of sodium taurocholate cotransporting polypeptide (NTCP) as an HBV entry receptor has enabled the establishment of hepatic cell lines for analyzing HBV infection and propagation. Using this new system, studies aimed at identifying host factors that regulate HBV propagation have increased. Approach & Results: We established an HBV-based-reporter gene expression system that mimics HBV replication from transcription to virus egress. Using this approach, we screened 1,827 Food and Drug Administration-approved compounds and identified glycogen synthase kinase 3 (GSK3)alpha/beta inhibitors, including AZD1080, CHIR-98014, CHIR-98021, BIO, and AZD2858, as anti-HBV compounds. These compounds suppressed hepatitis B e antigen (HBeAg) and hepatitis B surface antigen (HBsAg) production in HBV-infected human primary hepatocytes. Proteome analysis revealed that GSK3alpha/beta phosphorylated forkhead box K1/2 (FOXK1/2)s. A double-knockout of FOXK1/2 in HBV-infected HepG2-NTCP cells reduced HBeAg and HBsAg production. The rescue of FOXK2 expression, but not FOXK1 expression, in FOXK1/2-double-knockout cells restored HBeAg and HBsAg production. Importantly, phosphorylation of FOXK2 at Ser 424 is required for GSK3alpha/beta-mediated HBeAg and HBsAg production. We observed the binding of FOXK2 to HBV DNA in HepG2-NTCP cells. Conclusions: Our recombinant HBV-based screening system enables the discovery of new targets. Using our approach, we identified GSK3 inhibitors as potential anti-HBV agents.