Netrin-1, a neural guidance protein, restricts hepatitis b virus infection

Hepatitis B virus (HBV) infects more than 250 million people worldwide and can lead to chronic liver disease and liver cancer. Current antiviral therapies suppress viral replication but do not eliminate the virus, highlighting the urgent need for new strategies to block HBV entry into liver cells.

Netrin-1, a secreted laminin-related protein, is increasingly recognized not only for its established functions in neural guidance and immune regulation but also for its potential roles in viral pathogenesis. In previous studies, the researchers identified endothelial lipase (LIPG) as a host factor that facilitates hepatitis B virus attachment to hepatocytes via heparan sulfate proteoglycans (HSPGs) and/or the sodium taurocholate cotransporting polypeptide (NTCP). Using LIPG-based screening, the researchers identified Netrin-1 as an LIPG-interacting protein. Synthetic peptides derived from Netrin-1 sequences exhibited potent anti-HBV activity. In primary human hepatocytes, Netrin-1 effectively inhibited HBV infection, and in HepG2-NTCP-YFP cells, it suppressed both viral attachment and internalization.

Mechanistically, studies revealed that Netrin-1 binds LIPG via heparin-binding motifs in its V and C domains, disrupting the interaction of LIPG to HSPGs and LIPG to HBV. Additionally, Netrin-1 interacts with the extracellular domain of epidermal growth factor receptor (EGFR), preventing NTCP-EGFR complex formation and inhibiting EGFR dimerization and phosphorylation, independently of HSPGs. In vivo experiments using humanized hepatocyte chimeric mice demonstrated that recombinant Netrin-1 suppresses HBV infection. These findings establish Netrin-1 as a multifunctional host factor that interferes with multiple steps of HBV entry, highlighting its potential as a novel therapeutic strategy for HBV infection and chronic hepatitis B.

Professor Honda, the corresponding author, says, “Our study reveals a previously unrecognized role of Netrin-1 in blocking hepatitis B virus entry into hepatocytes by interfering with both viral attachment and internalization. We hope this work will inspire further research into multifunctional host factors that can be leveraged to combat viral infections.”

[Glossary]

• HBV (Hepatitis B Virus)
  Partially double-stranded DNA virus belonging to the Hepadnaviridae family that specifically targets hepatocytes. It is the causative agent of hepatitis B, which can progress to chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC).
• Netrin-1
  A laminin-related secreted protein originally identified as an axon guidance cue during neural development.
• LIPG (Endothelial Lipase)
  An enzyme primarily involved in lipoprotein metabolism, particularly the hydrolysis of phospholipids in high-density lipoproteins (HDL).
• HSPG (Heparan Sulfate Proteoglycans)
  Glycoproteins found on the cell surface and extracellular matrix that serve as the initial, low-affinity attachment receptors for HBV. They capture viral particles from the circulation and facilitate their accumulation on the hepatocyte surface prior to specific receptor binding.
• NTCP (Sodium-Taurocholate Cotransporting Polypeptide)
  A transmembrane transporter primarily responsible for the uptake of bile acids into hepatocytes. It functions as the specific, high-affinity entry receptor for HBV, which is essential for the virus to bind and enter the host cell.
• EGFR (Epidermal Growth Factor Receptor)
  A receptor tyrosine kinase that regulates cell proliferation, survival, and differentiation. In HBV infection, it acts as a critical entry co-factor that interacts with NTCP to trigger the internalization of the virus-receptor complex.

[Financial Support]

This research was supported by the Japan Agency for Medical Research and Development (Grants: JP24fk0310514 to M.H; JP25fk0310539 to M.H). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.