A cellular protein which binds hepatitis B virus but not hepatitis B surface antigen

Area of Science:

• Virology
• Molecular Biology
• Hepatology

Background:

• Hepatitis B virus (HBV) envelope proteins, including large (L), middle (M), and small (S) hepatitis B surface antigens (HBsAg), mediate viral entry.
• The preS1 sequence within L-HBsAg is hypothesized to be crucial for HBV attachment to cellular receptors, though the receptor remains unidentified.

Purpose of the Study:

• To identify cellular proteins interacting with the HBV preS1 region using a yeast two-hybrid system.
• To validate and characterize the interaction between preS1 and potential cellular binding partners.

Main Methods:

• Yeast two-hybrid screening of a human liver cDNA library with the HBV preS1 sequence.
• Baculovirus-expressed glutathione S-transferase (GST)-preS1 protein interaction assays with in vitro translated proteins.
• Competition assays using purified HBV and HBsAg to confirm binding specificity.
• Direct binding assays of GST-fusion proteins with HBV virions.

Main Results:

• Several cellular proteins interacting with HBV preS1 were identified via yeast two-hybrid screening.
• Independent validation confirmed interactions with an unidentified protein and a mitochondrial protein.
• Competition assays demonstrated that intact HBV virions, but not purified HBsAg, blocked preS1 binding to the unidentified protein.
• The unidentified protein, when expressed as a GST-fusion, directly bound HBV virions.

Conclusions:

• An unidentified cellular protein specifically interacts with the preS1 domain of HBV L-HBsAg.
• This interaction is mediated by intact HBV virions, suggesting a role in virus attachment.
• The identified protein represents a potential cellular receptor or co-receptor for HBV, offering new avenues for therapeutic intervention.