Hydrophobicity and oligomerization are essential parameters for membrane penetration activity of the VP4 peptide from Hepatitis A Virus (HAV)

Non-enveloped viruses require membrane-penetrating peptides for gaining entry inside the cytoplasm of host cells during the early stages of infection. Although several such peptides have been identified as essential components for non-enveloped virus entry, the molecular mechanism of membrane destabilization by these peptides is not well established. Here, we investigate the putative membrane penetrating peptide VP4 of Hepatitis A Virus (HAV) using a combination of molecular dynamics simulation and mutational studies. Using all-atom molecular dynamics simulation, we show that effective membrane disruption requires specific oligomeric forms (pentameric or hexameric) of VP4, while the monomeric form cannot cause similar disruption in target membranes. Reduction in hydrophobicity of VP4 significantly affects membrane penetration properties in silico, with even the oligomeric associations showing decreased membrane penetration efficiency. A synthetic peptide with a concurrent reduction in hydrophobicity is unable to disrupt liposomes in vitro, while the introduction of these mutations in the context of the viral genome adversely affects the propagation of HAV in cell culture. Taken together, our studies highlight hydrophobicity and oligomerization as some of the crucial mechanistic aspects of membrane penetration by capsid components of non-enveloped viruses.