Structural studies on cell entry of respiratory enteroviruses

Yue Liu, Purdue University

Abstract

Enteroviruses (EVs) represent a group of non-enveloped, positive strand RNA viruses with an icosahedral capsid shell of about 300 Å in diameter. A variety of EVs are notable for human infections, such as polioviruses, rhinoviruses, EV-A71, and EV-D68. EV-D68 causes childhood respiratory infections worldwide and has also been associated with neurological diseases. A lack of knowledge on the mechanisms of EV-D68 infection has hindered the development of antiviral interventions. Specifically, it remains obscure how the virus enters into host cells. Here, cell surface sialic acid has been identied to be indispensable for EV-D68 to attach onto and infect host cells. X-ray crystal structures of EV-D68 on its own and in complex with sialic acid receptor analogues show that binding of the sialic acid receptor to a depression on the virus outer surface destabilizes the virus. Receptor binding induces a cascade of conformational changes of the virus to eject a fatty-acid like molecule, the \pocket factor", that regulates virus stability. Furthermore, exposure of EV-D68 to an acidic environment triggers virus uncoating whereby the viral genome is released into host cell cytosol for replication and translation. In comparison with the native EV-D68 structure, the cryo-electron microscopic (cryo-EM) structure of an uncoating intermediate formed at late endosomal pH (pH 5.5) shows an expanded capsid where pores are formed at icosahedral two-fold axes and where segments of polypeptides are externalized to interact with host membranes. Because of the low stability of EV-D68, cryo-EM analyses of the virus at neutral pH indicate the involvement of multiple structural intermediates in the uncoating process. More importantly, a capsid binding compound, pleconaril, effectively inhibits EV-D68 infection by blocking virus attachment and uncoating. Pleconaril replaces the pocket factor in occupying a hydrophobic pocket in viral protein 1. Thus these results illuminate structural rearrangements of EV-D68 during cell entry and open up an avenue for developing antiviral treatments of EV-D68 infections.

Degree

Ph.D.

Advisors

Rossmann, Purdue University.

Subject Area

Biochemistry|Virology|Biophysics

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