The human metapneumovirus fusion protein mediates entry via an interaction with RGD-binding integrins

J Virol. 2012 Nov;86(22):12148-60. doi: 10.1128/JVI.01133-12. Epub 2012 Aug 29.

Abstract

Paramyxoviruses use a specialized fusion protein to merge the viral envelope with cell membranes and initiate infection. Most paramyxoviruses require the interaction of two viral proteins to enter cells; an attachment protein binds cell surface receptors, leading to the activation of a fusion (F) protein that fuses the viral envelope and host cell plasma membrane. In contrast, human metapneumovirus (HMPV) expressing only the F protein is replication competent, suggesting a primary role for HMPV F in attachment and fusion. We previously identified an invariant arginine-glycine-aspartate (RGD) motif in the HMPV F protein and showed that the RGD-binding integrin αVβ1-promoted HMPV infection. Here we show that both HMPV F-mediated binding and virus entry depend upon multiple RGD-binding integrins and that HMPV F can mediate binding and fusion in the absence of the viral attachment (G) protein. The invariant F-RGD motif is critical for infection, as an F-RAE virus was profoundly impaired. Further, F-integrin binding is required for productive viral RNA transcription, indicating that RGD-binding integrins serve as receptors for the HMPV fusion protein. Thus, HMPV F is triggered to induce virus-cell fusion by interactions with cellular receptors in a manner that is independent of the viral G protein. These results suggest a stepwise mechanism of HMPV entry mediated by the F protein through its interactions with cellular receptors, including RGD-binding integrins.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Motifs
  • Cell Line
  • Flow Cytometry / methods
  • Humans
  • Integrins / chemistry*
  • Membrane Fusion
  • Metapneumovirus / genetics*
  • Metapneumovirus / metabolism*
  • Microscopy, Electron / methods
  • Oligopeptides / chemistry*
  • Protein Binding
  • Receptors, Vitronectin / metabolism
  • Recombinant Proteins / chemistry
  • Viral Fusion Proteins / metabolism*
  • Virion / chemistry
  • Virus Internalization*

Substances

  • Integrins
  • Oligopeptides
  • Receptors, Vitronectin
  • Recombinant Proteins
  • Viral Fusion Proteins
  • integrin alphavbeta1
  • arginyl-glycyl-aspartic acid