title: The human metapneumovirus fusion protein mediates entry via an interaction with RGD-binding integrins.
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.
authors.affiliation: Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Reagan G
authors.initials: RG
authors.lastname: Cox
authors.forename: S Brent
authors.initials: SB
authors.lastname: Livesay
authors.forename: Monika
authors.initials: M
authors.lastname: Johnson
authors.forename: Melanie D
authors.initials: MD
authors.lastname: Ohi
authors.forename: John V
authors.initials: JV
authors.lastname: Williams
mesh_terms: D020816:Amino Acid Motifs; D002460:Cell Line; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D016023:Integrins / Q000737:chemistry*; D008561:Membrane Fusion; D029121:Metapneumovirus / Q000235:genetics* / Q000378:metabolism*; D008854:Microscopy, Electron / Q000379:methods; D009842:Oligopeptides / Q000737:chemistry*; D011485:Protein Binding; D019030:Receptors, Vitronectin / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D014760:Viral Fusion Proteins / Q000378:metabolism*; D014771:Virion / Q000737:chemistry; D053586:Virus Internalization
chemical_list: D016023:Integrins; D009842:Oligopeptides; D019030:Receptors, Vitronectin; D011994:Recombinant Proteins; D014760:Viral Fusion Proteins; C094340:integrin alphavbeta1; C047981:arginyl-glycyl-aspartic acid