tetano
Editor, Senior Moderator
J Virol. 2015 Jun 17. pii: JVI.00592-15. [Epub ahead of print]
[h=1]Structural analysis of the roles of influenza A virus membrane-associated proteins in assembly and morphology.[/h] Chlanda P[SUP]1[/SUP], Schraidt O[SUP]1[/SUP], Kummer S[SUP]2[/SUP], Riches J[SUP]1[/SUP], Oberwinkler H[SUP]2[/SUP], Prinz S[SUP]1[/SUP], Kr?usslich HG[SUP]2[/SUP], Briggs JA[SUP]3[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] The assembly of influenza A virus at the plasma membrane of infected cells leads to release of enveloped virions that are typically round in tissue-culture adapted strains, but filamentous in strains isolated from patients. The viral proteins hemagglutinin (HA), neuraminidase (NA), matrix protein 1 (M1) and the M2 ion channel all contribute to virus assembly. When expressed individually or in combination in the cells, they can all, under certain conditions, mediate release of membrane-enveloped particles, but their relative roles in virus assembly, release and morphology remain unclear. To investigate this, we have produced membrane-enveloped particles by plasmid-derived expression of combinations of HA, NA and M proteins (M1 and M2), or by infection with influenza A virus. We have monitored particle release, particle morphology, and plasma membrane morphology using biochemical methods, electron microscopy, electron tomography and cryo-electron tomography. Our data suggest that HA, NA or HANA expression leads to particle release through non-specific induction of membrane curvature. In contrast, co-expression with the M proteins clusters the glycoproteins into filamentous membrane protrusions, which by forming a constricted neck at the base, can be released as particles. HA and NA preferentially distribute to differently curved membranes within these particles. Both the budding intermediates and the released particles are morphologically similar to those produced during infection with influenza A virus. Together, our data provide new insights into influenza virus assembly and show that the M segment together with either of the glycoproteins is the minimal requirement to assemble and release membrane-enveloped particles that are truly virus-like.
[h=4]IMPORTANCE:[/h] Influenza A virus is a major respiratory pathogen. It assembles membrane-enveloped virus particles whose shapes vary from spherical to filamentous. Here we have studied the roles of individual viral proteins in mediating virus assembly and in determining virus shape. To do this, we used a range of electron microscopy techniques to obtain and compare 2D and 3D images of virus particles and virus-like particles during and after assembly. The virus-like particles were produced using different combinations of viral proteins. Among our results, we found that co-expression of one or both of the viral surface proteins (hemagglutinin and neuraminidase), together with the viral membrane associated proteins encoded in the M segment, results in assembly and release of filamentous virus-like particles in a manner very similar to the budding and release of influenza virions. These data provide novel insights into the roles played by individual viral proteins in influenza A virus assembly.
Copyright ? 2015, American Society for Microbiology. All Rights Reserved.
PMID: 26085153 [PubMed - as supplied by publisher]
[h=1]Structural analysis of the roles of influenza A virus membrane-associated proteins in assembly and morphology.[/h] Chlanda P[SUP]1[/SUP], Schraidt O[SUP]1[/SUP], Kummer S[SUP]2[/SUP], Riches J[SUP]1[/SUP], Oberwinkler H[SUP]2[/SUP], Prinz S[SUP]1[/SUP], Kr?usslich HG[SUP]2[/SUP], Briggs JA[SUP]3[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] The assembly of influenza A virus at the plasma membrane of infected cells leads to release of enveloped virions that are typically round in tissue-culture adapted strains, but filamentous in strains isolated from patients. The viral proteins hemagglutinin (HA), neuraminidase (NA), matrix protein 1 (M1) and the M2 ion channel all contribute to virus assembly. When expressed individually or in combination in the cells, they can all, under certain conditions, mediate release of membrane-enveloped particles, but their relative roles in virus assembly, release and morphology remain unclear. To investigate this, we have produced membrane-enveloped particles by plasmid-derived expression of combinations of HA, NA and M proteins (M1 and M2), or by infection with influenza A virus. We have monitored particle release, particle morphology, and plasma membrane morphology using biochemical methods, electron microscopy, electron tomography and cryo-electron tomography. Our data suggest that HA, NA or HANA expression leads to particle release through non-specific induction of membrane curvature. In contrast, co-expression with the M proteins clusters the glycoproteins into filamentous membrane protrusions, which by forming a constricted neck at the base, can be released as particles. HA and NA preferentially distribute to differently curved membranes within these particles. Both the budding intermediates and the released particles are morphologically similar to those produced during infection with influenza A virus. Together, our data provide new insights into influenza virus assembly and show that the M segment together with either of the glycoproteins is the minimal requirement to assemble and release membrane-enveloped particles that are truly virus-like.
[h=4]IMPORTANCE:[/h] Influenza A virus is a major respiratory pathogen. It assembles membrane-enveloped virus particles whose shapes vary from spherical to filamentous. Here we have studied the roles of individual viral proteins in mediating virus assembly and in determining virus shape. To do this, we used a range of electron microscopy techniques to obtain and compare 2D and 3D images of virus particles and virus-like particles during and after assembly. The virus-like particles were produced using different combinations of viral proteins. Among our results, we found that co-expression of one or both of the viral surface proteins (hemagglutinin and neuraminidase), together with the viral membrane associated proteins encoded in the M segment, results in assembly and release of filamentous virus-like particles in a manner very similar to the budding and release of influenza virions. These data provide novel insights into the roles played by individual viral proteins in influenza A virus assembly.
Copyright ? 2015, American Society for Microbiology. All Rights Reserved.
PMID: 26085153 [PubMed - as supplied by publisher]