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Differential use of importin-α isoforms governs cell tropism and host adaptation of influenza virus.

Gabriel G, Klingel K, Otte A, Thiele S, Hudjetz B, Arman-Kalcek G, Sauter M, Shmidt T, Rother F, Baumgarte S, Keiner B, Hartmann E, Bader M, Brownlee GG, Fodor E, Klenk HD - Nat Commun (2011)

Bottom Line: Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions.In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation.Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

View Article: PubMed Central - PubMed

Affiliation: 1] Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany. [2] Sir William Dunn School of Pathology, University of Oxford, Oxford, UK. [3] Institute of Virology, Philipps-University Marburg, Marburg, Germany.

ABSTRACT
Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions. Interspecies transmission requires adaptation of the viral polymerase to importin-α, a cellular protein that mediates transport into the nucleus where transcription and replication of the viral genome takes place. In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation. For efficient virus replication, the polymerase subunit PB2 and the nucleoprotein (NP) of avian viruses required importin-α3, whereas PB2 and NP of mammalian viruses showed importin-α7 specificity. H1N1v replication depended on both, importin-α3 and -α7, suggesting ongoing adaptation of this virus. Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

No MeSH data available.


Related in: MedlinePlus

Growth curves of avian and mammalian H7N7 mutant viruses in importin-silenced human cells.(a) Endogenous importins (α1–α7) were silenced using siRNA in human lung cells (A549). Importin-α7 antibody crossreacts with importin-α5. The doublet represents importin-α5 (upper band) and importin-α7 (lower band). (b–h) Virus growth in importin-α-silenced A549 cells infected with (b) SC35, (c) SC35M, (d) SC35-PB1SC35M, (e) SC35-PASC35M, (f) SC35-PB2SC35M, (g) SC35-NPSC35M and (h) the mutant SC35-PB2701N-NP319K. Growth curves show controls (black, filled diamonds), α1 (blue, squares), α3 (green, filled triangles), α4 (black, filled squares), α5 (black diamonds) and α7 (red triangles) silenced cells.
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f1: Growth curves of avian and mammalian H7N7 mutant viruses in importin-silenced human cells.(a) Endogenous importins (α1–α7) were silenced using siRNA in human lung cells (A549). Importin-α7 antibody crossreacts with importin-α5. The doublet represents importin-α5 (upper band) and importin-α7 (lower band). (b–h) Virus growth in importin-α-silenced A549 cells infected with (b) SC35, (c) SC35M, (d) SC35-PB1SC35M, (e) SC35-PASC35M, (f) SC35-PB2SC35M, (g) SC35-NPSC35M and (h) the mutant SC35-PB2701N-NP319K. Growth curves show controls (black, filled diamonds), α1 (blue, squares), α3 (green, filled triangles), α4 (black, filled squares), α5 (black diamonds) and α7 (red triangles) silenced cells.

Mentions: Human and chicken importin-α isoforms vary in their amino-acid sequences from 82 to 99% identity; namely, α1 (82%), α3 (99%), α4 (98%), α5 (95%), α6 (94%) and α7 (94%) (Supplementary Fig. S1). These data suggest that all importins show sufficient sequence divergence to potentially restrict interspecies transmission of influenza viruses. When individual importins were silenced in avian cells by small interfering RNA (siRNA; Supplementary Fig. S2a), the highly pathogenic avian influenza virus (HPAIV) SC35 (H7N7) and its murine variant SC35M10 grew to similar titres (Supplementary Fig. S2b,c) suggesting redundancy of chicken importins for influenza virus replication. In contrast, in importin-α-silenced human lung cells (Fig. 1a), SC35 growth was restricted by ≥1 log in importin-α1- and -α3-silenced cells (Fig. 1b). SC35M growth was not affected by importin-α3 silencing, but was strongly reduced (2 logs) in importin-α7-silenced human cells (Fig. 1c). Thus, in human cells, SC35 has a preference for importin-α3, whereas SC35M prefers importin-α7. Both viruses depend on importin-α1. The other importins appear to be redundant.


Differential use of importin-α isoforms governs cell tropism and host adaptation of influenza virus.

Gabriel G, Klingel K, Otte A, Thiele S, Hudjetz B, Arman-Kalcek G, Sauter M, Shmidt T, Rother F, Baumgarte S, Keiner B, Hartmann E, Bader M, Brownlee GG, Fodor E, Klenk HD - Nat Commun (2011)

Growth curves of avian and mammalian H7N7 mutant viruses in importin-silenced human cells.(a) Endogenous importins (α1–α7) were silenced using siRNA in human lung cells (A549). Importin-α7 antibody crossreacts with importin-α5. The doublet represents importin-α5 (upper band) and importin-α7 (lower band). (b–h) Virus growth in importin-α-silenced A549 cells infected with (b) SC35, (c) SC35M, (d) SC35-PB1SC35M, (e) SC35-PASC35M, (f) SC35-PB2SC35M, (g) SC35-NPSC35M and (h) the mutant SC35-PB2701N-NP319K. Growth curves show controls (black, filled diamonds), α1 (blue, squares), α3 (green, filled triangles), α4 (black, filled squares), α5 (black diamonds) and α7 (red triangles) silenced cells.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3105303&req=5

f1: Growth curves of avian and mammalian H7N7 mutant viruses in importin-silenced human cells.(a) Endogenous importins (α1–α7) were silenced using siRNA in human lung cells (A549). Importin-α7 antibody crossreacts with importin-α5. The doublet represents importin-α5 (upper band) and importin-α7 (lower band). (b–h) Virus growth in importin-α-silenced A549 cells infected with (b) SC35, (c) SC35M, (d) SC35-PB1SC35M, (e) SC35-PASC35M, (f) SC35-PB2SC35M, (g) SC35-NPSC35M and (h) the mutant SC35-PB2701N-NP319K. Growth curves show controls (black, filled diamonds), α1 (blue, squares), α3 (green, filled triangles), α4 (black, filled squares), α5 (black diamonds) and α7 (red triangles) silenced cells.
Mentions: Human and chicken importin-α isoforms vary in their amino-acid sequences from 82 to 99% identity; namely, α1 (82%), α3 (99%), α4 (98%), α5 (95%), α6 (94%) and α7 (94%) (Supplementary Fig. S1). These data suggest that all importins show sufficient sequence divergence to potentially restrict interspecies transmission of influenza viruses. When individual importins were silenced in avian cells by small interfering RNA (siRNA; Supplementary Fig. S2a), the highly pathogenic avian influenza virus (HPAIV) SC35 (H7N7) and its murine variant SC35M10 grew to similar titres (Supplementary Fig. S2b,c) suggesting redundancy of chicken importins for influenza virus replication. In contrast, in importin-α-silenced human lung cells (Fig. 1a), SC35 growth was restricted by ≥1 log in importin-α1- and -α3-silenced cells (Fig. 1b). SC35M growth was not affected by importin-α3 silencing, but was strongly reduced (2 logs) in importin-α7-silenced human cells (Fig. 1c). Thus, in human cells, SC35 has a preference for importin-α3, whereas SC35M prefers importin-α7. Both viruses depend on importin-α1. The other importins appear to be redundant.

Bottom Line: Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions.In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation.Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

View Article: PubMed Central - PubMed

Affiliation: 1] Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany. [2] Sir William Dunn School of Pathology, University of Oxford, Oxford, UK. [3] Institute of Virology, Philipps-University Marburg, Marburg, Germany.

ABSTRACT
Influenza A viruses are a threat to humans due to their ability to cross species barriers, as illustrated by the 2009 H1N1v pandemic and sporadic H5N1 transmissions. Interspecies transmission requires adaptation of the viral polymerase to importin-α, a cellular protein that mediates transport into the nucleus where transcription and replication of the viral genome takes place. In this study, we analysed replication, host specificity and pathogenicity of avian and mammalian influenza viruses, in importin-α-silenced cells and importin-α-knockout mice, to understand the role of individual importin-α isoforms in adaptation. For efficient virus replication, the polymerase subunit PB2 and the nucleoprotein (NP) of avian viruses required importin-α3, whereas PB2 and NP of mammalian viruses showed importin-α7 specificity. H1N1v replication depended on both, importin-α3 and -α7, suggesting ongoing adaptation of this virus. Thus, differences in importin-α specificity are determinants of host range underlining the importance of the nuclear envelope in interspecies transmission.

No MeSH data available.


Related in: MedlinePlus