Influenza A viral nucleoprotein interacts with cytoskeleton scaffolding protein α-actinin-4 for viral replication

FEBS J. 2014 Jul;281(13):2899-914. doi: 10.1111/febs.12828. Epub 2014 Jun 2.


Influenza A virus (IAV), similar to other viruses, exploits the machinery of human host cells for its survival and replication. We identified α-actinin-4, a host cytoskeletal protein, as an interacting partner of IAV nucleoprotein (NP). We confirmed this interaction using co-immunoprecipitation studies, first in a coupled in vitro transcription-translation assay and then in cells either transiently co-expressing the two proteins or infected with whole IAV. Importantly, the NP-actinin-4 interaction was observed in several IAV subtypes, including the 2009 H1N1 pandemic virus. Moreover, immunofluorescence studies revealed that both NP and actinin-4 co-localized largely around the nucleus and also in the cytoplasmic region of virus-infected A549 cells. Silencing of actinin-4 expression resulted in not only a significant decrease in NP, M2 and NS1 viral protein expression, but also a reduction of both NP mRNA and viral RNA levels, as well as viral titers, 24 h post-infection with IAV, suggesting that actinin-4 was critical for viral replication. Furthermore, actinin-4 depletion reduced the amount of NP localized in the nucleus. Treatment of infected cells with wortmannin, a known inhibitor of actinin-4, led to a decrease in NP mRNA levels and also caused the nuclear retention of NP, further strengthening our previous observations. Taken together, the results of the present study indicate that actinin-4, a novel interacting partner of IAV NP, plays a crucial role in viral replication and this interaction may participate in nuclear localization of NP and/or viral ribonucleoproteins.

Keywords: actinin-4; influenza virus; interaction; localization; nucleoprotein.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actinin / genetics
  • Actinin / metabolism*
  • HEK293 Cells
  • Host-Pathogen Interactions
  • Humans
  • Influenza A virus / physiology*
  • Nucleocapsid Proteins
  • Protein Interaction Mapping
  • Protein Transport
  • RNA-Binding Proteins / physiology*
  • Transcriptional Activation
  • Viral Core Proteins / physiology*
  • Virus Replication*


  • ACTN4 protein, human
  • NP protein, Influenza A virus
  • Nucleocapsid Proteins
  • RNA-Binding Proteins
  • Viral Core Proteins
  • Actinin