Avian and 1918 Spanish influenza a virus NS1 proteins bind to Crk/CrkL Src homology 3 domains to activate host cell signaling

J Biol Chem. 2008 Feb 29;283(9):5719-27. doi: 10.1074/jbc.M707195200. Epub 2007 Dec 28.


NS1 (nonstructural protein 1) is an important virulence factor of the influenza A virus. We observed that NS1 proteins of the 1918 pandemic virus (A/Brevig Mission/1/18) and many avian influenza A viruses contain a consensus Src homology 3 (SH3) domain-binding motif. Screening of a comprehensive human SH3 phage library revealed the N-terminal SH3 of Crk and CrkL as the preferred binding partners. Studies with recombinant proteins confirmed avid binding of NS1 proteins of the 1918 virus and a representative avian H7N3 strain to Crk/CrkL SH3 but not to other SH3 domains tested, including p85alpha and p85beta. Endogenous CrkL readily co-precipitated NS1 from cells infected with the H7N3 virus. In transfected cells association with CrkL was observed for NS1 of the 1918 and H7N3 viruses but not A/Udorn/72 or A/WSN/33 NS1 lacking this sequence motif. SH3 binding was dispensable for suppression of interferon-induced gene expression by NS1 but was associated with enhanced phosphatidylinositol 3-kinase signaling, as evidenced by increased Akt phosphorylation. Thus, the Spanish Flu virus resembles avian influenza A viruses in its ability to recruit Crk/CrkL to modulate host cell signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Motifs / physiology
  • Cell Line
  • Gene Expression Regulation, Viral / physiology
  • Humans
  • Influenza A Virus, H1N1 Subtype / genetics
  • Influenza A Virus, H1N1 Subtype / metabolism*
  • Influenza A Virus, H1N1 Subtype / pathogenicity
  • Interferons / metabolism
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation
  • Protein Binding / physiology
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Proto-Oncogene Proteins c-crk / genetics
  • Proto-Oncogene Proteins c-crk / metabolism*
  • Signal Transduction / physiology*
  • Species Specificity
  • Viral Nonstructural Proteins / genetics
  • Viral Nonstructural Proteins / metabolism*
  • Virulence Factors / genetics
  • Virulence Factors / metabolism*
  • src Homology Domains / physiology


  • Adaptor Proteins, Signal Transducing
  • CRK protein, human
  • CRKL protein
  • INS1 protein, influenza virus
  • Nuclear Proteins
  • Proto-Oncogene Proteins c-crk
  • Viral Nonstructural Proteins
  • Virulence Factors
  • Interferons
  • Phosphatidylinositol 3-Kinases
  • Proto-Oncogene Proteins c-akt