title: Avian and 1918 Spanish influenza a virus NS1 proteins bind to Crk/CrkL Src homology 3 domains to activate host cell signaling.
abstract: 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.
authors.affiliation: Department of Virology, Haartman Institute, University of Helsinki and Helsinki University Central Hospital, Haartmaninkatu 3 POB 21, FIN-00014, Helsinki, Finland.
authors.forename: Leena S
authors.initials: LS
authors.lastname: Heikkinen
authors.forename: Arunas
authors.initials: A
authors.lastname: Kazlauskas
authors.forename: Krister
authors.initials: K
authors.lastname: Melén
authors.forename: Ralf
authors.initials: R
authors.lastname: Wagner
authors.forename: Thedi
authors.initials: T
authors.lastname: Ziegler
authors.forename: Ilkka
authors.initials: I
authors.lastname: Julkunen
authors.forename: Kalle
authors.initials: K
authors.lastname: Saksela
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000502:physiology; D002460:Cell Line; D015967:Gene Expression Regulation, Viral / Q000502:physiology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D007372:Interferons / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013045:Species Specificity; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C485285:CRK protein, human; C082869:CRKL protein; C085820:INS1 protein, influenza virus; D009687:Nuclear Proteins; D050737:Proto-Oncogene Proteins c-crk; D017361:Viral Nonstructural Proteins; D037521:Virulence Factors; D007372:Interferons; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt