title: CRK adaptor protein expression is required for efficient replication of avian influenza A viruses and controls JNK-mediated apoptotic responses.
abstract: The non-structural protein 1 (A/NS1) of influenza A viruses (IAV) harbours several src-homology domain (SH) binding motifs that are required for interaction with cellular proteins. The SH3 binding motif at aa212-217 [PPLPPK] of A/NS1 was shown to be essential for binding to the cellular adaptor proteins CRK and CRKL. Both regulate diverse cellular effector pathways, including activation of the MAP-kinase JNK that in turn mediates antiviral responses to IAV infection. By studying functional consequences of A/NS1-CRK interaction we show here that A/NS1 binding to CRK contributes to suppression of the antiviral-acting JNK-ATF2 pathway. However, only IAV that encode an A/NS1-protein harbouring the CRK/CRKL SH3 binding motif PPLPPK were attenuated upon downregulation of CRKI/II and CRKL, but not of CRKII alone. The PPLPPK site-harbouring candidate strains could be discriminated from other strains by a pronounced viral activation of the JNK-ATF2 signalling module that was even further boosted upon knock-down of CRKI/II. Interestingly, this enhanced JNK activation did not alter type-I IFN-expression, but rather resulted in increased levels of virus-induced cell death. Our results imply that binding capacity of A/NS1 to CRK/CRKL has evolved in virus strains that over-induce the antiviral acting JNK-ATF2 signalling module and helps to suppress the detrimental apoptosis promoting action of this pathway.
authors.affiliation: Institute of Molecular Virology, ZMBE, Muenster, Germany.
authors.forename: Eike R
authors.initials: ER
authors.lastname: Hrincius
authors.forename: Viktor
authors.initials: V
authors.lastname: Wixler
authors.forename: Thorsten
authors.initials: T
authors.lastname: Wolff
authors.forename: Ralf
authors.initials: R
authors.lastname: Wagner
authors.forename: Stephan
authors.initials: S
authors.lastname: Ludwig
authors.forename: Christina
authors.initials: C
authors.lastname: Ehrhardt
mesh_terms: D051698:Activating Transcription Factor 2; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002642:Chick Embryo; D004285:Dogs; D006801:Humans; D009980:Influenza A virus / Q000254:growth & development*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D050737:Proto-Oncogene Proteins c-crk / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000378:metabolism*
chemical_list: C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; 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; D048031:JNK Mitogen-Activated Protein Kinases