Activation and function of the phosphatidylinositol-3-kinase signalling pathway in influenza virus infected cells
Final Report Abstract
Influenza A viruses (IAV), the causative agents for severe respiratory diseases strongly depend on the host cell machinery. However, the knowledge of virus host interactions is still incomplete. Several studies indicated seemingly antiviral acting signaling pathways to be manipulated by the virus to ensure efficient replication. In project-related work we introduced the phosphatidyl-inositol-3 kinase (PI3K) as a perfect example of this phenomenon that we characterized further. Major findings of our studies point to a complete novel concept in signaling-induced virus entry as well as a paradigm change of viral non-structural protein 1 (A/NS1) regulatory functions. We identified receptor tyrosine kinases (RTKs), activated by IAV binding, as mediators of virus internalization, transmitting signals across the cellular plasma membrane, resulting in the activation of factors, such as PI3K. Addressing further aspects of the PI3K signaling network, the initially introduced signaling blocker A/NS1 was identified as signaling activator. Several A/NS1 interaction partners, such as the regulatory subunit of PI3K (p85), the non-receptor tyrosine kinase c-Abl as well as the adapter proteins CRK and CRKL were characterized in detail within our studies. Investigation of interaction motives within A/NS1, responsible for interference with cellular factors, revealed strain-specific variations that are responsible for differences in regulatory functions. Disruption of the p85-A/NS1 interaction results in restricted virus spread in mouse lung and strongly reduced virulence. Binding capacity of A/NS1 to CRK/CRKL has evolved in virus strains that over-induce the antiviral acting JNK-ATF2 signaling module and helps to suppress the detrimental apoptosis promoting action of this pathway. And also A/NS1-mediated c-Abl regulation occurs in a subtype-specific manner, regulating cell fate and pathogenicity. Interestingly, besides A/NS1 we identified other viral factors counteracting host defense mechanisms in a strain-specific manner. The polymerase complex proteins PB1 and PA of IAV that harbor a specific amino-acid motive (ESIE) alter type I IFN response. In that line we recently were surprised to recognize a novel bacterial-mediated mechanism also promoting viral replication. Actually, metabolically active intracellular Staphylococcus aureus inhibits type I IFN-mediated STAT1 phosphorylation and STAT1-STAT2 dimerization. As a result, in the presence of S. aureus the first line of defence against IAV is interrupted, resulting in a boost of viral replication. In summary, these exciting findings represent perfect examples of the complex interplay of IAV with their hosts, but also with co-infecting pathogens.
Publications
- 2009. A new player in a deadly game: influenza viruses and the PI3K/Akt signalling pathway. Cell Microbiol 11: 863-871
Ehrhardt C, Ludwig S
- 2009. The influenza A virus matrix protein as a marker to monitor initial virus internalisation. Biological chemistry 390:509-515
Eierhoff T, Ludwig S, Ehrhardt C
- 2010. CRK adaptor protein expression is required for efficient replication of avian influenza A viruses and controls JNK-mediated apoptotic responses. Cellular microbiology 12:831-843
Hrincius ER, Wixler V, Wolff T, Wagner R, Ludwig S, Ehrhardt C
- 2010. The epidermal growth factor receptor (EGFR) promotes uptake of influenza A viruses (IAV) into host cells. PLoS pathogens 6:e1001099
Eierhoff T, Hrincius ER, Rescher U, Ludwig S, Ehrhardt C
- 2011. From virus entry to release: the diverse functions of PI3K during RNA virus infection. Future Virology 6:1225-1239
Ehrhardt, C
- 2011. Phosphatidylinositol-3-kinase (PI3K) is activated by influenza virus vRNA via the pathogen pattern receptor Rig-I to promote efficient type I interferon production. Cellular microbiology 13:1907-1919
Hrincius ER, Dierkes R, Anhlan D, Wixler V, Ludwig S, Ehrhardt C
- 2012. A single point mutation (Y89F) within the non-structural protein 1 of influenza A viruses limits epithelial cell tropism and virulence in mice. The American journal of pathology 180:2361- 2374
Hrincius ER, Hennecke AK, Gensler L, Nordhoff C, Anhlan D, Vogel P, McCullers JA, Ludwig S, Ehrhardt C
(See online at https://doi.org/10.1016/j.ajpath.2012.02.029) - 2012. Small molecule inhibitors of the c- Jun N-terminal kinase (JNK) possess antiviral activity against highly pathogenic avian and human pandemic influenza A viruses. Biological chemistry 393:525-534
Nacken W, Ehrhardt C, Ludwig S
(See online at https://doi.org/10.1515/hsz-2011-0270) - 2012. Synergistic adaptive mutations in the hemagglutinin and polymerase acidic protein lead to increased virulence of pandemic 2009 H1N1 influenza A virus in mice. The Journal of infectious diseases 205:262-271
Seyer R, Hrincius ER, Ritzel D, Abt M, Mellmann A, Marjuki H, Kühn J, Wolff T, Ludwig S, Ehrhardt C
(See online at https://doi.org/10.1093/infdis/jir716) - 2014. Activation of c-jun N-terminal kinase upon influenza A virus (IAV) infection is independent of pathogen-related receptors but dependent on amino acid sequence variations of IAV NS1. Journal of virology 88:8843-8852
Nacken W, Anhlan D, Hrincius ER, Mostafa A, Wolff T, Sadewasser A, Pleschka S, Ehrhardt C, Ludwig S
(See online at https://doi.org/10.1128/JVI.00424-14) - 2014. Avian influenza viruses inhibit the major cellular signalling integrator c-Abl. Cellular microbiology 16:1854-1874
Hrincius ER, Liedmann S, Anhlan D, Wolff T, Ludwig S, Ehrhardt C
(See online at https://doi.org/10.1111/cmi.12332) - 2014. New virulence determinants contribute to the enhanced immune response and reduced virulence of an influenza A virus A/PR8/34 variant. The Journal of infectious diseases 209:532-541
Liedmann S, Hrincius ER, Anhlan D, McCullers JA, Ludwig S, Ehrhardt C
(See online at https://doi.org/10.1093/infdis/jit463) - 2014. Viral suppressors of the RIG-I-mediated interferon response are pre-packaged in influenza virions. Nature communications 5:5645
Liedmann S, Hrincius ER, Guy C, Anhlan D, Dierkes R, Carter R, Wu G, Staeheli P, Green DR, Wolff T, McCullers JA, Ludwig S, Ehrhardt C
(See online at https://doi.org/10.1038/ncomms6645) - 2015. Super-infection with Staphylococcus aureus inhibits influenza virus-induced type I IFN signalling through impaired STAT1- STAT2 dimerization. Cellular microbiology 17:303-317
Warnking K, Klemm C, Löffler B, Niemann S, van Krüchten A, Peters G, Ludwig S, Ehrhardt C
(See online at https://doi.org/10.1111/cmi.12375)
