Impact of viral and cellular protein phosphorylation on the regulation of innate antiviral immune responses against influenza A virus infections

• Applicant: Professor Dr. Stephan Ludwig
• Subject Area: Virology
• Term: since 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 316675205

Influenza viruses are small RNA viruses with a limited coding capacity. Therefore, viral proteins have to fulfill multiple functions in the infected cell. This implies that there must be mechanisms allowing for the control of multi-functionality in a spatio-temporal manner. We hypothesized that dynamic phosphorylation of viral and cellular proteins is a so far underestimated layer of regulation of virus propagation and innate immune responses to infection. To address this, we followed a strategy to focus for in depth functional analysis on a set of individual functionally related viral and cellular phosphoproteins identified by our own phospho-proteomic screen with a suspected function in the innate immune response and viral replication. In the previous funding period, we were not only able to describe the regulatory function of phosphorylation of a range of viral and cellular proteins, but also identified targets that may be used for novel host-directed anti-infective strategies. We have now performed additional phospho-proteome and kinome screenings, which identified further novel phospho-sites of the viral IFN-antagonistic protein NS1 as well as kinases and kinase regulators that are central in a virusrelated functional network analysis. We now want to build on these findings and enhance our studies by functional characterization of the three newly identified sites in NS1, this time also considering dynamic interaction with neighboring phospho-acceptor sites. Furthermore, we will unravel the role of two particular kinases, Cdk1 and PKA, that are differentially phosphorylated and activated during the virus replication cycle and also are linked to innate immune responses and described to phosphorylate NS1. This study will provide deeper knowledge about the regulatory host-virus interplay and is key to uncover new leads for pharmaceutical intervention.

• DFG Programme: Research Grants