Characterisation of a novel interaction between Influenza A Virus protein M2 and human PP4R3α/SMEK1 protein

Abstract

Discovering new viral-host cell interactions is fundamental to the discovery of novel methods to target viral infections. Due to the parasitic nature in which virus’s replicate, it is important to identify the exact mechanisms by which they interact and hijack host cell protein machinery. A novel interaction between a human cellular protein and a viral proton channel protein was identified through a yeast two-hybrid screen. This interaction is between viral protein M2 and a protein phosphatase regulatory subunit. Protein phosphatases remove phosphate groups from proteins; this usually results in deactivation of proteins. Activation and deactivation of proteins by phosphorylation is fundamental for signalling cascades. The regulatory subunit PP4R3α (SMEK1) regulates protein phosphatase 4 (PP4), which is a complex formed with other subunits (PP4R2 and PP4c). PP4 has many functions within human cells. PP4 has been identified to be involved in the type-1 interferon signalling cascade, which plays a crucial role in viral recognition and immune response stimulation. The hypothesis was that this interaction has important implications for the host and the virus. The interaction between SMEK1 and M2 was confirmed by co-immunoprecipitation. It was also found that influenza A virus (IAV) infection caused an increase in PP4c expression in A549 lung epithelial cells. By understanding the way in which IAV M2 interacts with host cell systems and hijacks these systems we may identify novel strategies to combat or prevent infection.