Heat Shock Proteins and Their Interplay to Control Influenza A Virus Replication

Abstract

Purpose: A remarkable characteristic of the influenza A virus (IAV) is its ability to hijack the host machinery to complete its life cycle. A commonly targeted class of host factors are the heat shock proteins (Hsps). Hsps partake in stress response, protein translation, folding, degradation and cellular trafficking. Interaction between various Hsps and IAV proteins have been demonstrated to facilitate viral replication, virus assembly and virus-induced apoptosis while suppressing the host immune response. With emerging antibiotic resistance, there exists a dire need to identify host factors as novel antiviral targets. Here, we studied Hsp90, HspA8, Hsp40 and Hsp27 as host candidates and their interaction with IAV nucleoprotein (NP), the protein essential for viral replication and transcription. We also evaluated the modulation of viral replication under the influence of an Hsp inhibitor, 17-AAG. Methods & Materials: We performed liquid chromatography-mass spectrometry to screen for potential host factors interacting with NP. We explored the interaction of the NP-Hsp complex through co-immunoprecipitation studies and in silico analysis. To assess the therapeutic potential of this interaction, we investigated the effects of 17-AAG on IAV replication and endogenous Hsp expression levels in human lung adenocarcinoma (A549) cells via plaque assay and immunoblotting. Results: The direct interaction between NP and these Hsps was established. NP was found to target the ATP binding domains of Hsp90 and HspA8, J domain of Hsp40 and alpha-crystallin domain of Hsp27. Decreasing virus titers were observed in a drug dose-dependent manner upon 17-AAG treatment. Increasing endogenous levels of Hsp90, HspA8, Hsp40 and Hsp27 were seen, proving that 17-AAG plays an inhibitory role in IAV replication by modulating the function and expression levels of Hsps. Conclusion: Validation of the NP-Hsp interaction and identification of their corresponding functional domains implicate their role in cellular trafficking to assist NP in viral replication and transcription. The antiviral properties shown by 17-AAG emphasize the potential of the NP-Hsp complex as a therapeutic target. These outcomes allow for better understanding of the molecular pathogenesis of IAV and the novelty of a potential antiviral target and broad-spectrum therapeutic agent against not only IAV, but possibly other viral pathogens.