Role of the Chaperone Protein 14-3-3η in Regulation of the Infection Dynamics of the Influenza A (H1N1) Virus.

The 14-3-3 protein family, which includes the isoforms η, γ, ε, θ, β, and ζ, is essential for controlling a number of pathways linked to DNA and RNA viruses, including HIV, influenza A virus (IAV), measles virus, HRSV, and double-stranded DNA viruses. TRIM32, an E3 ubiquitin ligase, has been reported to target IAV's PB1 polymerase for species-specific degradation via ubiquitination. Notably, 14-3-3η binds to phosphorylated TRIM32, preventing its autoubiquitylation and forming soluble but inactive cytoplasmic aggregates that regulate TRIM32 levels. However, the functional link between 14-3-3η, TRIM32, and PB1 during viral infection remains unclear. In this study, we establish a mechanistic connection between 14-3-3η-TRIM32 and TRIM32-PB1 interactions in IAV (H1N1) infection. We demonstrate that 14-3-3η directly interacts with PB1, influencing viral replication. Using transient knockdown models, we show that 14-3-3η deficiency alters influenza virus-induced cytotoxicity, cell death, immune responses, and reactive oxygen species (ROS) production. Additionally, we observe a significant reduction in the soluble TRIM32 levels in 14-3-3η-deficient cells, which leads to increased PB1 accumulation and thus suggests a critical regulatory role for 14-3-3η in PB1 stability. Our findings reveal a novel function of 14-3-3η in influenza virus infection, demonstrating its role in PB1 regulation via TRIM32 and its impact on innate immune activation. This study highlights 14-3-3η as a possible target for antiviral treatments against influenza and offers fresh insights into the host-virus relationship.