Role of fibronectin-interacting cellular proteins in Influenza A virus infection in human lung epithelial cells

Abstract

Influenza A virus (IAV) alters the expression of many host cellular proteins in the infected cells; many of these proteins interact with fibronectin. Proteasome subunit alpha type-2 (PSMA2), Chloride intracellular channel protein 1(CLIC1) and Heat Shock Protein Family A (Hsp70) member 5 (HSPA5) are three fibronectin interacting proteins that were highly expressed in IAV-infected cells. PSMA2 is part of the 20S proteasome complex, involved in proteolytic modification and recycling of cellular proteins. CLIC1 is a chloride channel that regulates intracellular pH, cell volume and trans-epithelial ion transport. HSPA5 helps to translocate nascent proteins to endoplasmic reticulum and subsequent folding. In this study, I have investigated the importance of PSMA2, CLIC1 and HSPA5 in IAV replication cycle. The knockdown (KD) of PSMA2, CLIC1 and HSPA5 in A549 cells, caused a significant reduction in extracellular progeny IAV. Although CLIC1 KD did not affect viral protein translation, IAV-nucleoprotein (NP) was accumulated in HSPA5 KD and PSMA2 KD cells. Viral RNAs were significantly higher in CLIC1 KD cells after IAV infection, but transcription was unaffected in PSMA2 KD and HSPA5 KD cells. The results indicate that PSMA2, HSPA5 and CLIC1 are critical host factors for IAV and are possibly involve in the terminal stages of viral replication. Further proteomic analysis to understand the role of PSMA2 KD in IAV infection at the proteomic level revealed that NRF2-mediated oxidative stress response signaling, was inhibited by IAV infection but was significantly activated by PSMA2 KD. Reactive oxygen species (ROS) level was significantly inhibited in wild-type cells but significantly increased in PSMA2 KD cells after IAV infection. However, IAV infection also caused significantly higher nuclear translocation of NFR2, which was inhibited in the PSMA2 KD cells. Treatment with ROS scavenger was able to reduce the inhibitory impact of PSMA2 KD. This indicates that PSMA2 is required for NRF2-mediated ROS neutralization and that IAV uses PSMA2 to escape viral clearance via NRF2-mediated oxidative response. This study has extended our understanding of the significance of Fibronectin-interacting proteins in the IAV replication cycle; nevertheless, further research is needed to fully comprehend the mechanism and develop antiviral drugs targeting the proteins.