Human metapneumovirus induces autophagy through JNK and MEK/ERK pathway

Abstract Background: Human metapneumovirus (hMPV) is a ubiquitous respiratory pathogen, especially in infants and young children. Virus-host interaction affects viral replication and host immune responses. Autophagy plays an important role in virus-host interaction. Airway epithelial cells serve as the first line in host to against respiratory virus infection. However, it is still unknown whether autophagy is activated in human metapneumovirus (hMPV) infected host cells. Methods: In this study, we demonstrated the occurrence of autophagy through some autophagic features including the conversion of GFP-RFP-LC3 plasmid, RFP-LC3 puncta and expression of autophagic-related gene. The pathways involved in autophagy were detected by Western Blot and verified by specific pathway inhibitors. The relationship between the replication of hMPV and autophagy was tested by Rapamycin, 3-MA, siRNA-LC3 and pathway inhibitors. We also used BALB/c mice to verified the autophagy and pathways in hMPV infection. Results: We found that the GFP-RFP-LC3 plasmid, RFP-LC3 puncta and expression of ATG5, ATG7, Becllin1, LC3 were increased in hMPV group in vitro . JNK and MEK/ERK signaling pathway are activated in hMPV induced-autophagy and we confirmed the two pathways with specific inhibitors SP600125 and PD98059. Furthermore, we found that rapamycin suppressed hMPV infection significantly, but reversed when treated with autophagy inhibitor 3-MA, siRNA-LC3 and pathway inhibitors. hMPV infected mice also induce autophagy through JNK and MEK/ERK pathways. Conclusion: Taken together, our results show strong evidence that autophagy involved in hMPV infection through JNK, MEK/ERK pathway which plays an antiviral role in the process of hMPV infection.