Lysozyme (LYZ) promotes PEDV replication via degrading m⁶A methylation of RIG-I transcripts through YTHDF2

Porcine epidemic diarrhea virus (PEDV), a single-stranded positive RNA virus, can cause severe vomiting and diarrhea in piglets, causing huge economic losses to the breeding industry. Lysozyme (LYZ) is a globulin involved in innate immunity. The classic function of LYZ is antibacterial. However, whether LYZ regulates PEDV replication remains a mystery. In our study, we identified LYZ as the host protein interacting with NSP8 using immunoprecipitation-mass spectrometry (IP-MS). Then we used co-immunoprecipitation and laser confocal microscopy to further validate the interaction between LYZ and NSP8. Next, we found that LYZ was downregulated at transcription level and upregulated at protein level during PEDV infection. Furthermore, overexpression of LYZ promoted PEDV replication and knockdown of LYZ restrained PEDV replication, indicating that LYZ had a positive regulatory effect on PEDV infection. We further found that the domain of LYZ that regulates PEDV replication is in the N-terminal region. In addition, we found that LYZ inhibits IRF3 phosphorylation, nuclear translocation, and IFN-β production, Knockdown of LYZ showed the opposite trend. Mechanistically, LYZ downregulated the transcriptional level of RIG-I through the YTHDF2, thereby affecting the degradation of RIG-I endogenous proteins and inhibiting innate immunity. In conclusion, LYZ degrades RIG-I transcripts through the YTHDF2, inhibits IFN-β production, thus promotes viral replication. Our study provides novel insights into the pathogenesis of PEDV.