Potassium molybdate blocks APN-dependent coronavirus entry by degrading receptor via PIK3C3-mediated autophagy

Summary

Swine enteric coronaviruses pose a significant challenge to the global pig industry, inflicting severe diarrhea and high mortality rates among piglets, and resulting in substantial economic losses. In our clinical practice, we observed that the addition of potassium molybdate (PM) to the feed could dramatically reduce diarrhea and diarrhea-related mortality in piglets. However, the underlying mechanisms remain elusive and merit further investigation. In this study, we revealed that PM effectively inhibited the infection of both aminopeptidase N (APN)-dependent coronaviruses, transmissible gastroenteritis virus (TGEV), and porcine respiratory coronavirus (PRCV), both in vitro and ex vivo. Specifically, PM was found to block TGEV and PRCV penetration by degrading the cell receptor APN through the upregulation of phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3) expression. In addition, knockdown and knockout of PIK3C3 resulted in the attenuation of PM-induced autophagy, thereby rescuing APN expression and viral infection. Correspondingly, replenishment of PIK3C3 in PIK3C3-null ST cells restored PM-mediated APN degradation and successfully blocked viral entry. Furthermore, our findings demonstrated that PM promoted the assembly of the PIK3C3-BECN1-ATG14 complex, leading to induced autophagic degradation by upregulating PIK3C3 Ser249 phosphorylation. In vivo experiments further confirmed that PM-induced PIK3C3-mediated autophagic degradation of APN, thereby limiting the pathogenicity of TGEV. In summary, our study for the first time identified the mechanism by which PM blocked TGEV and PRCV internalization by degrading the cell receptor APN via PIK3C3-mediated autophagy. This study provides valuable insights and potential strategies for preventing APN-restricted coronavirus infection.