The glycoprotein 5 of porcine reproductive and respiratory syndrome virus stimulates mitochondrial ROS to facilitate viral replication

ABSTRACT Viruses have evolved sophisticated mechanisms to manipulate host cell organelles to serve as niches for persistence and proliferation. In the present study, we aimed to investigate the role of cellular organelles in the replication of porcine reproductive and respiratory syndrome virus (PRRSV). We found that the morphology of mitochondria and the endoplasmic reticulum (ER) were both altered, and the contact between these two organelles was enhanced during PRRSV infection. By the overexpression of PRRSV-encoded open reading frames, we identified that only glycoprotein 5 (GP5) was essential for ER-mitochondria contact. Further investigation revealed that GP5 interacted with the ER inositol 1,4,5-triphosphate receptor (IP3R) and the mitochondrial voltage-dependent anion channel (VDAC1) to promote the Ca 2+ efflux from ER into mitochondria. Excessive mitochondrial Ca 2+ uptake resulted in mitochondrial dysfunction and substantial mitochondrial reactive oxygen species (mROS) production. Elevated mROS activated autophagy through the AMPK/mROR/ULK1 axis to facilitate PRRSV replication. GP5-induced mROS also triggered the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome. Inhibition of autophagy augmented NLRP3 inflammasome activation and exhibited an anti-PRRSV effect, suggesting autophagy counteracted the NLRP3-mediated innate immune response. Overall, our findings highlighted the importance of cellular organelles in virus-host interactions and provided new insights into the complex interplay between virus replication and innate immune responses. IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV) presents a significant economic concern for the global swine industry due to its connection to serious production losses and increased mortality rates. There is currently no specific treatment for PRRSV. Previously, we had uncovered that PRRSV-activated lipophagy to facilitate viral replication. However, the precise mechanism that PRRSV used to trigger autophagy remained unclear. Here, we found that PRRSV GP5 enhanced mitochondrial Ca 2+ uptake from ER by promoting ER-mitochondria contact, resulting in mROS release. Elevated mROS induced autophagy, which alleviated NLRP3 inflammasome activation for optimal viral replication. Our study shed light on a novel mechanism revealing how PRRSV exploits mROS to facilitate viral replication.