Seneca Valley virus induces mitochondrial apoptosis by activating ER stress or the PERK pathway based on Ca2+ transfer from ER to mitochondria

Seneca Valley virus (SVV), also known as Senecavirus A, a porcine pathogen that causes vesicular diseases, is prevalent in pig herds worldwide. SVV Infection induces endoplasmic reticulum (ER) stress in PK-15 and BHK-21 cells, accompanied by activation of the protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) and activating transcription factor 6 (ATF6) pathways, which in turn facilitates SVV replication. ER stress is associated with the regulation of CA²⁺ homeostasis and mitochondrial Apoptosis. However, the precise role of CA²⁺ in SVV-induced Apoptosis remains unclear. In this study, western blotting, flow cytometry, and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) detection revealed that either ER stress or the PERK pathway is involved in the Apoptosis of SVV-infected cells treated with specific inhibitors. Furthermore, SVV-mediated ER stress markedly contributed to the transfer of CA²⁺ from the ER to mitochondria. The subsequent increase in mitochondrial CA²⁺ content was accompanied by an increased number of ER membranes near the mitochondria. Finally, the inhibition of mitochondrial CA²⁺ overload, ER stress, and the PERK pathway substantially attenuated SVV-mediated mitochondrial dysfunction, as evidenced by analyzing mitochondrial membrane potential (MMP), mitochondrial permeability transition poremPTP, reactive oxygen speciesROS, and adenosine 5'-triphosphate ATP, and the levels of mitochondrial Apoptosis. These findings demonstrate that SVV induces mitochondrial Apoptosis, which is dependent on ER stress-mediated transmission of CA²⁺ from the ER to the mitochondria.

Importance: Viruses have developed multiple mechanisms to facilitate their proliferation or persistence through manipulating various organelles in cells. Seneca Valley virus (SVV), as a novel emerging pathogen associated with vesicular disease, is clinically and economically important infections that affect farm Animals. Previously, we had confirmed that SVV-induced endoplasmic reticulum (ER) stress benefited for viral replication. CA²⁺, as an intracellular signaling messenger mainly stored in the ER, is regulated by ER stress and then involved in Apoptosis. However, the precise mechanism that CA²⁺ transfer induced by SVV Infection triggered Apoptosis remained unclear. Here, we found that SVV Infection triggered the CA²⁺ transform from ER to mitochondria, resulting in mitochondrial dysfunction, and finally induced mitochondrial Apoptosis. Our study shed light on a novel mechanism revealing how ER stress manipulates CA²⁺ homeostasis to induce mitochondrial Apoptosis and regulate viral proliferation.