African Swine Fever Virus MGF110-7L Induces Host Cell Translation Suppression and Stress Granule Formation by Activating the PERK/PKR-eIF2α Pathway

African swine fever (ASF) is a highly contagious and often lethal disease of pigs caused by ASF virus (ASFV) and recognized as the biggest killer in global swine industry. Despite exhibiting incredible self-sufficiency, ASFV remains unconditionally dependent on the host translation machinery for its mRNA translation. However, less is yet known regarding how ASFV-encoded proteins regulate host translation machinery in infected cells. Here, we examined how ASFV interacts with the eukaryotic initiation factor 2 alpha (eIF2 alpha) signaling axis, which directs host translation control and adaptation to cellular stress. We found that ASFV MGF110-7L, a previously uncharacterized member of the multigene family 110, remarkably enhanced the phosphorylation level of eIF2 alpha. In porcine alveolar macrophage 3D4/21 and porcine kidney-15 cells, MGF110-7L triggered eIF2a signaling and the integrated stress response, resulting in the suppression of host translation and the formation of stress granules (SGs). Mechanistically, MGF110-7L-induced phosphorylation of eIF2 alpha was mediated via protein kinase R (PKR) and PKR-like endoplasmic reticulum (ER) kinase (PERK), and this process was essential for host translation repression and SG formation. Notably, our subsequent analyses confirmed that MGF110-7L was overwhelmingly retained in the ER and caused a specific reorganization of the secretory pathway. Further proteomic analyses and biochemical experiments revealed that MGF110-7L could trigger ER stress and activate the unfolded protein response, thus contributing to eIF2 alpha phosphorylation and translation reprogramming. Overall, our study both identifies a novel mechanism by which ASFV MGF110-7L subverts the host protein synthesis machinery and provides further insights into the translation regulation that occurs during ASFV infection. IMPORTANCE African swine fever (ASF) has become a socioeconomic burden and a threat to food security and biodiversity, but no commercial vaccines or antivirals are available currently. Understanding the viral strategies to subvert the host translation machinery during ASF virus (ASFV) infection could potentially lead to new vaccines and antiviral therapies. In this study, we dissected how ASFV MGF110-7L interacts with the eIF2 alpha signaling axis controlling translational reprogramming, and we addressed the role of MGF110-7L in induction of cellular stress responses, eIF2 alpha phosphorylation, translation suppression, and stress granule formation. These results define several molecular interfaces by which ASFV MGF110-7L subverts host cell translation, which may guide research on antiviral strategies and dissection of ASFV pathogenesis.

Automated summary

African swine fever (ASF) is a highly contagious and lethal disease of pigs caused by ASF virus (ASFV). In this study, the researchers investigated how ASFV MGF110-7L interacts with the eIF2 alpha signaling axis to control host translation and induce stress responses. They found that MGF110-7L triggers eIF2 alpha phosphorylation, translation suppression, and stress granule formation. Furthermore, MGF110-7L induces ER stress and the unfolded protein response, leading to translation reprogramming. These findings provide important insights into the translation regulation during ASFV infection and could guide the development of antiviral strategies.