Cytoplasmic translocation of tripartite motif-containing 28 is critical for PRRSV-induced autophagy through promoting Vps34-Beclin1 complex formation.

Autophagy, as a highly conserved cellular metabolic regulation mechanism, is a double-edged sword and plays multiple roles in viral infections processes. As a member of the Arteriviridae family within the order Nidovirales, the porcine reproductive and respiratory syndrome virus (PRRSV) induces cell autophagy both in vitro and in vivo. However, the direct or indirect causation of autophagy by PRRSV remains unclear. Identified as an autophagy-related factor, tripartite motif-containing 28 (TRIM28) shows an undefined relationship with autophagy during PRRSV infection. This study investigates the dynamic changes in autophagy and TRIM28 during PRRSV infection, revealing that PRRSV Nsp4 is identified as a key component responsible for the nuclear export of TRIM28 via a CRM1-dependent pathway, promoting the formation of the Vps34-Beclin1 complex and ultimately initiating autophagy. As a host protein, TRIM28 has exerted a certain antiviral effect, but the mechanism is not yet clear. This study provides detailed insight into the mechanism of PRRSV-mediated autophagy for the first time, offering valuable information for understanding the pathogenesis of porcine reproductive and respiratory syndrome. IMPORTANCE: PRRS is one of the major diseases affecting the global swine industry. Infection with PRRSV can cause respiratory disease in pigs of all ages and reproductive disorders in sows. Therefore, understanding the interaction between PRRSV and host factors may help to develop new antiviral strategies against PRRSV. We found that PRRSV Nsp4 was important for nuclear export of TRIM28 in a CRM1-dependent manner during PRRSV infection. TRIM28 in the cytoplasm increases the formation of VPS34-Beclin1 complex by interacting with Vps34, further initiating autophagy. Hence, our study reveals a novel mechanism of PRRSV-mediated autophagy and provides valuable information for further understanding the pathogenesis of PRRS, which might contribute to the development of novel antiviral drugs.