MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, Jiangsu, China.
College of Veterinary Medicine, Chungnam National University, Daejeon, South Korea.
J Virol. 2021 Apr 12;95(9). doi: 10.1128/JVI.02344-20.
Porcine epidemic diarrhea virus (PEDV) is an α-coronavirus causing severe diarrhea and high mortality rates in suckling piglets and posing significant economic impact. PEDV replication is completed and results in a large amount of RNA in the cytoplasm. Stress granules (SGs) are dynamic cytosolic RNA granules formed under various stress conditions, including viral infections. Several previous studies suggested that SGs were involved in the antiviral activity of host cells to limit viral propagation. However, the underlying mechanisms are poorly understood. This study aimed to delineate the molecular mechanisms regulating the SG response to PEDV infection. SG formation is induced early during PEDV infection, but as infection proceeds, this ability is lost and SGs disappear at late stages of infection (>18 h postinfection). PEDV infection resulted in the cleavage of Ras-GTPase-activating protein-binding protein 1 (G3BP1) mediated by caspase-8. Using mutational analysis, the PEDV-induced cleavage site within G3BP1 was identified, which differed from the 3C protease cleavage site previously identified. Furthermore, G3BP1 cleavage by caspase-8 at D168 and D169 was confirmed as well as The overexpression of cleavage-resistant G3BP1 conferred persistent SG formation and suppression of viral replication. Additionally, the knockdown of endogenous G3BP1 abolished SG formation and potentiated viral replication. Taken together, these data provide new insights into novel strategies in which PEDV limits the host stress response and antiviral responses and indicate that caspase-8-mediated G3BP1 cleavage is important in the failure of host defense against PEDV infection. Coronaviruses (CoVs) are drawing extensive attention again since the outbreaks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019. CoVs are prone to variation and own the transmission capability by crossing the species barrier resulting in reemergence. How CoVs manipulate the antiviral responses of their hosts needs to be explored. Overall, the study provides new insight into how porcine epidemic diarrhea virus (PEDV) impaired SG assembly by targeting G3BP1 via the host proteinase caspase-8. These findings enhanced the understanding of PEDV infection and might help identify new antiviral targets that could inhibit viral replication and limit the pathogenesis of PEDV.
猪流行性腹泻病毒（PEDV）是一种α冠状病毒，可导致仔猪严重腹泻和高死亡率，并造成重大经济影响。PEDV 的复制在细胞质中完成，并导致大量 RNA 的产生。应激颗粒（SGs）是在各种应激条件下形成的动态细胞质 RNA 颗粒，包括病毒感染。先前的几项研究表明，SGs 参与宿主细胞的抗病毒活性，以限制病毒的繁殖。然而，其潜在机制尚不清楚。本研究旨在阐明调节 SG 对 PEDV 感染反应的分子机制。SG 的形成在 PEDV 感染早期被诱导，但随着感染的进行，这种能力丧失，SG 在感染后期（感染后 18 小时以上）消失。PEDV 感染导致 Ras-GTPase-激活蛋白结合蛋白 1（G3BP1）被半胱天冬酶-8 切割。通过突变分析，确定了 G3BP1 内由 PEDV 诱导的切割位点，该位点与先前鉴定的 3C 蛋白酶切割位点不同。此外，还证实了半胱天冬酶-8 在 D168 和 D169 处对 G3BP1 的切割以及对切割抗性 G3BP1 的过表达赋予了持续的 SG 形成和抑制病毒复制的能力。此外，内源性 G3BP1 的敲低消除了 SG 的形成并增强了病毒的复制。总之，这些数据为 PEDV 限制宿主应激反应和抗病毒反应的新策略提供了新的见解，并表明半胱天冬酶-8 介导的 G3BP1 切割在宿主防御对抗 PEDV 感染的失败中很重要。自 2019 年严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）爆发以来，冠状病毒再次引起广泛关注。冠状病毒容易发生变异，并具有通过跨越物种屏障传播的能力，从而导致再次出现。冠状病毒如何操纵宿主的抗病毒反应需要进一步研究。总的来说，本研究提供了新的见解，即猪流行性腹泻病毒（PEDV）通过宿主蛋白酶半胱天冬酶-8 靶向 G3BP1 来破坏 SG 的组装。这些发现加深了对 PEDV 感染的认识，并可能有助于确定新的抗病毒靶点，从而抑制病毒复制并限制 PEDV 的发病机制。
