College of Veterinary Medicine, Jilin University, Changchun, Jilin, China.
Key Laboratory of Animal Immunology of the Ministry of Agriculture, Henan Provincial Key Laboratory of Animal Immunology, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China.
J Virol. 2020 May 4;94(10). doi: 10.1128/JVI.00097-20.
Porcine reproductive and respiratory syndrome (PRRS) is a serious viral disease affecting the global swine industry. Its causative agent, PRRS virus (PRRSV), is an enveloped virus, and therefore membrane fusion between its envelope and host cell target membrane is critical for viral infection. Though much research has focused on PRRSV infection, the detailed mechanisms involved in its membrane fusion remain to be elucidated. In the present study, we performed confocal microscopy in combination with a constitutively active (CA) or dominant negative (DN) mutant, specific inhibitors, and small interfering RNAs (siRNAs), as well as multiple other approaches, to explore PRRSV membrane fusion. We first observed that PRRSV membrane fusion occurred in Rab11-recycling endosomes during early infection using labeled virions and subcellular markers. We further demonstrated that low pH and cathepsin E in Rab11-recycling endosomes are critical for PRRSV membrane fusion. Moreover, PRRSV glycoprotein 5 (GP5) is identified as being cleaved by cathepsin E during this process. Taken together, our findings provide in-depth information regarding PRRSV pathogenesis, which support a novel basis for the development of antiviral drugs and vaccines. PRRS, caused by PRRSV, is an economically critical factor in pig farming worldwide. As PRRSV is a lipid membrane-wrapped virus, merging of the PRRSV envelope with the host cell membrane is indispensable for viral infection. However, there is a lack of knowledge on its membrane fusion. Here, we first explored when and where PRRSV membrane fusion occurs. Furthermore, we determined which host cell factors were involved in the process. Importantly, PRRSV GP5 is shown to be cleaved by cathepsin E during membrane fusion. Our work not only provides information on PRRSV membrane fusion for the first time but also deepens our understanding of the molecular mechanisms of PRRSV infection, which provides a foundation for future applications in the prevention and control of PRRS.
猪繁殖与呼吸综合征（PRRS）是一种严重影响全球养猪业的病毒性疾病。其病原体是猪繁殖与呼吸综合征病毒（PRRSV），它是一种包膜病毒，因此包膜与宿主细胞膜之间的膜融合对于病毒感染至关重要。尽管已经有大量研究关注 PRRSV 的感染，但病毒膜融合的详细机制仍有待阐明。在本研究中，我们使用标记的病毒粒子和亚细胞标记物，通过共聚焦显微镜观察，以及采用组成型激活（CA）或显性负性（DN）突变体、特异性抑制剂和小干扰 RNA（siRNA）等多种方法，来探索 PRRSV 的膜融合。我们首先观察到，在早期感染过程中，PRRSV 膜融合发生在 Rab11 再循环内体中。我们进一步证明，Rab11 再循环内体中的低 pH 值和组织蛋白酶 E 对于 PRRSV 膜融合至关重要。此外，PRRSV 糖蛋白 5（GP5）在这个过程中被组织蛋白酶 E 切割。总之，我们的研究结果为 PRRSV 的发病机制提供了深入的信息，为抗病毒药物和疫苗的开发提供了新的依据。由 PRRSV 引起的 PRRS 是全球养猪业的一个具有重大经济意义的因素。由于 PRRSV 是一种脂质膜包裹的病毒，因此 PRRSV 包膜与宿主细胞膜的融合对于病毒感染是必不可少的。然而，对于其膜融合的机制仍知之甚少。在这里，我们首次探索了 PRRSV 膜融合发生的时间和地点。此外，我们确定了哪些宿主细胞因子参与了这一过程。重要的是，PRRSV GP5 在膜融合过程中被组织蛋白酶 E 切割。我们的工作不仅首次提供了关于 PRRSV 膜融合的信息，还加深了我们对 PRRSV 感染分子机制的理解，为今后在 PRRS 的预防和控制方面的应用提供了基础。
