College of Veterinary Medicine, Hebei Agricultural University, Baoding, China.
Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China.
Front Immunol. 2022 Apr 26;13:887054. doi: 10.3389/fimmu.2022.887054. eCollection 2022.
Porcine reproductive and respiratory syndrome virus (PRRSV) is an RNA virus that causes great economic losses globally to the swine industry. Innate immune RNA receptors mainly sense it during infection. As a DNA sensor, cyclic GMP-AMP synthase (cGAS) plays an important role in sensing cytosolic DNA and activating innate immunity to induce IFN-I and establish an antiviral cellular state. In contrast, the role of innate immune DNA sensors during PRRSV infection has not been elucidated. In this study, we found that cGAS facilitates the production of IFN-β during PRRSV infection. Western blot and virus titer assays suggested that cGAS overexpression suppressed the replication of multiple PRRSV strains, while knockout of cGAS increased viral titer and nucleocapsid protein expression. Besides, our results indicated that the mitochondria were damaged during PRRSV infection and leaked mitochondrial DNA (mtDNA) into the cytoplasm. The mtDNA in the cytoplasm co-localizes with the cGAS, and the cGAMP activity was increased when the cGAS was overexpressed during PRRSV infection. Furthermore, the cGAMP also possesses an anti-PRRSV effect. These results indicate for the first time that cGAS restricts PRRSV replication by sensing the mtDNA in the cytoplasm to increase cGAMP activity, which not only explains the molecular mechanism by which cGAS inhibits PRRSV replication but also provides research ideas for studying the role of the cGAS-STING signaling pathway in the process of RNA virus infection.
猪繁殖与呼吸综合征病毒（PRRSV）是一种 RNA 病毒，它会给全球的养猪业造成巨大的经济损失。固有免疫 RNA 受体主要在感染过程中感知它。作为一种 DNA 传感器，环鸟苷酸-腺苷酸合酶（cGAS）在感知细胞质 DNA 和激活固有免疫以诱导 IFN-I 并建立抗病毒细胞状态方面发挥着重要作用。相比之下，固有免疫 DNA 传感器在 PRRSV 感染过程中的作用尚未阐明。在本研究中，我们发现 cGAS 促进了 PRRSV 感染期间 IFN-β 的产生。Western blot 和病毒滴度测定表明，cGAS 过表达抑制了多种 PRRSV 株的复制，而 cGAS 的敲除则增加了病毒滴度和核衣壳蛋白的表达。此外，我们的结果表明，PRRSV 感染会导致线粒体受损，并将线粒体 DNA（mtDNA）漏入细胞质。细胞质中的 mtDNA 与 cGAS 共定位，并且当 cGAS 在 PRRSV 感染过程中过表达时，cGAMP 活性增加。此外，cGAMP 还具有抗 PRRSV 的作用。这些结果首次表明，cGAS 通过感知细胞质中的 mtDNA 来增加 cGAMP 活性来限制 PRRSV 的复制，这不仅解释了 cGAS 抑制 PRRSV 复制的分子机制，也为研究 cGAS-STING 信号通路在 RNA 病毒感染过程中的作用提供了研究思路。
