College of Veterinary Medicine, Hunan Agricultural University, Changsha, 410125, China.
Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, 410125, China.
J Microbiol. 2023 Apr;61(4):433-448. doi: 10.1007/s12275-023-00038-4. Epub 2023 Apr 3.
Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen that can infect humans in contact with infected pigs or their byproducts. It can employ different types of genes to defend against oxidative stress and ensure its survival. The thioredoxin (Trx) system is a key antioxidant system that contributes adversity adaptation and pathogenicity. SS2 has been shown to encode putative thioredoxin genes, but the biological roles, coding sequence, and underlying mechanisms remains uncharacterized. Here, we demonstrated that SSU05_0237-ORF, from a clinical SS2 strain, ZJ081101, encodes a protein of 104 amino acids with a canonical CGPC active motif and an identity 70-85% similar to the thioredoxin A (TrxA) in other microorganisms. Recombinant TrxA efficiently catalyzed the thiol-disulfide oxidoreduction of insulin. The deletion of TrxA led to a significantly slow growth and markedly compromised tolerance of the pathogen to temperature stress, as well as impaired adhesion ability to pig intestinal epithelial cells (IPEC-J2). However, it was not involved in HO and paraquat-induced oxidative stress. Compared with the wild-type strain, the ΔTrxA strain was more susceptible to killing by macrophages through increasing NO production. Treatment with TrxA mutant strain also significantly attenuated cytotoxic effects on RAW 264.7 cells by inhibiting inflammatory response and apoptosis. Knockdown of pentraxin 3 in RAW 264.7 cells was more vulnerable to phagocytic activity, and TrxA promoted SS2 survival in phagocytic cells depending on pentraxin 3 activity compared with the wild-type strain. Moreover, a co-inoculation experiment in mice revealed that TrxA mutant strain is far more easily cleared from the body than the wild type strain in the period from 8-24 h, and exhibits significantly attenuated oxidative stress and liver injury. In summary, we reveal the important role of TrxA in the pathogenesis of SS2.
猪链球菌 2 型（SS2）是一种重要的人畜共患病病原体，可通过接触感染猪或其副产品而感染人类。它可以利用不同类型的基因来抵御氧化应激并确保其存活。硫氧还蛋白（Trx）系统是一种关键的抗氧化系统，有助于逆境适应和致病性。已经表明 SS2 编码了推定的硫氧还蛋白基因，但生物学作用、编码序列和潜在机制仍未被描述。在这里，我们证明了来自临床 SS2 菌株 ZJ081101 的 SSU05_0237-ORF 编码了一种 104 个氨基酸的蛋白质，具有典型的 CGPC 活性基序，与其他微生物中的硫氧还蛋白 A（TrxA）的同一性为 70-85%。重组 TrxA 有效地催化胰岛素的巯基-二硫键氧化还原反应。TrxA 的缺失导致病原体的生长明显缓慢，对温度应激的耐受性显著降低，对猪肠上皮细胞（IPEC-J2）的粘附能力也受损。然而，它不参与 HO 和百草枯诱导的氧化应激。与野生型菌株相比，ΔTrxA 菌株更容易被巨噬细胞通过增加 NO 产生而杀伤。用 TrxA 突变株处理也显著抑制了 RAW 264.7 细胞的细胞毒性作用，通过抑制炎症反应和细胞凋亡。RAW 264.7 细胞中 pentraxin 3 的敲低更容易受到吞噬活性的影响，并且 TrxA 促进了 SS2 在吞噬细胞中的存活，这依赖于 pentraxin 3 的活性，与野生型菌株相比。此外，在小鼠中的共接种实验表明，与野生型菌株相比，TrxA 突变株在 8-24 小时期间从体内更易被清除，并且表现出明显减轻的氧化应激和肝损伤。总之，我们揭示了 TrxA 在 SS2 发病机制中的重要作用。
