Li Quan, Fu Yang, Guo Genglin, Wang Zhuohao, Zhang Wei
MOE Joint International Research Laboratory of Animal Health and Food Safety, Key Lab of Animal Bacteriology of Ministry of Agriculture, OIE Reference Lab for Swine Streptococcosis, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, China.
College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.
AMB Express. 2020 Jun 1;10(1):103. doi: 10.1186/s13568-020-01042-2.
Streptococcus suis, a major emerging pathogen in swine and humans, expresses immunoglobulin G (IgG)-binding proteins (IBPs), which contribute to the ability of organism to evasion of host immune system. The objective of this study was to identify novel pig IgG (pIgG) and human IgG (hIgG)-binding proteins and characterize the binding regions of enolase from Streptococcus suis serotype 2 (S. suis 2). Here, four pIgG-binding proteins (pIBPs) and five hIgG-binding proteins (hIBPs) were identified from S. suis 2 surface proteins by 2D-Far-western blot assays. All the newly captured proteins were expressed and further confirmed their binding activity to pIgG or hIgG by Far-western blot and dot blot. In addition to previously identified factor H, fibronectin, collagen, fibrinogen, plasminogen and laminin, we also found that both pIgG and hIgG can specifically interact with enolase. Binding assays indicated that interactions of S. suis 2 enolase with pIgG and hIgG is primarily mediated by the enolase C-terminal portion (Enolase-C, a.a. 142-432). We found that hIgG exhibited stronger binding ability to Enolase-C than pIgG. Further analysis of the C-terminal regions of enolase (Enolase-C1 and Enolase-C2) suggested that the C-terminus possessed two different binding domains with distinct host IgG proteins. Strikingly, we confirmed that pIgG interacted with the Enolase-C1 (a.a. 142-271) and hIgG interacted with the Enolase-C2 (a.a. 271-432). These observations of enolase provide interesting insights in the pathogenesis of S. suis infection.
猪链球菌是猪和人类中一种主要的新兴病原体，它表达免疫球蛋白G（IgG）结合蛋白（IBP），这有助于该生物体逃避宿主免疫系统。本研究的目的是鉴定新的猪IgG（pIgG）和人IgG（hIgG）结合蛋白，并表征2型猪链球菌（猪链球菌2型）烯醇化酶的结合区域。在此，通过二维Far-Western印迹分析从猪链球菌2型表面蛋白中鉴定出四种pIgG结合蛋白（pIBP）和五种hIgG结合蛋白（hIBP）。所有新捕获的蛋白均被表达，并通过Far-Western印迹和斑点印迹进一步证实它们与pIgG或hIgG的结合活性。除了先前鉴定的因子H、纤连蛋白、胶原蛋白、纤维蛋白原、纤溶酶原和层粘连蛋白外，我们还发现pIgG和hIgG均可与烯醇化酶特异性相互作用。结合试验表明，猪链球菌2型烯醇化酶与pIgG和hIgG的相互作用主要由烯醇化酶C末端部分（烯醇化酶-C；氨基酸142 - 432）介导。我们发现hIgG对烯醇化酶-C的结合能力比pIgG更强。对烯醇化酶C末端区域（烯醇化酶-C1和烯醇化酶-C2）的进一步分析表明，C末端具有两个不同的与不同宿主IgG蛋白结合的结构域。令人惊讶的是，我们证实pIgG与烯醇化酶-C1（氨基酸142 - 271）相互作用，而hIgG与烯醇化酶-C2（氨基酸271 - 432）相互作用。这些关于烯醇化酶的数据为猪链球菌感染的发病机制提供了有趣的见解。
