人畜共患病原体2型猪链球菌分泌蛋白SibA参与细胞分裂与致病的分子机制

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen. The secreted antigens play critical roles in bacterial infection. Here, we report a secreted protein referred to SibA from the epidemic strain 05ZYH33 of SS2. To test enzymatic activity in vitro, we over-expressed and purified the mature form of the SibA protein and its CHAP domain. By employing Western blot and immunoelectron microscopy with anti-SibA rabbit polyserum, we tried to probe its sub-cellular location of SibA on SS2 and its secretion into the growth medium. Through genetic inactivation of the sibA gene from SS2 and functional complementation of the △sibA mutant, we assayed its potential role in bacterial cell division. We conducted cell line and mice-based infection experiments to elucidate contribution of SibA to SS2 infectivity. We also examined the interaction between SibA and the two cell division-related proteins FtsE/FtsX, as well as its relevance to bacterial pathogenesis. These findings might extend our understanding of SS2 pathogenesis, and provide basis for the design of small molecule drug targeting the SS2 SibA protein.

2型猪链球菌(SS2)是一类严重的人畜共患病原体，其致病机理需要诸多分泌蛋白的参与。本项目将基于申请人前期发现的一个SS2分泌蛋白(SibA)开展其功能研究。拟获得SS2的SibA蛋白的成熟形式及其CHAP功能域，用于酶学机制研究；制备SibA蛋白的多抗血清，开展Western blot和免疫电镜等实验，解析其在SS2的胞外分泌及其亚细胞定位；构建sibA基因的缺失突变体和互补株，分析其在细胞分裂中的作用；基于细胞生物学和实验动物感染实验，阐述sibA基因对SS2感染的贡献；探明SibA与细胞分裂相关的2个蛋白（FtsE和FtsX）的互作，揭示其对细菌形态建成和感染侵袭的作用。该课题的实施将丰富对SS2感染机制的认识，并为靶向细胞分裂相关的SibA蛋白的药物研发奠定基础。

II型猪链球菌 (SS2)是一类严重的人畜共患病原体，其致病机理需要诸多分泌蛋白的参与。本项目基于申请人前期发现的一个SS2分泌蛋白(SibA)开展其功能研究。业已获得SS2的SibA蛋白的全长形式及其CHAP功能域，并开展了肽聚糖酶的酶学研究；制备SibA蛋白的多抗血清，进行了Western blot和免疫电镜分析，确认了其亚细胞定位和胞外分泌的特征；构建了sibA基因的缺失突变体与互补株，探明了其在细胞分裂中发挥了关键作用；基于细胞生物学和实验动物感染实验，夯实了sibA基因在SS2成功感染中扮演了重要角色。与此同时，本研究证实了SibA的2个互作蛋白(FtsE和FtsX)对于细菌的形态建成和感染侵袭不可或缺。此外，该课题亦拓展到SS2的NAD+代谢稳态的调控机制。简言之，该课题的开展，丰富了我们对SS2生理与感染机制的理论认知，为靶向“细胞分裂”这一新靶点的先导化合物的筛选与分子设计提供理论基础。