儿茶酚胺类激素与胸膜肺炎放线杆菌组氨酸激酶YgiY的相互作用及其信号传导通路

The host catecholamines can modulate many bacterial behaviors including growth and virulence. The interactions between microbes and host stress signals have provided new explanations of the reason why stress can increase the susceptibility of humans and animals to infectious disease. These phenomena have also opened a new perspective of study on bacterial pathogenesis. Actinobacillus pleuropneumoniae is an important swine respiratory pathogen, causing substantial global economic losses in the pig industry. Our previous work has discovered that A. pleuropneumoniae can actively respond to catecholamines. On one hand, catecholamines promote A. pleuropneumoniae growth by regulating iron metabolism. On the other hand, many infection-associated genes of A. pleuropneumoniae can be regulated by catecholamines, possibly dependent on the candidate hormone receptor YgiY, a histidine kinase of A. pleuropneumoniae. In addition, the YgiY mediated regulations don’t play roles in the growth stimulation. This project aims to further confirm the function of YgiY as catecholamines receptor and the interaction structures between the hormones and the receptor, and also investigate the catecholamines signaling pathways in A. pleuropneumoniae mediated by YgiY. The results will give further understandings of the mechanism of A. pleuropneumoniae response to catecholamines and A. pleuropneumoniae pathogenesis. Meanwhile, this study can contribute to more explanations of the essential roles of pathogenic bacteria in the processes of stress and disease development, and also help to develop novel anti-bacteria drugs and disease prevention strategies.

宿主的儿茶酚胺类激素能调节细菌的生长和毒力等多种行为，这种微生物与宿主应激激素之间的相互作用现象为应激导致人和动物对疾病易感性增加的现象提供了新的解释，也开辟了病原菌致病机理研究的新视角。胸膜肺炎放线杆菌（APP）是严重危害世界养猪业的重要呼吸道病原菌。申请人前期研究发现APP能主动响应儿茶酚胺类激素，一方面通过铁代谢机制调节APP生长，另一方面可能通过候选激素受体（组氨酸激酶YgiY）调控大量APP感染相关基因的表达，但不参与生长调节。本项目拟进一步验证YgiY的儿茶酚胺类激素受体功能及其与激素互作的结构位点，并解析其介导的激素信号传导通路。研究结果能够深入阐释APP对儿茶酚胺类激素的响应机制，为APP的致病机理以及病原菌在应激和感染性疾病中扮演的重要角色提供新的理论依据，对新型抗菌药物和抗感染策略的研发具有重要的意义。

当应激发生时，神经激素能直接作用于免疫系统，影响免疫系统的功能。同时，病原微生物能够主动感应宿主的应激激素，调节自身的生长以及毒力基因的表达等行为。这种现象为应激导致人和动物对疾病易感性增加这一普遍现象提供了新的解释，也开辟了病原菌致病机理研究的新视角。目前已有较多报道表明多种病原菌能主动响应宿主的儿茶酚胺类激素，但仅在大肠中解析了激素受体及其介导的信号传导通路，且病原菌感应宿主激素的机制一直存在“铁利用机制假说”和“激素受体假说”之争，对激素调控病原菌行为的机制尚无定论。本项目以猪的病原菌胸膜肺炎放线杆菌（APP）对象，对儿茶酚胺类激素在该菌中的受体及其下游的信号传导通路进行了研究。研究中证明了低剂量的儿茶酚胺类激素能够增加APP在动物体内的的致病性。以前期研究发现的APP中受到儿茶酚胺类激素调控的双组份系统QseC/B（YgiY/X）和NarQ/P为对象，验证了组氨酸激酶QseC（YgiY）是APP的儿茶酚胺类激素受体。通过磷酸化传递实验，鉴定了QseB（YgiX）和NarP都是QseC下游的调控蛋白。建立了一种细菌中高通量筛选转录因子结合序列的DAP-Seq方法，用该方法鉴定了QseB和NarP的靶基因，其中2个靶基因在APP感染中的功能已知，解析了另外2个靶基因flp1和ftpA在APP生长和毒力调控中的功能。同时，用转录组学方法初步解析了QseC/B和NarP介导的APP在缺铁环境下感应激素的信号传导通路。本项目的研究结果结合本研究前期工作基础，证明了APP中同时存在“铁利用”和“激素受体”机制感应宿主的儿茶酚胺类激素，为病原菌感应应激激素的机制提供了新的理论依据，为APP等病原菌在宿主应激环境下致病性增加这一现象提供了新的解释，也为研发抗应激和抗感染性疾病的防控策略提供了新的线索。