毒力因子EspN调控巨噬细胞增加病原菌致病性的作用机制研究

近年来新的强致病性病原体不断出现，获得外源基因促使其感染能力和毒力增强是重要原因。前噬菌体是细菌间基因水平转移的重要载体，编码许多重要毒素或新的毒力因子。因此挖掘前噬菌体携带的潜在毒力因子，阐明其作用机制具有重要意义。本课题组前期通过比较基因组发现了一个前噬菌体编码分子EspN，在病原菌间广泛存在，但生理功能和作用机制均未有报道。前期我们发现EspN显著提高病原菌在巨噬细胞的定殖水平，增加感染小鼠死亡率，并且定位于宿主细胞溶酶体，提示它是一个新型毒力因子通过调控宿主溶酶体活性提升病原菌感染能力，但具体机制还有待阐释。本课题拟在上述基础上，阐明EspN调控宿主细胞溶酶体方式和作用靶点，解析EspN三维结构揭示其关键序列及与靶点相互作用方式，从病原和宿主两个角度解析EspN在感染致病中的作用，同时检测其随前噬菌体在病原菌转移的能力，以丰富病原菌对抗宿主防御系统理论，为病原菌防治提供研究基础。

Recent years, many new pathogens with strong virulence have emerged, and the acquisition of new virulence genes is an important reason. As an important carrier for horizontal transfer of virulence genes between bacteria, prophages encodes most of known toxins or virulence factors. It is very important to discover these new virulence factors in prophages and elucidate their mechanism of action in pathogen infection. In our previous study, we discovered a novel effector EspN encoded by prophage, which is widely existed in many pathogenic bacteria. We found that EspN was secreted into the host cells and located in the lysosome during pathogen infection, and significantly improved the pathogenicity of pathogen. All these results suggested that EspN is a potential virulence factor that regulates the lysosomal activity of host cells. However, the detailed function and molecular mechanism of EspN in pathogen infection remains to be explained. In this research, we will identified the the interaction targets of EspN in the lysosomes of host cells. And we will analyze the three-dimensional structure of EspN to reveal the key sequences or sites. Moreover, we will explore the physiological function of EspN during pathogen infection in cell or animal levles. Finally, we will analyze the possibility that the prohpages spread the espN gene in the genomes of different pathogens. This study will be helpful to deepen the understanding of the pathogenic bacteria pathogenesis, increase the knowledge about the mechanism of bacteria interaction with the lysosome of host cells, and enrich the theory of bacteria regulation of host response.