小核糖核酸Spot42调控大肠杆菌致病因素的研究

Pathogenic Escherichia coli can cause serious food poisoning, urinary tract infections or even death. Better understanding of E. coli virulence regulation and mechanisms can provide clues for development of new therapeutic strategies. E. coli is a prokaryotic model micro-organism. Information obtained from E. coli can shed lights on virulence regulation of other pathogens. Regulation of bacterial virulence is mediated by numerous regulatory factors, among which are small non-coding RNAs. Spot42 is a small non-coding RNA known to optimize catabolite repression by inhibiting some cyclic AMP receptor protein (CRP)-activated genes. Recently, our preliminary data have revealed the following：1. Spot42 enhances acid resistance and motility, two important virulence traits, of E.coli; 2. Spot42 enhances motility by reducing indole production; 3. Spot42 responds to acidic pH by increasing its own expression; 4. the glycolysis product pyruvate induces the expression of Spot42. These results indicate that there is a link among bacterial metabolism, indole signaling and virulence and that Spot42 is a key player mediating this process. In this project, we propose to systematically investigate Spot42 regulation of bacterial virulence traits and the underlying molecular mechanisms. The objects of this project include: 1. to identify Spot42-regulated genes and corresponding pathways; 2. to determine the pathway where Spot42 represses the indole production; 3. to identify upstream regulators of Spot42; 4. to determine the mechanism by which pyruvate induces Spot42; 5. to elucidate how Spot42 responds to acidic pH; 6. to uncover the Spot42-centered regulatory system linking bacterial metabolism, indole signling and virulence.

多数大肠杆菌对人体无害，但致病性大肠杆菌可引起严重腹泻，甚至死亡。了解大肠杆菌致病及调控机制对于更好地控制疾病至关重要。小核糖核酸是重要的细菌致病因素调控因子。本团队发现：1.小核糖核酸Spot42显著增强大肠杆菌抗酸和运动能力（两个致病因素）；2. 通过抑制信号分子吲哚的产生促进运动能力；3.感知环境酸性变化；4.受糖酵解产物丙酮酸激活。这些发现提示细菌代谢、细胞间信号传递和致病因素三者间存在关联，而Spot42则是三者的纽带。本项目将对此展开深入分析，完成下述目标：1. 确定Spot42调控抗酸和运动能力的靶基因；2.确定Spot42抑制吲哚的机制；3.确定Spot42的上游调控因子；4.确定丙酮酸激活Spot42的通路；5.确定Spot42对酸性环境作出反应的通路；6.明确Spot42为中心的代谢，信号传递和致病调控网络。

虽然大肠杆菌是人体肠道共栖菌，但有些种类的大肠杆菌可引起严重的肠道感染、炎症甚至癌症。了解大肠杆菌致病及调控机制以及识别致病性大肠杆菌对于更好地控制疾病至关重要，而小核糖核酸是重要的细菌致病因素和调控因子。本团队发现：1.小核糖核酸Spot42显著增强大肠杆菌抗外环境不利刺激（如酸刺激）；2. 通过抑制信号分子吲哚的产生促进运动能力；3.感知环境酸性变化；4.受糖酵解产物丙酮酸激活； 5. 某些Spot42(+)大肠杆菌与结肠癌的发生和转移相关； 6. 这些Spot42(+)大肠杆菌通过产生alpha-溶血酶刺激结肠上皮细胞的葡萄糖吸收，从而促进肿瘤的生成。这些发现提示细菌代谢、细胞间信号传递和致癌因素三者间的密切关联，而Spot42则是三者的纽带。这些研究成果对于深刻理解肠道疾病尤其是结肠癌的发病机制以及指导疾病早期发现和有效治疗具有深远的意义。