(p)ppGpp合成酶RelA与HPrK互作调控猪链球菌碳代谢和致病性的分子机制

细菌耐药性问题日益严重，新抗菌药物靶标的发现是开发抗耐药菌感染的关键。针对病原菌特异代谢途径和毒力因子是抗菌药物靶标发现的两个重要途径。我们的前期研究发现，细菌第二信使(p)ppGpp合成酶RelA不仅调控猪链球菌（SS）碳源饥饿下的严谨反应，还可以调控SS的致病性；RelA可以与SS的PTS/CCR信号通路中的组蛋白丝氨酸激酶（HPrK）互作并增强其激酶活性。由此我们提出了“RelA通过与HPrK互作增强HPrK激酶活性，通过CCR调控SS的碳代谢和致病性”的科学假设。本项目将鉴定RelA-HPrK互作的结构域/位点，构建相应的基因缺失或突变菌株，并用这些菌株和野生型菌株研究RelA、HPrK及其相互作用对HPrK激酶活性、碳代谢和毒力的调控作用及机制，评价RelA和HPrK作为抗菌药物靶标的潜力，为同时作用于病原菌代谢途径和毒力的抗菌药物靶标的发现及药物设计与筛选提供新思路。

Antimicrobial resistance (AMR) is becoming more and more serious worldwide. The discovery of new antimicrobial targets is the key to the development of novel drugs to tackle the challenge of AMR. The specific metabolic pathways and virulence factors are two most important routes for the discovery of antimicrobial targets. Our previous study found that RelA, the synthetase of (p)ppGpp, the second messenger of bacteria, not only regulates the stringent response induced by carbon source starvation in Streptococcus suis (SS), but also regulates its pathogenicity. RelA could interact with histone serine kinase (HPrK) in the PTS/CCR carbon transport and metabolic pathway, and enhance the kinase activity of HPrK. Therefore, we propose a scientific hypothesis that RelA-HPrK interaction can enhance the kinase activity of HPrK, and regulate the carbon metabolism and pathogenicity of SS through the CCR pathway. In this proposal, we will first identify the RelA-HPrK interaction domains and sites, and then construct the corresponding gene-deletion or mutation strains, and use these strains and the wild-type strain to study the regulatory effects and mechanisms of RelA, HPrK and their interaction on the kinase activity HPrK, carbon metabolism and virulence, and evaluate the potential of RelA and HPrK as antimicrobial targets. This will provide a promising strategy to identify novel antimicrobial drug targets simultaneously acting on the metabolic pathway and virulence of pathogenic bacteria.