变异链球菌的致龋毒力与对环境刺激的耐受力密切相关，应激反应过程中， HSP100/ClpATPase通过双向调控作用调节细胞壁完整性和感受态形成，促进毒力因子进化。影响细胞壁稳定性和抑制感受态形成可降低变异链球菌致龋毒力，但目前尚未发现明确和有效的作用靶点。本课题组前期研究发现缺失细胞壁合成关键酶谷氨酸消旋酶（MurI）负向调控变异链球菌致龋毒力和胁迫反应；对HSP100/ClpATPase家族成员ClpX和ClpC可能存在表达、功能与分子水平多层次的调节作用，但具体机制尚不明确。本项目拟构建以MurI蛋白为靶标的小分子抑制剂高通量筛选模型，探讨MurI小分子抑制剂对ClpX和ClpC的调控分子机制，明确其影响细菌壁膜结构和生物学行为的作用模式，分析ComRS感受态形成信号通路关键基因及功能蛋白的表达改变，为确立以MurI和HSP100/ClpATPase为龋病防治新靶点提供科学依据。

Streptococcus mutans (S. mutans) is the primary causative agent of dental caries. Its virulence is tightly integrated with stress tolerance. Coping with environmental insults and fluctuations, HSP100/ClpATPase plays a vital role in cell envelope biogenesis/homeostasis and affects competence development by S. mutans, traits critical to cariogenicity. Control the pathways regulating competence development or (and) destabilize cell wall integrity may reduce cariogenic potentials of this bacterium. However, the accurate targets have not yet been characterized. Our previous study showed that inactivation of glutamate racemase (MurI), an essential enzyme in cell wall biosynthesis, had a negative effect on virulence properties and stress response in S. mutans. Further studies revealed that specifically targeting MurI regulated the expression of HSP100/ClpATPase at different levels. To in-depth investigate the exact underlying mechanism, this project will conduct a high throughput screening for small-molecule inhibitors based on the protein crystal structure of MurI from S. mutans. The effect of inhibitors on the biological phenotypes associated with cariogenicity will be examined. Based on the above, the regulatory mechanisms of HSP100/ClpATPase in S. mutans during exposure to the inhibitors, as well as the expression of critical genes and proteins of ComRS competence development pathways, will be further elucidated. This study will provide evidence for establishing MurI and HSP100/ClpATPase as useful targets for therapeutics to diminish the virulence of S. mutans.