金黄色葡萄球菌三组分碳源转运调控系统HptA/S/R的分子机制及结构基础

Staphylococcus aureus is an important opportunistic pathogen that can cause both superficial and invasive, potentially life-threatening, infections such as sepsis, endocarditis and pneumonia. Due to the rapid evolution of various types of drug-resistant strains in S. aureus, it poses a great challenge to the clinical treatment and drug development. The Hexose Phosphate Transport (HPT) Three-component system, which consists of HptA, HptS and HptR, is an efficient pathway to ensure the absorbance of carbon source glucose-6-phosphate (G6P) from host environment. When glucose-6-phosphate (G6P) turns to be the only available carbon source during the infection, HptA/S/R system is activated, which then initiates the transport of G6P into S. aureus cells. So, controlling the uptake of carbon source G6P in S. aureus by blocking the HptA/S/R signal pathway appears to be a promising strategy to suppress S. aureus proliferation. However, the detailed mechanism of this process remains poorly understood, such as how the HptA sense extracellular G6P and in turn activate the histidine kinase HptS; how the activated HptS transducts the extracellular signal into cells and phosphorylates the HptR; how the phosphorylated HptR induces the expression of UhpT to facilitate G6P uptake. Here we propose to uncover the structural basis and regulation mechanism underlying the HPT system through combinatorial use of structure biology and cellular assays; identify novel drug targets functioning as the switch of the HPT signal transduction. Hopefully, our research will accelerate the development of antagonistic drugs against S. aureus infection in host from the perspective of nutrition supply.

金黄色葡萄球菌是一种重要的机会型致病菌，感染人体后可分泌大量毒力因子引发多种疾病。金葡菌易产生各种耐药菌株，这给金葡菌感染的临床治疗和药物开发带来了极大的挑战。金葡菌感染人体后通过HptA/S/R三组分系统调节自身碳源转运能力，从而高效利用宿主体内的G6P作为主要碳源供生长增殖所需。鉴于该系统在金葡菌感染宿主后的碳源代谢过程中所起到的决定性作用，本项目拟通过蛋白质晶体学、生物化学及细胞生物学方法在分子水平阐明HptA与G6P、HptA与HptS、HptR与uhpT基因启动子间的相互作用关系，从胞内到胞外完整揭示HptA/S/R调控系统在信号识别、信号跨膜传递、膜内效应蛋白激活及转录调控等各环节的结构基础及分子机制。该工作的开展将有助于设计和开发以金葡菌G6P摄入调控系统为靶点的新型抗生素类先导化合物，并对金葡菌感染的临床治疗和控制提供帮助。

为了适应不断变化的环境，细菌必须迅速地将细胞外信息转化为适当的细胞内部反应。双组分系统（TCS）是原核细胞将环境刺激转化为细胞反应的主要信号转导蛋白，它通常由膜包埋组氨酸激酶和胞质反应调节器组成。HptRSA是一种新近发现的TCS，由G6P相关传感器蛋白（HptA）、跨膜组氨酸激酶（HptS）和细胞质效应器（HptR）组成。HptRSA介导葡萄糖-6-磷酸（G6P）摄取，支持金黄色葡萄球菌在不同宿主细胞内的生长和增殖，但HptRSA传感器复合物感知G6P信号并触发下游反应的分子机制一直以来都还是个谜。. 通过几年时间的艰苦探索，我们分别解析无底物状态和G6P结合状态的HptA结构，以及HptA蛋白与HptS蛋白细胞周质结构域（HptSp）的复合物结构，揭示了HptA结合G6P以后，引发HptSp旋转，并使两个HptSp的C末端相互靠近，进而引发胞外信号向胞内转导的机制。在此基础上，我们提出了界面开关介导的G6P-HptRSA信号转导机制。该工作于2020年11月16日发表在美国科学院院刊《PNAS》上，论文标题为“Interface switch mediates signal transmission in a two-component system” 。. 本项目研究结果为细菌的营养感应机制提供了重要线索，扩展了学界对TCS传递外部信号的激活模式的理解。同时还将为金葡菌碳源摄取抑制药物设计提供新的靶点和设计思路。

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