Bacterial anti-inflammatory lipid mediators

项目摘要 先天免疫系统对感染的快速反应依赖于病原体相关的检测。 分子模式(PAMP)，如脂多糖，激活强烈的炎症反应 入侵的生物。我的研究计划关注的是一种未被赏识的对策 减弱对PAMPs的免疫反应的共生细菌和病原体。油酸水合酶(Ohya) 是一种在共生菌和重要的人类病原体葡萄球菌中表达的酶 金星。Ohya立体专一地水合不饱和脂肪酸的9-顺式双键，以产生10- 羟基脂肪酸(HFAS)；然而，表达Ohya的细菌不合成不饱和脂肪酸。 Ohya底物只出现在宿主组织的界面上，在那里不饱和脂肪酸 很丰富。我假设由共生体或病原体产生的HFAS起信号作用 削弱对PAMP的先天免疫反应的分子。事实上，金黄色葡萄球菌Ohya基因敲除未能 在小鼠中建立感染，说明Ohya和HFAS对金黄色葡萄球菌毒力的重要性。因此，HFAS， 最先在肠道微生物组中发现的，可能提供了一种重要的共生机制 细菌可以减轻胃肠道炎症，创造耐受的共生环境。我的飞行员 实验和以前的一些报告为HFAS的抗炎作用提供了初步证据， 但HFAS抑制免疫的机制(S)尚不清楚。为了解决这一缺点，我将 在保罗博士的实验室通过课程学习和动手培训接受正式的免疫学指导 在K99阶段，免疫学家托马斯说。我们将确定HFAS是否直接对抗 胞外PAMP与免疫细胞受体结合，与T细胞受体的CD1脂质递呈分子结合 识别以拮抗T细胞激活，或拦截PAMP受体激活下游的信号 刺激G蛋白偶联受体和/或PAPR。这些实验的结果将揭示 HFA修饰免疫细胞反应的机制基础。Ohya没有哺乳动物的同源物，而且 验证Ohya对毒力的重要性，结合Ohya的X射线结构将提供关键 确定Ohya是否为抗微生物药物发现的候选目标所需的信息。在.期间 在R00期，我将检验Ohya被包装成由S. 金黄色葡萄球菌与周围宿主组织相互作用，在感染部位周围形成HFA介体的光环。我的 这些发现将提供对Ohya如何与膜结合并影响膜的原子机制的理解 结构以促进囊泡的形成。K99/R00研究计划旨在利用我在 生物化学和结构生物学，同时接受新的免疫学培训，以增进对 关于细菌免疫调节的研究，并开始了富有成效和成功的职业生涯，我将在其中领导一项研究 阐明细菌脂类产品在控制宿主反应中的作用的计划。

Project Summary The rapid response of the innate immune system to infections relies on the detection of pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharides, that activate a robust inflammatory response to invading organisms. My research program focuses on an unappreciated countermeasure deployed by commensal bacteria and pathogens that attenuates the immune response to PAMPs. Oleate hydratase (OhyA) is an enzyme that is expressed in commensal bacteria and the important human pathogen Staphylococcus aureus. OhyA stereospecifically hydrates the 9-cis double bond of unsaturated fatty acids to produce 10- hydroxy-fatty acids (hFAs); however, bacteria expressing OhyA do not synthesize unsaturated fatty acids. OhyA substrates are only encountered at the interface of host tissues, where unsaturated fatty acids are abundant. I hypothesize that hFAs produced by commensal or pathogenic organisms serve as signaling molecules that blunt the innate immune response to PAMPs. Indeed, S. aureus ohyA knockouts fail to establish infections in mice, illustrating the importance of OhyA and hFAs to S. aureus virulence. Thus, hFAs, which were first discovered in the gut microbiome, may provide an important mechanism for commensal bacteria to attenuate gastrointestinal inflammation and create tolerant, symbiotic environments. My pilot experiments and some previous reports provide preliminary evidence for the anti-inflammatory action of hFAs, but the mechanism(s) of immune suppression by hFAs are unknown. To address this shortcoming, I will receive formal immunology instruction through coursework and hands-on training in the laboratory of Dr. Paul Thomas, an expert immunologist, during the K99 phase. We will determine whether hFAs directly antagonize extracellular PAMP binding to immune cell receptors, bind to CD1 lipid-presenting molecules for T-cell receptor recognition to antagonize T cell activation, or intercept signaling downstream of PAMP-receptor activation by stimulating G-protein coupled receptors and/or PAPR. The results of these experiments will uncover the mechanistic basis for hFA modification of immune cell responses. OhyA has no mammalian homolog, and validating the importance of OhyA for virulence coupled with the X-ray structures of OhyA will provide the key information required to determine whether OhyA is a candidate target for antimicrobial drug discovery. During the R00 phase, I will test the hypothesis that OhyA is packaged into extracellular vesicles released by S. aureus to interact with surrounding host tissues to form a halo of hFA mediators around the infection site. My findings will provide an atomistic mechanistic understanding of how OhyA binds to and influences membrane structure to promote vesicle formation. The K99/R00 research plan is designed to leverage my expertise in biochemistry and structural biology, while receiving new training in immunology, to advance the understanding of immune regulation by bacteria and launch a productive and successful career in which I will lead a research program to elucidate the role bacteria lipid products play in controlling host responses.