Pseudomonas detection and metabolism of sphingosine

描述（由申请方提供）：铜绿假单胞菌肺部感染危及生命，并构成巨大的医疗负担。宿主免疫应答的调节是病原体用于启动和延长感染的一种范例。初步数据表明，铜绿假单胞菌可以降解有效的免疫信号分子鞘氨醇-1-磷酸（S1 P）及其前体鞘氨醇。S1 P降解将允许铜绿假单胞菌改变宿主免疫应答，这可能对感染的进展和疾病的发病机制产生深远影响。本提案中描述了一种以前未表征的转录因子，其调节铜绿假单胞菌响应S1 P和鞘氨醇的基因表达，并且是其降解所需的。该转录因子的缺失降低了铜绿假单胞菌体内毒力，突出了该途径在感染期间的重要性。铜绿假单胞菌对鞘氨醇的检测和代谢的表征将为了解细菌生物学和发病机制中的鞘氨醇相关化合物做出具体贡献。长期目标是了解铜绿假单胞菌S1 P和鞘氨醇代谢在肺部感染过程中的作用。为了实现这一长期目标，本申请的总体目标是表征 以及铜绿假单胞菌用于响应S1 P的降解系统，并确定S1 P降解对肺中铜绿假单胞菌毒力的影响。中心假设是铜绿假单胞菌检测到S1 P诱导S1 P降解所必需的基因，这促进了毒力。中心假设将通过追求三个具体目标进行检验：（1）表征铜绿假单胞菌中S1 P和鞘氨醇依赖性转录~（2）鉴定S1 P降解途径的组分~（3）测试S1 P降解对铜绿假单胞菌感染的影响。目的1的目标是确定的配体和启动子结合特异性的鞘氨醇反应性转录因子的启动子定位，DNA结合，和报告分析，并确定其贡献的鞘氨醇调节子使用微阵列分析。目标2的目标是使用遗传筛选、代谢物追踪和体外酶测定来鉴定铜绿假单胞菌S1 P磷酸酶和降解鞘氨醇的酶。最后，目标3的目的是使用申请人实验室建立的肺部感染小鼠模型，检验转录因子突变体的毒力降低是由于缺乏S1 P降解，而不是与降解无关的基因的调节。这一提议是创新的，因为它将促进对以前未表征的鞘氨醇检测和代谢途径的理解，这可能被铜绿假单胞菌用于检测宿主并干扰有效的宿主信号传导途径。这项拟议中的研究意义重大，因为它将扩大对细菌病原体与宿主之间代谢联系的理解，也许会导致新的抗菌或抗毒疗法。

DESCRIPTION (provided by applicant): Pseudomonas aeruginosa lung infections are life threatening and constitute a large health-care burden. Modulation of host immune responses is one paradigm used by pathogens to initiate and prolong infections. Preliminary data demonstrate that P. aeruginosa can degrade the potent immune signaling molecule sphingosine-1-phosphate (S1P) and its precursor sphingosine. S1P degradation would allow P. aeruginosa to alter the host immune response, which could have profound effects on progression of infection and the pathogenesis of disease. Described in this proposal is a previously uncharacterized transcription factor that regulates P. aeruginosa gene expression in response to S1P and sphingosine and is required for their degradation. Deletion of this transcription factor reduces P. aeruginosa virulence in vivo, highlighting the importance of this pathway during infection. Characterization of the detection and metabolism of sphingosine by P. aeruginosa will be a concrete contribution to understanding of sphingosine-related compounds in bacterial biology and pathogenesis. The long term goal is to understand the role of P. aeruginosa S1P and sphingosine metabolism during the course of lung infection. In pursuit of this long-term goal, the overall objectives of this application are to characterize the recognition and degradation system used by P. aeruginosa to respond to S1P and determine the impact of S1P degradation on P. aeruginosa virulence in the lung. The central hypothesis is that P. aeruginosa detection of S1P induces genes necessary for S1P degradation, which promotes virulence. The central hypothesis will be tested by pursuing three specific aims: (1) Characterize S1P and sphingosine-dependent transcription in P. aeruginosa~ (2) Identify the components of the S1P degradation pathway~ and (3) Test the impact of S1P degradation on P. aeruginosa infection. The goals of Aim 1 are to determine the ligand and promoter-binding specificities of the sphingosine-responsive transcription factor by promoter mapping, DNA binding, and reporter assays, and determine its contribution to the sphingosine regulon using microarray analysis. The goal of Aim 2 is to identify the P. aeruginosa S1P phosphatase and the enzymes that degrade sphingosine using genetic screens, metabolite tracking, and in vitro enzymatic assays. Finally, the goal of Aim 3 is to test the hypothesis that the reduced virulence of the transcription factor mutant is due to lack of S1P degradation, versus regulation of genes unrelated to degradation, using a mouse model of lung infection established in the applicant's lab. This proposal is innovative because it will advance understanding of a previously uncharacterized sphingosine detection and metabolic pathway, which may be used by P. aeruginosa to detect the host and interfere with a potent host signaling pathway. The proposed research is significant because it will expand understanding of the metabolic links between bacterial pathogens and the host, perhaps leading to novel antimicrobial or anti-virulence therapies.