Transcriptional regulation of lipid homeostasis in mycobacteria

描述（由申请人提供）：结核分枝杆菌是人类结核病（TB）的病原，一直是世界范围内的一个主要健康问题。霉菌酸是分枝杆菌外膜最重要的脂质之一，与细菌毒力和抗生素耐药性密切相关，其生物合成途径是结核病治疗的主要靶点之一。霉菌酸的生物合成涉及两种结构不同的脂肪酸合成酶系统，fas - 1和fas - 2，它们应该以良好的协调方式保持脂质稳态的严格调节。本研究的主要目标是了解分枝杆菌如何对其膜脂的生物合成施加这种精细的控制，并找出在转录水平上控制脂肪酸和霉菌酸生物合成的调控网络的关键组成部分。为了实现这些目标，我们建议采用多学科方法，包括对耻垢分枝杆菌和结核分枝杆菌中fas和mabR（主要fasII操纵子的转录调节因子）的条件突变菌株进行遗传分析，通过生化和光谱技术鉴定和表征mabR和fas - 1 / fas - ii调节网络中涉及的任何其他调节蛋白感知的代谢信号，最后用x射线晶体学测定MabR的结构。更好地了解分枝杆菌中脂质稳态调节的复杂过程将极大地有助于开发控制这种疾病的新策略，包括设计或鉴定可以解除脂肪酸生物合成调节并诱导细菌死亡的化合物。

DESCRIPTION (provided by applicant): Mycobacterium tuberculosis, the etiologic agent of tuberculosis (TB) in humans, continues to be a major health problem worldwide. Mycolic acids, one of the most important lipids of the outer membrane of mycobacteria, have been largely associated with bacterial virulence and antibiotic resistance and its biosynthesis pathway is one of the main targets for TB treatment. Biosynthesis of mycolic acids involves two structural distinct fatty acid synthase systems, FAS-I and FAS-II, which should work in a finely coordinate manner to keep lipid homeostasis tightly regulated. The main goal of this proposal is to understand how mycobacteria exert this exquisite control over the biosynthesis of their membrane lipids and find out the key components of the regulatory network that control fatty acid and mycolic acid biosynthesis at the transcriptional level. To achieve these goals we propose to use a multidisciplinary approach including genetic analysis of conditional mutant strains in fas and mabR (the transcriptional regulator of the main fasII operon), both in Mycobacterium smegmatis and M. tuberculosis, the identification and characterization of the metabolic signals that are sensed by MabR and any other regulatory proteins involved in the FAS-I/FAS-II regulatory network, by using biochemical and spectroscopic techniques, and finally the determination of MabR structure by X-ray crystallography. A better understanding of this complex process of regulation of lipid homeostasis in mycobacteria will greatly contribute to the development of new strategies to control this disease, including the design or identification of compounds that could deregulate fatty acid biosynthesis and induce bacterial death. PUBLIC HEALTH RELEVANCE: Since fatty acid biosynthesis is essential and energetically expensive, organisms have developed mechanisms that maintain the concentration of lipids tightly regulated. In M. tuberculosis, the etiological agent of tuberculosis, fatty acid biosynthesis is even more relevant since these molecules are also the precursors of other more complex lipids, the mycolic acids, which are essential for conferring virulence and antibiotic resistance to these organisms. Biosynthesis of these metabolic pathways needs to be tightly regulated and disruption of this regulation should be highly damaging for cell survival. Our project proposes to identify and characterize all the components of this complex net of regulation and hopefully identify new drug targets that could act by globally affecting lipid metabolism.