The role of host-derived lipids in Mycobacterium tuberculosis infection

结核分枝杆菌是一种全球性杀手，每年造成100多万人死于结核病。因此，它是人类健康的一个重大负担。为了减少结核病的致命影响，我们需要更好地了解结核分枝杆菌为适应其代谢而使用的策略，以便在人类宿主遇到的可变环境中生存；这将有助于我们设计更好的治疗和控制结核病的方法。所有细胞都需要对环境变化做出反应，比如酸性pH值，这是胃和吞噬分枝杆菌的巨噬细胞都会遇到的情况。大肠杆菌、霍乱弧菌和幽门螺杆菌等细菌对酸的反应已经得到了广泛的研究，这些细菌都遇到了胃的极酸性（pH值2-3）。相比之下，关于能够在人类细胞内生存的细菌病原体（如结核分枝杆菌）如何在巨噬细胞等细胞内的酸性液泡中存活和复制的信息却很少。根据巨噬细胞的激活状态，结核分枝杆菌所在的巨噬细胞腔室的pH值在6.2至4.5之间。我们可以在实验室中研究细菌对培养瓶pH变化的反应和生存，以及在培养的巨噬细胞中识别帮助它们生存的细菌因子。改变结核分枝杆菌的代谢是在环境变化中生存的一种方式，干扰这些过程是治疗结核病的一种有吸引力的方法。我们已经确定了一种camp依赖性赖氨酸乙酰转移酶（Rv0998, KATmt）参与酸性生存，根据我们的初步数据，我们假设KATmt在结核分枝杆菌对细胞内生命的代谢适应中起关键作用，这是结核分枝杆菌发病的关键部分。为了解决这一假设，我们建议在整个细胞水平上研究KATmt在结核分枝杆菌代谢重组中的作用。为实现这一目标，我们的目标是：利用结核分枝杆菌KATmt的基因突变体确定KATmt的代谢途径及其如何被调节。确定KATmt活性的底物，这可能是新的和有吸引力的药物靶点。2. 利用生物能量学和代谢组学来确定KATmt在宿主巨噬细胞代谢组重塑中的作用。结核分枝杆菌操纵其宿主细胞，为其生存和复制创造更有利的环境，了解它是如何做到这一点的，是找到新的干预措施的关键。3. 我们将比较KATmt突变体在TB小鼠模型中的表现，与亲本菌株和补充菌株相比，寻找细菌存活的变化以及与感染相关的宿主脂质的变化。通过这种方式，我们将阐明KATmt介导结核分枝杆菌对感染过程中遇到的酸性胁迫的机制，不仅通过改变其自身代谢，还通过操纵宿主巨噬细胞脂质代谢。总的来说，这将确定和验证结核分枝杆菌发病机制的关键途径，为小分子干预开辟新的途径。

The bacteria Mycobacterium tuberculosis is a global killer causing over a million deaths from tuberculosis (TB) every year. It is therefore a major burden to human health. To reduce the deadly impact of TB, we need a better understanding of the strategies used by M. tuberculosis to adapt its metabolism in order to survive in the variable environments encountered in the human host; this will help us design better ways to treat and control TB. All cells need to respond to environmental changes such as acidic pH, a condition encountered within the stomach as well as the macrophages that engulf mycobacteria. Responses to acid have been studied extensively in bacteria such as Escherichia coli, Vibrio cholerae, and Helicobacter pylori, that all encounter the extremely acidic pH (pH 2-3) of the stomach. In contrast, there is little information on how bacterial pathogens that can live inside human cells, like M. tuberculosis, survive and replicate within acid vacuoles inside cells like macrophages. The pH of the macrophage compartment in which M. tuberculosis resides ranges from pH 6.2 to 4.5, depending on the activation state of the macrophage. We can study how bacteria respond to and survive changes in pH in culture flasks in the laboratory, as well as in cultured macrophages to identify bacterial factors that help them survive. Changing M. tuberculosis metabolism is one way to survive changes in the environment and interfering with these processes presents an attractive method for treating TB. We have identified an enzyme cAMP-dependant-lysine acetyl transferase (Rv0998, KATmt) involved in acid survival, and based on our preliminary data we hypothesize that KATmt plays a key role in the metabolic adaptation of M. tuberculosis to intracellular life a key part of M. tuberculosis pathogenesis.To address this hypothesis, we propose to study the role of KATmt in rewiring the metabolism of M. tuberculosis at a whole cell level. To achieve this goal our objectives are to:1. Use genetic mutants of M. tuberculosis KATmt to identify the metabolic pathways KATmt and how this is regulated. Identify substrates for KATmt activity, which may represent new and attractive drug targets. 2. Use bioenergetics and metabolomics to determine the role KATmt plays in host macrophage metabolome remodelling. M. tuberculosis manipulates its host cell to generate a more favourable environment for its survival and replication, and understanding how it does this is key to finding new interventions. 3. We will compare how the KATmt mutant behave in the mouse model of TB, compared to the parental and complemented strains, looking for changes in bacterial survival and changes in host lipids associated with infection.In this way, we will elucidate the mechanisms by which KATmt mediates the resistance of M. tuberculosis to the acidic stress encountered during infection not only by altering its own metabolism, but also by manipulating host macrophage lipid metabolism Overall, this will identify and validate key pathways in M. tuberculosis pathogenesis, opening up new avenues for small molecule interventions.