Exogenous Carbohydrates are Required for Survival for M. tuberculosis

描述（由申请人提供）：结核分枝杆菌（Mtb）每年在全球造成约200万人死亡，每年约有1000万新病例。像其他几种细胞内病原体一样，在大多数感染过程中，这种生物的首选生态位是宿主巨噬细胞的一个经过修饰的吞噬体样隔室。虽然这种致病策略有明显的优势，但在宿主源性膜内生长也面临许多挑战。也许最基本的是获取营养。结核分枝杆菌或任何其他空泡病原体如何在这个生态位中获得营养尚不清楚。此外，吞噬体内部的环境不是静止的，而是随着疾病的发展而变化的。结核分枝杆菌感染可分为至少两个不同的阶段：早期免疫前/急性期和晚期免疫后/慢性期。以前，我们使用了一种全球遗传相互作用作图策略来表征胆固醇摄取系统，称为“Mce4”。这种转运体仅在感染的慢性阶段为生存所必需，这表明细菌可利用的营养物质随着疾病的进展而改变。急性期使用的碳源尚不清楚。利用高通量筛选在急性感染中生长缺陷的转座子突变体，我们发现了两种假定的碳水化合物摄取系统和一种己糖激酶，它们对该阶段的生长至关重要。在感染的早期阶段，假定的糖进口商糖abc， rv2038c-2040c和己糖激酶ppgK对存活很重要，这表明碳水化合物可能是这一阶段重要的营养物质。我们提出了一种模型，其中适应性免疫反应改变了结核分枝杆菌所在的隔室，细菌通过从碳水化合物转变为基于胆固醇的代谢来进行调整。为了验证这一假设，我们建议表征这些碳水化合物转运体和己糖激酶，确定作为营养物质的宿主底物，并确定新的治疗靶点。这些研究将提供有价值的新药物靶点，并深入了解病原体如何适应宿主体内营养有限的环境。

DESCRIPTION (provided by applicant): Mycobacterium tuberculosis (Mtb) is responsible for about two million deaths worldwide each year with approximately ten million new cases annually. Like several other intracellular pathogens, the preferred niche for this organism throughout most of the infection, is a modified phagosome-like compartment of the host macrophage. While there are clearly advantages to this pathogenic strategy, growth within a host-derived membrane also poses many challenges. Perhaps the most fundamental is the acquisition of nutrients. How Mtb, or any other vacuolar pathogen, obtains nutrients in this niche is unclear. Furthermore, the environment found inside the phagosome is not static, but rather changes as the disease progresses. Infection with Mtb can be divided into at least two distinct stages: the early preimmune/acute phase and the late postimmune/chronic phase. Previously we used a global genetic interaction mapping strategy to characterize a cholesterol uptake system, called "Mce4." This transporter is only required for survival during the chronic stages of infection, suggesting that the nutrients available to the bacterium change as disease progresses. The carbon source(s) used in the acute phase remains unclear. Using a high-throughput screen for transposon mutants that are defective for growth in acute infection, we have found two putative carbohydrate uptake systems and a hexose kinase that are critical for growth during this phase. The putative sugar importers sugABC, rv2038c-2040c and the hexose kinase ppgK, are important for survival during the early stages of infection suggesting that carbohydrates may serve as important nutrients during this phase. We propose a model in which the adaptive immune response alters the compartment in which Mtb resides, and the bacterium adjusts by shifting from carbohydrate to a cholesterol-based metabolism. To test this hypothesis, we propose to characterize these carbohydrate transporters and hexose kinase, identify the host substrates that serve as nutrients, and identify new therapeutic targets. These studies will provide valuable new drug targets and insight regarding how pathogens adapt in nutrient limited environments inside the host. PUBLIC HEALTH RELEVANCE: Part of Mycobacteria tuberculosis (Mtb) success in virulence, is due to its ability to acquire nutrients during infection. We have developed a high-throughput genetic interaction screen for Mtb, to identify pathways needed for nutrient uptake and survival inside the host. Data from these genetic interaction screens can be used to determine what nutrients are required for infection in the host.