Exogenous Carbohydrates are Required for Survival for M. tuberculosis

描述(申请人提供)：结核分枝杆菌(Mtb)每年导致全球约200万人死亡，每年约有1000万新病例。与其他几种细胞内病原体一样，在大多数感染过程中，这种微生物的首选生态位是宿主巨噬细胞的一个修改后的吞噬体样隔间。虽然这种致病策略有明显的优势，但在宿主衍生的膜内生长也构成了许多挑战。也许最根本的是获取营养。结核分枝杆菌或任何其他液泡病原体是如何在这个利基中获得营养的尚不清楚。此外，吞噬小体内的环境并不是静止的，而是随着疾病的进展而变化。结核分枝杆菌感染至少可分为两个不同的阶段：早期免疫前/急性阶段和晚期免疫后/慢性阶段。在此之前，我们使用了一种全球遗传交互作图策略来描述一种称为“Mce4”的胆固醇摄取系统。这种转运蛋白只有在感染的慢性阶段才需要生存，这表明细菌可获得的营养物质随着疾病的进展而改变。急性期使用的碳源(S)仍不清楚。使用高通量筛选在急性感染中生长有缺陷的转座子突变体，我们发现了两个假定的碳水化合物摄取系统和一个己糖激酶，它们在这一阶段对生长至关重要。推测的糖进口子SugABC，rv2038c-2040c和己糖激酶ppgK，对于感染早期的生存是重要的，这表明碳水化合物在这一阶段可能是重要的营养物质。我们提出了一个模型，在这个模型中，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移到基于胆固醇的新陈代谢来进行调整。为了验证这一假设，我们建议对这些碳水化合物转运蛋白和己糖激酶进行表征，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靶点和洞察病原体如何适应宿主内营养有限的环境。 公共卫生相关性：结核分枝杆菌(Mtb)在毒力方面取得成功的部分原因是它在感染期间获得营养的能力。我们已经为结核分枝杆菌开发了一种高通量的遗传相互作用筛选，以确定宿主内营养吸收和生存所需的途径。来自这些遗传交互作用筛选的数据可以用来确定宿主感染所需的营养物质。

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.