Origins of zinc starvation in Mycobacterium tuberculosis during chronic infection

总结 结核病（TB）是世界上一个主要的公共卫生负担：超过一百万人死于结核病。 据估计，世界上三分之一的人口携带这种病原体 结核分枝杆菌（Mtb）。治疗结核病需要6至9个月的抗生素 包括多种抗生素的方案。结核病治疗的困难主要归因于 病原体中的非遗传性耐药性被认为是由于独特的 在宿主的微环境（如营养耗尽，缺氧和抗生素暴露）。最近， 我们发现了这样一种情况：锌饥饿。对于锌饥饿， 耻垢分枝杆菌和结核分枝杆菌诱导核糖体重塑， 核糖体冬眠核糖体重塑涉及多个核糖体（r-） 含有锌结合CXXC基序的蛋白质（因此称为C+ r-蛋白质）， 自由C-旁系同源物。核糖体冬眠涉及分枝杆菌蛋白Y（Mpy）与 核糖体的解码中心。核糖体重塑发生在锌浓度， 允许生长，而核糖体冬眠发生在生长限制浓度的锌。 此外，携带重塑和冬眠核糖体的分枝杆菌细胞对抗结核药物具有抗性。 氨基糖苷和壮观酰胺。此外，我们证明了宿主肺中的锌 慢性Mtb感染期间的环境低到足以诱导核糖体重塑和Mpy- 对链霉素（一种用于治疗多药耐药的氨基糖苷类）的依赖性耐药 耐药结核病。然而，慢性感染期间结核分枝杆菌锌饥饿的根本原因是 不知道。基于细菌感染期间金属离子饥饿是先天宿主的想法， 防御策略，称为营养免疫，我们建议确定宿主的成分 免疫系统负责锌饥饿结核病（目的1），并确定锌的潜力 氧化物纳米颗粒作为辅助治疗剂（目的2）。项目完成后，我们将获得 进一步了解锌饥饿和相关核糖体重塑/冬眠的原因， 结核病慢性感染过程中，并制定治疗策略，以尽量减少耐药性 由结核分枝杆菌核糖体的这些变化引起。

Summary Tuberculosis (TB) is a major public health burden in the world: over a million people die of the disease every year and an estimated one third of the world’s population harbor the pathogen Mycobacterium tuberculosis (Mtb). Treatment of TB requires 6 to 9 months of an antibiotic regimen comprising of multiple antibiotics. Difficulties in treatment of TB are largely attributed to non-inheritable drug resistance in the pathogen that are considered to be developed due to unique microenvironments in the host (e.g. nutrient depletion, hypoxia and antibiotic exposure). Recently, we uncovered one such condition: zinc starvation. In response to zinc starvation both Mycobacterium smegmatis and Mycobacterium tuberculosis induce ribosome remodeling and ribosome hibernation. Ribosome remodeling involves replacement of multiple ribosomal (r-) proteins containing the zinc-binding CXXC motif (therefore called C+ r-proteins) by their motif- free C- paralogues. Ribosome hibernation involves binding of mycobacterial protein Y (Mpy) to the decoding center of the C- ribosome. Ribosome remodeling occurs at a zinc concentration that permits growth, whereas ribosome hibernation occurs at a growth-restrictive concentration of zinc. Moreover, mycobacterial cells harboring remodeled and hibernating ribosomes are resistant to aminoglycosides and spectinamides. Furthermore, we demonstrated that zinc in the host lung environment during chronic Mtb infection is low enough to induce ribosome remodeling and Mpy- dependent resistance to streptomycin, an aminoglycoside used in the treatment of multi-drug resistant TB. However, the underlying cause for zinc starvation in Mtb during chronic infection is not known. Based on the idea that metal ion starvation during bacterial infections is an innate host defense strategy, called nutritional immunity, we propose to identify the components of host immune system responsible for zinc starvation in Mtb (Aim 1), and determine the potential of zinc oxide nanoparticles as an adjunct therapeutic (Aim 2). Upon completion of the project we will gain further insight into the cause of zinc starvation and related ribosome remodeling/hibernation in Mtb during chronic infection, and develop a therapeutic strategy to minimize the drug resistance caused by these changes to the ribosome in Mtb.