The role of Esx-3 in mediating drug resistance

结核病是全世界人类痛苦的一个主要原因，有180万人死亡，104万人死亡 2015年新增病例为100万例。尽管治疗结核病的有效药物方案已经存在，但它们 是漫长的，并涉及多种抗生素，以实现灭菌和防止复发。这个 目前的结核病治疗方法复杂而漫长，需要至少6个月的4种药物。 对于最简单的情况。目前尚不清楚为什么药物治疗时间如此之长，尽管有几个 关于细菌的生理状态的理论已经被提出；这些理论包括 在感染期间存在耐药人群，存在非复制(或缓慢- 复制细菌)和缺乏药物对感染部位的渗透。 最近在表型筛选上花费了大量的努力来识别新的分子系列 用于药物发现和开发；同时还有一种化学基因组学方法 使用这些屏幕中确定的命中化合物来寻找新的药物靶点。我们很感兴趣 在开发新药和了解这些药物如何起作用方面都是如此。我们已经确定了一个 结核分枝杆菌对几个化学无关系列耐药的共同机制 这涉及到III型分泌系统(T7SS)的突变。 我们已经确定了具有有趣生物活性的化合物，这些化合物似乎通过 类似的机制，或者至少是阻力是由相同的机制产生的。我们的建议 目的是确定这些化合物的作用模式。我们建议，行动模式是通过 具有额外下游效应的金属离子动态平衡的破坏，这将是一种新的 未来药物发现工作的机制。 我们已经在ESX-3 T7SS的几个组成部分(EccA3、EccB3、EccC3)中发现了突变 和EccD3)，它们对三个化合物系列具有抗性。ESX-3系统不太可能 是这些化合物的细胞靶点，因为在四个不同的基因中发现了突变， 包括一种不会形成复合体一部分的胞浆蛋白。因此看起来很有可能 这种抗性是由一种不同于失去化合物-靶标结合的机制引起的。 我们建议采取多种方法结合微生物学、分子生物学和 生物化学(I)确定化合物系列的作用方式(Ii)确定ESX- 3、T7SS可介导复合抗性；(3)识别和表征每种抗性的靶标 系列片。

Tuberculosis is a major cause of human suffering worldwide, with 1.8 million deaths and 10.4 million new cases in 2015. Although effective drug regimens for the treatment of TB exist, they are lengthy and involve multiple antibiotics to achieve sterilization and prevent relapse. The current treatment for TB is complex and lengthy requiring a minimum of six months with four drugs for the simplest of cases. It is not clear why drug therapy is so prolonged, although several theories relating to the physiological state of the bacteria have been proposed; these include the existence of drug-tolerant populations during infection, the presence of non-replicating (or slowly- replicating bacilli) and the lack of drug penetration to the sites of infection. Much recent effort has been expended in phenotypic screening to identify new molecular series for drug discovery and development; alongside which a chemical genomics approach has been taken to find novel drug targets using hit compounds identified in these screens. We are interested both in developing novel drugs and in understanding how such drugs work. We have identified a common mechanism of resistance to several, chemically-unrelated series in M. tuberculosis which involves mutation in a type VII secretion system (T7SS). We have identified compounds with interesting biological activities and which appear to work via similar mechanisms, or at least resistance is engendered by the same mechanism. Our proposal aims to determine the mode of action of these compounds. We propose that mode of action is via disruption of metal ion homeostasis with additional downstream effects, which would be a novel mechanism for future drug discovery efforts. We have identified mutations in several components of the Esx-3 T7SS (EccA3, EccB3, EccC3 and EccD3) which confer resistance to three compound series. It is unlikely that the Esx-3 system is the cellular target for these compounds, since mutations were found in four different genes, including one cytosolic protein that would not form part of the complex. Therefore it seems likely that resistance arises from a mechanism distinct from loss of compound-target binding. We propose to take a number of approaches combining microbiology, molecular biology and biochemistry to (i) determine the mode of action of compound series (ii) determine how the Esx- 3 T7SS can mediate compound resistance, and (iii) identify and characterize the targets of each series.