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，10.4%的人死于结核病。 2015年新增病例100万例。尽管存在治疗结核病的有效药物方案， 是漫长的，涉及多种抗生素，以实现绝育和防止复发。的 目前的结核病治疗复杂而漫长，需要至少六个月的时间， 对于最简单的情况。目前尚不清楚为什么药物治疗如此延长，尽管有几个 已经提出了与细菌的生理状态有关的理论;这些理论包括 在感染过程中存在耐药群体，存在非复制（或缓慢- 复制杆菌）和缺乏药物渗透到感染部位。 最近在表型筛选以鉴定新的分子系列方面已经花费了很多努力 用于药物发现和开发;与此同时， 利用这些筛选中发现的命中化合物来寻找新的药物靶点。我们感兴趣 无论是开发新药还是了解这些药物的作用机制。我们已经确定了一 对几种化学上不相关的M.结核 其涉及VII型分泌系统（T7 SS）中的突变。 我们已经鉴定出具有有趣生物活性的化合物，它们似乎通过以下途径起作用： 类似的机制，或者至少是由相同的机制产生的阻力。我们的建议 旨在确定这些化合物的作用方式。我们建议，作用方式是通过 破坏金属离子的稳态与额外的下游影响，这将是一个新的 未来药物发现的机制。 我们已经鉴定了Esx-3 T7 SS的几个组分（EccA 3、EccB 3、EccC 3）中的突变 和EccD 3），其赋予对三种化合物系列的抗性。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物一部分的胞质蛋白。因此， 该抗性产生于与化合物-靶结合丧失不同的机制。 我们建议采取多种方法，将微生物学、分子生物学和 生物化学以（i）确定化合物系列的作用模式（ii）确定Esx- 3 T7 SS可以介导化合物抗性，和（iii）鉴定和表征每种的靶标 系列.

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.