ABSTRACT
Drug resistance is a major problem in
Mycobacterium tuberculosis
control, and it is critical to identify novel drug targets and new antimycobacterial compounds. We have previously identified an imidazo[1,2-
a
]pyridine-4-carbonitrile-based agent, MP-III-71, with strong activity against
M. tuberculosis
. In this study, we evaluated mechanisms of resistance to MP-III-71. We derived three independent
M. tuberculosis
mutants resistant to MP-III-71 and conducted whole-genome sequencing of these mutants. Loss-of-function mutations in
Rv2887
were common to all three MP-III-71-resistant mutants, and we confirmed the role of
Rv2887
as a gene required for MP-III-71 susceptibility using complementation. The Rv2887 protein was previously unannotated, but domain and homology analyses suggested it to be a transcriptional regulator in the MarR (multiple antibiotic resistance repressor) family, a group of proteins first identified in
Escherichia coli
to negatively regulate efflux pumps and other mechanisms of multidrug resistance. We found that two efflux pump inhibitors, verapamil and chlorpromazine, potentiate the action of MP-III-71 and that mutation of
Rv2887
abrogates their activity. We also used transcriptome sequencing (RNA-seq) to identify genes which are differentially expressed in the presence and absence of a functional Rv2887 protein. We found that genes involved in benzoquinone and menaquinone biosynthesis were repressed by functional Rv2887. Thus, inactivating mutations of
Rv2887
, encoding a putative MarR-like transcriptional regulator, confer resistance to MP-III-71, an effective antimycobacterial compound that shows no cross-resistance to existing antituberculosis drugs. The mechanism of resistance of
M. tuberculosis
Rv2887
mutants may involve efflux pump upregulation and also drug methylation.
摘要
耐药性是结核分枝杆菌
结核分枝杆菌
耐药性是结核分枝杆菌控制中的主要问题,因此确定新的药物靶点和新的抗分枝杆菌化合物至关重要。我们之前发现了一种咪唑并[1,2-
a
]吡啶-4-甲腈类药物 MP-III-71 对结核杆菌具有很强的活性。
结核杆菌
.在本研究中,我们评估了 MP-III-71 的抗药性机制。我们得出了三种独立的
结核杆菌
突变体,并对这些突变体进行了全基因组测序。功能缺失突变
Rv2887
的功能缺失突变是所有三个耐 MP-III-71 突变体的共同点,我们证实了
Rv2887
作为 MP-III-71 易感性所需基因的作用。Rv2887 蛋白以前未被标注,但结构域和同源性分析表明它是 MarR(多重抗生素抗性抑制因子)家族中的一个转录调节因子。
大肠杆菌
这组蛋白首先在大肠杆菌中被发现,用于负向调节外排泵和其他多药耐药性机制。我们发现,维拉帕米和氯丙嗪这两种外排泵抑制剂能增强 MP-III-71 的作用,而 Rv2887 的突变也能增强 MP-III-71 的作用。
Rv2887
会削弱它们的活性。我们还利用转录组测序(RNA-seq)来确定在存在和不存在功能性 Rv2887 蛋白时表达不同的基因。我们发现,参与苯醌和甲萘醌生物合成的基因受到了功能性 Rv2887 的抑制。因此,Rv2887 的失活突变
Rv2887
对 MP-III-71 产生耐药性,MP-III-71 是一种有效的抗结核化合物,与现有的抗结核药物没有交叉耐药性。结核杆菌的抗药性机制
结核杆菌
Rv2887
突变体的抗药性机制可能涉及外排泵上调和药物甲基化。