Lin Kan, O'Brien Kathryn M, Trujillo Carolina, Wang Ruojun, Wallach Joshua B, Schnappinger Dirk, Ehrt Sabine
Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America.
Program in Immunology and Microbial Pathogenesis, Weill Graduate School of Medical Sciences of Cornell University, New York, New York, United States of America.
PLoS Pathog. 2016 Jun 1;12(6):e1005675. doi: 10.1371/journal.ppat.1005675. eCollection 2016 Jun.
Mycobacterium tuberculosis (Mtb) must cope with exogenous oxidative stress imposed by the host. Unlike other antioxidant enzymes, Mtb's thioredoxin reductase TrxB2 has been predicted to be essential not only to fight host defenses but also for in vitro growth. However, the specific physiological role of TrxB2 and its importance for Mtb pathogenesis remain undefined. Here we show that genetic inactivation of thioredoxin reductase perturbed several growth-essential processes, including sulfur and DNA metabolism and rapidly killed and lysed Mtb. Death was due to cidal thiol-specific oxidizing stress and prevented by a disulfide reductant. In contrast, thioredoxin reductase deficiency did not significantly increase susceptibility to oxidative and nitrosative stress. In vivo targeting TrxB2 eradicated Mtb during both acute and chronic phases of mouse infection. Deliberately leaky knockdown mutants identified the specificity of TrxB2 inhibitors and showed that partial inactivation of TrxB2 increased Mtb's susceptibility to rifampicin. These studies reveal TrxB2 as essential thiol-reducing enzyme in Mtb in vitro and during infection, establish the value of targeting TrxB2, and provide tools to accelerate the development of TrxB2 inhibitors.
结核分枝杆菌（Mtb）必须应对宿主施加的外源性氧化应激。与其他抗氧化酶不同，Mtb的硫氧还蛋白还原酶TrxB2不仅被预测对于对抗宿主防御至关重要，而且对于体外生长也必不可少。然而，TrxB2的具体生理作用及其对Mtb致病机制的重要性仍不明确。在此我们表明，硫氧还蛋白还原酶的基因失活扰乱了几个生长必需过程，包括硫和DNA代谢，并迅速杀死并裂解了Mtb。死亡是由于具有杀菌作用的硫醇特异性氧化应激所致，可被二硫键还原剂阻止。相比之下，硫氧还蛋白还原酶缺乏并未显著增加对氧化应激和亚硝化应激的敏感性。在小鼠感染的急性和慢性阶段，体内靶向TrxB2可根除Mtb。故意渗漏的敲低突变体确定了TrxB2抑制剂的特异性，并表明TrxB2的部分失活增加了Mtb对利福平的敏感性。这些研究揭示了TrxB2是Mtb在体外和感染期间必不可少的硫醇还原酶，确立了靶向TrxB2的价值，并提供了加速TrxB2抑制剂开发的工具。
