From the National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
From the National Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
J Biol Chem. 2018 Oct 26;293(43):16741-16750. doi: 10.1074/jbc.RA118.002693. Epub 2018 Sep 5.
Isoniazid (INH) and ethambutol (EMB) are two major first-line drugs for managing tuberculosis (TB), caused by the microbe Although co-use of these two drugs is common in clinical practice, the mechanism for the potential synergistic interplay between them remains unclear. Here, we present first evidence that INH and EMB act synergistically through a transcriptional repressor of the gene, the target gene of INH encoding an enoyl-acyl carrier protein reductase of the fatty acid synthase type II system required for bacterial cell wall integrity. We report that EMB binds a hypothetical transcription factor encoded by the gene, designated here as EtbR. Using DNA footprinting, we found that EtbR specifically recognizes a motif sequence in the upstream region of the gene. Using isothermal titration calorimetry and surface plasmon resonance assays, we observed that EMB binds EtbR in a 1:1 ratio and thereby stimulates its DNA-binding activity. When a nonlethal dose of EMB was delivered in combination with INH, EMB increased the INH susceptibility of cultured cells. In summary, EMB induces EtbR-mediated repression of and thereby enhances the mycobactericidal effect of INH. Our findings uncover a molecular mechanism for the synergistic activity of two important anti-TB drugs.
异烟肼（INH）和乙胺丁醇（EMB）是治疗结核病（TB）的两种主要一线药物，由微生物引起。虽然这两种药物在临床实践中经常同时使用，但它们之间潜在协同作用的机制尚不清楚。在这里，我们首次提供证据表明，INH 和 EMB 通过 INH 编码的基因的转录抑制剂发挥协同作用，该基因编码脂肪酸合成酶 II 系统的烯酰基酰基载体蛋白还原酶，这是细菌细胞壁完整性所必需的。我们报告说，EMB 结合了由基因编码的假定转录因子，这里称为 EtbR。通过 DNA 足迹实验，我们发现 EtbR 特异性识别基因上游区域的一个模体序列。通过等温滴定量热法和表面等离子体共振测定，我们观察到 EMB 以 1:1 的比例结合 EtbR，从而刺激其 DNA 结合活性。当以非致死剂量的 EMB 与 INH 联合给药时，EMB 增加了培养的细胞对 INH 的敏感性。总之，EMB 诱导 EtbR 介导的基因抑制，从而增强了 INH 的杀菌作用。我们的发现揭示了两种重要抗结核药物协同作用的分子机制。
