Mechanisms of Susceptibility and Resistance of Mycobacterium tuberculosis to Isoxyl and Thiacetazone

结核分枝杆菌对异木酚和硫醋酮的敏感性和耐药性机制

• 批准号: 9303706
• 负责人: Mary Jackson
• 金额: $ 20.81万
• 依托单位: COLORADO STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-02-10 至 2019-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9303706
• 关键词: AIDS/HIV problem; Accounting; Anabolism; Antitubercular Agents; Biochemistry; Biological Assay; Bypass; Calorimetry; Cell Death; Cells; Cessation of life; Clinical Treatment; Dehydration; Development; Drug Targeting; Drug resistance in tuberculosis; Enzymatic Biochemistry; Enzymes; Flavins; Genetic; Goals; HIV; Hydro-Lyases; In Vitro; Interruption; Investigation; Knowledge; Membrane; Missense Mutation; Mixed Function Oxygenases; Molecular; Molecular Mechanisms of Action; Multi-Drug Resistance; Mycobacterium tuberculosis; Mycolic Acid; Pathway interactions; Pharmaceutical Preparations; Pharmacology; Poverty; Predisposition; Prodrugs; Property; Public Health; Research Personnel; Resistance; Resistance development; Saint Jude Children' s Research Hospital; Specificity; Structure-Activity Relationship; Surface Plasmon Resonance; Testing; Therapeutic Agents; Titrations; Tuberculosis; bactericide; extensive drug resistance; fatty acid synthase II; improved; inhibitor/antagonist; interest; killings; mutant; mycobacterial; novel; novel therapeutics; pandemic disease; prevent; resistance frequency; resistance mechanism; resistant strain; trend; tuberculosis drugs; tuberculosis treatment

Project Summary Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a major public health problem worldwide and the most common presenting illness among people living with HIV accounting for one in four HIV/AIDS-associated deaths. The continuing rise of multidrug-resistant strains of Mtb makes the development of new effective anti-TB drugs a high priority. In this context, re-examining the molecular mechanism of action of established antitubercular drugs that target the same well-validated biosynthetic pathway as front-line anti- TB agents but at a distinct catalytic step, thereby bypassing widespread resistance mechanisms, could have a major impact on the treatment of drug-resistant TB. Two such drugs previously used in the clinical treatment of TB, Isoxyl (ISO) and Thiacetazone (TAC), are the object of our investigations. ISO and TAC are thiocarbamide-containing prodrugs that require activation of their thiocarbonyl moiety by the Mtb flavin-dependent monooxygenase EthA for bactericidal activity. Following activation, ISO and TAC inhibit the biosynthesis of mycolic acids thereby abolishing the formation of the outer membrane of Mtb and leading to cell death. We recently identified the dehydration step of the type II fatty acid synthase (FAS-II) elongation cycle as the point at which both ISO and TAC inhibit the biosynthesis of mycolic acids. Specifically, we found that ISO and TAC block the FAS-II elongation cycle by covalently modifying the essential FAS-II dehydratase, HadAB. Despite this important breakthrough, it is still unclear whether ISO and TAC also inhibit the (non- essential) FAS-II dehydratase HadBC, and the mechanism(s) through which missense mutations in HadC increase 16 to 32-fold the resistance of Mtb to both drugs remain(s) unexplained. This application is to complete our understanding of the mechanisms of susceptibility and resistance of Mtb to ISO and TAC with the long-term goal of developing novel inhibitors of the dehydration step of FAS-II with reduced resistance frequencies and much improved potency, specificity and pharmacological features than ISO and TAC. Specifically, we propose under Aim 1 to determine whether ISO and TAC inhibit HadBC in vitro and in whole Mtb cells and, in Aim 2, to define the molecular mechanisms through which HadC missense mutations confer resistance to both drugs.

项目摘要 结核分枝杆菌（MTB）引起的结核病（TB）仍然是一个主要的公共卫生问题 全球和最常见的艾滋病毒患者中最常见的疾病占四分之一的 艾滋病毒/艾滋病相关的死亡。 MTB多耐药菌株的持续增长使得开发 新有效的抗TB药物的优先级。在这种情况下，重新验证了作用的分子机理 已建立的抗结核药物的靶向与前线抗 - TB剂，但在一个明显的催化步骤中，因此绕过广泛的抵抗机制，可能具有 对耐药结核病治疗的主要影响。以前在临床治疗的两种此类药物 TB，Isoxyl（ISO）和噻唑酮（TAC）是我们研究的对象。 ISO和TAC是含硫代氨基胺的前药，需要通过 MTB黄素依赖性单加氧酶Etha用于杀菌活性。激活后，ISO和TAC抑制 霉菌酸的生物合成，从而消除了MTB外膜的形成，并导致 细胞死亡。我们最近确定了II型脂肪酸合酶（FAS-II）伸长的脱水步骤 循环是ISO和TAC都抑制霉菌酸的生物合成的点。具体来说，我们发现 ISO和TAC通过共价修改必需的FAS-II脱氢酶，阻止FAS-II伸长周期 hadab。尽管有这一重要突破，但尚不清楚ISO和TAC是否也抑制（非 - 必需）FAS-II脱氢酶HADBC，以及HADC中的错义突变的机制 增加了MTB对两种药物的抗性的16至32倍，无法解释。 该应用是为了完成我们对MTB易感性和抵抗力机制的理解 ISO和TAC的长期目标是开发FAS-II脱水步骤的新型抑制剂 降低的电阻频率和更高的效力，特异性和药理学特征比 ISO和TAC。具体而言，我们提出的AIM 1提议以确定ISO和TAC是否在体外抑制HADBC 在整个MTB细胞中，在AIM 2中定义了Hadc错过的分子机制 突变赋予两种药物的抗性。