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 由结核分枝杆菌（Mycobacterium tuberculosis，Mtb）引起的结核病（tuberculosis，TB）仍然是一个主要的公共卫生问题 艾滋病毒感染者中最常见的疾病占四分之一 与艾滋病毒/艾滋病有关的死亡。耐多药结核病菌株的持续增加使得结核病的发展 新的有效的抗结核病药物的高度优先事项。在此背景下，重新审视分子作用机制 已建立的抗结核药物，其靶向与一线抗结核药物相同的经过充分验证的生物合成途径， 结核病药物，但在一个独特的催化步骤，从而绕过广泛的耐药机制，可能有一个 对耐药结核病的治疗产生重大影响。这两种药物以前用于临床治疗 TB，Isoxyl（ISO）和Thiacetazone（TAC）是我们调查的对象。 ISO和TAC是含硫脲的前药，其需要通过硫代氨基甲酸酯活化其硫代羰基部分。 用于杀菌活性的Mtb黄素依赖性单加氧酶EthA。激活后，ISO和TAC抑制 分枝菌酸的生物合成，从而消除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）延伸的脱水步骤 循环的点，在这两个ISO和TAC抑制分枝菌酸的生物合成。具体来说，我们发现 ISO和TAC通过共价修饰必需的FAS-II脂肪酶来阻断FAS-II延伸循环， HadAB。尽管有这一重要突破，但目前尚不清楚ISO和TAC是否也抑制了（非 必需的）FAS-II突变酶HadBC，以及HadC中错义突变的机制 结核分枝杆菌对这两种药物的耐药性增加16至32倍仍然无法解释。 本申请是为了完成我们对结核分枝杆菌易感性和耐药性机制的理解， ISO和TAC的长期目标是开发FAS-II脱水步骤的新型抑制剂， 降低了耐药频率，大大改善了效力、特异性和药理学特征， ISO和TAC。具体而言，我们在目标1下提出确定ISO和TAC是否在体外抑制HadBC 以及在整个Mtb细胞中，以及在Aim 2中，确定HadC错义的分子机制。 突变会导致对这两种药物的耐药性。