The Mechanisms of Heme Toxicity and Detoxification in Staphylococcus aureus

金黄色葡萄球菌血红素毒性和解毒机制

• 批准号: 8316552
• 负责人: Catherine Ann Wakeman
• 金额: $ 5.22万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8316552
• 关键词: Address; Affect; Aminoglycoside Antibiotics; Aminoglycoside resistance; Aminoglycosides; Anabolism; Antibiotic Resistance; Antibiotic Therapy; Antibiotics; Bacillus anthracis; Bacteria; Biochemical; Clinical; Corynebacterium diphtheriae; Data; Defect; Disease; Drug Delivery Systems; Drug Design; Drug Metabolic Detoxication; Electron Transport; Environment; Environmental Risk Factor; Genetic; Growth; Health; Heme; Heme Iron; Human; Infection; Invaded; Iron; Knowledge; Ligands; Link; Listeria monocytogenes; Multi-Drug Resistance; Mutation; Names; Nature; Nutrient; Organ; Organism; Oxidative Stress; Pathway interactions; Patients; Phenotype; Physiology; Play; Predisposition; Property; Regulation; Resistance; Respiration; Respiratory Chain; Role; Screening procedure; Signal Transduction; Source; Staphylococcus aureus; Stress; Surface; System; Techniques; Testing; Tetrapyrroles; Toxic effect; Variant; Virulence; Vitamin K 2; Work; antimicrobial; base; clinically relevant; coping; design; efflux pump; experience; heme a; insight; killings; metabolomics; mutant; oxidative damage; pathogen; pathogenic bacteria; resistant strain; sensor; therapeutic target; uptake

DESCRIPTION (provided by applicant): Staphylococcus aureus is a human pathogen known to infect virtually every organ and cause numerous diseases. Antibiotic-resistant S. aureus strains are rapidly emerging; therefore, new drug targets are being sought. One of the mechanisms utilized by the host to restrict the growth of invading pathogens is the sequestration of the essential nutrient iron within the tetrapyrrole molecule heme. S. aureus employs sophisticated heme uptake systems in order to gain access to this iron source; however, the presence of excess heme is highly toxic to this and many other organisms. The nature of heme toxicity is not fully characterized but is thought to be, at least in part, due to oxidative damage induced by the reactive properties of the iron atom within the heme molecule. S. aureus possesses a heme detoxification system, a predicted transporter named HrtAB, although little is known about its mechanism of action. In the preliminary data presented in this application, we performed a transposon screen in the background of the heme-susceptible hrtA mutant, screening for strains with increased heme-resistance. All mutants identified targeted the menaquinone (MK) biosynthesis pathway. These data suggest that a component of the MK biosynthesis pathway potentiates heme stress. Interestingly, S. aureus strains deficient in MK biosynthesis, known as small colony variants (SCV), are commonly isolated from patients experiencing persistent infections. While multiple factors may contribute to the selection for MK-deficient S. aureus strains, it seems likely that resistance to the toxic effects of heme, an abundant molecule within the vertebrate host, could be playing a role. Based on these data, we predict that conditions of heme stress are directly relevant to the environment experienced by S. aureus during human infection. Therefore, we propose that a thorough understanding of the sources of heme stress in S. aureus and the mechanisms utilized by this pathogen to overcome the toxic effects of heme is essential to advancing our knowledge of staphylococcal physiology within the host environment. To address this issue we propose the following Aims: Aim 1. Determine the mechanism by which MK biosynthesis potentiates heme stress in S. aureus. Aim 2. Define the mechanism of the HrtAB system utilized by S. aureus to alleviate heme toxicity. Previous studies have suggested the use of the MK biosynthesis pathway as a potential antimicrobial target; however, evidence presented in this application indicates that disruption of the MK pathway might selectively induce the formation of persistent and heme-resistant infections. Instead, the heme detoxification system of S. aureus might represent a more viable drug target. By defining the regulation and function of the HrtAB heme detoxification system found in S. aureus and other pathogens such as Bacillus anthracis, Corynebacterium diphtheriae, and Listeria monocytogenes, we will provide potential insight into targeted therapeutic design exploiting the heme-susceptibility of these organisms. PUBLIC HEALTH RELEVANCE: Staphylococcus aureus is a global threat to human health because it is capable of causing numerous diseases and multi-drug resistant strains are rapidly emerging. Our proposed studies will further the understanding of heme stress in S. aureus, a condition likely experienced during human infection, and define the mechanisms utilized by this bacterium to cope with heme toxicity. Results obtained from these studies may provide insight into how the heme-susceptibility of S. aureus can be exploited as a drug target.

描述(申请人提供)：金黄色葡萄球菌是一种已知的人类病原体，可感染几乎每个器官并导致多种疾病。具有抗药性的金黄色葡萄球菌菌株正在迅速出现；因此，人们正在寻找新的药物靶点。寄主用来限制入侵病原体生长的机制之一是将必需的营养铁隔离在四吡咯分子血红素中。金黄色葡萄球菌使用复杂的血红素吸收系统来获得这种铁源；然而，过量的血红素的存在对这种生物和许多其他生物都是高度有毒的。血红素毒性的性质尚未完全确定，但被认为至少部分是由于氧化损伤。 由血红素分子中铁原子的反应性质引起的。金黄色葡萄球菌拥有一种血红素解毒系统，一种被预测为HrtAB的转运蛋白，尽管人们对其作用机制知之甚少。在本申请提供的初步数据中，我们在对血红素敏感的hrtA突变体的背景中进行了转座子筛选，筛选出对血红素抗性增强的菌株。所有已鉴定的突变体都针对孟喹酮(MK)的生物合成途径。这些数据表明，MK生物合成途径的一个组成部分加强了血红素应激。有趣的是，缺乏MK生物合成的金黄色葡萄球菌菌株，被称为小菌落变种(SCV)，通常是从经历持续感染的患者中分离出来的。虽然多个因素可能有助于选择缺乏MK的金黄色葡萄球菌菌株，但对血红素毒性效应的抵抗力似乎可能起到作用，血红素是脊椎动物宿主中丰富的分子。基于这些数据，我们预测，血红素应激的条件与金黄色葡萄球菌在人类感染期间所经历的环境直接相关。因此，我们认为，彻底了解金黄色葡萄球菌中血红素应激的来源以及这种病原体用来克服血红素毒性效应的机制，对于促进我们对宿主环境中葡萄球菌生理学的了解是至关重要的。为了解决这一问题，我们提出了以下目标：目的1.确定MK生物合成增强金黄色葡萄球菌中血红素胁迫的机制。目的2.明确金黄色葡萄球菌利用HrtAB系统减轻血红素毒性的机制。先前的研究表明，MK生物合成途径被用作潜在的抗菌靶点；然而，在这一应用中提出的证据表明，MK途径的中断可能选择性地诱导持久的和对血红素具有抗药性的感染的形成。相反，金黄色葡萄球菌的血红素解毒系统可能代表了一个更可行的药物靶点。通过定义金黄色葡萄球菌和其他病原体(如炭疽杆菌、白喉棒状杆菌和单核细胞增生性李斯特菌)中发现的HrtAB血红素解毒系统的调节和功能，我们将为利用这些生物对血红素的敏感性进行靶向治疗设计提供潜在的见解。 公共卫生相关性：金黄色葡萄球菌是对人类健康的全球威胁，因为它能够导致多种疾病，而且多重耐药菌株正在迅速出现。我们建议的研究将进一步了解金黄色葡萄球菌中的血红素应激，这可能是人类感染期间经历的一种情况，并确定这种细菌用来应对血红素毒性的机制。这些研究的结果可能为如何利用金黄色葡萄球菌的血红素敏感性作为药物靶标提供洞察力。