Novel Mechanisms of Beta-lactam Resistance in Staph Aureus

金黄色葡萄球菌β-内酰胺耐药的新机制

• 批准号: 10078841
• 负责人: Som Chatterjee
• 金额: $ 65.37万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10078841
• 关键词: Adenosine Monophosphate; Affect; Affinity; Ampicillin; Antibiotics; Attenuated; Bacteria; Binding; Biochemical; Biological Assay; Biology; Cell Wall; Cell physiology; Cell surface; Cells; Chemicals; Cleaved cell; Clinical; Cyclic AMP; Cytolysins; Data; Defect; Follow-Up Studies; Future; Gene Expression; Genetic; Genetic Transcription; Genus staphylococcus; Goals; Human; Investigation; Knowledge; Lead; Mediating; Mediator of activation protein; Methicillin Resistance; Missense Mutation; Molecular Weight; Monobactams; Morbidity - disease rate; Mutation; Penicillin-Binding Proteins; Penicillins; Peptidyltransferase; Periodicity; Pharmaceutical Preparations; Phenotype; Physiological; Process; Production; Promoter Regions; Proteins; Proteomics; RNA; Regulation; Research; Resistance; Role; Second Messenger Systems; Signal Transduction; Staphylococcus aureus; Structure; Treatment Failure; Virulence; Virulence Factors; Yin-Yang; beta-Lactam Resistance; beta-Lactamase; beta-Lactams; cost; crosslink; experimental study; genome sequencing; in vivo; inhibitor/antagonist; lead candidate; loss of function mutation; mortality; novel; novel therapeutic intervention; overexpression; pathogen; pathogenic bacteria; phosphoric diester hydrolase; promoter; resistance mechanism; screening; whole genome

Abstract We have identified a novel mode of high-level, broad-spectrum β-lactam resistance in S. aureus that is not mediated by PBP2a, the penicillin-binding protein (PBP) that confers methicillin resistance. PBP4, a non- essential PBP, and GdpP, the only known phosphodiesterase (PDE) that mediates cyclic-di-adenosine-mono- phosphate (CDA) degradation, have critical roles in this type of resistance. Mutations that enhance PBP4's ability to make a highly cross-linked bacterial cell wall and loss-of-function mutations in GdpP are the genetic basis responsible for this uncanonical resistance. The highly cross-linked cell wall formation is driven either independently or cooperatively by two distinct biochemical features of PBP4, a) structural changes in its protein due to missense mutations and b) its overexpression due to mutations in its promoter region. The loss-of-function mutations in GdpP result in elevated concentrations of CDA in bacterial cells. CDA is a newly discovered cell-signaling second messenger in bacteria which acts as an allosteric regulator by binding to its effectors (proteins and RNAs). CDA broadly affects gene expression and controls GdpP related β-lactam resistant phenotypes in a concentration dependent manner, suggesting that it is the deterministic factor in resistance. However, the precise role(s) of CDA in mediating β-lactam resistance as well as other vital processes of S. aureus is currently unknown. These functional alterations of PBP4 and GdpP likely come at the cost of bacterial virulence due to depletion of cell wall associated proteins and attenuated production of cytolysins, respectively. This indicates a unique yin-yang relationship between two key pathogenic factors of S. aureus, β-lactam resistance and virulence. We will investigate the fundamental basis of the functional changes in PBP4 and GdpP that lead to resistance and their impact on bacterial virulence. Aim 1: To determine the mechanism of PBP4-mediated β-lactam resistance and the role of PBP4 in cell wall composition. The relative contribution of PBP4 missense and promoter mutations on cell wall synthesis will be evaluated biochemically and structurally. The mechanism(s) that control pbp4 expression will be investigated to identify regulator(s) and to determine how they confer PBP4-mediated β-lactam resistance. PBP4's role on bacterial cell surface associated virulence factor expression will be determined. Aim 2: To define the role of cyclic-di-adenosine-mono-phosphate (CDA) signaling in S. aureus. Genetic and chemical proteomic approaches will be taken to identify CDA mediator/s in the bacteria that are responsible for β-lactam resistance and virulence defect. Finally, our preliminary data suggest the presence of a novel CDA specific phosphodiesterase in S. aureus besides GdpP. We will identify this novel phosphodiesterase. The proposed research will advance knowledge of basic cellular processes in S. aureus.

抽象的 我们在金黄色葡萄球菌中发现了一种高水平、广谱 β-内酰胺耐药性的新模式，该模式不是 由 PBP2a 介导，PBP2a 是一种青霉素结合蛋白 (PBP)，可赋予甲氧西林耐药性。 PBP4，非 必需的 PBP 和 GdpP，唯一已知的介导环二腺苷单-的磷酸二酯酶 (PDE) 磷酸盐 (CDA) 降解在此类耐药性中发挥着关键作用。增强 PBP4 的突变 产生高度交联的细菌细胞壁的能力和 GdpP 的功能丧失突变是遗传因素 造成这种非规范抵抗的基础。高度交联的细胞壁形成是由以下任一因素驱动的 PBP4 的两个不同生化特征独立或协同作用，a) 其蛋白质的结构变化 由于错义突变和 b) 由于其启动子区域的突变导致其过度表达。 GdpP 的功能丧失突变导致细菌细胞中 CDA 浓度升高。 CDA 是细菌中新发现的细胞信号第二信使，通过以下方式发挥变构调节剂的作用： 与其效应器（蛋白质和 RNA）结合。 CDA 广泛影响基因表达并控制 GdpP 相关 β-内酰胺耐药表型以浓度依赖性方式出现，表明它是确定性的 阻力因素。然而，CDA 在介导 β-内酰胺耐药性以及其他方面的确切作用 金黄色葡萄球菌的重要过程目前尚不清楚。 PBP4 和 GdpP 的这些功能改变可能以细菌毒力为代价，因为 分别消耗细胞壁相关蛋白和减弱溶细胞素的产生。这表明一个 金黄色葡萄球菌的两个关键致病因子β-内酰胺耐药性和 毒力。我们将研究 PBP4 和 GdpP 功能变化的根本基础，从而导致 耐药性及其对细菌毒力的影响。目的 1：确定 PBP4 介导的机制 β-内酰胺抗性和 PBP4 在细胞壁组成中的作用。 PBP4的相对贡献 细胞壁合成的错义和启动子突变将从生化和结构上进行评估。这 将研究控制 pbp4 表达的机制，以确定调节因子并确定如何 它们赋予 PBP4 介导的 β-内酰胺抗性。 PBP4 对细菌细胞表面相关毒力的作用 因子表达将被确定。目标 2：明确环二腺苷单磷酸的作用 金黄色葡萄球菌中的 (CDA) 信号传导。将采用遗传和化学蛋白质组学方法来鉴定 CDA 细菌中负责β-内酰胺耐药性和毒力缺陷的介质。最后，我们的 初步数据表明，除了 GdpP 之外，金黄色葡萄球菌中还存在一种新型 CDA 特异性磷酸二酯酶。 我们将鉴定这种新型磷酸二酯酶。拟议的研究将增进对基本细胞的了解 金黄色葡萄球菌中的过程。