STAPHYLOCIDAL MECHANISM OF PLATELET MICROBICIDAL PROTEIN

传统上，血小板被认为是促进 血管内感染，如感染性心内膜炎（IE）， 粘附在受损内皮上的表面，用于通过循环 微生物的相反，最近的证据表明，血小板 对于血管内发展的重要宿主防御作用 内皮损伤部位的感染，通过内源性 杀微生物肽，称为凝血酶诱导的血小板杀微生物肽 蛋白质或tPMP。初步研究揭示了以下数据：i）tPMP 以nM浓度杀死最常见的血管内病原体; ii） 无IE的菌血症患者的微生物菌株显著高于无IE的菌血症患者的微生物菌株。 在体外对tPMP的杀菌作用比菌株更敏感 来自患有IE的菌血症患者。这表明表型tPMP- 抗性为生物体提供了生存优势， 诱导IE; iii）tPMP与常规药物组合是协同的 抗生素对S.金黄色葡萄球菌;和iv） 细菌细胞膜似乎是tPMP诱导的主要靶点。 本提案的总体目的是界定 tPMP对S.金黄色，最 血管内感染的致命性和最常见的总体原因，通过：i） 定量tPMP与葡萄球菌膜的结合; ii）描绘 细菌跨膜电位在杀葡萄球菌作用中的作用 iii）鉴定tPMP的膜组装体和随后的 通过tPMP的膜透化和孔形成;和iv）定义 表型tPMP抗性的机制，使用遗传相关的 来自共同基因组背景的葡萄球菌菌株， tPMP易感性的表型。这些研究最终可能会定义 新的杀葡萄球菌靶标或独特的杀葡萄球菌机制。这些 研究还将为定义葡萄球菌杀 分子生物学技术研究tPMP的结构域。tPMP还将用于 作为设计模板，用于开发具有潜在毒性的合成同系物 抗菌活性

Traditionally, platelets have been thought to promote the development of endovascular infections such as infective endocarditis (lE), by providing a adhesive surface upon damaged endothelium for colonization by circulating microorganisms. In contrast, recent evidence suggests that platelets serve an important host defense role against the development of endovascular infections at sites of endothelial damage via local secretion of endogenous microbicidal peptides , termed thrombin-induced platelet microbicidal protein or tPMP. Preliminary studies revealed the following data: i) tPMP kills the most common endovascular pathogens in nM concentrations; ii) microbial strains from bacteremic patients without IE were significantly more susceptible in vitro to the microbicidal action of tPMP than strains from bacteremic patients with IE. This suggested that phenotypic tPMP- resistance provides the organism with a survival advantage as regards induction of IE; iii) tPMP is synergistic in combination with conventional antibiotics in the killing and growth.inhibition of S. aureus ; and iv) the bacterial cell membrane appears to be a primary target for tPMP-induced lethality.The overall purpose of the current proposal is to define the fundamental microbicidal mechanisms of tPMP against S. aureus, the most virulent and commonest overall cause of endovascular infections, by: i) quantifying tPMP binding to the staphylococcal membrane; ii) delineating the role of bacterial transmembrane potential in the staphylocidal actions tPMP; iii) identifying membrane assembly of tPMP and subsequent membrane permeabilization and pore formation by tPMP; and iv) defining the mechanisms of phenotypic tPMP resistance, using genetically-related staphylococcal strains from a common genomic background which differ phenotypically in tPMP susceptibility. These studies may eventually define novel staphylocidal targets or unique staphylocidal mechanisms. These studies will also provide a solid foundation for defining the staphylocidal domains of tPMP by molecular biologic techniques. tPMP will also serve as a design template for development of synthetic congeners with potent antimicrobial activity.