Structure Function Analysis of Staphylococcal Complement Inhibitors

描述(申请人提供)：金黄色葡萄球菌是一种广泛存在的、持久的人类病原体，对人类健康的负面影响由来已久。它是医院和社区获得性感染的主要原因，包括几种可能致命的循环系统疾病，如心内膜炎和败血症，以及与植入的医疗设备相关的感染，如血管内导管、起搏器和输液泵。最近的研究表明，金黄色葡萄球菌表达几种抑制人类免疫系统固有和适应性成分的蛋白质，大量证据表明，这些蛋白质对金黄色葡萄球菌作为病原体的成功至关重要。虽然补体系统的适当功能对于金黄色葡萄球菌的有效免疫反应是必不可少的，但这种生物已经实现了几种强大和复杂的机制来减弱补体功能。与新发现的EHP同源物一起，细胞外纤维蛋白原结合蛋白(EFB)定义了一个新的补体抑制蛋白家族，通过与天然的、未加工的人类补体成分3(C3)形成强大的复合体，扰乱天然免疫的下游功能。然而，对这些蛋白在这种日益危险的病原体的免疫抑制体系中的结构和功能机制缺乏详细的了解。1.研究EFB/C3复合体的结构/功能关系2.表征EHP/C3复合体的结构、动力学和功能3.研究EFB和EHP介导的增强因子H与C3结合的结构基础和相关功能。通过研究这些蛋白的结构和功能来研究EFB与纤维蛋白原结合的分子基础和功能，我们将进一步了解金黄色葡萄球菌逃避免疫系统的机制。反过来，这将促进我们对病理情况下C3识别和抑制的结构和机制的了解。从长远来看，这些研究将为以下临床前景提供重要的见解：(A)旨在阻断金黄色葡萄球菌免疫抑制毒力因子功能的抗菌预防措施，以及(B)通过阻断补体系统病理性过度激活来模拟其活动的分子，如在自身免疫和生物不相容疾病中所看到的那样。项目简介：金黄色葡萄球菌补体抑制剂的结构/功能分析金黄色葡萄球菌是一种广泛、持久的人类病原体，它表达几种抑制人类免疫系统成分的蛋白质。其中，分泌蛋白EFB家族通过结合和失活补体成分C3来干扰补体反应的下游功能。在这项工作中，我们打算研究这些蛋白质及其与C3的络合物的结构和功能。这些结果将进一步加深我们对C3在病理情况下识别和抑制C3的结构和机制的理解。此外，对这些金黄色葡萄球菌蛋白的研究将为干扰或模拟其功能的治疗提供重要的临床前景。

DESCRIPTION (provided by applicant): Staphylococcus aureus is a widespread, persistent human pathogen that has a long-standing and increasingly negative impact on human health. It is a leading cause of nosocomial and community-acquired infections, including several potentially fatal conditions of the circulatory system such as endocarditis and septicemia, as well as infections associated with implanted medical devices, such as intravascular catheters, pacemakers, and delivery pumps. Recent studies have demonstrated that S. aureus expresses several proteins that inhibit the innate and adaptive components of the human immune system and a body of evidence suggests that these proteins are critical to the success of S. aureus as a pathogen. While proper function of the complement system is essential for an efficient immune response against S. aureus, this organism has achieved several powerful and sophisticated mechanisms to attenuate complement function. Together with a newly identified homolog denoted Ehp, the Extracellular Fibrinogen-binding Protein (Efb) defines a novel family of complement inhibitory proteins that disrupt downstream functions of innate immunity by forming a potent complex with the native, unprocessed form of human complement component 3 (C3). However, a detailed understanding of the structure and mechanism of function for these proteins in the immunosuppressive repertoire of this ever more dangerous pathogen is lacking. To address this need during the requested funding period, we propose the following Specific Aims: 1. To Study the Structure/ Function Relationships of the Efb/C3 Complex 2. To Characterize the Structure, Dynamics, and Functions of the Ehp/C3 Complex 3. To Investigate the Structural Basis and Associated functions of Efb and Ehp-mediated Enhancement of Factor H Binding to C3 4. To Investigate the Molecular Basis and Functions of Efb Binding to Fibrinogen By studying the structure and function of these proteins, we will further our understanding of the mechanisms used by S. aureus to evade the immune system. In turn, this will promote our knowledge of the structure and mechanism of C3 recognition and inhibition during pathological situations. In the long term, these studies will provide important insights into the clinical promise for (a) antibacterial preventative measures that are designed to block the functions of immunosuppressive virulence factors from S. aureus, and (b) molecules which mimic their activities by blocking pathological overactivation of the complement system, as is seen in autoimmune and bioincompatibility disorders. Project Narrative: Structure/Function Analysis of Staphylococcal Complement Inhibitors Staphylococcus aureus is a widespread, persistent human pathogen that expresses several proteins that inhibit components of the human immune system. Among these, the Efb-family of secreted proteins has been shown to disrupt downstream function of complement response by binding and inactivating complement component C3. In this work, we propose to study the structure and function of these proteins and their complexes with C3. The results attained will further our understanding of the structure and mechanism of C3 recognition and inhibition of C3 during pathological situations. In addition, study of these S. aureus proteins should provide important insights into the clinical promise for therapeutics that either disrupt or mimic their function.