Structure Function Analysis of Staphylococcal Complement Inhibitors

描述（由申请人提供）：金黄色葡萄球菌是一种广泛存在的持久性人类病原体，对人类健康有着长期且日益严重的负面影响。它是院内和社区获得性感染的主要原因，包括心内膜炎和败血症等几种可能致命的循环系统疾病，以及与植入医疗器械相关的感染，如血管内导管、起搏器和输送泵。最近的研究表明，金黄色葡萄球菌表达了几种抑制人类免疫系统先天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。虽然补体系统的正常功能对于有效的免疫应答金黄色葡萄球菌至关重要，但这种生物已经实现了几种强大而复杂的机制来减弱补体功能。细胞外纤维蛋白原结合蛋白（Efb）与新发现的同系物Ehp一起，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）形成有效的复合物，破坏先天免疫的下游功能。然而，缺乏对这些蛋白质在这种更加危险的病原体的免疫抑制库中的结构和功能机制的详细了解。为了在要求的资助期内满足这一需求，我们提出以下具体目标：研究Efb/C3配合物的结构/功能关系表征Ehp/C3复合物的结构、动力学和功能探讨Efb和ehp介导的因子H与c3c4结合增强的结构基础和相关功能。探讨Efb与纤维蛋白原结合的分子基础和功能，通过研究这些蛋白的结构和功能，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，这些研究将为以下方面的临床前景提供重要见解：(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)通过阻断补体系统的病理性过度激活来模拟其活性的分子，如在自身免疫和生物不相容疾病中所见。金黄色葡萄球菌是一种广泛存在的、持续存在的人类病原体，它表达几种抑制人类免疫系统成分的蛋白质。其中，efb家族的分泌蛋白已被证明通过结合和灭活补体成分C3来破坏补体反应的下游功能。在这项工作中，我们拟研究这些蛋白及其与C3复合物的结构和功能。这些结果将进一步加深我们对C3识别的结构和机制以及病理情况下C3的抑制的理解。此外，对这些金黄色葡萄球菌蛋白的研究应该为破坏或模仿其功能的治疗方法的临床前景提供重要的见解。

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.