IRAK Family Function in Bacterial Infection

IRAK 家族在细菌感染中的功能

• 批准号: 6470438
• 负责人: JAMES Alanson THOMAS
• 金额: $ 19.82万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-05-01 至 2007-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6470438
• 关键词: Klebsiella pneumoniae; RNase protection assay; Staphylococcus aureus; Streptococcus pneumoniae; antigen antibody reaction; attenuated microorganism; bacteria infection mechanism; biological signal transduction; cellular immunity; cytokine receptors; disease /disorder model; enzyme activity; enzyme linked immunosorbent assay; gene deletion mutation; genetically modified animals; gram negative bacteria; gram positive bacteria; host organism interaction; inflammation; laboratory mouse; lipopolysaccharides; macrophage; protein kinase; protein structure function; tissue /cell culture; toll like receptor

Infection represents one of the most fundamental threats to host integrity. When bacterial pathogens breach an epithelial barrier, the host innate immune system detects the attack and triggers a response to contain and eliminate the invader. Cellular sensors, such as macrophages and dendritic cells, detect pathogen through receptors that recognize bacterial macromolecules. These cells then mount a proinflammatory reaction that leads to cellular responses that contain and eliminate the infection. Thus, the innate immune response contains both afferent (pathogen-sensing) and efferent (proinflammatory) limbs. The Toll/IL-1 signal transduction pathway mediates both arms of this innate response to infection. This conserved signaling cascade consists of the proteins MyD88, the interleukin-1 receptor-associated kinase (IRAK) family of molecules (IRAK, IRAK2, and IRAK-M) and the tumor necrosis factor associated factor 6. It processes signals from at least 10 Toll-like receptors (TLRs) and three IL-1 receptor family members (IL-1, IL-18, and Ti/ST2), distributing them to multiple downstream targets, including NF-kB and several mitogen activated protein kinase cascades. We have genetically deleted IRAK, the primary proximal kinase in this pathway, in mice. IRAK-deficient animals and macrophages exhibit impaired responses to lipopolysachharide (LPS), peptidoglycan (PGN), lipotechoic acid (LTA), and CpG DNA, bacterial molecules that activate the afferent arm of innate immunity through TLR4 and TLR2. These mice also exhibit attenuated proinflammatory (efferent) responses due to disrupted IL-1 and IL-18 signaling. The overall objective of this proposal is to determine IRAK function in the host response to Gram-negative and Gram-positive infections. Aim 1 is to determine the role of IRAK in the acute inflammatory response to Gram-negative and Gram-positive infections. We will subject IRAK- deficient macrophages and mice to increasingly complex models of these infections, using toxin challenges, stimulation with nonreplicating bacteria, and Klesiella pneumoniae and Staphylococcus aureus pneumonia. Aim 2 is to isolate IRAK function genetically to either the TLR4 or IL-1receptor pathway by generating IRAK/IL-121 and IRAK/TLR4 double knockout animals and comparing the responses of double and single KO macrophages and mice to LPS stimulation, nonreplicating K. pneumoniae, and K. pneumoniae pneumonia. Aim 3 is to determine the contributions of IRAK2 and IRAK-M to residual TLR signaling in IRAK-deficient cells, as deletion of IRAK impairs, but does not completely abrogate signaling. These studies should provide fundamental new information about the role of IRAK in the innate immune response to acute bacterial infection and may eventually lead to the development of strategies to modulate deleterious aspects of this response.

感染是对宿主完整性的最根本威胁之一。当细菌突破上皮屏障时，宿主的固有免疫系统会检测到攻击并触发反应，以遏制和消除入侵者。巨噬细胞和树突状细胞等细胞传感器通过识别细菌大分子的受体检测病原体。然后，这些细胞启动促炎反应，导致细胞反应，遏制和消除感染。因此，先天免疫反应包括传入(病原体感知)和传出(促炎)肢体。Toll/IL-1信号转导通路介导了这种先天感染反应的两个臂。这个保守的信号通路由MyD88蛋白、白介素1受体相关激酶(IRAK)家族分子(IRAK、IRAK2和IRAK-M)和肿瘤坏死因子相关因子6组成。它处理来自至少10个Toll样受体(TLRs)和3个IL-1受体家族成员(IL-1、IL-18和Ti/ST2)的信号，将信号分配给多个下游靶点，包括核因子-kB和几个丝裂原激活的蛋白激酶级联。我们已经在小鼠中从基因上删除了IRAK，这是这一途径中的主要近端激酶。IRAK缺陷动物和巨噬细胞对脂多糖(LPS)、肽聚糖(PGN)、脂磷壁酸(LTA)和CpG DNA的反应受损，这些细菌分子通过TLR4和TLR2激活天然免疫的传入臂。由于IL-1和IL-18信号的中断，这些小鼠也表现出减弱的促炎(传出)反应。这项建议的总体目标是确定IRAK在宿主对革兰氏阴性和革兰氏阳性感染反应中的功能。目的1确定IRAK在革兰氏阴性和革兰氏阳性感染的急性炎症反应中的作用。我们将使IRAK缺陷的巨噬细胞和小鼠受到越来越复杂的这些感染模型，使用毒素挑战、非复制细菌刺激以及肺炎克雷西菌和金黄色葡萄球菌肺炎。目的2通过建立IRAK/IL-121和IRAK/TLR4双基因敲除动物，并比较双KO巨噬细胞和单KO巨噬细胞和小鼠对脂多糖刺激、非复制型肺炎克雷伯菌和肺炎克雷伯菌的反应，来分离IRAK对TLR4或IL-1受体途径的遗传功能。目的3是确定IRAK缺失细胞中IRAK2和IRAK-M对残留的TLR信号的贡献，因为IRAK的缺失会损害信号转导，但不能完全消除信号转导。这些研究应该提供关于IRAK在急性细菌感染的先天性免疫反应中所起作用的基本新信息，并最终可能导致开发调节这种反应的有害方面的策略。