IRAK Family Function in Bacterial Infection

IRAK 家族在细菌感染中的功能

• 批准号: 6623845
• 负责人: JAMES Alanson THOMAS
• 金额: $ 31.2万
• 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/6623845
• 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.

感染是对主机完整性的最根本威胁之一。 当细菌病原体突破上皮屏障时，宿主的先天免疫系统检测到攻击并触发反应以遏制和消除入侵者。 细胞传感器，如巨噬细胞和树突状细胞，通过识别细菌大分子的受体检测病原体。 然后这些细胞产生促炎反应，导致细胞反应，从而抑制和消除感染。 因此，先天免疫反应包含传入（病原体感应）和传出（促炎）分支。 Toll/IL-1信号转导通路介导这种对感染的先天性应答的两个分支。 这种保守的信号级联由蛋白质MyD 88、白细胞介素-1受体相关激酶（IRAK）分子家族（IRAK、IRAK 2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（TLR）和三个IL-1受体家族成员（IL-1、IL-18和Ti/ST 2）的信号，将它们分配给多个下游靶标，包括NF-κ B和几个促分裂原活化蛋白激酶级联。 我们已经在小鼠中基因删除了IRAK，这是该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）、脂技术酸（LTA）和CpG DNA的反应受损，这些细菌分子通过TLR 4和TLR 2激活先天免疫的传入臂。 由于IL-1和IL-18信号传导被破坏，这些小鼠还表现出减弱的促炎（传出）应答。本提案的总体目标是确定IRAK在革兰氏阴性和革兰氏阳性感染的宿主应答中的功能。 目的1是确定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经受这些感染的日益复杂的模型，使用毒素挑战，用非复制细菌刺激，以及肺炎克雷伯菌和金黄色葡萄球菌肺炎。 目的二是通过建立IRAK/IL-121和IRAK/TLR-4双敲除动物模型，比较双敲除和单敲除巨噬细胞和小鼠对LPS刺激、非复制型K. pneumoniae和K.肺炎 目的3是确定IRAK 2和IRAK-M对IRAK缺陷细胞中残留TLR信号传导的贡献，因为IRAK的缺失损害但不完全消除信号传导。这些研究应该提供有关IRAK在对急性细菌感染的先天免疫应答中的作用的基本新信息，并可能最终导致调节这种应答的有害方面的策略的发展。