IRAK Family Function in Bacterial Infection

IRAK 家族在细菌感染中的功能

• 批准号: 6885330
• 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/6885330
• 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最根本的威胁之一。 当细菌病原体突破上皮屏障时，宿主先天免疫系统会检测到攻击并触发反应以遏制和消灭入侵者。 细胞传感器，例如巨噬细胞和树突状细胞，通过识别细菌大分子的受体来检测病原体。 然后，这些细胞会产生促炎反应，从而导致抑制和消除感染的细胞反应。 因此，先天免疫反应包含传入（病原体感应）和传出（促炎）肢体。 Toll/IL-1 信号转导途径介导这种对感染的先天反应的两个方面。 这种保守的信号级联由蛋白质 MyD88、白细胞介素 1 受体相关激酶 (IRAK) 分子家族（IRAK、IRAK2 和 IRAK-M）以及肿瘤坏死因子相关因子 6 组成。它处理来自至少 10 个信号通路的信号。 Toll 样受体 (TLR) 和三个 IL-1 受体家族成员（IL-1、IL-18 和 Ti/ST2），将它们分布到多个下游靶标，包括NF-kB 和几种有丝分裂原激活的蛋白激酶级联。 我们在小鼠体内基因删除了该通路中主要的近端激酶 IRAK。 缺乏IRAK的动物和巨噬细胞对脂多糖（LPS）、肽聚糖（PGN）、脂磷壁酸（LTA）和CpG DNA（通过TLR4和TLR2激活先天免疫传入臂的细菌分子）的反应受损。 由于 IL-1 和 IL-18 信号传导中断，这些小鼠还表现出促炎（传出）反应减弱。该提案的总体目标是确定 IRAK 在宿主对革兰氏阴性和革兰氏阳性感染的反应中的功能。 目标 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。 我们将对缺乏IRAK的巨噬细胞和小鼠进行越来越复杂的感染模型，使用毒素挑战、非复制细菌刺激以及肺炎克雷氏菌和金黄色葡萄球菌肺炎。 目标 2 是通过生成 IRAK/IL-121 和 IRAK/TLR4 双敲除动物并比较双敲除和单敲除巨噬细胞和小鼠对 LPS 刺激、非复制性 K.肺炎克雷伯菌和肺炎克雷伯菌肺炎。 目标 3 是确定 IRAK2 和 IRAK-M 对 IRAK 缺陷细胞中残留 TLR 信号传导的贡献，因为 IRAK 的缺失会损害但不会完全消除信号传导。这些研究应该提供有关 IRAK 在针对急性细菌感染的先天免疫反应中的作用的基本新信息，并可能最终导致制定调节这种反应的有害方面的策略。