IRAK Family Function in Bacterial Infection

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，宿主先天免疫系统检测到攻击并触发反应来遏制和消除入侵者。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，遏制并消除感染。因此，先天免疫反应包含传入（病原体感知）和传出（促炎）两种肢体。Toll/IL-1信号转导通路介导这种对感染的先天反应的两个方面。这个保守的信号级联由蛋白MyD88、白细胞介素-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，将它们分配到多个下游靶点，包括NF-kB和几个有丝分裂原激活的蛋白激酶级联。我们在小鼠中基因上删除了IRAK，这是该途径中主要的近端激酶。irak缺失的动物和巨噬细胞对脂多糖（LPS）、肽聚糖（PGN）、脂techacid （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信号被破坏，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缺陷巨噬细胞和小鼠接受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，肺炎克雷希菌和金黄色葡萄球菌肺炎。目的2是通过产生IRAK/IL-121和IRAK/TLR4双敲除动物，比较双和单KO巨噬细胞和小鼠对LPS刺激、非复制性肺炎克雷伯菌和肺炎克雷伯菌肺炎的反应，从基因上分离IRAK对TLR4或il -1受体通路的功能。目的3是确定IRAK2和IRAK- m对IRAK缺陷细胞中残留TLR信号的贡献，因为IRAK的缺失会损害信号传导，但不会完全消除信号传导。这些研究应该为IRAK在急性细菌感染的先天免疫反应中的作用提供基本的新信息，并可能最终导致调节这种反应有害方面的策略的发展。

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.