The novel role and regulation of IRAK in innate immunity

描述(申请人提供)：Toll样受体(TLR)介导的天然免疫信号调节炎症过程的各个方面。TLRs的激活导致多种转录因子(包括NFkB、IRFs和Stats)介导的不同基因表达。导致差异转录差异激活的具体调控机制尚不清楚。前人和本实验室的研究表明，白介素1受体相关蛋白1(IRAK1)是TLR介导的天然免疫信号通路中的关键信号分子。虽然目前认为IRAK1是一种近端信号分子，与IRAK4一起在激活NFkB方面扮演着某种多余的角色，但IRAK1基因敲除的小鼠仍然保留了IPS诱导的NFkB激活。我们最近对IRAK1缺陷小鼠的研究表明，IRAK1在激活转录因子STAT3并随后负责IL-10基因表达方面发挥了新的作用。值得注意的是，我们还发现泛素化的IRAK1在IPS攻击后进入细胞核，并通过染色质免疫沉淀试验直接与内源性IL-10启动子结合。这提出了一个新的问题，即IRAK1除了作为传统的近端信号分子发挥功能外，还直接作为转录调节因子发挥作用。此外，我们观察到IRAK1在动脉粥样硬化患者外周血单个核细胞中持续泛素化并分布于核中，与血清IL-10水平升高相关。升高的IL-10可能是动脉粥样硬化时防止过度炎症的一种自我保护机制。根据这些新的发现，我们假设IRAK1在TLR信号通路中具有独特的位置，可以特异性地激活STAT3。这项资助的目的是在生化水平上进一步表征IRAK1如何关键地参与STAT3的激活和IL-10基因的表达。此外，由于IRAK1在动脉粥样硬化患者中持续泛素化，我们推测IRAK1可能与动脉粥样硬化的发病或缓解密切相关。目标1将阐述IRAK1泛素化、核进入以及与STAT3相互作用的机制。AIM2将研究IRAK1介导的IL-10基因表达的机制。AIM3将研究IRAK1缺失对动脉粥样硬化发病和/或缓解的影响。

DESCRIPTION (provided by applicant): Toll-like-receptor (TLR) mediated innate immunity signaling regulates various aspects of inflammation processes. Activations of TLRs lead to diverse gene expressions mediated by various transcription factors including NFkB, IRFs, as well as Stats. The specific regulatory mechanism leading to differential activation of distinct transcription is not clearly understood. Studies from others as well as our lab indicate that interleukin-1 receptor associate kinase 1 (IRAK1) is a key signaling molecule in the TLR mediated innate immunity signaling pathway. Although IRAK1 is currently thought to be a proximal signaling molecule playing a somewhat redundant role together with IRAK4 in activating NFkB, IRAK1 knockout mice still retain IPS inducible NFkB activation. Our recent study using IRAK1 deficient mice indicates that IRAK1 is playing a novel role in activating the transcription factor Stat3 and subsequently responsible for IL-10 gene expression. Strikingly, we also found that ubiquitinated IRAK1 enters nucleus upon IPS challenge and directly binds with endogenous IL-10 promoter element as determined by chromatin immunoprecipitation assay. This raises a novel issue of IRAK1 serving directly as a transcriptional regulator besides functioning as a conventional proximal signaling molecule. Furthermore, we have observed that IRAK1 is consistently ubiquitinated and distributed in the nucleus of peripheral blood mononuclear cells from atherosclerosis patients, correlating with the elevated serum IL-10 levels. Elevated IL-10 may be a self-protective mechanism preventing excessive inflammation during atherosclerosis. With these novel findings, we hypothesize that IRAK1 is uniquely positioned in the TLR signaling pathway to specifically activate Stat3. The objective of this grant is to further characterize, at the biochemical level, how IRAK1 is critically involved in Stat3 activation and IL-10 gene expression. Furthermore, since IRAK1 is consistently ubiquitinated in atherosclerosis patient, we hypothesize that IRAK1 may be intimately involved in either the pathogenesis or resolution of atherosclerosis. Aim 1 will address the mechanism of IRAK1 ubiquitination, nuclear entry, and interaction with Stat3. Aim2 will examine the mechanism for IRAK1 mediated IL-10 gene expression. Aim3 will study the effect of IRAK1 deletion on the pathogenesis and/or resolution of atherosclerosis.