The novel role and regulation of IRAK in innate immunity

描述（由申请人提供）：Toll样受体（TLR）介导的先天免疫信号传导调节炎症过程的各个方面。TLR的激活导致由各种转录因子（包括NF κ B、IRF以及Stats）介导的不同基因表达。导致不同转录的差异激活的具体调控机制尚不清楚。本实验室和其他研究表明，白细胞介素1受体相关激酶1（IRAK 1）是TLR介导的先天免疫信号通路中的关键信号分子。虽然IRAK 1目前被认为是一种近端信号分子，与IRAK 4一起在激活NFkB中发挥某种冗余作用，但IRAK 1敲除小鼠仍保留IPS诱导的NFkB激活。我们最近使用IRAK 1缺陷小鼠的研究表明，IRAK 1在激活转录因子Stat 3和随后负责IL-10基因表达方面发挥着新的作用。引人注目的是，我们还发现泛素化的IRAK 1在IPS攻击后进入细胞核，并直接与内源性IL-10启动子元件结合，如染色质免疫沉淀测定所确定的。这提出了一个新的问题，IRAK 1除了作为一个传统的近端信号分子发挥作用外，还直接作为一个转录调节因子。此外，我们观察到IRAK 1在动脉粥样硬化患者外周血单核细胞的细胞核中始终被泛素化并分布，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期间防止过度炎症的自我保护机制。通过这些新的发现，我们假设IRAK 1在TLR信号通路中具有独特的位置，可以特异性地激活Stat 3。这项研究的目的是在生物化学水平上进一步表征IRAK 1如何关键参与Stat 3激活和IL-10基因表达。此外，由于IRAK 1在动脉粥样硬化患者中一直是泛素化的，我们假设IRAK 1可能密切参与动脉粥样硬化的发病机制或解决。目的1将解决IRAK 1泛素化，核进入，并与Stat 3相互作用的机制。Aim 2将检查IRAK 1介导的IL-10基因表达的机制。Aim 3将研究IRAK 1缺失对动脉粥样硬化发病机制和/或消退的影响。

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.