Toll-like receptor 2 negative regulation of Liver X Receptors function

描述（由申请人提供）：巨噬细胞肝X受体（LXRs）是转录因子核受体超家族的成员，由天然存在的氧化甾醇结合和激活。LXRs是脂质稳态和炎症的中枢调节因子，在动物模型中具有抑制动脉粥样硬化的重要作用。最近的研究表明，SUMOylation-dependent通路调节LXR的抗炎功能。我们的初步数据表明，尽管LXRs和PPAR激动剂可以抑制toll样受体（TLR） 4和干扰素诱导的基因激活，但当我们用TLR2配体刺激细胞时，LXR的转抑制被选择性地消除。这证明了信号和核受体特异性机制可以超越LXRs的sumoylation依赖性抗炎功能。本研究旨在探讨TLR2负调控LXR抗炎功能的分子机制。本研究提出了三个具体目的。首先，我将通过生化分析，通过CaMKII诱导LXR的直接相互作用和磷酸化来确定TLR2是否会阻断LXR的功能。第二个目的是验证camkii介导的磷酸化导致LXR的deSUMOylation的假设，这可能会改变LXR对NCoR复合物的亲和力及其在siRNA敲低研究中的转抑制能力。第三个目的是利用微阵列和chlp测序技术验证TLR2激活CaMKII在全基因组水平上阻断LXR功能的假设。巨噬细胞介导的炎症反应是许多慢性炎症性疾病的重要因素，包括动脉粥样硬化和糖尿病。了解LXR功能调控的分子机制可以为设计治疗动脉粥样硬化和其他慢性炎症性疾病的治疗方法提供重要信息。

DESCRIPTION (provided by applicant): Macrophage liver X receptors (LXRs) are members of the nuclear receptor superfamily of transcription factors and are bound and activated by naturally occurring oxysterols. LXRs are central regulators of lipid homeostasis and inflammation, and play an important role to inhibit atherosclerosis in animal models. Recent studies suggest that a SUMOylation-dependent pathway regulates LXR anti-inflammatory function. Our preliminary data suggests that although Toll-like-receptor (TLR) 4 and interferon induced gene activation can be repressed by LXRs and PPAR agonists, LXR transrepression is selectively abolished when we stimulate the cells with TLR2 ligands. This argues for a signal and nuclear receptor specific mechanism in over-ridding the SUMOylation-dependent anti-inflammatory function of LXRs. The aim of this proposal is to investigate the molecular mechanisms by which TLR2 negatively regulates the anti-inflammatory function of LXR. Three specific aims are proposed for this investigation. First, I will determine whether TLR2 blocks LXR function by inducing direct interaction and phosphorylation of LXR by CaMKII using biochemical assays. The second aim is to test the hypothesis that CaMKII-mediated phosphorylation leads to deSUMOylation of LXR, which may alter the affinity of LXR for NCoR complex and its ability to transrepress in siRNA knockdown studies. The third aim is to test the hypothesis that TLR2 activated CaMKII blocks LXR function at a genome-wide level using microarray and ChlP-Sequencing technologies. Macrophage-mediated inflammatory responses are important contributors to many chronic inflammatory diseases, including atherosclerosis and diabetes. Understanding of the molecular mechanisms of regulation of LXR function could provide important information for designing therapeutic approaches for treating atherosclerosis and other chronic inflammatory diseases.