The Role and Mechanism of NLRX1-mediated Cell Stress Response in Insulin Resistan

描述（由申请人提供）：肥胖和糖尿病等慢性代谢性疾病的发病率急剧增加，是对全球健康的主要威胁之一。最近的研究表明，细胞应激反应在2型糖尿病（T2D）的发病机制中起着重要作用。氧化应激和内质网应激共同促进细胞功能障碍、细胞凋亡和胰岛素抵抗。虽然细胞应激的激活因子和下游效应已被部分描述，但细胞应激反应的调控分子机制尚不清楚。我们的实验室和其他人最近表征了NLR （NBD-LRR）蛋白家族，该家族已被证明可以介导细胞对微生物和环境应激源的应激反应。我的初步数据表明，NLRX1是线粒体定位的NLR蛋白，通过介导线粒体活性氧（mROS）的产生来促进内质网应激反应。在机制上，NLRX1与ECSIT （Toll通路中进化上保守的信号介质）和TRAF6 （TNF受体相关因子6）直接相关，两者在线粒体呼吸链组装中都很重要。Nlrx1缺陷（Nlrx1-/-）细胞不受内质网应激抑制的胰岛素- pi3k - akt通路的影响。此外，Nlrx1-/-小鼠通过高脂饮食（HFD）喂养可以避免肥胖引起的胰岛素抵抗。因此，我假设NLRX1通过促进ECSIT-TRAF6功能介导mROS的产生，进而促进内质网应激，并且NLRX1介导的细胞应激反应损害胰岛素靶组织中的胰岛素信号传导。我将采用T2D （HFD喂养和瘦素缺乏的ob/ob小鼠）动物模型来研究nlrx1介导的细胞应激反应在胰岛素抵抗中的功能。我将研究NLRX1如何控制ECSIT功能和mROS的产生。该提案的目的是研究nlrx1介导的氧化应激和内质网应激在促进细胞功能障碍和胰岛素信号缺陷中的相互作用机制。提出的遗传和生化分析以及动物模型研究将为代谢信号通路的调节和功能提供新的见解。进一步的研究可能会导致新的治疗靶点的确定，并最终帮助制定合理的，基于机制的治疗策略，针对肥胖和糖尿病。

DESCRIPTION (provided by applicant): The incidence of chronic metabolic diseases such as obesity and diabetes has increased dramatically and constitutes one of the major threats to global health. Recent studies have indicated that cell stress response plays an essential role in the pathogenesis of type 2 diabetes (T2D). Oxidative stress and endoplasmic reticulum (ER) stress cooperatively promote cell dysfunction, apoptosis and insulin resistance. While the activators and downstream effects of cell stress have been partially characterized, much is unknown regarding the molecular mechanisms by which the cell stress responses are regulated. Our lab and others have recently characterized the NLR (NBD-LRR) family of proteins, which have been shown to mediate the cell stress response to microbes and environmental stressors. My preliminary data indicates that NLRX1, a mitochondria-localized NLR protein, promotes ER stress response by mediating the generation of mitochondrial reactive oxygen species (mROS). Mechanistically, NLRX1 directly associates with ECSIT (evolutionarily conserved signaling intermediate in Toll pathways) and TRAF6 (TNF receptor-associated factor 6), both of which are important in mitochondrial respiratory chain assembly. NLRX1-deficient (Nlrx1-/-) cells are protected from ER stress-inhibited insulin-PI3K-Akt pathway. Moreover, Nlrx1-/- mice were protected from obesity- induced insulin resistance by high-fat diet (HFD) feeding. Therefore, I hypothesize that NLRX1 mediates mROS generation by facilitating ECSIT-TRAF6 function, which subsequently promotes ER stress, and that the NLRX1-mediated cell stress responses impair insulin signaling in insulin target tissues. I will employ T2D (HFD feeding and leptin-deficient ob/ob mice) animal models to examine the function of NLRX1-mediated cell stress responses in insulin resistance. I will examine how NLRX1 controls ECSIT function and mROS generation. The goal of the proposal is to examine the mechanism of the interaction between NLRX1-mediated oxidative stress and ER stress in promoting cell dysfunction and a defect in insulin signaling. The proposed genetic and biochemical analyses and animal model studies will provide novel insights into the regulation and function of metabolic signaling pathways. Further studies could lead to the identification of new therapeutic targets and ultimately help develop rational, mechanism-based treatment strategies that target obesity and diabetes.