Activation of the NOD1 and NOD2 signaling pathways

项目总结 Nod1和Nod2是模式识别受体，可以感知细菌肽多聚糖片段， 并能够检测细胞过程中的扰动，如肌动蛋白细胞骨架的调制和 内质网(ER)动态平衡紊乱。在不同的压力条件下，如细菌 以及病毒感染、蛋白质错误折叠和钙稳态紊乱，内质网无法维持 动态平衡并激活未折叠蛋白反应(UPR)。内质网应激三种跨膜 受体IRE1、、PERK和ATF6被激活，并调节生物过程，如抑制蛋白质 翻译、自噬和炎症以重建细胞内环境平衡。Nod1和NOD2已经 参与内质网应激诱导的炎症，通过作用于UPR下游诱导NF-B激活 和IL-6的产生。NOD1和NOD2感受内质网应激的确切机制目前尚不清楚。 Nod1和Nod2也可以感觉到小的Rho GTP酶的激活，如rac1。Rac1激活导致 膜褶皱以及转录因子NF-B的激活。我们和其他人已经证明 Nod1和NOD2在细胞膜上与rac1相互作用。Rac1介导的潜在机制 Nod1和NOD2的激活目前未知。在应用中，我们建议研究其作用机制。 肌动蛋白细胞骨架和肌动蛋白对NOD1和NOD2的非依赖性激活 Thapsigarin诱导内质网应激。我们的中心假设是NOD1和NOD2可以检测到细胞 与肽聚糖识别无关的微扰。我们将使用 以下具体目标概述了合乎逻辑和创新的方法。 具体目的1.确定NOD1和NOD2在内质网应激反应中的作用。我们将确定 内质网钙流量在内质网应激诱导NOD1和NOD2激活中对线粒体的贡献。 我们将验证我们的假设，即内质网应激损伤的线粒体释放损伤相关分子 激活NOD1和NOD2的图案(阻尼器)。 具体目标2.细胞过程中的扰动决定了NOD1和NOD2的定位。我们 将研究NOD1和NOD2在thapsigargin诱导ER的细胞中的细胞定位 应激和在细胞中表达活性的rac1或rac1突变形式，这些突变形式要么诱导细胞骨架重塑，要么 核因子-B的激活。肽聚糖非依赖性NOD1和NOD1机制的研究 NOD2的激活为观察到病毒和寄生虫触发NOD1提供了一个可信的解释 和NOD2信令。这些发现是创新的新概念，将显著影响当前的 NOD1和NOD2生物学的概念。

PROJECT SUMMARY NOD1 and NOD2 are pattern recognition receptors that sense fragments of bacterial peptidoglycans, and are able to detect perturbations in cellular processes such as the modulation of the actin cytoskeleton and disturbance in endoplasmic reticulum (ER) homeostasis. Under different stressful conditions, such as bacterial and viral infections, protein misfolding and perturbations in calcium homeostasis, the ER is unable to maintain homeostasis and activates the unfolded protein response (UPR). Upon ER stress three transmembrane receptors, IRE1, PERK and ATF6 are activated and regulate biological processes such as inhibition of protein translation, autophagy, and inflammation to reestablish cellular homeostasis. NOD1 and NOD2 have been implicated in ER stress-induced inflammation, by acting downstream in the UPR to induce NF-B activation and IL-6 production. The exact mechanism how NOD1 and NOD2 can sense ER stress is currently unknown. NOD1 and NOD2 can also sense the activation of small Rho GTPases such as Rac1. Rac1 activation leads to membrane ruffling as well as activation of the transcription factor NF-B. We and others have shown that NOD1 and NOD2 interact with Rac1 at the cell membrane. The underlying mechanism of Rac1-mediated NOD1 and NOD2 activation is currently unknown. In the application we propose to study the mechanisms of peptidoglycan-independent activation of NOD1 and NOD2 by modulation of the actin cytoskeleton and thapsigargin-induced ER stress. Our central hypothesis is that NOD1 and NOD2 can detect cellular perturbations independent of peptidoglycan recognition. We will test key aspects of our hypothesis using the logical and innovative approach outlined in the following specific aims. Specific Aim 1. Determine the role of NOD1 and NOD2 in sensing ER stress. We will determine the contribution of calcium flux from the ER to the mitochondria in ER stress induced NOD1 and NOD2 activation. We will test our hypothesis that mitochondria damaged by ER stress release damage-associated molecular patterns (DAMPs) that activate NOD1 and NOD2. Specific Aim 2. Perturbations in cellular processes determines NOD1 and NOD2 localization. We will investigate the cellular localization of NOD1 and NOD2 in cells treated with thapsigargin to induce ER stress and in cells that express active Rac1 or Rac1 mutant forms that either induce cytoskeletal remodeling or NF-B activation. Characterizing and understanding the mechanisms of peptidoglycan-independent NOD1 and NOD2 activation provides a plausible explanation for the observation that viruses and parasites trigger NOD1 and NOD2 signaling. These findings are innovative new concepts and would markedly influence the current concepts of NOD1 and NOD2 biology.