Activation of the NOD1 and NOD2 signaling pathways

项目摘要 NOD 1和NOD 2是模式识别受体，其感测细菌肽聚糖的片段， 并且能够检测细胞过程中的扰动，例如肌动蛋白细胞骨架的调节， 内质网（ER）稳态紊乱。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的扰动， 体内平衡和激活未折叠蛋白反应（UPR）。ER应激后，三个跨膜 受体IRE1 β、PERK和ATF6被激活并调节生物过程，例如蛋白质表达的抑制， 翻译、自噬和炎症以重建细胞内稳态。NOD1和NOD2已经被 参与ER应激诱导的炎症，通过作用于UPR下游诱导NF-κ B B活化 和IL-6的产生。NOD1和NOD2如何感知内质网应激的确切机制目前尚不清楚。 NOD1和NOD2也可以感知小Rho GTP酶如Rac1的激活。Rac1激活导致 膜皱褶以及转录因子NF-κ B 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的激活目前尚不清楚。在本申请中，我们提出研究 通过调节肌动蛋白细胞骨架，非肽聚糖依赖性激活NOD1和NOD2， 毒胡萝卜素诱导的内质网应激。我们的中心假设是NOD1和NOD2可以检测细胞 不依赖于肽聚糖识别的扰动。我们将测试我们的假设的关键方面使用 在以下具体目标中概述了逻辑和创新方法。 具体目标1。确定NOD1和NOD2在感受ER应力中的作用。康贝特人将以 在内质网应激诱导的NOD1和NOD2激活中，从内质网到线粒体的钙流的贡献。 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DAMP。 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在用毒胡萝卜素处理以诱导ER的细胞中的细胞定位 应激和表达活性Rac 1或Rac 1突变体形式的细胞中，所述活性Rac 1或Rac 1突变体形式诱导细胞骨架重塑或 NF-κ B B活化。表征和理解肽聚糖非依赖性NOD 1和 NOD2激活为病毒和寄生虫触发NOD1的观察提供了合理的解释 NOD2信号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.