Signaling Cross-talk Between Endoplasmic Reticulum And Oxidative Stresses

生物体必须对它们在其生命周期中可能遇到的各种压力作出反应。压力经常发生，不是作为一个单一的事件，而是作为多个压力同时冲击生物体。应激如毒素应激、氧化应激、低氧（缺氧）应激和内质网（ER）应激常常同时发生。多重应激之间的“串扰”通常涉及响应于多种细胞外和细胞内信号的共同蛋白质因子。我的研究项目集中在一个这样的蛋白质，响应多种信号传导过程，并研究这些信号如何相互作用，无论是协同或拮抗，影响其功能。类红细胞核因子2样1（NFE 2L 1或Nrf 1）是一种“帽”领”碱性亮氨酸拉链转录因子，其与小Maf蛋白异二聚化并结合称为抗氧化反应元件/亲电反应元件的DNA元件，其是反式激活抗氧化酶、1相和2相解毒酶和蛋白酶体亚基基因表达所需的。nrf 1响应氧化应激并调节脂质代谢、氨基酸代谢、蛋白酶体降解、柠檬酸循环和线粒体呼吸链中的途径。一个尚未回答的问题是Nrf 1也可能对ER应激做出反应，但这是如何发生的以及环境应激（毒素应激，缺氧，氧化应激）如何与ER应激协同作用以影响Nrf 1功能仍有待研究。我们最近证明，a）缺氧影响Nrf 1蛋白水解加工的方式，B）各种环境毒素影响Nrf 1向细胞核的易位，以及c）蛋白上关键酪氨酸的磷酸化影响其泛素化和锚定到ER。本提案中概述的目标旨在证明在哺乳动物细胞中，多种环境应激源和ER应激对Nrf 1功能的影响之间存在串扰。目的1将研究负责Nrf 1蛋白水解加工的因素，以及这些因素如何被环境胁迫改变。目的2将集中在应激依赖的Nrf 1蛋白的翻译后修饰，影响其糖基化，蛋白水解加工和释放从ER在不同的应激条件下。目的3将研究环境应力与ER应力在激活Nrf 1中的相互作用。我的长期目标是阐明Nrf 1在广泛的细胞应激反应中的重要性，以及这些应激如何影响其a）翻译后修饰，B）从ER释放并易位到细胞核，c）蛋白水解加工以及确定多种细胞外和细胞内信号对Nrf 1的协同或拮抗作用。类似的机制可能适用于许多不同的应激反应蛋白。

Organisms must respond to a broad array of stresses which they may encounter during their lifespan. Stresses often occur, not as a single occurrence, but as multiple stresses which impinge upon the organism simultaneously. Stresses such as toxin stress, oxidative stress, low oxygen (hypoxic) stress and endoplasmic reticulum (ER) stress often occur concurrently. “Crosstalk” between multiple stresses often involves common protein factors which respond to a variety of extra- and intra-cellular signals. My research program focuses on one such protein that responds to multiple signalling processes and examines how these signals interact, either synergistically or antagonistically, to affect its function. Nuclear factor erythroid 2 like 1 (NFE2L1 or Nrf1) is a "cap'n'collar" basic leucine zipper transcription factor that heterodimerizes with small Maf proteins and bind to a DNA element known as the Antioxidant Response Element/Electrophile Response Element, required to transactivate antioxidant enzyme, phase 1 and 2 detoxification enzyme and proteasome subunit gene expression. Nrf1 responds to oxidative stress and regulates pathways involved in lipid metabolism, amino acid metabolism, proteasomal degradation, the citric acid cycle, and the mitochondrial respiratory chain. An unanswered question is the possibility that Nrf1 may also respond to ER stress, but how this occurs and how environmental stresses (toxin stress, hypoxia, oxidative stress) work in tandem with ER stress to affect Nrf1 function remains to be investigated. We recently demonstrated that a) hypoxia affects the way that Nrf1 is proteolytically processed, b) various environmental toxins affect the translocation of Nrf1 to the nucleus and c) phosphorylation of key tyrosines on the protein affect its ubiquitination and anchoring to the ER. The aims outlined in this proposal set out to demonstrate that cross-talk occurs between multiple environmental stressors and ER stress on Nrf1 function in mammalian cells. Aim 1 will examine the factors responsible for the proteolytic processing of Nrf1 and how these are altered by environmental stresses. Aim 2 will focus on stress-dependent post-translational modifications of the Nrf1 protein that affect its glycosylation, proteolytic processing and release from the ER under different stress conditions. Aim 3 will investigate the cross-talk between environmental stresses with ER stress in activating Nrf1. My long-term goals are to illustrate the importance of Nrf1 in the response to a broad range of cellular stresses and how these stresses act to affect its a) post-translational modification, b) release from the ER and translocation to the nucleus, c) proteolytic processing as well as determining whether multiple extra- and intracellular signals act synergistically or antagonistically on Nrf1. Similar mechanisms may apply to a number of different stress-response proteins.