Signaling Cross-talk Between Endoplasmic Reticulum And Oxidative Stresses

生物体必须对它们在一生中可能遇到的一系列压力做出反应。压力经常发生，不是作为一个单一的事件，而是作为同时作用于生物体的多个压力。毒素应激、氧化应激、低氧(低氧)应激和内质网(ER)应激等应激反应常常同时发生。多重压力之间的“串音”通常涉及共同的蛋白质因子，它们对各种细胞外和细胞内信号做出反应。我的研究项目集中在一种这样的蛋白质上，它对多种信号过程做出反应，并研究这些信号是如何相互作用的，无论是协同作用还是拮抗作用，以影响其功能。核因子红血球2样蛋白1(NFE2L1或Nrf1)是一种与小分子MAF蛋白异源二聚化的碱性亮氨酸拉链转录因子，与被称为抗氧化剂反应元件/电子反应元件的DNA元件结合，是反式激活抗氧化酶、1期和2期解毒酶以及蛋白酶体亚单位基因表达所必需的。NRF1对氧化应激作出反应，并调节涉及脂类代谢、氨基酸代谢、蛋白酶体降解、柠檬酸循环和线粒体呼吸链的途径。一个悬而未决的问题是Nrf1也可能对内质网应激做出反应，但这种反应是如何发生的，以及环境应激(毒素应激、低氧、氧化应激)如何与内质网应激一起影响Nrf1的功能仍有待研究。我们最近证实，a)低氧影响Nrf1被蛋白质降解的方式，b)各种环境毒素影响Nrf1到核的移位，c)蛋白质上关键酪氨酸的磷酸化影响其泛素化和锚定到内质网。这项提案中概述的目标旨在证明多种环境应激源和内质网应激对哺乳动物细胞中Nrf1功能的影响之间存在交互作用。目标1将研究负责Nrf1蛋白分解过程的因素，以及这些因素如何因环境压力而改变。目的2将重点介绍在不同的应激条件下，Nrf1蛋白的应激依赖的翻译后修饰对其糖基化、蛋白降解过程和内质网释放的影响。目的3将研究环境应激与内质网应激在激活Nrf1过程中的相互作用。我的长期目标是阐明Nrf1在应对广泛的细胞压力中的重要性，以及这些应激是如何影响其a)翻译后修饰，b)从内质网释放并转位到细胞核，c)蛋白质降解过程以及确定多种细胞外和细胞内信号对Nrf1是协同作用还是拮抗作用。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.