Deciphering a Novel Mechanism for Iron-sensing at Mitochondria and Its Role in Erythropoiesis

摘要 铁是真核生物生命所必需的，是各种蛋白质的生物催化中心，参与多种 细胞过程。在人类体内，全身铁的最大部分可以被发现为血红素(一种含铁的 卟啉)，其中大部分以血红蛋白的形式存在于红细胞中，血红蛋白携带来自 肺通向全身。铁、血红素或珠蛋白的不平衡供应导致 功能性血红蛋白，导致各种类型的贫血。铁供应不足尤其严重，因为它 导致所谓的缺铁性贫血，这是世界上最常见的贫血形式。了解 调节红系细胞中的血红蛋白合成对于开发新的治疗策略非常重要。 治疗红血球疾病。然而，这种调控的分子机制还没有得到证实。 完全理解。这项研究计划旨在通过描绘铁依赖来揭示这些机制。 线粒体蛋白DELE1的调控。最近的研究表明，作为回应，线粒体 应激，DELE1是应激反应激酶HRI的激活剂，HRI是珠蛋白的成熟调节因子 翻译成红系血统。这项建议的初步结果表明，DELE1激活HRI 通过一种与以前报道的机制不同的新机制来抑制铁耗竭细胞。这些结果也 提示线粒体输入DELE1及其随后的蛋白质稳定性受到严格的 细胞内铁的可利用性。因此，这一提议将检验依赖铁的线粒体的假设 蛋白质稳定和DELE1的输入调控是新的线粒体铁敏感的核心组成部分 调节HRI介导的应激反应的途径。线粒体DELE1激活的机制 用多种高级分子生物学方法研究缺铁条件下的胞质HRI 技术，与基于质谱学的蛋白质组学相结合。环境与发展部--人权研究所的参与 将使用小鼠红白血病(MEL)细胞研究红系终末分化的途径 一个已建立的红系细胞模型，以及最近产生的DELE1缺陷小鼠。这个 这项拟议工作的成功将为线粒体铁感应和 揭示负责线粒体和线粒体之间通讯的关键分子角色 在缺铁条件下维持细胞动态平衡的胞浆。

Abstract Iron is essential for eukaryotic life acting as a biological catalytic center of various proteins involved in diverse cellular processes. In human, the greatest portion of total body iron can be found as heme (an iron-containing porphyrin), the majority of which is in red blood cells in the form of hemoglobin that carries oxygen from the lung to the whole body. An imbalanced supply of iron, heme, or globin proteins leads to the shortage of functional hemoglobin, resulting in various types of anemia. Insufficient iron supply is particularly critical, as it causes so-called iron deficiency anemia, the most common form of anemia worldwide. Understanding the regulation of hemoglobin synthesis in erythroid cells is important for developing novel therapeutic strategies to treat red blood cell disorders. However, the molecular mechanisms underlying this regulation have not been fully understood. This research proposal aims to uncover these mechanisms by delineating iron-dependent regulation of the mitochondrial protein DELE1. It has been recently shown that in response mitochondrial stress, DELE1 acts as an activator of the stress responsive kinase HRI, a well-established regulator of globin translation in the erythroid lineage. Preliminary results in this proposal indicate that DELE1 activates HRI in iron-depleted cells by a novel mechanism distinct from previously reported mechanisms. These results also suggest the mitochondrial import of DELE1 and its subsequent protein stability is strictly regulated by intracellular iron availability. Thus, this proposal will test the hypothesis that iron-dependent mitochondrial proteostasis and import regulation of DELE1 are the core components of a novel mitochondrial iron-sensing pathway regulating the HRI-mediated stress response. The mechanisms how mitochondrial DELE1 activates cytosolic HRI in iron deficient conditions will be investigated using multiple advanced molecular biology techniques, in combination with mass spectrometry-based proteomics. The involvement of the DELE1-HRI pathway in terminal erythroid differentiation will be addressed using a murine erythroleukemia (MEL) cell line, an established erythroid cellular model, as well as a recently generated DELE1 deficient mouse. The success of the proposed work will provide novel molecular insights into mitochondrial iron-sensing and reveal the critical molecular players that are responsible for the communication between mitochondria and the cytosol in order to maintain cellular homeostasis under iron-deficient conditions.