Regulation Of Intracellular Iron Metabolism

细胞内铁代谢的调节

• 批准号: 8149279
• 负责人: TRACEY A. ROUAULT
• 金额: $ 111.67万
• 依托单位: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8149279
• 关键词: Aconitate Hydratase; Adult; Affect; Anemia; Animals; Binding; Biochemical; Biological Assay; Cessation of life; Disease; Elements; Embryo; Erythropoietic Protoporphyria; Ferritin; Gait abnormality; Gene Expression; Goals; H ferritin; Human; Indium; Iron; Iron Regulatory Protein 1; Iron Regulatory Protein 2; Iron-Sulfur Proteins; Laboratories; Lead; Mammals; Messenger RNA; Molecular; Motor Neurons; Mus; Nerve Degeneration; Neurologic; Neurons; Oligodendroglia; Phenotype; Physiology; Protein Binding; Proteins; RNA; Regulation; Staging; Stimulus; Sulfur; Syndrome; Transcript; Transferrin Receptor; Translations; Work; axonal degeneration; base; blastomere structure; iron metabolism; multicatalytic endopeptidase complex; prevent; protein function; small molecule; tempol

This project aims to understand the molecular basis for regulation of intracellular iron metabolism. The cis and trans elements mediating the iron-dependent alterations in abundance of ferritin and the transferrin receptor have been identified and characterized in previous years in this laboratory. Iron- responsive elements (IREs) are RNA stem-loops found in the 5 end of ferritin mRNA and the 3 end of transferrin receptor mRNA. We have cloned, expressed, and characterized two essential iron- sensing proteins, Iron Regulatory Protein 1 (IRP1) and Iron Regulatory Protein 2 (IRP2). IRPs bind IREs when iron levels are depleted, resulting in the inhibition of translation of ferritin mRNA and other transcripts that contain an IRE in the 5 untranslated regions, or in stabilization of the transferrin receptor mRNA and possibly other transcripts that contain IREs in the 3UTR. The IRE-binding activity of IRP1 depends on whether the protein contains an iron-sulfur cluster (see project 1 Z01 HD008814-01). IRP2 also binds IREs in iron-depleted cells, but unlike IRP1, IRP2 is degraded in cells that are iron- replete. In iron-replete cells, IRP2 is selectively ubiquitinated by FBXL5 and degraded by the proteasome. To approach questions about the physiology of iron metabolism, loss of function mutations of IRP1 and IRP2 have been generated in mice through homologous recombination in embryonic cell lines. In the absence of provocative stimuli, there are subtle abnormalities in iron metabolism associated with loss of IRP1 function. IRP2-/- mice develop a progressive neurologic syndrome characterized by gait abnormalities and axonal degeneration. Ferritin over-expression occurs in affected neurons, and in protrusions of oligodendrocytes into the space created by axonal degeneration. IRP2-/- animals develop iron-insufficiency anemia and erythropoietic protoporphyria. In animals that lack IRP1, IRP 2 compensates for loss of IRP1 regulatory activity. Animals that lack both IRP1 and IRP2 die as early embryos. The adult-onset neurodegeneration of adult IRP2-/- mice is exacerbated when one copy of IRP1 is also deleted. IRP2-/- mice offer a unique example of spontaneous adult-onset slowly progressive neurodegeneration, and analyses of gene expression and iron status at various stages of disease are ongoing. We have found that lower motor neurons are very adversely affected, developing axonopathy and death. In addition, small molecule treatment with the stable nitroxide, Tempol, prevents neurodegeneration in IRP2-/- animals.

本项目旨在了解细胞内铁代谢调控的分子基础。在过去的几年中，本实验室已经确定并表征了介导铁蛋白和转铁蛋白受体丰度的铁依赖性改变的顺式和反式元素。铁反应元件（IREs）是存在于铁蛋白mRNA的5端和转铁蛋白受体mRNA的3端的RNA茎环。我们克隆、表达并鉴定了两种必需的铁敏感蛋白，铁调节蛋白1（IRP 1）和铁调节蛋白2（IRP 2）。当铁水平耗尽时，IRP结合IRE，导致铁蛋白mRNA和在5个非翻译区中含有IRE的其他转录物的翻译抑制，或转铁蛋白受体mRNA和在3UTR中含有IRE的可能的其他转录物的稳定。IRP 1的IRE结合活性取决于蛋白质是否含有铁硫簇（见项目1 Z 01 HD 008814 -01）。 IRP 2也结合铁耗尽细胞中的IRE，但与IRP 1不同的是，IRP 2在铁充足的细胞中被降解。 在充满铁的细胞中，IRP 2被FBXL 5选择性地泛素化并被蛋白酶体降解。为了探讨铁代谢的生理学问题，通过胚胎细胞系中的同源重组，在小鼠中产生了IRP 1和IRP 2的功能丧失突变。在没有刺激的情况下，与IRP 1功能丧失相关的铁代谢存在细微异常。IRP 2-/-小鼠发生以步态异常和轴突变性为特征的进行性神经系统综合征。铁蛋白过度表达发生在受影响的神经元中，以及少突胶质细胞突起到轴突变性产生的空间中。IRP 2-/-动物发生铁不足性贫血和红细胞生成性原卟啉症。在缺乏IRP 1的动物中，IRP 2补偿IRP 1调节活性的损失。缺乏IRP 1和IRP 2的动物在早期胚胎中死亡。当IRP 1的一个拷贝也被删除时，成年IRP 2-/-小鼠的成年发病神经变性会加剧。IRP 2-/-小鼠提供了一个独特的自发性成人发病缓慢进行性神经变性的例子，在疾病的各个阶段的基因表达和铁状态的分析正在进行中。我们发现，下运动神经元受到非常不利的影响，发展轴突病变和死亡。此外，用稳定的氮氧化物Tempol进行的小分子治疗可预防IRP 2-/-动物的神经变性。