Regulation Of Intracellular Iron Metabolism

细胞内铁代谢的调节

• 批准号: 7594181
• 负责人: TRACEY A. ROUAULT
• 金额: $ 113.08万
• 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/7594181
• 关键词: 5' Untranslated Regions; Aconitate Hydratase; Adult; Affect; Anemia; Animals; Binding; Biochemical; Biological Assay; Cell Line; Cells; 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; Mediating; Messenger RNA; Molecular; Mus; Nerve Degeneration; Neurologic; Neurons; Oligodendroglia; Phenotype; Physiology; Protein Binding; Proteins; RNA; Regulation; Staging; Stimulus; Sulfur; Syndrome; Transcript; Transferrin Receptor; Translations; Work; base; blastomere structure; homologous recombination; human WNT2 protein; iron metabolism; loss of function mutation; mouse model; multicatalytic endopeptidase complex; oxidation; prevent; progressive neurodegeneration; protein function; small molecule; stem

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. Experimental evidence indicates that IRP2 binds iron and undergoes iron-catalyzed oxidation. In iron-replete cells, IRP2 is selectively ubiquitinated 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 no 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. In addition, small molecule treatments to prevent neurodegeneration have yielded promising results.

本项目旨在了解细胞内铁代谢调控的分子基础。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件已在该实验室的前几年被鉴定和表征。铁响应元件（IREs）是在铁蛋白mRNA的5端和转铁蛋白受体mRNA的3端发现的RNA茎环。我们克隆、表达并鉴定了两个必需的铁敏感蛋白，铁调节蛋白1 （IRP1）和铁调节蛋白2 （IRP2）。当铁水平降低时，IRPs结合IREs，导致铁蛋白mRNA和其他在5个非翻译区含有IRE的转录本的翻译受到抑制，或导致转铁蛋白受体mRNA和可能在3UTR中含有IREs的其他转录本的稳定。IRP1的ire结合活性取决于该蛋白是否含有铁硫簇（见项目1 Z01 HD008814-01）。IRP2也在缺铁细胞中结合IREs，但与IRP1不同的是，IRP2在缺铁细胞中被降解。实验证据表明，IRP2结合铁并经历铁催化氧化。在富含铁的细胞中，IRP2被蛋白酶体选择性地泛素化并降解。为了解决铁代谢的生理问题，在小鼠胚胎细胞系中通过同源重组产生了IRP1和IRP2的功能缺失突变。在没有刺激的情况下，铁代谢不存在与IRP1功能丧失相关的异常。IRP2-/-小鼠发展为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，以及少突胶质细胞向轴突变性产生的空隙中突出。IRP2-/-动物发生缺铁性贫血和红细胞生成性原生卟啉症。在缺乏IRP1的动物中，irp2补偿IRP1调节活性的丧失。缺乏IRP1和IRP2的动物在早期胚胎中死亡。当IRP1的一个拷贝也被删除时，成年IRP2-/-小鼠的成年发病神经退行性变会加剧。IRP2-/-小鼠提供了一个独特的成人自发性缓慢进行性神经退行性变的例子，并且正在进行疾病不同阶段的基因表达和铁状态分析。此外，预防神经退行性变的小分子治疗也取得了可喜的成果。