Heme trafficking and recycling in iron metabolism

铁代谢中的血红素运输和回收

基本信息

批准号：
10440269
负责人：
Iqbal Hamza
金额：
$ 15.45万
依托单位：
UNIV OF MARYLAND, COLLEGE PARK
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2022-08-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10440269
关键词：
Adult Anemia Animal Genetics Animal Model Antiparasitic Agents Biological Biological Assay Blood Bone Marrow Caenorhabditis elegans Candidate Disease Gene Cells Chloroquine Clinical Co-Immunoprecipitations Crystallization Cytoplasm Cytosol Degradation Pathway Development Dichloromethylene Diphosphonate Drug Metabolic Detoxication Elements Embryo Erythrocytes Erythrophagocytosis Erythropoiesis FTH1 gene Ferritin Funding Genes Genetic Genetic Transcription Goals Hematology Heme Heme Iron Hemoglobin Homeostasis Homologous Gene Human Human body Hydrophobicity Impairment In Situ Ingestion Investigation Iron Lead Ligation Liver Lysosomal Storage Diseases Lysosomes Mammals Mediating Membrane Metabolism Molecular Monitor Mus Mutation Nutrient Nutrition Disorders Organ Organism Oxygenases Pathway interactions Perinatal mortality demographics Phagocytosis Phagolysosome Pharmacology Physiological Production Proteins RNA Interference Recycling Regulation Reticuloendothelial System Role Sickle Cell Anemia Spleen Technology Testing Time Toxic effect Transgenic Mice Variant auxotrophy base cofactor cytotoxic design feeding genetic approach hemozoin in vivo inhibitor iron deficiency iron metabolism macrophage metal transporting protein 1 prevent protein complex response senescence trafficking transcriptome sequencing

项目摘要

The long-term goals of this proposal are to define heme transport and recycling in iron metabolism. Iron deficiency is the most common nutritional disorder in the world. The most common clinical manifestation of iron deficiency is anemia due to impaired hemoglobinization of red blood cells (RBCs). This is because over 70% of iron in the human body is used as heme in hemoglobin production. In healthy adults, about 90% of body iron is derived from recycled heme-iron. Each day, reticuloendothelial system (RES) macrophages recycle heme-iron by ingesting almost 5 million senescent or damaged RBCs per second; the bone marrow utilizes this recycled iron to produce new RBCs. As a consequence genetic defects in macrophage iron recycling result in anemia. Despite the importance of heme in iron recycling, the pathways responsible for heme transport and trafficking in RES macrophages remain poorly understood. After erythrophagocytosis, the iron is enzymatically released from heme by heme oxygenases (HMOX1) in the cytosol. This iron can either be stored in ferritin (FTH1) or exported out of the cell by ferroportin (FPN1) to be reutilized for new RBC production in the bone marrow. Consequently, genetic disruption in HMOX1, FPN1, and FTH1 – steps in the heme-iron recycling pathway – causes embryonic lethality in mice. We identified the first eukaryotic heme importer/transporter, HRG1 and showed that it is essential for transporting heme from the macrophage phagolysosome into the cytoplasm in macrophages. Our recent studies show that HRG1-deficient mice are viable even though they are incapable of recycling heme-iron and accumulate 10-fold excess heme within macrophages. The mice are tolerant to heme toxicity because they sequester heme inside lysosomes, which become 10-100 times larger than normal, by forming hemozoin - large multimeric heme crystals heretofore only identified in blood-feeding organisms to detoxify heme. Heme tolerance requires a fully-operational heme degradation pathway as haploinsufficiency of HMOX1 combined with HRG1 deficiency causes perinatal lethality, demonstrating a synthetic lethal interaction. Our exciting results suggest the existence of a previously unanticipated pathway for heme detoxification and tolerance in mammals. The studies in this proposal are designed to uncover the molecular basis of HRG1-mediated heme tolerance. We will test the hypotheses that heme tolerance is conferred by the coordinated regulation of heme transport by HRG1 and its genetic and physical interactions with heme degradation and additional components of the heme trafficking machinery. We will utilize (a) a genetic approach to elucidate the regulatory mechanisms of hemozoin formation and heme tolerance; and (b) a cell biological approach to identify the mechanisms for the synthetic lethal interactions between HRG1 and HMOX1. Our goals are to acquire a deep understanding for the molecular basis for heme trafficking and recycling and its role in heme tolerance in mammals.

该提案的长期目标是定义铁代谢中的血红素运输和回收利用。铁缺乏症是世界上最常见的营养障碍。铁缺乏症的最常见临床表现是由于红细胞（RBC）的血红蛋白受损而导致贫血。这是因为在血红蛋白产生中，人体中超过70％的铁被用作血红素。在健康的成年人中，大约90％的人铁衍生自回收的血红素铁。每天，通过每秒摄入近500万个感觉或损坏的RBC来回收巨噬细胞的网状内皮系统（RES）巨噬细胞；骨髓利用这种再生铁生产新的RBC。结果，巨噬细胞铁回收的遗传缺陷导致贫血。尽管血红素在铁回收中很重要，但负责血红素运输和贩运巨噬细胞的途径仍然很少了解。红细胞增多症后，铁酶（HMOX1）在细胞质中从血红素释放了铁。该铁可以储存在铁蛋白（FTH1）中，也可以通过铁托蛋白（FPN1）从细胞中出口，以在骨髓中重新提供新的RBC产生。因此，HMOX1，FPN1和FTH1的遗传破坏 - 血红素铁回收途径的步骤 - 导致小鼠的胚胎致死性。我们确定了第一个真核血红素进口蛋白/转运蛋白HRG1，并表明它对于将血红素从巨噬细胞吞噬体转运到巨噬细胞中至关重要。我们最近的研究表明，即使HRG1缺陷小鼠无法回收血红素铁并在巨噬细胞中积累10倍过量的血红素，它们也是可行的。这些小鼠对血红素毒性具有耐受性，因为它们通过形成血液燃料 - 大型多媒体血红素晶体，迄今仅在血液喂养生物体中鉴定出可解毒的血红素，它们将血红素内部的血红素内部的血红素隔离，比正常情况大10-100倍。血红素的耐受性需要完全操作的血红素降解途径，因为HMOX1的单倍不足与HRG1缺乏症相结合导致围产期致死性，表明是合成的致命相互作用。我们令人兴奋的结果表明，存在先前意外的哺乳动物血红素解毒和耐受性的途径。该建议中的研究旨在揭示HRG1介导的血红素耐受性的分子基础。我们将检验的假设是，HRG1对血红素转运的协调调节及其与血红素降解的遗传和物理相互作用以及血红素运输机制的其他成分所赋予的血红素耐受性。我们将利用（a）一种遗传方法来阐明血红素形成和血红素耐受的调节机制；（b）一种细胞生物学方法，以识别HRG1和HMOX1之间合成致命相互作用的机制。我们的目标是对血红素贩运和回收的分子基础有深入的了解，以及其在哺乳动物中血红素耐受性中的作用。