Heme trafficking and its impact on systemic iron homeostasis

血红素运输及其对全身铁稳态的影响

• 批准号: 8668043
• 负责人: Janis L Abkowitz
• 金额: $ 33.93万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-05-01 至 2016-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8668043
• 关键词: Albumins; Bile fluid; Cell Line; Cells; Chronic; Clinical; Complex; Data; Diet; Duodenum; Equilibrium; Erythrocytes; Feline Leukemia Virus; Gastrointestinal tract structure; Goals; Grant; Heme; Heme Iron; Hemochromatosis; Hemoglobin; Hemolysis; Hemopexin; Hepatocyte; Homeostasis; In Vitro; Inflammation; Ingestion; Iron; Kidney; Kupffer Cells; Liver; Marrow; Modeling; Mus; Mutagenesis; Persons; Physiological; Process; Production; Recycling; Regulation; Science; Site; Skin; Structure; Subgroup; Tissues; Transferrin; Xenopus oocyte; absorption; electron crystallography; extracellular; gastrointestinal; heme-binding protein; in vivo; insight; macrophage; metal transporting protein 1; receptor; senescence; tool; trafficking

DESCRIPTION (provided by applicant): The goal of this project is to study how heme trafficking might impact systemic iron homeostasis. As 25 mg of iron is required daily to maintain red cell production, only 1-2 mg/d is absorbed from the GI tract, and 1-2 mg/d is lost through sloughed gastrointestinal, skin and kidney mucosal cells, most iron is recycled. The traditional view is that when macrophages engulf senescent red cells, their hemoglobin is degraded to heme then iron, which is exported via ferroportin to transferrin for delivery to the liver (for storage) or to the marrow (for new red cell production). In previous studies, we determined that the feline leukemia virus-C receptor, FLVCR, specifically exports heme from cells (Cell 118:757-66, 2004). On western analysis, FLVCR is highly expressed in the duodenum, liver and macrophage, tissues critical for iron absorption and trafficking; and Flvcr-deleted mice have excess iron at these sites, in addition to red cell aplasia (Science 319:825-828, 2008). These observations, plus studies of cell lines and primary macrophages in vitro, led us to hypothesize that heme, not only iron, is trafficked. This grant will define FLVCR structure and discern the mechanism by which it exports heme to heme-binding proteins, such as hemopexin and albumin, using mutagenesis analyses, Xenopus oocytes studies, and electron crystallography. We will determine how iron regulates the intercellular localization of FLVCR to aid systemic iron balance. In addition, we will determine the fate of heme from red cells after the cells are ingested by macrophages by studying macrophages from Flvcrflox/flox;LysM-cre mice in vitro and in vivo; determine the fate of heme once delivered to liver by studying Flvcrflox/flox;alb-cre mice; determine if hepatocytes can secrete heme via FLVCR into the bile permitting iron to exit the body; and explore the implications of these findings in models of hemolysis, chronic inflammation, and hemochromatosis. Together these studies should demonstrate that the physiologic regulation of iron is more intricate and complex than previously appreciated.

描述（由申请人提供）：该项目的目的是研究血红素贩运可能会影响系统性铁稳态。由于每天需要25 mg铁以维持红细胞的产生，因此仅从胃肠道吸收1-2 mg/d，而通过胃肠道，皮肤和肾粘膜细胞损失了1-2 mg/d，大多数铁是回收的。传统观点是，当巨噬细胞吞噬衰老的红细胞时，其血红蛋白被降解为血红素，然后铁，通过铁托蛋白出口到转移蛋白，以递送至肝脏（用于储存）或骨髓（用于新的红细胞生产）。在先前的研究中，我们确定了猫白血病病毒-C受体FLVCR，特异性从细胞中导出了血红素（细胞118：757-66，2004）。在西方分析中，FLVCR在十二指肠，肝脏和巨噬细胞中高度表达，对铁吸收和运输至关重要。除了红细胞的性质外，这些位点的flvcr小鼠在这些部位具有多余的铁（Science 319：825-828，2008）。这些观察结果以及对细胞系和原发性巨噬细胞体外的研究，导致我们假设血红素不仅是铁。该赠款将使用诱变分析，Xenopus oocytes研究和电子晶体学，将血红素导出到血红素结合蛋白（例如血红素和白蛋白）中的血红素结合蛋白（例如血红素和白蛋白）的机制。我们将确定铁如何调节FLVCR的细胞间定位以帮助全身铁平衡。此外，我们将通过研究体外和体内的flvcrflox/flox; lysm-cre小鼠的巨噬细胞来确定细胞被巨噬细胞摄入巨噬细胞后的血红素的命运。通过研究flvcrflox/flox； alb-cre小鼠，确定血红素一旦传递到肝脏的命运；确定肝细胞是否可以通过FLVCR分泌血红素到胆汁中允许铁退出身体；并探讨了这些发现在溶血，慢性炎症和血色素沉着病模型中的含义。这些研究共同表明，铁的生理调节比以前所欣赏的更复杂和复杂。