The Transport of Nutritional Heme in Animal Development

动物发育中营养血红素的运输

基本信息

批准号：
8054236
负责人：
Iqbal Hamza
金额：
$ 29.22万
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：
2010
资助国家：
美国
起止时间：
2010-04-01 至 2014-03-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8054236
关键词：
Anemia Animal Model Animals Binding Bioavailable Biological Biological Assay Blood Substitutes Caenorhabditis elegans Candidate Disease Gene Cell Line Cell membrane Cell model Cells Chimera organism Complex Consumption Defect Development Diffuse Digestion Elements Enterocytes Erythrocytes Erythrophagocytosis Funding Gene Expression Genes Genetic Genetic Screening Goals Growth Heme Heme Iron Hemeproteins Hemoglobin Homeostasis Homologous Gene Human Hydrocephalus Individual Infant Iron Lead Ligand Binding M cell Mammalian Cell Mammals Measures Mediating Membrane Membrane Protein Traffic Metabolic Modeling Molecular Mothers Mus Nature Nematoda Nutraceutical Nutrition Disorders Nutritional Pathway interactions Patients Phagocytosis Phagolysosome Phenotype Protein Biosynthesis Proteins RNA RNA Interference Recycling Reporter Reporter Genes Reproduction Saccharomyces cerevisiae Site Source Structure System Testing Transgenic Organisms Tube Variant Yeasts Zebrafish analog auxotrophy base cytotoxic design heme 1 iron (III) reductase iron protoporphyrin IX macrophage mutant nutrition paralogous gene permease positional cloning pregnant prototype public health relevance response senescence small hairpin RNA trafficking uptake zinc mesoporphyrin

项目摘要

DESCRIPTION (provided by applicant): The long-term objective of our studies is to define the cellular and molecular determinants of heme homeostasis in human nutrition. Iron deficiency is the most common nutritional disorder. Dietary heme (iron-protoporphyrin IX) is a significant source of bioavailable iron, but the genes and pathways responsible for heme transport and utilization in human enterocytes remain elusive. In humans, greater than 60% of total body iron is present as heme in hemoglobin. Iron from heme is recycled by phagocytosis of senescent red blood cells and proteolytic digestion of hemoglobin in macrophages. Similar to enterocytes, the pathways for heme transport and utilization across the phagolysosomal membrane in macrophages are unknown. Since heme is a hydrophobic, cytotoxic macrocycle, we assert that heme does not passively diffuse through membranes but is actively transported via specific intra- and inter-cellular pathways that comprise heme uptake, trafficking, and sequestration. We have demonstrated that the roundworm Caenorhabditis elegans is an excellent animal model to identify heme transport pathways because it synthesizes a large number of hemoproteins with human homologs but does not synthesize heme de novo. Worms require dietary heme for growth and reproduction. Thus, the worm model provides a clean genetic background devoid of endogenous heme and the ability to externally manipulate the metabolic flux of intracellular heme. Utilizing C. elegans as a genetic animal model of heme auxotrophy, we identified HRG-1, the first eukaryotic heme importer/ transporter (Nature 2008). HRG-1 is a permease that is conserved in humans and binds and transports heme. The worm and human HRG-1 proteins co-localize to the endo-lysosomal compartment. Knockdown of hrg-1 in zebrafish causes hydrocephalus, yolk tube defects, and anemia - phenotypes that are fully rescued by worm HRG-1. These studies established a conserved model for cellular heme transport and validated C. elegans as a bona fide model for the identification of heme homeostasis pathways. The studies in this proposal are designed to elucidate the precise mechanisms of heme transport by HRG-1 at the molecular, cellular, and organismal levels. We seek to test the hypothesis that heme transport mediated by HRG-1 is an integral component of the heme homeostasis regulatory network in animals. We will utilize a structure-function approach to identify the functional elements of HRG-1 responsible for heme transport, a cell biological approach to establish HRG-1 as the vesicular transporter for heme-iron recycling, and a systems approach to identify the complex regulatory circuit which integrates HRG-1 with organismal heme trafficking. Our goal is to obtain a comprehensive understanding of the pathways which mediate heme homeostasis in mammals that have, heretofore, remained poorly understood. PUBLIC HEALTH RELEVANCE: Iron deficiency is the world's number one nutritional disorder, and heme is the most bioavailable form of iron for human consumption. Identification of how heme is transported for the synthesis of proteins containing iron and heme will permit the design of synthetic heme-based "nutraceuticals" specifically targeted to iron-deficient individuals including pregnant mothers and infants. Identifying the molecular basis of heme-iron recycling to produce hemoglobin will lead to new strategies for the synthesis of artificial blood.

描述（由申请人提供）：我们研究的长期目标是定义人类营养中血红素稳态的细胞和分子决定因素。铁缺乏是最常见的营养障碍。饮食血红素（铁核磷脂IX）是生物利用铁的重要来源，但是负责人肠细胞中血红素传输和利用的基因和途径仍然难以捉摸。在人类中，总体铁的60％以上是血红蛋白中的血红素。血红素的铁通过衰老红细胞的吞噬作用和巨噬细胞中血红蛋白的蛋白水解消化而回收。与肠上皮细胞相似，跨巨噬细胞中跨吞噬性膜的血红素转运和利用的途径尚不清楚。由于血红素是一种疏水，细胞毒性的大环，因此我们断言血红素不会被动地通过膜扩散，而是通过特定的细胞内和细胞间途径积极地运输，包括血红素摄取，运输和螯合。我们已经证明，round虫秀丽隐杆线虫是识别血红素传输途径的出色动物模型，因为它与人类同源物合成了大量的血op蛋白，但未合成血红素de。蠕虫需要饮食血红素才能生长和繁殖。因此，蠕虫模型提供了没有内源性血红素和外部操纵细胞内血红素的代谢通量的能力的干净遗传背景。我们利用秀丽隐杆线虫作为血红素合子植物的遗传动物模型，我们确定了HRG-1，这是第一个真核血红素进口商/转运蛋白（Nature 2008）。 HRG-1是在人类中保守并结合和运输血红素的渗透酶。蠕虫和人类HRG-1蛋白共定位到内部溶酶体室。斑马鱼中HRG-1的敲低导致脑积水，蛋黄管缺陷和贫血 - 表型，这些表型被蠕虫HRG-1完全救出。这些研究建立了一个用于细胞血红素转运的保守模型，并验证了秀丽隐杆线虫作为鉴定血红素稳态途径的真正模型。该提案中的研究旨在阐明HRG-1在分子，细胞和生物水平上通过HRG-1运输的精确机制。我们试图检验以下假设：HRG-1介导的血红素转运是动物血红素稳态调节网络的组成部分。我们将利用一种结构功能方法来识别负责血红素转运的HRG-1的功能元件，一种将HRG-1建立为血红素铁回收的囊泡转运蛋白的细胞生物学方法，以及确定将HRG-1与生物血红素运输相结合的复杂调节电路的系统方法。我们的目标是对介导的哺乳动物中血红素稳态的途径进行全面的了解，而哺乳动物的血红素稳态仍然知之甚少。公共卫生相关性：铁缺乏症是世界上排名第一的营养障碍，而血红素是人类消费的最有生物利用形式。鉴定如何运输血红素以合成含铁和血红素的蛋白质，将允许设计基于血红素的“营养剂”，专门针对铁缺陷的个体，包括怀孕的母亲和婴儿。确定血红素回收的分子基础以产生血红蛋白，将导致新的人造血液合成的策略。