Intestinal Iron Transport in Iron Deficiency/Anemia

缺铁/贫血时的肠道铁转运

• 批准号: 7116198
• 负责人: James F. Collins
• 金额: $ 18.88万
• 依托单位: STATE UNIVERSITY OF NEW YORK AT BUFFALO
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7116198
• 关键词: DNA footprinting; adenosinetriphosphatase; brush border membrane; copper; duodenum; enzyme activity; ferroxidase; gastrointestinal absorption /transport; gel mobility shift assay; gene expression; gene induction /repression; genetic promoter element; genetic regulation; genetic transcription; glycosylphosphatidylinositols; homeostasis; immunocytochemistry; intestinal mucosa; iron; laboratory rat; microcytic /hypochromic anemia; polymerase chain reaction; posttranslational modifications; site directed mutagenesis; transport proteins; western blottings

DESCRIPTION (provided by applicant): Intestinal iron absorption is mediated by several proteins that have only recently been identified. However, several lines of experimental pursuit have suggested that there are other unknown genes involved in this important physiological process. Thus, we performed comparative gene chips studies designed to identify changes in the expression of known and unknown genes involved in iron transport in the duodenal mucosa of anemic rats at 8 days, 21 days, 6 weeks, 12 and 26-weeks-of-age. Our results demonstrate changes in gene expression that are unique at the different ages, but we also found that certain genes change across all age groups studied. We found that among iron transport genes, only the genes encoding the brush-border membrane proteins dcytb and DMT1 were consistently induced in anemia, while other genes involved in iron export from enterocytes such as ferroportin and hephaestin did not show changes in the iron deficient state. Interestingly however, we found consistent upregulation of genes that have not been described to be involved in iron transport in the mammalian duodenum. These changes include 4-12-fold upregulation of the basolateral membrane-specific copper ATPase (Atp7a), and 2-5-fold increases in a membrane bound form of ceruloplasmin, a multi-copper ferroxidase, which was seen in adult rats. As the brush-border membrane copper transporter Ctrl did not change expression levels, we suggest that copper may enter enterocytes via DMT1. There is a well-known link between copper and iron homeostasis as copper deficiency causes anemia and iron deficiency anemia leads to increased body copper levels. From these findings, we hypothesize that chronic iron deficiency leads to compensatory increases in the expression of brush-border iron transport proteins dcytb and DMT1 (which may also transport copper), increased basolateral export of copper via the copper ATPase, and increased expression of GPI-anchored ceruloplasmin, all of which may work in concert to enhance body iron delivery. In order to explore this possibility, we plan to pursue the following Specific AIMS: 1) decipher transcriptional regulation of dcytb and DMT1 by iron, and 2) characterize basolateral copper ATPase activity and protein expression in iron deficiency and characterize expression of membrane-associated ceruloplasmin in the duodenum of iron deficient rats. Overall, these studies will likely lead to increased understanding of the interplay between intestinal iron absorption and body copper homeostasis and will explore the role of GPI-anchored ceruloplasmin in intestinal iron transport.

描述（由申请人提供）：肠道铁吸收是由最近才被鉴定的几种蛋白质介导的。然而，几项实验研究表明，还有其他未知基因参与了这一重要的生理过程。因此，我们进行了比较基因芯片研究，旨在识别 8 天、21 天、6 周、12 和 26 周龄贫血大鼠十二指肠粘膜中参与铁转运的已知和未知基因表达的变化。我们的结果表明，基因表达的变化在不同年龄是独特的，但我们也发现某些基因在所研究的所有年龄组中都会发生变化。我们发现，在铁转运基因中，只有编码刷状缘膜蛋白 dcytb 和 DMT1 的基因在贫血中持续被诱导，而其他参与肠细胞铁输出的基因，如膜转运蛋白和铁黄蛋白，在缺铁状态下没有表现出变化。 。然而有趣的是，我们发现尚未被描述参与哺乳动物十二指肠铁转运的基因持续上调。这些变化包括基底外侧膜特异性铜 ATP 酶 (Atp7a) 上调 4-12 倍，以及膜结合形式的铜蓝蛋白（一种多铜亚铁氧化酶）增加 2-5 倍，这在成年大鼠中可见。由于刷状缘膜铜转运蛋白 Ctrl 没有改变表达水平，我们认为铜可能通过 DMT1 进入肠细胞。铜和铁的体内平衡之间存在众所周知的联系，因为缺铜会导致贫血，而缺铁性贫血会导致体内铜水平升高。根据这些发现，我们假设慢性铁缺乏导致刷状缘铁转运蛋白 dcytb 和 DMT1（也可能转运铜）表达代偿性增加，通过铜 ATP 酶增加铜的基底外侧输出，以及 GPI 表达增加-锚定铜蓝蛋白，所有这些都可以协同作用以增强体内铁的输送。为了探索这种可能性，我们计划追求以下具体目标：1）破译铁对 dcytb 和 DMT1 的转录调节，2）表征缺铁时基底外侧铜 ATP 酶活性和蛋白表达，并表征膜相关铜蓝蛋白的表达在缺铁大鼠的十二指肠中。总体而言，这些研究可能会加深对肠道铁吸收与体内铜稳态之间相互作用的了解，并将探讨 GPI 锚定的铜蓝蛋白在肠道铁转运中的作用。