The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Shelley M. Payne - One of the best experts on this subject based on the ideXlab platform.
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vibrio Iron Transport evolutionary adaptation to life in multiple envIronments
Microbiology and Molecular Biology Reviews, 2016Co-Authors: Shelley M. Payne, Elizabeth E WyckoffAbstract:SUMMARY Iron is an essential element for Vibrio spp., but the acquisition of Iron is complicated by its tendency to form insoluble ferric complexes in nature and its association with high-affinity Iron-binding proteins in the host. Vibrios occupy a variety of different niches, and each of these niches presents particular challenges for acquiring sufficient Iron. Vibrio species have evolved a wide array of Iron Transport systems that allow the bacteria to compete for this essential element in each of its habitats. These systems include the secretion and uptake of high-affinity Iron-binding compounds (siderophores) as well as Transport systems for Iron bound to host complexes. Transporters for ferric and ferrous Iron not complexed to siderophores are also common to Vibrio species. Some of the genes encoding these systems show evidence of horizontal transmission, and the ability to acquire and incorporate additional Iron Transport systems may have allowed Vibrio species to more rapidly adapt to new envIronmental niches. While too little Iron prevents growth of the bacteria, too much can be lethal. The appropriate balance is maintained in vibrios through complex regulatory networks involving transcriptional repressors and activators and small RNAs (sRNAs) that act posttranscriptionally. Examination of the number and variety of Iron Transport systems found in Vibrio spp. offers insights into how this group of bacteria has adapted to such a wide range of habitats.
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Iron Transport in bacteria
2004Co-Authors: Jorge H Crosa, Alexandra R Mey, Shelley M. PayneAbstract:Iron Transport in Bacteria, a survey of research conducted over the past 50 years, examines the advances in technology and the recent availability of sequences of microbial genomes that have led to an explosion of knowledge in the field of Iron Transport systems. Analysis of genomes has identified new systems, and new models for Transport have been suggested by crystallography and structural determinations of the membrane Transport proteins. Providing an overview of up-to-date information available on Iron and microbial virulence, Iron Transport in Bacteria offers insight into development and future directions that will fascinate graduate and advanced undergraduate students and equip instructors in pathogenesis and infectious diseases. The book comprises five concise sections; the first discusses the structures, chemical properties, and biosynthesis of the microbial products, such as siderophores and hemophores used by these organisms to acquire Iron. The second section explores the Transport of these compounds into gram-negative bacteria. The remaining sections cover Iron Transport in the prototype, E. coli K-12; Iron Transport systems in selected pathogenic microorganisms; and Iron Transport in ecology. Hardcover, 499 pages, full-color insert, illustrations, index.
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tonb dependent systems of uropathogenic escherichia coli aerobactin and heme Transport and tonb are required for virulence in the mouse
Infection and Immunity, 2001Co-Authors: Alfredo G Torres, Peter Redford, Rodney A Welch, Shelley M. PayneAbstract:The uropathogenic Escherichia coli strain CFT073 has multiple Iron acquisition systems, including heme and siderophore Transporters. A tonB mutant derivative of CFT073 failed to use heme as an Iron source or to utilize the siderophores enterobactin and aerobactin, indicating that Transport of these compounds in CFT073 is TonB dependent. The TonB− derivative showed reduced virulence in a mouse model of urinary tract infection. Virulence was restored when the tonB gene was introduced on a plasmid. To determine the importance of the individual TonB-dependent Iron Transport systems during urinary tract infections, mutants defective in each of the CFT073 high-affinity Iron Transport systems were constructed and tested in the mouse model. Mouse virulence assays indicated that mutants defective in a single Iron Transport system were able to infect the kidney when inoculated as a pure culture but were unable to efficiently compete with the wild-type strain in mixed infections. These results indicate a role for TonB-dependent systems in the virulence of uropathogenic E. coli strains.
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the shi 3 Iron Transport island of shigella boydii 0 1392 carries the genes for aerobactin synthesis and Transport
Journal of Bacteriology, 2001Co-Authors: Georgiana E Purdy, Shelley M. PayneAbstract:In Shigella boydii 0-1392, genes encoding the synthesis and Transport of the hydroxamate siderophore aerobactin are located within a 21-kb Iron Transport island between lysU and the pheU tRNA gene. DNA sequence analysis of the S. boydii 0-1392 island, designated SHI-3 for Shigella island 3, revealed a conserved aerobactin operon associated with a P4 prophage-like integrase gene and numerous insertion sequences (IS). SHI-3 is present at the pheU tRNA locus in some S. boydii isolates but not in others. The map locations of the aerobactin genes vary among closely related species. The association of the aerobactin operon with phage genes and mobile elements and its presence at different locations within the genomes of enteric pathogens suggest that these virulence-enhancing genes may have been acquired by bacteriophage integration or IS element-mediated transposition. An S. boydii aerobactin synthesis mutant, 0-1392 iucB, was constructed and was similar to the wild type in tissue culture assays of invasion and intercellular spread.
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haem Iron Transport system in enterohaemorrhagic escherichia coli o157 h7
Molecular Microbiology, 1997Co-Authors: Alfredo G Torres, Shelley M. PayneAbstract:In this study, we identified the Iron-Transport systems of Escherichia coli O157:H7 strain EDL933. This strain synthesized and Transported enterobactin and had a ferric citrate Transport system but lacked the ability to produce or use aerobactin. It used haem and haemoglobin, but not transferrin or lactoferrin, as Iron sources. We cloned the gene encoding an Iron-regulated haem-Transport protein and showed that this E. coli haem-utilization gene (chuA) encoded a 69 kDa outer membrane protein that was synthesized in response to Iron limitation. Expression of this protein in a laboratory strain of E. coli was sufficient for utilization of haem or haemoglobin as Iron sources. Mutation of the chromosomal chuA and tonB genes in E. coli O157:H7 demonstrated that the utilization of haemin and haemoglobin was ChuA- and TonB-dependent. Nucleotide sequence analysis of chuA revealed features characteristic of TonB-dependent, Fur-regulated, outer membrane Iron-Transport proteins. It was highly homologous to the shuA gene of Shigella dysenteriae and less closely related to hemR of Yersinia enterocolitica and hmuR of Yersinia pestis. A conserved Fur box was identified upstream of the chuA gene, and regulation by Fur was confirmed.
Gregory J. Anderson - One of the best experts on this subject based on the ideXlab platform.
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Modulation of Iron Transport proteins in human colorectal carcinogenesis
Gut, 2006Co-Authors: Matthew J. Brookes, Andrew T. Mckie, Sharon Hughes, Frances E. Turner, Gary M. Reynolds, Naveen Sharma, Tariq Ismail, Geert Berx, Neil A. Hotchin, Gregory J. AndersonAbstract:Background and aims: Total body Iron and high dietary Iron intake are risk factors for colorectal cancer. To date there is no comprehensive characterisation of Iron Transport proteins in progression to colorectal carcinoma. In this study, we examined expression of Iron import (duodenal cytochrome b (DCYTB), divalent metal Transporter 1 (DMT1), and transferrin receptor 1 (TfR1)) and export (hephaestin (HEPH) and ferroportin (FPN)) proteins in colorectal carcinoma. Methods: Perl’s staining was used to examine colonocyte Iron content. Real time polymerase chain reaction (PCR) and western blotting were used to examine mRNA and protein levels of the molecules of interest in 11 human colorectal cancers. Semiquantitative immunohistochemistry was used to verify protein levels and information on cellular localisation. The effect of Iron loading on E-cadherin expression in SW480 and Caco-2 cell lines was examined by promoter assays, real time PCR and western blotting. Results: Perl’s staining showed increased Iron in colorectal cancers, and there was a corresponding overexpression of components of the intracellular Iron import machinery (DCYTB, DMT1, and TfR1). The Iron exporter FPN was also overexpressed, but its intracellular location, combined with reduced HEPH levels, suggests reduced Iron efflux in the majority of colorectal cancers examined. Loss of HEPH and FPN expression was associated with more advanced disease. Iron loading Caco-2 and SW480 cells caused cellular proliferation and E-cadherin repression. Conclusions: Progression to colorectal cancer is associated with increased expression in Iron import proteins and a block in Iron export due to decreased expression and aberrant localisation of HEPH and FPN, respectively. This results in increased intracellular Iron which may induce proliferation and repress cell adhesion.
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a rapid decrease in the expression of dmt1 and dcytb but not ireg1 or hephaestin explains the mucosal block phenomenon of Iron absorption
Gut, 2003Co-Authors: David M Frazer, Christopher D. Vulpe, Andrew T. Mckie, Sarah J. Wilkins, E M Becker, T L Murphy, Gregory J. AndersonAbstract:Background: A large oral dose of Iron will reduce the absorption of a subsequent smaller dose of Iron in a phenomenon known as mucosal block. Molecular analysis of this process may provide insights into the regulation of intestinal Iron absorption. Aims: To determine the effect of an oral bolus of Iron on duodenal expression of molecules associated with intestinal Iron Transport in rats and to relate this to changes in Iron absorption. Methods: Rats were given an oral dose of Iron and duodenal expression of divalent metal Transporter 1 (DMT1), Dcytb, Ireg1, and hephaestin (Hp) was determined using the ribonuclease protection assay, western blotting, and immunofluorescence. Iron absorption was measured using radioactive 59Fe. Results: A decrease in intestinal Iron absorption occurred following an oral dose of Iron and this was associated with increased enterocyte Iron levels, as assessed by Iron regulatory protein activity and immunoblotting for ferritin. Reduced absorption was also accompanied by a rapid decrease in expression of the mRNAs encoding the brush border Iron Transport molecules Dcytb and the Iron responsive element (IRE) containing the splice variant of DMT1. No such change was seen in expression of the non-IRE splice variant of DMT1 or the basolateral Iron Transport molecules Ireg1 and Hp. Similar changes were observed at the protein level. Conclusions: These data indicate that brush border, but not basolateral, Iron Transport components are regulated locally by enterocyte Iron levels and support the hypothesis that systemic stimuli exert their primary effect on basolateral Transport molecules.
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relationship between intestinal Iron Transporter expression hepatic hepcidin levels and the control of Iron absorption
Biochemical Society Transactions, 2001Co-Authors: Gregory J. Anderson, Andrew T. Mckie, Sarah J. Wilkins, E M Becker, K N Millard, T L Murphy, Christopher D. VulpeAbstract:Hepcidin is an anti-microbial peptide predicted to be involved in the regulation of intestinal Iron absorption. We have examined the relationship between the expression of hepcidin in the liver and the expression of the Iron-Transport molecules divalent-metal Transporter 1, duodenal cytochrome b , hephaestin and Ireg1 in the duodenum of rats switched from an Iron-replete to an Iron-deficient diet or treated to induce an acute phase response. In each case, elevated hepcidin expression correlated with reduced Iron absorption and depressed levels of Iron-Transport molecules. These data are consistent with hepcidin playing a role as a negative regulator of intestinal Iron absorption.
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hephaestin a ceruloplasmin homologue implicated in intestinal Iron Transport is defective in the sla mouse
Nature Genetics, 1999Co-Authors: Christopher D. Vulpe, T L Murphy, Candice C. Askwith, Yienming Kuo, L Cowley, Natasha Libina, Jane Gitschier, Gregory J. AndersonAbstract:Iron is essential for many cellular functions; consequently, disturbances of Iron homeostasis, leading to either Iron deficiency or Iron overload, can have significant clinical consequences. Despite the clinical prevalence of these disorders, the mechanism by which dietary Iron is absorbed into the body is poorly understood. We have identified a key component in intestinal Iron Transport by study of the sex–linked anaemia (sla) mouse, which has a block in intestinal Iron Transport1. Mice carrying the sla mutation develop moderate to severe microcytic hypochromic anaemia1. Although these mice take up Iron from the intestinal lumen into mature epithelial cells normally2, the subsequent exit of Iron into the circulation is diminished3. As a result, Iron accumulates in enterocytes and is lost during turnover of the intestinal epithelium4. Biochemical studies have failed to identify the underlying difference between sla and normal mice, therefore, we used a genetic approach to identify the gene mutant in sla mice. We describe here a novel gene, Heph, encoding a transmembrane–bound ceruloplasmin homologue that is mutant in the sla mouse and highly expressed in intestine. We suggest that the hephaestin protein is a multi–copper ferroxidase necessary for Iron egress from intestinal enterocytes into the circulation and that it is an important link between copper and Iron metabolism in mammals.
Jerry Kaplan - One of the best experts on this subject based on the ideXlab platform.
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ferroportin mediated Iron Transport expression and regulation
Biochimica et Biophysica Acta, 2012Co-Authors: Diane M Ward, Jerry KaplanAbstract:The distinguishing feature between Iron homeostasis in single versus multicellular organisms is the need for multicellular organisms to transfer Iron from sites of absorption to sites of utilization and storage. Ferroportin is the only known Iron exporter and ferroportin plays an essential role in the export of Iron from cells to blood. Ferroportin can be regulated at many different levels including transcriptionally, post-transcriptionally, through mRNA stability and post-translationally, through protein turnover. Additionally, ferroportin may be regulated in both cell-dependent and cell-autonomous fashions. Regulation of ferroportin is critical for Iron homeostasis as alterations in ferroportin may result in either Iron deficiency or Iron overload. This article is part of a Special Issue entitled: Cell Biology of Metals.
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an oxidase permease based Iron Transport system in schizosaccharomyces pombe and its expression in saccharomyces cerevisiae
Journal of Biological Chemistry, 1997Co-Authors: Candice C. Askwith, Jerry KaplanAbstract:Genetic studies have demonstrated that high affinity ferrous Transport in Saccharomyces cerevisiae requires an oxidase (Fet3p) and a permease (Ftr1p). Using an Iron-independent galactose-based expression system, we show that expression of these two genes can mediate high affinity ferrous Iron Transport, indicating that these two genes are not only necessary, but sufficient for high affinity Iron Transport. Schizosaccharomyces pombe also employ an oxidase-permease system for high affinity Iron Transport. The S. pombe genes, fio1+ (ferrous Iron oxidase) and fip1+ (ferriferous permease), share significant similarity to FET3 and FTR1 from S. cerevisiae. Both fio1+ and fip1+ are transcriptionally regulated by Iron need, and disruption of fio1+ results in a loss of high affinity Iron Transport. Expression of fio1+ alone in an S. cerevisiae fet3 disruption strain does not result in high affinity Iron Transport. This result indicates that the S. pombe ferroxidase, while functionally homologous to the S. cerevisiae ferroxidase, does not have enough similarity to interact with the S. cerevisiae permease. Simultaneous expression of both S. pombe genes, fio1+ and fip1+, in S. cerevisiae can reconstitute high affinity Iron Transport. These results demonstrate that the oxidase and permease are all that is required to reconstitute high affinity Iron Transport and suggest that such Transport systems are found in other eukaryotes.
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The FET3 Gene Product Required for High Affinity Iron Transport in Yeast Is a Cell Surface Ferroxidase
The Journal of biological chemistry, 1995Co-Authors: Deepika De Silva, Candice C. Askwith, David J. Eide, Jerry KaplanAbstract:The yeast FET3 gene is required for high affinity Iron Transport (Askwith, C., Eide, D., Ho, A. V., Bernard, P. S., Li, L., Davis-Kaplan, S., Sipe, D. M., and Kaplan, J. (1994) Cell 76, 403-410). The gene has extensive sequence homology to the family of multi-copper oxidases. In this communication, we demonstrate that the gene product is a cell surface ferroxidase involved in Iron Transport. Cells that contain a functional FET3 gene product exhibited an Iron-dependent non-mitochondrial increase in oxygen consumption. Comparison of the rate of Iron oxidation to O2 consumption yielded an approximate value of 4:1, as predicted for a ferroxidase. Spheroplasts obtained from cells grown under low Iron conditions also displayed an Iron-dependent increase in O2 consumption. Treatment of spheroplasts with trypsin or affinity-purified antibodies directed against the putative external ferroxidase domain of Fet3 had no effect on basal O2 consumption but inhibited the Iron-dependent increase in O2 consumption. Anti-peptide antibodies directed against the cytosolic domain of Fet3 had no effect on O2 consumption. These studies indicate that Fet3 is a plasma membrane ferroxidase required for high affinity Iron uptake, in which the ferroxidase-containing domain is localized on the external cell surface.
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the fet3 gene of s cerevisiae encodes a multicopper oxidase required for ferrous Iron uptake
Cell, 1994Co-Authors: Candice C. Askwith, David Eide, Anthony Van Ho, Philip S Bernard, Sandra Daviskaplan, David Sipe, Jerry KaplanAbstract:S. cerevisiae accumulate Iron by a process requiring a ferrireductase and a ferrous Transporter. We have isolated a mutant, fet3, defective for high affinity Fe(II) uptake. The wild-type FET3 gene was isolated by complementation of the mutant defect. Sequence analysis of the gene revealed the presence of an open reading frame coding for a protein with strong similarity to the family of blue multicopper oxidoreductases. Consistent with the role of copper in Iron Transport, growth of wild-type cells in copper-deficient media resulted in decreased ferrous Iron Transport. Addition of copper, but not other transition metals (manganese or zinc), to the assay media resulted in the recovery of Fe(II) Transporter activity. We suggest that the catalytic activity of the Fet3 protein is required for cellular Iron accumulation.
James R. Connor - One of the best experts on this subject based on the ideXlab platform.
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evidence for communication of peripheral Iron status to cerebrospinal fluid clinical implications for therapeutic strategy
Fluids and Barriers of the CNS, 2020Co-Authors: James R. Connor, Ian A Simpson, Kari A. Duck, S Patton, Lynn Marie Trotti, Richard P Allen, Christopher J Earley, David B RyeAbstract:Background Iron is crucial for proper functioning of all organs including the brain. Deficiencies and excess of Iron are common and contribute to substantial morbidity and mortality. Whereas Iron's involvement in erythropoiesis drives clinical practice, the guidelines informing interventional strategies for Iron repletion in neurological disorders are poorly defined. The objective of this study was to determine if peripheral Iron status is communicated to the brain. Methods We used a bi-chamber cell culture model of the blood-brain-barrier to determine transcytosis of Iron delivered by transferrin as a metric of Iron Transport. In the apical chamber (representative of the blood) we placed transferrin complexed with Iron59 and in the basal chamber (representative of the brain) we placed human cerebrospinal fluid. Cerebrospinal fluid (CSF) samples (N = 24) were collected via lumbar puncture. The integrity of the tight junctions were monitored throughout the experiments using RITC-Dextran. Results We demonstrate that Iron Transport correlates positively with plasma hemoglobin concentrations but not serum ferritin levels. Conclusions The clinical ramifications of these findings are several- fold. They suggest that erythropoietic demands for Iron take precedence over brain requirements, and that the metric traditionally considered to be the most specific test reflecting total body Iron stores and relied upon to inform treatment decisions-i.e., serum ferritin-may not be the preferred peripheral indicator when attempting to promote brain Iron uptake. The future direction of this line of investigation is to identify the factor(s) in the CSF that influence Iron Transport at the level of the BBB.
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Iron uptake and Transport across physiological barriers
BioMetals, 2016Co-Authors: Kari A. Duck, James R. ConnorAbstract:Iron is an essential element for human development. It is a major requirement for cellular processes such as oxygen Transport, energy metabolism, neurotransmitter synthesis, and myelin synthesis. Despite its crucial role in these processes, Iron in the ferric form can also produce toxic reactive oxygen species. The duality of Iron’s function highlights the importance of maintaining a strict balance of Iron levels in the body. As a result, organisms have developed elegant mechanisms of Iron uptake, Transport, and storage. This review will focus on the mechanisms that have evolved at physiological barriers, such as the intestine, the placenta, and the blood–brain barrier (BBB), where Iron must be Transported. Much has been written about the processes for Iron Transport across the intestine and the placenta, but less is known about Iron Transport mechanisms at the BBB. In this review, we compare the established pathways at the intestine and the placenta as well as describe what is currently known about Iron Transport at the BBB and how brain Iron uptake correlates with processes at these other physiological barriers.
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distribution of divalent metal Transporter 1 and metal Transport protein 1 in the normal and belgrade rat
Journal of Neuroscience Research, 2001Co-Authors: Joseph R Burdo, Laura M. Garrick, Michael D Garrick, Sharon Menzies, Ian A Simpson, Kevin G Dolan, D J Haile, John L Beard, James R. ConnorAbstract:Iron accumulation in the brain occurs in a number of neurodegenerative diseases. Two new Iron Transport proteins have been identified that may help elucidate the mechanism of abnormal Iron accumulation. The Divalent Metal Transporter 1 (DMT1), is responsible for Iron uptake from the gut and Transport from endosomes. The Metal Transport Protein 1 (MTP1) promotes Iron export. In this study we determined the cellular and regional expression of these two Transporters in the brains of normal adult and Belgrade rats. Belgrade rats have a defect in DMT1 that is associated with lower levels of Iron in the brain. In the normal rat, DMT1 expression is highest in neurons in the striatum, cerebellum, thalamus, ependymal cells lining the third ventricle, and vascular cells throughout the brain. The staining in the ependymal cells and endothelial cells suggests that DMT1 has an important role in Iron Transport into the brain. In Belgrade rats, there is generalized decrease in immunodetectable DMT1 compared to normal rats except in the ependymal cells. This decrease in immunoreactivity, however, was absent on immunoblots. The immunoblot analysis indicates that this protein did not upregulate to compensate for the chronic defect in Iron Transport. MTP1 staining is found in most brain regions. MTP1 expression in the brain is robust in pyramidal neurons of the cerebral cortex but is not detected in the vascular endothelial cells and ependymal cells. MTP1 staining in Belgrade rats was decreased compared to normal, but similar to DMT1 this decrease was not corroborated by immunoblotting. These results indicate that DMT1 and MTP1 are involved in brain Iron Transport and this involvement is regionally and cellularly specific.
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distribution of divalent metal Transporter 1 and metal Transport protein 1 in the normal and belgrade rat
Journal of Neuroscience Research, 2001Co-Authors: Joseph R Burdo, Laura M. Garrick, Michael D Garrick, Sharon Menzies, Ian A Simpson, Kevin G Dolan, D J Haile, John L Beard, James R. ConnorAbstract:Iron accumulation in the brain occurs in a number of neurodegenerative diseases. Two new Iron Transport proteins have been identified that may help elucidate the mechanism of abnormal Iron accumulation. The Divalent Metal Transporter 1 (DMT1), is responsible for Iron uptake from the gut and Transport from endosomes. The Metal Transport Protein 1 (MTP1) promotes Iron export. In this study we determined the cellular and regional expression of these two Transporters in the brains of normal adult and Belgrade rats. Belgrade rats have a defect in DMT1 that is associated with lower levels of Iron in the brain. In the normal rat, DMT1 expression is highest in neurons in the striatum, cerebellum, thalamus, ependymal cells lining the third ventricle, and vascular cells throughout the brain. The staining in the ependymal cells and endothelial cells suggests that DMT1 has an important role in Iron Transport into the brain. In Belgrade rats, there is generalized decrease in immunodetectable DMT1 compared to normal rats except in the ependymal cells. This decrease in immunoreactivity, however, was absent on immunoblots. The immunoblot analysis indicates that this protein did not upregulate to compensate for the chronic defect in Iron Transport. MTP1 staining is found in most brain regions. MTP1 expression in the brain is robust in pyramidal neurons of the cerebral cortex but is not detected in the vascular endothelial cells and ependymal cells. MTP1 staining in Belgrade rats was decreased compared to normal, but similar to DMT1 this decrease was not corroborated by immunoblotting. These results indicate that DMT1 and MTP1 are involved in brain Iron Transport and this involvement is regionally and cellularly specific. J Neurosci. Res. 66:1198–1207, 2001. © 2001 Wiley-Liss, Inc.
Christopher D. Vulpe - One of the best experts on this subject based on the ideXlab platform.
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Mammalian Iron Transport
Cellular and Molecular Life Sciences, 2009Co-Authors: Gregory Jon Anderson, Christopher D. VulpeAbstract:Iron is essential for basic cellular processes but is toxic when present in excess. Consequently, Iron Transport into and out of cells is tightly regulated. Most Iron is delivered to cells bound to plasma transferrin via a process that involves transferrin receptor 1, divalent metal-ion Transporter 1 and several other proteins. Non-transferrin-bound Iron can also be taken up efficiently by cells, although the mechanism is poorly understood. Cells can divest themselves of Iron via the Iron export protein ferroportin in conjunction with an Iron oxidase. The linking of an oxidoreductase to a membrane permease is a common theme in membrane Iron Transport. At the systemic level, Iron Transport is regulated by the liver-derived peptide hepcidin which acts on ferroportin to control Iron release to the plasma.
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a rapid decrease in the expression of dmt1 and dcytb but not ireg1 or hephaestin explains the mucosal block phenomenon of Iron absorption
Gut, 2003Co-Authors: David M Frazer, Christopher D. Vulpe, Andrew T. Mckie, Sarah J. Wilkins, E M Becker, T L Murphy, Gregory J. AndersonAbstract:Background: A large oral dose of Iron will reduce the absorption of a subsequent smaller dose of Iron in a phenomenon known as mucosal block. Molecular analysis of this process may provide insights into the regulation of intestinal Iron absorption. Aims: To determine the effect of an oral bolus of Iron on duodenal expression of molecules associated with intestinal Iron Transport in rats and to relate this to changes in Iron absorption. Methods: Rats were given an oral dose of Iron and duodenal expression of divalent metal Transporter 1 (DMT1), Dcytb, Ireg1, and hephaestin (Hp) was determined using the ribonuclease protection assay, western blotting, and immunofluorescence. Iron absorption was measured using radioactive 59Fe. Results: A decrease in intestinal Iron absorption occurred following an oral dose of Iron and this was associated with increased enterocyte Iron levels, as assessed by Iron regulatory protein activity and immunoblotting for ferritin. Reduced absorption was also accompanied by a rapid decrease in expression of the mRNAs encoding the brush border Iron Transport molecules Dcytb and the Iron responsive element (IRE) containing the splice variant of DMT1. No such change was seen in expression of the non-IRE splice variant of DMT1 or the basolateral Iron Transport molecules Ireg1 and Hp. Similar changes were observed at the protein level. Conclusions: These data indicate that brush border, but not basolateral, Iron Transport components are regulated locally by enterocyte Iron levels and support the hypothesis that systemic stimuli exert their primary effect on basolateral Transport molecules.
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relationship between intestinal Iron Transporter expression hepatic hepcidin levels and the control of Iron absorption
Biochemical Society Transactions, 2001Co-Authors: Gregory J. Anderson, Andrew T. Mckie, Sarah J. Wilkins, E M Becker, K N Millard, T L Murphy, Christopher D. VulpeAbstract:Hepcidin is an anti-microbial peptide predicted to be involved in the regulation of intestinal Iron absorption. We have examined the relationship between the expression of hepcidin in the liver and the expression of the Iron-Transport molecules divalent-metal Transporter 1, duodenal cytochrome b , hephaestin and Ireg1 in the duodenum of rats switched from an Iron-replete to an Iron-deficient diet or treated to induce an acute phase response. In each case, elevated hepcidin expression correlated with reduced Iron absorption and depressed levels of Iron-Transport molecules. These data are consistent with hepcidin playing a role as a negative regulator of intestinal Iron absorption.
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hephaestin a ceruloplasmin homologue implicated in intestinal Iron Transport is defective in the sla mouse
Nature Genetics, 1999Co-Authors: Christopher D. Vulpe, T L Murphy, Candice C. Askwith, Yienming Kuo, L Cowley, Natasha Libina, Jane Gitschier, Gregory J. AndersonAbstract:Iron is essential for many cellular functions; consequently, disturbances of Iron homeostasis, leading to either Iron deficiency or Iron overload, can have significant clinical consequences. Despite the clinical prevalence of these disorders, the mechanism by which dietary Iron is absorbed into the body is poorly understood. We have identified a key component in intestinal Iron Transport by study of the sex–linked anaemia (sla) mouse, which has a block in intestinal Iron Transport1. Mice carrying the sla mutation develop moderate to severe microcytic hypochromic anaemia1. Although these mice take up Iron from the intestinal lumen into mature epithelial cells normally2, the subsequent exit of Iron into the circulation is diminished3. As a result, Iron accumulates in enterocytes and is lost during turnover of the intestinal epithelium4. Biochemical studies have failed to identify the underlying difference between sla and normal mice, therefore, we used a genetic approach to identify the gene mutant in sla mice. We describe here a novel gene, Heph, encoding a transmembrane–bound ceruloplasmin homologue that is mutant in the sla mouse and highly expressed in intestine. We suggest that the hephaestin protein is a multi–copper ferroxidase necessary for Iron egress from intestinal enterocytes into the circulation and that it is an important link between copper and Iron metabolism in mammals.
