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Helman SL, Zhou J, Fuqua BK, Lu Y, Collins JF, Chen H, Vulpe CD, Anderson GJ, Frazer DM. The biology of mammalian multi-copper ferroxidases. Biometals 2023; 36:263-281. [PMID: 35167013 PMCID: PMC9376197 DOI: 10.1007/s10534-022-00370-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 02/04/2022] [Indexed: 12/24/2022]
Abstract
The mammalian multicopper ferroxidases (MCFs) ceruloplasmin (CP), hephaestin (HEPH) and zyklopen (ZP) comprise a family of conserved enzymes that are essential for body iron homeostasis. Each of these enzymes contains six biosynthetically incorporated copper atoms which act as intermediate electron acceptors, and the oxidation of iron is associated with the four electron reduction of dioxygen to generate two water molecules. CP occurs in both a secreted and GPI-linked (membrane-bound) form, while HEPH and ZP each contain a single C-terminal transmembrane domain. These enzymes function to ensure the efficient oxidation of iron so that it can be effectively released from tissues via the iron export protein ferroportin and subsequently bound to the iron carrier protein transferrin in the blood. CP is particularly important in facilitating iron release from the liver and central nervous system, HEPH is the major MCF in the small intestine and is critical for dietary iron absorption, and ZP is important for normal hair development. CP and HEPH (and possibly ZP) function in multiple tissues. These proteins also play other (non-iron-related) physiological roles, but many of these are ill-defined. In addition to disrupting iron homeostasis, MCF dysfunction perturbs neurological and immune function, alters cancer susceptibility, and causes hair loss, but, despite their importance, how MCFs co-ordinately maintain body iron homeostasis and perform other functions remains incompletely understood.
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Affiliation(s)
- Sheridan L Helman
- Molecular Nutrition Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - Jie Zhou
- Department of Physiological Sciences, University of Florida, Gainsville, FL, USA
| | - Brie K Fuqua
- David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Yan Lu
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Road, Brisbane, QLD, 4006, Australia
- Mucosal Immunology Group, QIMR Berghofer Medical Research Institute, Brisbane, Australia
| | - James F Collins
- Food Science and Human Nutrition Department, University of Florida, Gainsville, FL, USA
| | - Huijun Chen
- Jiangsu Key Laboratory of Molecular Medicine, Medical School of Nanjing University, Nanjing, China
| | - Christopher D Vulpe
- Department of Physiological Sciences, University of Florida, Gainsville, FL, USA
| | - Gregory J Anderson
- Iron Metabolism Laboratory, QIMR Berghofer Medical Research Institute, 300 Herston Road, Brisbane, QLD, 4006, Australia.
- School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, Australia.
| | - David M Frazer
- Molecular Nutrition Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Australia
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2
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Silva AM, Moniz T, de Castro B, Rangel M. Human transferrin: An inorganic biochemistry perspective. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214186] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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3
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Sakajiri T, Nakatsuji M, Teraoka Y, Furuta K, Ikuta K, Shibusa K, Sugano E, Tomita H, Inui T, Yamamura T. Zinc mediates the interaction between ceruloplasmin and apo-transferrin for the efficient transfer of Fe(III) ions. Metallomics 2021; 13:6427378. [PMID: 34791391 DOI: 10.1093/mtomcs/mfab065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 11/02/2021] [Indexed: 11/14/2022]
Abstract
Fe(II) exported from cells is oxidized to Fe(III), possibly by a multi-copper ferroxidase (MCF) such as ceruloplasmin (CP), to efficiently bind with the plasma iron transport protein transferrin (TF). As unbound Fe(III) is highly insoluble and reactive, its release into the blood during the transfer from MCF to TF must be prevented. A likely mechanism for preventing the release of unbound Fe(III) is via direct interaction between MCF and TF; however, the occurrence of this phenomenon remains controversial. This study aimed to reveal the interaction between these proteins, possibly mediated by zinc. Using spectrophotometric, isothermal titration calorimetric, and surface plasmon resonance methods, we found that Zn(II)-bound CP bound to iron-free TF (apo-TF) with a Kd of 4.2 μM and a stoichiometry CP:TF of ∼2:1. Computational modeling of the complex between CP and apo-TF predicted that each of the three Zn(II) ions that bind to CP further binds to acidic amino acid residues of apo-TF to play a role as a cross-linker connecting both proteins. Domain 4 of one CP molecule and domain 6 of the other CP molecule fit tightly into the clefts in the N- and C-lobes of apo-TF, respectively. Upon the binding of two Fe(III) ions to apo-TF, the resulting diferric TF [Fe(III)2TF] dissociated from CP by conformational changes in TF. In human blood plasma, zinc deficiency reduced the production of Fe(III)2TF and concomitantly increased the production of non-TF-bound iron. Our findings suggest that zinc may be involved in the transfer of iron between CP and TF.
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Affiliation(s)
- Tetsuya Sakajiri
- Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.,Faculty of Nutritional Sciences, the University of Morioka, 808 Sunakomi, Takizawa, Iwate 020-0694, Japan.,Qualtec Co. Ltd., 4-230 Sambo-cho, Sakai, Osaka 590-0906, Japan.,Department of Nutrition, Kyushu Nutrition Welfare University, 5-1-1 Shimoitozu, Kitakyushu Kokurakita-ku, Fukuoka 803-0846, Japan
| | - Masatoshi Nakatsuji
- Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Yoshiaki Teraoka
- Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Kosuke Furuta
- Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Katsuya Ikuta
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa, Hokkaido 078-8510, Japan.,Japanese Red Cross Hokkaido Blood Center, 2-1 Nijuyonken, Nishi-ku, Sapporo, Hokkaido 063-0802, Japan
| | - Kotoe Shibusa
- Division of Gastroenterology and Hematology/Oncology, Department of Medicine, Asahikawa Medical University, 2-1-1-1 Midorigaoka-Higashi, Asahikawa, Hokkaido 078-8510, Japan.,Hokkaido System Science Co., Ltd., 2-1 Shinkawa Nishi, Kita-ku, Sapporo, Hokkaido 001-0932, Japan
| | - Eriko Sugano
- Department of Chemistry and Biological Sciences, Faculty of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan
| | - Hiroshi Tomita
- Department of Chemistry and Biological Sciences, Faculty of Science and Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan
| | - Takashi Inui
- Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Takaki Yamamura
- Laboratory of Biological Macromolecules, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.,Faculty of Nutritional Sciences, the University of Morioka, 808 Sunakomi, Takizawa, Iwate 020-0694, Japan
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Aslan ES, N White K, A Syed B, S Srai K, W Evans R. Expression of soluble, active, fluorescently tagged hephaestin in COS and CHO cell lines. ACTA ACUST UNITED AC 2020; 44:393-405. [PMID: 33402866 PMCID: PMC7759196 DOI: 10.3906/biy-2005-39] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 09/23/2020] [Indexed: 11/29/2022]
Abstract
Hephaestin (Hp) is a trans-membrane protein, which plays a critical role in intestinal iron absorption. Hp was originally identified as the gene responsible for the phenotype of sex-linked anaemia in the
sla
mouse. The mutation in the
sla
protein causes accumulation of dietary iron in duodenal cells, causing severe microcytic hypochromic anaemia. Although mucosal uptake of dietary iron is normal, export from the duodenum is inhibited. Hp is homologous to ceruloplasmin (Cp), a member of the family of multi copper ferroxidases (MCFs) and possesses ferroxidase activity that facilitates iron release from the duodenum and load onto the serum iron transport protein transferrin. In the present study, attempts were made to produce biologically active recombinant mouse hephaestin as a secretory form tagged with green fluorescent protein (GFP), Hpsec-GFP. Plasmid expressing Hpsec-GFP was constructed and transfected into COS and CHO cells. The GFP aided the monitoring expression in real time to select the best conditions to maximise expression and provided a tag for purifying and analysing Hpsec-GFP. The protein had detectable oxidase activity as shown by in-gel and solution-based assays. The methods described here can provide the basis for further work to probe the interaction of hephaestin with other proteins using complementary fluorescent tags on target proteins that would facilitate the fluorescence resonance energy transfer measurements, for example with transferrin or colocalisation studies, and help to discover more about hephaestin works at the molecular level.
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Affiliation(s)
- Elif Sibel Aslan
- Department of Molecular Biology and Genetics, Faculty of Engineer and Natural Science, Biruni University, İstanbul Turkey
| | - Kenneth N White
- School of Human Sciences, London Metropolitan University, London UK
| | | | - Kaila S Srai
- Division of Biosciences, University College London, London UK
| | - Robert W Evans
- Metalloprotein Research Group, Division of Biosciences, School of Health Sciences and Social Care, Brunel University, Uxbridge UK
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5
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Looking for a partner: ceruloplasmin in protein-protein interactions. Biometals 2019; 32:195-210. [PMID: 30895493 DOI: 10.1007/s10534-019-00189-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Accepted: 03/18/2019] [Indexed: 10/27/2022]
Abstract
Ceruloplasmin (CP) is a mammalian blood plasma ferroxidase. More than 95% of the copper found in plasma is carried by this protein, which is a member of the multicopper oxidase family. Proteins from this group are able to oxidize substrates through the transfer of four electrons to oxygen. The essential role of CP in iron metabolism in humans is particularly evident in the case of loss-of-function mutations in the CP gene resulting in a neurodegenerative syndrome known as aceruloplasminaemia. However, the functions of CP are not limited to the oxidation of ferrous iron to ferric iron, which allows loading of the ferric iron into transferrin and prevents the deleterious reactions of Fenton chemistry. In recent years, a number of novel CP functions have been reported, and many of these functions depend on the ability of CP to form stable complexes with a number of proteins.
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6
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Doguer C, Ha JH, Collins JF. Intersection of Iron and Copper Metabolism in the Mammalian Intestine and Liver. Compr Physiol 2018; 8:1433-1461. [PMID: 30215866 DOI: 10.1002/cphy.c170045] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Iron and copper have similar physiochemical properties; thus, physiologically relevant interactions seem likely. Indeed, points of intersection between these two essential trace minerals have been recognized for many decades, but mechanistic details have been lacking. Investigations in recent years have revealed that copper may positively influence iron homeostasis, and also that iron may antagonize copper metabolism. For example, when body iron stores are low, copper is apparently redistributed to tissues important for regulating iron balance, including enterocytes of upper small bowel, the liver, and blood. Copper in enterocytes may positively influence iron transport, and hepatic copper may enhance biosynthesis of a circulating ferroxidase, ceruloplasmin, which potentiates iron release from stores. Moreover, many intestinal genes related to iron absorption are transactivated by a hypoxia-inducible transcription factor, hypoxia-inducible factor-2α (HIF2α), during iron deficiency. Interestingly, copper influences the DNA-binding activity of the HIF factors, thus further exemplifying how copper may modulate intestinal iron homeostasis. Copper may also alter the activity of the iron-regulatory hormone hepcidin. Furthermore, copper depletion has been noted in iron-loading disorders, such as hereditary hemochromatosis. Copper depletion may also be caused by high-dose iron supplementation, raising concerns particularly in pregnancy when iron supplementation is widely recommended. This review will cover the basic physiology of intestinal iron and copper absorption as well as the metabolism of these minerals in the liver. Also considered in detail will be current experimental work in this field, with a focus on molecular aspects of intestinal and hepatic iron-copper interplay and how this relates to various disease states. © 2018 American Physiological Society. Compr Physiol 8:1433-1461, 2018.
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Affiliation(s)
- Caglar Doguer
- Food Science and Human Nutrition Department, University of Florida, Florida, Gainesville, USA.,Nutrition and Dietetics Department, Namık Kemal University, Tekirdag, Turkey
| | - Jung-Heun Ha
- Food Science and Human Nutrition Department, University of Florida, Florida, Gainesville, USA.,Department of Food and Nutrition, Chosun University Note: Caglar Doguer and Jung-Heun Ha have contributed equally to this work., Gwangju, Korea
| | - James F Collins
- Food Science and Human Nutrition Department, University of Florida, Florida, Gainesville, USA
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Sokolov AV, Voynova IV, Kostevich VA, Vlasenko AY, Zakharova ET, Vasilyev VB. Comparison of interaction between ceruloplasmin and lactoferrin/transferrin: to bind or not to bind. BIOCHEMISTRY (MOSCOW) 2017; 82:1073-1078. [DOI: 10.1134/s0006297917090115] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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8
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A novel model for brain iron uptake: introducing the concept of regulation. J Cereb Blood Flow Metab 2015; 35:48-57. [PMID: 25315861 PMCID: PMC4294394 DOI: 10.1038/jcbfm.2014.168] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 09/03/2014] [Accepted: 09/04/2014] [Indexed: 01/07/2023]
Abstract
Neurologic disorders such as Alzheimer's, Parkinson's disease, and Restless Legs Syndrome involve a loss of brain iron homeostasis. Moreover, iron deficiency is the most prevalent nutritional concern worldwide with many associated cognitive and neural ramifications. Therefore, understanding the mechanisms by which iron enters the brain and how those processes are regulated addresses significant global health issues. The existing paradigm assumes that the endothelial cells (ECs) forming the blood-brain barrier (BBB) serve as a simple conduit for transport of transferrin-bound iron. This concept is a significant oversimplification, at minimum failing to account for the iron needs of the ECs. Using an in vivo model of brain iron deficiency, the Belgrade rat, we show the distribution of transferrin receptors in brain microvasculature is altered in luminal, intracellular, and abluminal membranes dependent on brain iron status. We used a cell culture model of the BBB to show the presence of factors that influence iron release in non-human primate cerebrospinal fluid and conditioned media from astrocytes; specifically apo-transferrin and hepcidin were found to increase and decrease iron release, respectively. These data have been integrated into an interactive model where BBB ECs are central in the regulation of cerebral iron metabolism.
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9
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Solomon EI, Heppner DE, Johnston EM, Ginsbach JW, Cirera J, Qayyum M, Kieber-Emmons MT, Kjaergaard CH, Hadt RG, Tian L. Copper active sites in biology. Chem Rev 2014; 114:3659-853. [PMID: 24588098 PMCID: PMC4040215 DOI: 10.1021/cr400327t] [Citation(s) in RCA: 1133] [Impact Index Per Article: 113.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | - David E. Heppner
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | - Jake W. Ginsbach
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Jordi Cirera
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Munzarin Qayyum
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | | | - Ryan G. Hadt
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Li Tian
- Department of Chemistry, Stanford University, Stanford, CA, 94305
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10
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Multi-copper oxidases and human iron metabolism. Nutrients 2013; 5:2289-313. [PMID: 23807651 PMCID: PMC3738974 DOI: 10.3390/nu5072289] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/29/2013] [Accepted: 06/06/2013] [Indexed: 01/13/2023] Open
Abstract
Multi-copper oxidases (MCOs) are a small group of enzymes that oxidize their substrate with the concomitant reduction of dioxygen to two water molecules. Generally, multi-copper oxidases are promiscuous with regards to their reducing substrates and are capable of performing various functions in different species. To date, three multi-copper oxidases have been detected in humans—ceruloplasmin, hephaestin and zyklopen. Each of these enzymes has a high specificity towards iron with the resulting ferroxidase activity being associated with ferroportin, the only known iron exporter protein in humans. Ferroportin exports iron as Fe2+, but transferrin, the major iron transporter protein of blood, can bind only Fe3+ effectively. Iron oxidation in enterocytes is mediated mainly by hephaestin thus allowing dietary iron to enter the bloodstream. Zyklopen is involved in iron efflux from placental trophoblasts during iron transfer from mother to fetus. Release of iron from the liver relies on ferroportin and the ferroxidase activity of ceruloplasmin which is found in blood in a soluble form. Ceruloplasmin, hephaestin and zyklopen show distinctive expression patterns and have unique mechanisms for regulating their expression. These features of human multi-copper ferroxidases can serve as a basis for the precise control of iron efflux in different tissues. In this manuscript, we review the biochemical and biological properties of the three human MCOs and discuss their potential roles in human iron homeostasis.
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11
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The transfer of iron between ceruloplasmin and transferrins. Biochim Biophys Acta Gen Subj 2012; 1820:411-6. [DOI: 10.1016/j.bbagen.2011.10.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 10/10/2011] [Accepted: 10/15/2011] [Indexed: 11/23/2022]
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12
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Lambert LA. Molecular evolution of the transferrin family and associated receptors. Biochim Biophys Acta Gen Subj 2011; 1820:244-55. [PMID: 21693173 DOI: 10.1016/j.bbagen.2011.06.002] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 06/01/2011] [Accepted: 06/07/2011] [Indexed: 12/26/2022]
Abstract
BACKGROUND In vertebrates, serum transferrins are essential iron transporters that have bind and release Fe(III) in response to receptor binding and changes in pH. Some family members such as lactoferrin and melanotransferrin can also bind iron while others have lost this ability and have gained other functions, e.g., inhibitor of carbonic anhydrase (mammals), saxiphilin (frogs) and otolith matrix protein 1 (fish). SCOPE OF REVIEW This article provides an overview of the known transferrin family members and their associated receptors and interacting partners. MAJOR CONCLUSIONS The number of transferrin genes has proliferated as a result of multiple duplication events, and the resulting paralogs have developed a wide array of new functions. Some homologs in the most primitive metazoan groups resemble both serum and melanotransferrins, but the major yolk proteins show considerable divergence from the rest of the family. Among the transferrin receptors, the lack of TFR2 in birds and reptiles, and the lack of any TFR homologs among the insects draw attention to the differences in iron transport and regulation in those groups. GENERAL SIGNIFICANCE The transferrin family members are important because of their clinical significance, interesting biochemical properties, and evolutionary history. More work is needed to better understand the functions and evolution of the non-vertebrate family members. This article is part of a Special Issue entitled Molecular Mechanisms of Iron Transport and Disorders.
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Affiliation(s)
- Lisa A Lambert
- Department of Biology, Chatham University, Woodland Road, Pittsburgh, PA 15232, USA.
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13
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Ha-Duong NT, Eid C, Hémadi M, El Hage Chahine JM. In Vitro Interaction between Ceruloplasmin and Human Serum Transferrin. Biochemistry 2010; 49:10261-3. [DOI: 10.1021/bi1014503] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nguyêt-Thanh Ha-Duong
- Laboratoire ITODYS (Interfaces, Traitements et Organisation des Systèmes), Université Paris-Diderot, CNRS UMR 7086, Bâtiment Lavoisier, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France
| | - Chantal Eid
- Laboratoire ITODYS (Interfaces, Traitements et Organisation des Systèmes), Université Paris-Diderot, CNRS UMR 7086, Bâtiment Lavoisier, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France
| | - Miryana Hémadi
- Laboratoire ITODYS (Interfaces, Traitements et Organisation des Systèmes), Université Paris-Diderot, CNRS UMR 7086, Bâtiment Lavoisier, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France
| | - Jean-Michel El Hage Chahine
- Laboratoire ITODYS (Interfaces, Traitements et Organisation des Systèmes), Université Paris-Diderot, CNRS UMR 7086, Bâtiment Lavoisier, 15 rue Jean-Antoine de Baïf, 75205 Paris Cedex 13, France
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Abstract
The human body cannot actively excrete excess iron. As a consequence, iron absorption must be strictly regulated to ensure adequate iron uptake and prevent toxic iron accumulation. Iron absorption is controlled chiefly by hepcidin, the iron-regulatory hormone. Produced by the liver and secreted into the circulation, hepcidin regulates iron metabolism by inhibiting iron release from cells, including duodenal enterocytes, which mediate the absorption of dietary iron. Hepcidin production increases in response to iron loading and decreases in iron deficiency. Such regulation of hepcidin expression serves to modulate iron absorption to meet body iron demand. This review discusses the proteins that orchestrate hepatic hepcidin production and iron absorption by the intestine. Emphasis is placed on the proteins that directly sense iron and how they coordinate and fine-tune the molecular, cellular, and physiologic responses to iron deficiency and overload.
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Affiliation(s)
- Mitchell D Knutson
- Food Science and Human Nutrition Department, University of Florida, Gainesville, Florida 32611-2710, USA.
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15
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Effect of lactoferrin on oxidative features of ceruloplasmin. Biometals 2009; 22:521-9. [PMID: 19189056 DOI: 10.1007/s10534-009-9209-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Accepted: 01/19/2009] [Indexed: 12/15/2022]
Abstract
In our previous report we first described a complex between lactoferrin (Lf) and ceruloplasmin (Cp) with K (d) approximately 1.8 microM. The presence of this complex in colostrum that never contains more than 0.3 microM Cp questions the reliability of K (d) value. We carefully studied Lf binding to Cp and investigated the enzymatic activity of the latter in the presence of Lf, which allowed obtaining a new value for K (d) of Cp-Lf complex. Lf interacting with Cp changes its oxidizing activity with various substrates, such as Fe(2+), o-dianisidine (o-DA), p-phenylenediamine (p-PD) and dihydroxyphenylalanine (DOPA). The presence of at least two binding sites for Lf in Cp molecule is deduced from comparison of substrates' oxidation kinetics with and without Lf. When Lf binds to the first site affinity of Cp to Fe(2+) and to o-DA increases, but it decreases towards DOPA and remains unchanged towards p-PD. Oxidation rate of Fe(2+) grows, while that of o-DA, p-PD and DOPA goes down. Subsequent Lf binding to the second center has no effect on iron oxidation, hampers DOPA and o-DA oxidation, and reduces affinity towards p-PD. Scatchard plot for Lf sorbing to Cp-Sepharose allowed estimating K (d) for Lf binding to high-affinity (approximately 13.4 nM) and low-affinity (approximately 211 nM) sites. The observed effect of Lf on ferroxidase activity of Cp is likely to have physiological implications.
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