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Krijt M, Jirkovska A, Kabickova T, Melenovsky V, Petrak J, Vyoral D. Detection and quantitation of iron in ferritin, transferrin and labile iron pool (LIP) in cardiomyocytes using 55Fe and storage phosphorimaging. Biochim Biophys Acta Gen Subj 2018; 1862:2895-2901. [PMID: 30279145 DOI: 10.1016/j.bbagen.2018.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 09/06/2018] [Accepted: 09/07/2018] [Indexed: 11/28/2022]
Abstract
Dysregulated iron metabolism has a detrimental effect on cardiac function. The importance of iron homeostasis in cardiac health and disease warrants detailed studies of cardiomyocyte iron uptake, utilization and recycling at the molecular level. In this study, we have performed metabolic labeling of primary cultures of neonatal rat cardiomyocytes with radioactive iron coupled with separation of labeled iron-containing molecules by native electrophoresis followed by detection and quantification of incorporated radioiron by storage phosphorimaging. For the radiolabeling we used a safe and convenient beta emitter 55Fe which enabled sensitive and simultaneous detection and quantitation of iron in cardiomyocyte ferritin, transferrin and the labile iron pool (LIP). The LIP is believed to represent potentially dangerous redox-active iron bound to uncharacterized molecules. Using size-exclusion chromatography spin micro columns, we demonstrate that iron in the LIP is bound to high molecular weight molecule(s) (≥5000 Da) in the neonatal cardiomyocytes.
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Affiliation(s)
- M Krijt
- Institute of Hematology and Blood Transfusion, Prague, Czech Republic
| | - A Jirkovska
- Charles University, Faculty of Pharmacy in Hradec Kralove, Department of Biochemical Sciences, Hradec Kralove, Czech Republic
| | - T Kabickova
- Institute of Hematology and Blood Transfusion, Prague, Czech Republic; Department of Cell Biology, Faculty of Natural Sciences, Charles University, Prague, Czech Republic
| | - V Melenovsky
- Department of Cardiology, Institute for Clinical and Experimental Medicine (IKEM), Prague, Czech Republic
| | - J Petrak
- BIOCEV, First Faculty of Medicine, Charles University, Vestec, Czech Republic; Institute of Hematology and Blood Transfusion, Prague, Czech Republic
| | - D Vyoral
- Institute of Hematology and Blood Transfusion, Prague, Czech Republic; Institute of Pathological Physiology, First Faculty of Medicine, Charles University, Prague, Czech Republic.
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2
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Bhupanapadu Sunkesula SR, Luo X, Das D, Singh A, Singh N. Iron content of ferritin modulates its uptake by intestinal epithelium: implications for co-transport of prions. Mol Brain 2010; 3:14. [PMID: 20429907 PMCID: PMC2873590 DOI: 10.1186/1756-6606-3-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 04/29/2010] [Indexed: 11/13/2022] Open
Abstract
The spread of Chronic Wasting Disease (CWD) in the deer and elk population has caused serious public health concerns due to its potential to infect farm animals and humans. Like other prion disorders such a sporadic Creutzfeldt-Jakob-disease of humans and Mad Cow Disease of cattle, CWD is caused by PrP-scrapie (PrPSc), a β-sheet rich isoform of a normal cell surface glycoprotein, the prion protein (PrPC). Since PrPSc is sufficient to cause infection and neurotoxicity if ingested by a susceptible host, it is important to understand the mechanism by which it crosses the stringent epithelial cell barrier of the small intestine. Possible mechanisms include co-transport with ferritin in ingested food and uptake by dendritic cells. Since ferritin is ubiquitously expressed and shares considerable homology among species, co-transport of PrPSc with ferritin can result in cross-species spread with deleterious consequences. We have used a combination of in vitro and in vivo models of intestinal epithelial cell barrier to understand the role of ferritin in mediating PrPSc uptake and transport. In this report, we demonstrate that PrPSc and ferritin from CWD affected deer and elk brains and scrapie from sheep resist degradation by digestive enzymes, and are transcytosed across a tight monolayer of human epithelial cells with significant efficiency. Likewise, ferritin from hamster brains is taken up by mouse intestinal epithelial cells in vivo, indicating that uptake of ferritin is not limited by species differences as described for prions. More importantly, the iron content of ferritin determines its efficiency of uptake and transport by Caco-2 cells and mouse models, providing insight into the mechanism(s) of ferritin and PrPSc uptake by intestinal epithelial cells.
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3
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Singh A, Kong Q, Luo X, Petersen RB, Meyerson H, Singh N. Prion protein (PrP) knock-out mice show altered iron metabolism: a functional role for PrP in iron uptake and transport. PLoS One 2009; 4:e6115. [PMID: 19568430 PMCID: PMC2699477 DOI: 10.1371/journal.pone.0006115] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 05/20/2009] [Indexed: 11/23/2022] Open
Abstract
Despite overwhelming evidence implicating the prion protein (PrP) in prion disease pathogenesis, the normal function of this cell surface glycoprotein remains unclear. In previous reports we demonstrated that PrP mediates cellular iron uptake and transport, and aggregation of PrP to the disease causing PrP-scrapie (PrPSc) form results in imbalance of iron homeostasis in prion disease affected human and animal brains. Here, we show that selective deletion of PrP in transgenic mice (PrPKO) alters systemic iron homeostasis as reflected in hematological parameters and levels of total iron and iron regulatory proteins in the plasma, liver, spleen, and brain of PrPKO mice relative to matched wild type controls. Introduction of radiolabeled iron (59FeCl3) to Wt and PrPKO mice by gastric gavage reveals inefficient transport of 59Fe from the duodenum to the blood stream, an early abortive spike of erythropoiesis in the long bones and spleen, and eventual decreased 59Fe content in red blood cells and all major organs of PrPKO mice relative to Wt controls. The iron deficient phenotype of PrPKO mice is reversed by expressing Wt PrP in the PrPKO background, demonstrating a functional role for PrP in iron uptake and transport. Since iron is required for essential metabolic processes and is also potentially toxic if mismanaged, these results suggest that loss of normal function of PrP due to aggregation to the PrPSc form induces imbalance of brain iron homeostasis, resulting in disease associated neurotoxicity.
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Affiliation(s)
- Ajay Singh
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Qingzhong Kong
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Xiu Luo
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Robert B. Petersen
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Howard Meyerson
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Neena Singh
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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4
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Nramp1 promotes efficient macrophage recycling of iron following erythrophagocytosis in vivo. Proc Natl Acad Sci U S A 2009; 106:5960-5. [PMID: 19321419 DOI: 10.1073/pnas.0900808106] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Natural resistance-associated macrophage protein 1 (Nramp1) is a divalent metal transporter expressed exclusively in phagocytic cells. We hypothesized that macrophage Nramp1 may participate in the recycling of iron acquired from phagocytosed senescent erythrocytes. To evaluate the role of Nramp1 in vivo, the iron parameters of WT and KO mice were analyzed after acute and chronic induction of hemolytic anemia. We found that untreated KO mice exhibited greater serum transferrin saturation and splenic iron content with higher duodenal ferroportin (Fpn) and divalent metal transporter 1 (DMT1) expression. Furthermore, hepatocyte iron content and hepcidin mRNA levels were dramatically lower in KO mice, indicating that hepcidin levels can be regulated by low-hepatocyte iron stores despite increased transferrin saturation. After acute treatment with the hemolytic agent phenylhydrazine (Phz), KO mice experienced a significant decrease in transferrin saturation and hematocrit, whereas WT mice were relatively unaffected. After a month-long Phz regimen, KO mice retained markedly increased quantities of iron within the liver and spleen and exhibited more pronounced splenomegaly and reticulocytosis than WT mice. After injection of (59)Fe-labeled heat-damaged reticulocytes, KO animals accumulated erythrophagocytosed (59)Fe within their liver and spleen, whereas WT animals efficiently recycled phagocytosed (59)Fe to the marrow and erythrocytes. These data imply that without Nramp1, iron accumulates within the liver and spleen during erythrophagocytosis and hemolytic anemia, supporting our hypothesis that Nramp1 promotes efficient hemoglobin iron recycling in macrophages. Our observations suggest that mutations in Nramp1 could result in a novel form of human hereditary iron overload.
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Singh A, Isaac AO, Luo X, Mohan ML, Cohen ML, Chen F, Kong Q, Bartz J, Singh N. Abnormal brain iron homeostasis in human and animal prion disorders. PLoS Pathog 2009; 5:e1000336. [PMID: 19283067 PMCID: PMC2652663 DOI: 10.1371/journal.ppat.1000336] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Accepted: 02/12/2009] [Indexed: 11/18/2022] Open
Abstract
Neurotoxicity in all prion disorders is believed to result from the accumulation of PrP-scrapie (PrP(Sc)), a beta-sheet rich isoform of a normal cell-surface glycoprotein, the prion protein (PrP(C)). Limited reports suggest imbalance of brain iron homeostasis as a significant associated cause of neurotoxicity in prion-infected cell and mouse models. However, systematic studies on the generality of this phenomenon and the underlying mechanism(s) leading to iron dyshomeostasis in diseased brains are lacking. In this report, we demonstrate that prion disease-affected human, hamster, and mouse brains show increased total and redox-active Fe (II) iron, and a paradoxical increase in major iron uptake proteins transferrin (Tf) and transferrin receptor (TfR) at the end stage of disease. Furthermore, examination of scrapie-inoculated hamster brains at different timepoints following infection shows increased levels of Tf with time, suggesting increasing iron deficiency with disease progression. Sporadic Creutzfeldt-Jakob disease (sCJD)-affected human brains show a similar increase in total iron and a direct correlation between PrP and Tf levels, implicating PrP(Sc) as the underlying cause of iron deficiency. Increased binding of Tf to the cerebellar Purkinje cell neurons of sCJD brains further indicates upregulation of TfR and a phenotype of neuronal iron deficiency in diseased brains despite increased iron levels. The likely cause of this phenotype is sequestration of iron in brain ferritin that becomes detergent-insoluble in PrP(Sc)-infected cell lines and sCJD brain homogenates. These results suggest that sequestration of iron in PrP(Sc)-ferritin complexes induces a state of iron bio-insufficiency in prion disease-affected brains, resulting in increased uptake and a state of iron dyshomeostasis. An additional unexpected observation is the resistance of Tf to digestion by proteinase-K, providing a reliable marker for iron levels in postmortem human brains. These data implicate redox-iron in prion disease-associated neurotoxicity, a novel observation with significant implications for prion disease pathogenesis.
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Affiliation(s)
- Ajay Singh
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Alfred Orina Isaac
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Xiu Luo
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Maradumane L. Mohan
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Mark L. Cohen
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Fusong Chen
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Qingzhong Kong
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Jason Bartz
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, United States of America
| | - Neena Singh
- Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
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Singh A, Mohan ML, Isaac AO, Luo X, Petrak J, Vyoral D, Singh N. Prion protein modulates cellular iron uptake: a novel function with implications for prion disease pathogenesis. PLoS One 2009; 4:e4468. [PMID: 19212444 PMCID: PMC2637434 DOI: 10.1371/journal.pone.0004468] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 12/26/2008] [Indexed: 01/18/2023] Open
Abstract
Converging evidence leaves little doubt that a change in the conformation of prion protein (PrPC) from a mainly α-helical to a β-sheet rich PrP-scrapie (PrPSc) form is the main event responsible for prion disease associated neurotoxicity. However, neither the mechanism of toxicity by PrPSc, nor the normal function of PrPC is entirely clear. Recent reports suggest that imbalance of iron homeostasis is a common feature of prion infected cells and mouse models, implicating redox-iron in prion disease pathogenesis. In this report, we provide evidence that PrPC mediates cellular iron uptake and transport, and mutant PrP forms alter cellular iron levels differentially. Using human neuroblastoma cells as models, we demonstrate that over-expression of PrPC increases intra-cellular iron relative to non-transfected controls as indicated by an increase in total cellular iron, the cellular labile iron pool (LIP), and iron content of ferritin. As a result, the levels of iron uptake proteins transferrin (Tf) and transferrin receptor (TfR) are decreased, and expression of iron storage protein ferritin is increased. The positive effect of PrPC on ferritin iron content is enhanced by stimulating PrPC endocytosis, and reversed by cross-linking PrPC on the plasma membrane. Expression of mutant PrP forms lacking the octapeptide-repeats, the membrane anchor, or carrying the pathogenic mutation PrP102L decreases ferritin iron content significantly relative to PrPC expressing cells, but the effect on cellular LIP and levels of Tf, TfR, and ferritin is complex, varying with the mutation. Neither PrPC nor the mutant PrP forms influence the rate or amount of iron released into the medium, suggesting a functional role for PrPC in cellular iron uptake and transport to ferritin, and dysfunction of PrPC as a significant contributing factor of brain iron imbalance in prion disorders.
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Affiliation(s)
- Ajay Singh
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Maradumane L. Mohan
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Alfred Orina Isaac
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Xiu Luo
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Jiri Petrak
- Department of Pathological Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
| | - Daniel Vyoral
- Department of Pathological Physiology, First Faculty of Medicine, Charles University in Prague, Prague, Czech Republic
| | - Neena Singh
- The Department of Pathology, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail: .
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Zhang AS, Canonne-Hergaux F, Gruenheid S, Gros P, Ponka P. Use of Nramp2-transfected Chinese hamster ovary cells and reticulocytes from mk/mk mice to study iron transport mechanisms. Exp Hematol 2008; 36:1227-35. [PMID: 18722041 PMCID: PMC2655630 DOI: 10.1016/j.exphem.2008.04.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Revised: 04/21/2008] [Accepted: 04/24/2008] [Indexed: 01/09/2023]
Abstract
OBJECTIVE We investigated mechanisms involved in iron (Fe) transport by DMT1 (endosomal Fe(II) exporter, encoded by the Nramp2 gene) using wild-type Chinese hamster ovary (CHO) cells and Nramp2-transfected CHO cells, as well as reticulocytes from normal and mk/mk mice that have a defect in DMT1. MATERIALS AND METHODS CHO cells and reticulocytes were incubated with 59Fe bound to various ligands. The radioiron was present in its Fe(II) or Fe(III) forms or bound to transferrin (Tf), and the internalized 59Fe measured under varying experimental conditions. Additionally, 125I-Tf interaction with reticulocytes was investigated and 59Fe incorporation into their heme was determined. RESULTS Hyperexpression of DMT1 in CHO cells greatly increases their capacity to acquire ferrous iron. Although CHO-Nramp2 cells showed an increase in Fe(III) uptake as compared to CHO cells, they transported Fe(III) with much lower efficacy than Fe(II). In addition to their defect in Fe uptake, mk/mk reticulocytes also showed a decrease in Tf receptor levels. CONCLUSIONS Given that CHO cells acquire iron from Fe(II)-ascorbate with much higher rates than from Fe(III)-Tf, Tf-receptor levels represent the rate-limiting step in their iron uptake. As Fe(III) transport by CHO-Nramp2 cells can be inhibited by the impermeable oxidant K3Fe(CN)6, a membrane ferric reductase is probably needed for reduction of Fe(III) to Fe(II), which is then transported by DMT1. DMT1 is not a limiting factor in Fe acquisition by normal reticulocytes and their heme synthesis.
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Affiliation(s)
- An-Sheng Zhang
- Department of Cell and Developmental Biology, Oregon Health and Science University, Portland, OR, USA
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8
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Basu S, Mohan ML, Luo X, Kundu B, Kong Q, Singh N. Modulation of proteinase K-resistant prion protein in cells and infectious brain homogenate by redox iron: implications for prion replication and disease pathogenesis. Mol Biol Cell 2007; 18:3302-12. [PMID: 17567949 PMCID: PMC1951779 DOI: 10.1091/mbc.e07-04-0317] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Revised: 05/31/2007] [Accepted: 06/04/2007] [Indexed: 12/18/2022] Open
Abstract
The principal infectious and pathogenic agent in all prion disorders is a beta-sheet-rich isoform of the cellular prion protein (PrP(C)) termed PrP-scrapie (PrP(Sc)). Once initiated, PrP(Sc) is self-replicating and toxic to neuronal cells, but the underlying mechanisms remain unclear. In this report, we demonstrate that PrP(C) binds iron and transforms to a PrP(Sc)-like form (*PrP(Sc)) when human neuroblastoma cells are exposed to an inorganic source of redox iron. The *PrP(Sc) thus generated is itself redox active, and it induces the transformation of additional PrP(C), simulating *PrP(Sc) propagation in the absence of brain-derived PrP(Sc). Moreover, limited depletion of iron from prion disease-affected human and mouse brain homogenates and scrapie-infected mouse neuroblastoma cells results in 4- to 10-fold reduction in proteinase K (PK)-resistant PrP(Sc), implicating redox iron in the generation, propagation, and stability of PK-resistant PrP(Sc). Furthermore, we demonstrate increased redox-active ferrous iron levels in prion disease-affected brains, suggesting that accumulation of PrP(Sc) is modulated by the combined effect of imbalance in brain iron homeostasis and the redox-active nature of PrP(Sc). These data provide information on the mechanism of replication and toxicity by PrP(Sc), and they evoke predictable and therapeutically amenable ways of modulating PrP(Sc) load.
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Affiliation(s)
- Subhabrata Basu
- *Department of Pathology, Case Western Reserve University, Cleveland, OH 44106; and
| | - Maradumane L. Mohan
- *Department of Pathology, Case Western Reserve University, Cleveland, OH 44106; and
| | - Xiu Luo
- *Department of Pathology, Case Western Reserve University, Cleveland, OH 44106; and
| | - Bishwajit Kundu
- Department of Biochemical Engineering and Biotechnology, The Indian Institute of Technology, New Delhi, India 110016
| | - Qingzhong Kong
- *Department of Pathology, Case Western Reserve University, Cleveland, OH 44106; and
| | - Neena Singh
- *Department of Pathology, Case Western Reserve University, Cleveland, OH 44106; and
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9
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Babusiak M, Man P, Sutak R, Petrak J, Vyoral D. Identification of heme binding protein complexes in murine erythroleukemic cells: Study by a novel two-dimensional native separation - liquid chromatography and electrophoresis. Proteomics 2005; 5:340-50. [PMID: 15627969 DOI: 10.1002/pmic.200400935] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the current postgenomic era there is a growing interest in analysis of protein complexes in their native state. Here we present a novel two-dimensional separation technique for assessment of native protein complexes. The method combines native chromatography with native electrophoresis. The approach was used to study heme-binding protein complexes in murine erythroleukemia cells. The cells were metabolically labeled with [(59)Fe]-heme and cellular lysates were separated by anion-exchange chromatography. Fractions containing the (59)Fe isotope were collected, concentrated and further separated by native gel electrophoresis. A total of 13 radioactive protein bands were detected and analyzed by liquid chromatography-tandem mass spectrometry. Thirty-three individual proteins were identified and attributed to four novel multiprotein complexes representing four different 'snapshots' of cellular events involved in hemoglobin biosynthesis.
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Affiliation(s)
- Marek Babusiak
- Institute of Hematology and Blood Transfusion, Prague, Czech Republic.
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10
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Goulet V, Britigan B, Nakayama K, Grenier D. Cleavage of human transferrin by Porphyromonas gingivalis gingipains promotes growth and formation of hydroxyl radicals. Infect Immun 2004; 72:4351-6. [PMID: 15271890 PMCID: PMC470592 DOI: 10.1128/iai.72.8.4351-4356.2004] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Porphyromonas gingivalis, a gram-negative anaerobic bacterium associated with active lesions of chronic periodontitis, produces several proteinases which are presumably involved in host colonization, perturbation of the immune system, and tissue destruction. The aims of this study were to investigate the degradation of human transferrin by gingipain cysteine proteinases of P. gingivalis and to demonstrate the production of toxic hydroxyl radicals (HO*) catalyzed by the iron-containing transferrin fragments generated or by release of iron itself. Analysis by polyacrylamide gel electrophoresis and Western immunoblotting showed that preparations of Arg- and Lys-gingipains of P. gingivalis cleave transferrin (iron-free and iron-saturated forms) into fragments of various sizes. Interestingly, gingival crevicular fluid samples from diseased periodontal sites but not samples from healthy periodontal sites contained fragments of transferrin. By using (55)Fe-transferrin, it was found that degradation by P. gingivalis gingipains resulted in the production of free iron, as well as iron bound to lower-molecular-mass fragments. Subsequent to the degradation of transferrin, bacterial cells assimilated intracellularly the radiolabeled iron. Growth of P. gingivalis ATCC 33277, but not growth of an Arg-gingipain- and Lys-gingipain-deficient mutant, was possible in a chemically defined medium containing 30% iron-saturated transferrin as the only source of iron and peptides, suggesting that gingipains play a critical role in the acquisition of essential growth nutrients. Finally, the transferrin degradation products generated by Arg-gingipains A and B were capable of catalyzing the formation of HO*, as determined by a hypoxanthine/xanthine oxidase system and spin trapping-electron paramagnetic resonance spectrometry. Our study indicates that P. gingivalis gingipains degrade human transferrin, providing sources of iron and peptides. The iron-containing transferrin fragments or the release of iron itself may contribute to tissue destruction by catalyzing the formation of toxic HO*.
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Affiliation(s)
- Véronique Goulet
- Groupe de Recherche en Ecologie Buccale and Faculté de Médecine Dentaire, Université Laval, Quebec, Canada G1K 7P4
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11
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Suchan P, Vyoral D, Petrák J, Šut'ák R, Rasoloson D, Nohýnková E, Doležal P, Tachezy J. Incorporation of iron into Tritrichomonas foetus cell compartments reveals ferredoxin as a major iron-binding protein in hydrogenosomes. MICROBIOLOGY (READING, ENGLAND) 2003; 149:1911-1921. [PMID: 12855742 DOI: 10.1099/mic.0.26122-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The intracellular transport of iron and its incorporation into organelles are poorly understood processes in eukaryotes and virtually unknown in parasitic protists. The transport of iron is of particular interest in trichomonads, which possess hydrogenosomes instead of mitochondria. The metabolic functions of hydrogenosomes, which contain a specific set of FeS proteins, entirely depend on iron acquisition. In this work the incorporation of iron into the cattle parasite Tritrichomonas foetus was monitored. Iron was efficiently taken up from (59)Fe-nitrilotriacetic acid and accumulated in the cytosol (88.9 %) and hydrogenosomes (4.7 % of the total radioactivity). Using atomic absorption spectrophotometry, an unusually high steady-state iron concentration in hydrogenosomes was determined [54.4+/-1.1 nmol Fe (mg protein)(-1)]. The concentration of iron in the cytosol was 13.4+/-0.5 nmol Fe (mg protein)(-1). Qualitative analysis of incorporated iron was performed using native gradient PAGE. The majority of the (59)Fe in the cytosol appeared as the labile-iron pool, which represents weakly bound iron associated with compounds of molecular mass ranging from 5000 to 30000 Da. Ferritin was not observed in Tt. foetus, nor in two other anaerobic protists, Entamoeba histolytica and Giardia intestinalis. Analysis of Tt. foetus hydrogenosomes showed at least nine iron-binding compounds, which were absent in metronidazole-resistant mutants. The major iron-binding compound was identified as [2Fe-2S] ferredoxin of the adrenodoxin type.
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Affiliation(s)
- Pavel Suchan
- Department of Parasitology, Faculty of Science, Charles University, Viničná 7, 128 44, Prague 2, Czech Republic
| | - Daniel Vyoral
- Institute of Hematology and Blood Transfusion, U Nemocnice 1, 128 44, Prague 2, Czech Republic
| | - Jiří Petrák
- Institute of Hematology and Blood Transfusion, U Nemocnice 1, 128 44, Prague 2, Czech Republic
| | - Robert Šut'ák
- Department of Parasitology, Faculty of Science, Charles University, Viničná 7, 128 44, Prague 2, Czech Republic
| | - Dominique Rasoloson
- Johns Hopkins University, Bloomberg School of Public Health, W. Harry Feinstone Department of Molecular Microbiology and Immunology, 615 North Wolfe Street, Baltimore 21205, MD, USA
| | - Eva Nohýnková
- Department of the Tropical Medicine, 1st Faculty of Medicine, Charles University, Faculty Hospital Bulovka, Studničkova 7, 128 00, Prague 2, Czech Republic
| | - Pavel Doležal
- Department of Parasitology, Faculty of Science, Charles University, Viničná 7, 128 44, Prague 2, Czech Republic
| | - Jan Tachezy
- Department of Parasitology, Faculty of Science, Charles University, Viničná 7, 128 44, Prague 2, Czech Republic
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12
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Petrák JV, Vyoral D. Detection of iron-containing proteins contributing to the cellular labile iron pool by a native electrophoresis metal blotting technique. J Inorg Biochem 2001; 86:669-75. [PMID: 11583784 DOI: 10.1016/s0162-0134(01)00232-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The labile iron pool (LIP) plays a role in generation of free radicals and is thus the target of chelators used for the treatment of iron overload. We have previously shown that the LIP is bound mostly to high molecular weight carriers (MW>5000). However, the iron does not remain associated with these proteins during native gel electrophoresis. In this study we describe a new method to reconstruct the interaction of iron with iron-binding proteins. Proteins were separated by native gradient polyacrylamide gel electrophoresis and transfered to polyvinilidene difluoride membrane under native conditions. The immobilized iron-binding proteins are then labeled by 59Fe using a 'titrational blotting' technique and visualized by storage phosphorimaging. At least six proteins, in addition to ferritin and transferrin, are specifically labeled in cellular lysates of human erythroleukemic cells. This technique enables separation and detection of iron-binding proteins or other metal-protein complexes under near-physiological conditions and facilitates identification of weak iron-protein complexes. Using a new native metal blotting method, we have confirmed that specific high molecular weight proteins bind the labile iron pool.
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Affiliation(s)
- J V Petrák
- Institute of Hematology and Blood Transfusion, U nemocnice 1, 128 20 2, Praha, Czech Republic.
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13
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Vyoral D, Petrák J. Iron transport in K562 cells: a kinetic study using native gel electrophoresis and 59Fe autoradiography. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1403:179-88. [PMID: 9630620 DOI: 10.1016/s0167-4889(98)00039-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The exact mechanisms of iron transport from endosomes to the target iron containing cellular proteins are currently unknown. To investigate this problem, we used the gradient gel electrophoresis and the sensitive detection of 59Fe by autoradiography to detect separate cellular iron compounds and their iron kinetics. Cells of human leukemic line K562 were labeled with [59Fe]transferrin for 30-600 s and cellular iron compounds in cell lysates were analyzed by native electrophoretic separation followed by 59Fe autoradiography. Starting with the first 30 s of iron uptake, iron was detectable in a large membrane bound protein complex (Band I) and in ferritin. Significant amounts of iron were also found in labile iron compound(s) with the molecular weight larger than 5000 as judged by ultrafiltration. Iron kinetics in these compartments was studied. Band I was the only compound with the kinetic properties of an intermediate. Transferrin, transferrin receptor and additional proteins of the approximate molecular weights of 130000, 66000 and 49000 were found to be present in Band I. The labile iron compounds and ferritin behaved kinetically as end products. No evidence for low molecular weight transport intermediates was found. These results suggest that intracellular iron transport is highly compartmentalized, that iron released from endosomal transferrin passes to its cellular targets in a direct contact with the endosomal membrane complex assigned as Band I. The nature of the labile iron pool and its susceptibility to iron chelation is discussed.
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Affiliation(s)
- D Vyoral
- Institute of Hematology and Blood Transfusion, U nemocnice 1, 128 20, Praha 2, Czech Republic.
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