The hereditary hemochromatosis protein, HFE, lowers intracellular iron levels independently of transferrin receptor 1 in TRVb cells

Blood ◽  
2005 ◽  
Vol 105 (6) ◽  
pp. 2564-2570 ◽  
Author(s):  
Hanqian Carlson ◽  
An-Sheng Zhang ◽  
William H. Fleming ◽  
Caroline A. Enns
Keyword(s):  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Cell Types ◽  
Single Amino Acid ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Transferrin Receptor 1 ◽  
A Cell

AbstractHereditary hemochromatosis (HH) is an autosomal recessive disease that leads to parenchymal iron accumulation. The most common form of HH is caused by a single amino acid substitution in the HH protein, HFE, but the mechanism by which HFE regulates iron homeostasis is not known. In the absence of transferrin (Tf), HFE interacts with transferrin receptor 1 (TfR1) and the 2 proteins co-internalize, and in vitro studies have shown that HFE and Tf compete for TfR1 binding. Using a cell line lacking endogenous transferrin receptors (TRVb cells) transfected with different forms of HFE and TfR1, we demonstrate that even at low concentrations Tf competes effectively with HFE for binding to TfR1 on living cells. Transfection of TRVb cells or the derivative line TRVb1 (which stably expresses human TfR1) with HFE resulted in lower ferritin levels and decreased Fe2+ uptake. These data indicate that HFE can regulate intracellular iron storage independently of its interaction with TfR1. Earlier studies found that in HeLa cells, HFE expression lowers Tf-mediated iron uptake; here we show that HFE lowers non–Tf-bound iron in TRVb cells and add to a growing body of evidence that HFE may play different roles in different cell types.

HFE Downregulates Iron Uptake From Transferrin and Induces Iron-Regulatory Protein Activity in Stably Transfected Cells

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3915-3921 ◽  
Author(s):  
H.D. Riedel ◽  
M.U. Muckenthaler ◽  
S.G. Gehrke ◽  
I. Mohr ◽  
K. Brennan ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Regulatory Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron

Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder of iron metabolism. More than 80% of HH patients are homozygous for a point mutation in a major histocompatibility complex (MHC) class I type protein (HFE), which results in a lack of HFE expression on the cell surface. A previously identified interaction of HFE and the transferrin receptor suggests a possible regulatory role of HFE in cellular iron absorption. Using an HeLa cell line stably transfected with HFE under the control of a tetracycline-sensitive promoter, we investigated the effect of HFE expression on cellular iron uptake. We demonstrate that the overproduction of HFE results in decreased iron uptake from diferric transferrin. Moreover, HFE expression activates the key regulators of intracellular iron homeostasis, the iron-regulatory proteins (IRPs), implying that HFE can affect the intracellular “labile iron pool.” The increase in IRP activity is accompanied by the downregulation of the iron-storage protein, ferritin, and an upregulation of transferrin receptor levels. These findings are discussed in the context of the pathophysiology of HH and a possible role of iron-responsive element (IRE)-containing mRNAs.

HFE Downregulates Iron Uptake From Transferrin and Induces Iron-Regulatory Protein Activity in Stably Transfected Cells

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3915-3921 ◽  
Author(s):  
H.D. Riedel ◽  
M.U. Muckenthaler ◽  
S.G. Gehrke ◽  
I. Mohr ◽  
K. Brennan ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Regulatory Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron

Abstract Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder of iron metabolism. More than 80% of HH patients are homozygous for a point mutation in a major histocompatibility complex (MHC) class I type protein (HFE), which results in a lack of HFE expression on the cell surface. A previously identified interaction of HFE and the transferrin receptor suggests a possible regulatory role of HFE in cellular iron absorption. Using an HeLa cell line stably transfected with HFE under the control of a tetracycline-sensitive promoter, we investigated the effect of HFE expression on cellular iron uptake. We demonstrate that the overproduction of HFE results in decreased iron uptake from diferric transferrin. Moreover, HFE expression activates the key regulators of intracellular iron homeostasis, the iron-regulatory proteins (IRPs), implying that HFE can affect the intracellular “labile iron pool.” The increase in IRP activity is accompanied by the downregulation of the iron-storage protein, ferritin, and an upregulation of transferrin receptor levels. These findings are discussed in the context of the pathophysiology of HH and a possible role of iron-responsive element (IRE)-containing mRNAs.

scholarly journals Cryo-EM structures and functional characterization of homo- and heteropolymers of human ferritin variants

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jose Irimia-Dominguez ◽  
Chen Sun ◽  
Kunpeng Li ◽  
Barry B. Muhoberac ◽  
Grace I. Hallinan ◽  
...  
Keyword(s):  
Iron Homeostasis ◽  
Functional Characterization ◽  
Protein Solubility ◽  
Cell Types ◽  
Brain Iron ◽  
Iron Storage ◽  
Human Ferritin ◽  
And Function ◽  
Brain Iron Metabolism

AbstractThe role of abnormal brain iron metabolism in neurodegenerative diseases is still insufficiently understood. Here, we investigate the molecular basis of the neurodegenerative disease hereditary ferritinopathy (HF), in which dysregulation of brain iron homeostasis is the primary cause of neurodegeneration. We mutagenized ferritin’s three-fold pores (3FPs), i.e. the main entry route for iron, to investigate ferritin’s iron management when iron must traverse the protein shell through the disrupted four-fold pores (4FPs) generated by mutations in the ferritin light chain (FtL) gene in HF. We assessed the structure and properties of ferritins using cryo-electron microscopy and a range of functional analyses in vitro. Loss of 3FP function did not alter ferritin structure but led to a decrease in protein solubility and iron storage. Abnormal 4FPs acted as alternate routes for iron entry and exit in the absence of functional 3FPs, further reducing ferritin iron-storage capacity. Importantly, even a small number of MtFtL subunits significantly compromises ferritin solubility and function, providing a rationale for the presence of ferritin aggregates in cell types expressing different levels of FtLs in patients with HF. These findings led us to discuss whether modifying pores could be used as a pharmacological target in HF.

scholarly journals A Ferritin Mutant of Mycobacterium tuberculosis Is Highly Susceptible to Killing by Antibiotics and Is Unable To Establish a Chronic Infection in Mice

2012 ◽  
Vol 80 (10) ◽  
pp. 3650-3659 ◽  
Author(s):  
Ruchi Pandey ◽  
G. Marcela Rodriguez
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Iron Homeostasis ◽  
Storage Proteins ◽  
Iron Acquisition ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Content Type ◽  
Iron Storage Proteins

ABSTRACTIron is an essential, elusive, and potentially toxic nutrient for most pathogens, includingMycobacterium tuberculosis. Due to the poor solubility of ferric iron under aerobic conditions, free iron is not found in the host.M. tuberculosisrequires specialized iron acquisition systems to replicate and cause disease. It also depends on a strict control of iron metabolism and intracellular iron levels to prevent iron-mediated toxicity. Under conditions of iron sufficiency,M. tuberculosisrepresses iron acquisition and induces iron storage, suggesting an important role for iron storage proteins in iron homeostasis.M. tuberculosissynthesizes two iron storage proteins, a ferritin (BfrB) and a bacterioferritin (BfrA). The individual contributions of these proteins to the adaptive response ofM. tuberculosisto changes in iron availability are not clear. By generating individual knockout strains ofbfrAandbfrB, the contribution of each one of these proteins to the maintenance of iron homeostasis was determined. The effect of altered iron homeostasis, resulting from impaired iron storage, on the resistance ofM. tuberculosistoin vitroandin vivostresses was examined. The results show that ferritin is required to maintain iron homeostasis, whereas bacterioferritin seems to be dispensable for this function.M. tuberculosislacking ferritin suffers from iron-mediated toxicity, is unable to persist in mice, and, most importantly, is highly susceptible to killing by antibiotics, showing that endogenous oxidative stress can enhance the antibiotic killing of this important pathogen. These results are relevant for the design of new therapeutic strategies againstM. tuberculosis.

scholarly journals Heterotypic interactions between transferrin receptor and transferrin receptor 2

Blood ◽  
2003 ◽  
Vol 101 (5) ◽  
pp. 2008-2014 ◽  
Author(s):  
Todd M. Vogt ◽  
Aaron D. Blackwell ◽  
Anthony M. Giannetti ◽  
Pamela J. Bjorkman ◽  
Caroline A. Enns
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Critical Role ◽  
Hereditary Hemochromatosis ◽  
Metabolic Labeling ◽  
Western Blots ◽  
Cellular Iron ◽  
Transferrin Receptor 2

Cellular iron uptake in most tissues occurs via endocytosis of diferric transferrin (Tf) bound to the transferrin receptor (TfR). Recently, a second transferrin receptor, transferrin receptor 2 (TfR2), has been identified and shown to play a critical role in iron metabolism. TfR2 is capable of Tf-mediated iron uptake and mutations in this gene result in a rare form of hereditary hemochromatosis unrelated to the hereditary hemochromatosis protein, HFE. Unlike TfR, TfR2 expression is not controlled by cellular iron concentrations and little information is currently available regarding the role of TfR2 in cellular iron homeostasis. To investigate the relationship between TfR and TfR2, we performed a series of in vivo and in vitro experiments using antibodies generated to each receptor. Western blots demonstrate that TfR2 protein is expressed strongest in erythroid/myeloid cell lines. Metabolic labeling studies indicate that TfR2 protein levels are approximately 20-fold lower than TfR in these cells. TfR and TfR2 have similar cellular localizations in K562 cells and coimmunoprecipitate to only a very limited extent. Western analysis of the receptors under nonreducing conditions reveals that they can form heterodimers.

A single viral protein HCMV US2 affects antigen presentation and intracellular iron homeostasis by degradation of classical HLA class I and HFE molecules

Blood ◽  
2003 ◽  
Vol 101 (7) ◽  
pp. 2858-2864 ◽  
Author(s):  
Sayeh Vahdati-Ben Arieh ◽  
Nihay Laham ◽  
Chana Schechter ◽  
Jon W. Yewdell ◽  
John E. Coligan ◽  
...  
Keyword(s):  
Iron Metabolism ◽  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Cytotoxic T Lymphocyte ◽  
Expression System ◽  
Hereditary Hemochromatosis ◽  
Class I ◽  
Intracellular Iron ◽  
Hek 293 ◽  
Classical Class

HFE is a nonclassical class I molecule that associates with β2-microglobulin (β2m) and with the transferrin receptor. HFE accumulates in transferrin-containing endosomes, and its overexpression in human cell lines correlates with decreased transferrin receptor (TFR)–mediated iron uptake and decreased intracellular iron pools. A mutation that interferes with proper folding and assembly of HFE complexes results in a severe iron-overload disease hereditary hemochromatosis. We previously suggested that viruses could also interfere with iron metabolism through the production of proteins that inactivate HFE, similarly to classical class I proteins. In particular, we demonstrated in a transient expression system that human cytomegalovirus (HCMV) US2 targeted HFE for proteasomal degradation. Here we demonstrate that the stable expression of HCMV US2 in HEK 293 cells constitutively expressing HFE leads to loss of HFE expression both intracellularly and on the cell surface, and the significant reduction of classical class I expression. Both HFE and classical class I molecules are targeted to degradation via a similar pathway. This HCMV US2-mediated degradation of HFE leads to increased intracellular iron pools as indicated by reduced synthesis of TfR and increased ferritin synthesis. Whether this interference with regulation of iron metabolism potentiates viral replication and/or promotes damage of HCMV-infected tissues remains to be determined. Nevertheless, the deleterious effect of US2 on the expression of HFE and classical class I major histo-compatibility complexes (MHC) provides HCMV with an efficient tool for altering cellular metabolic functions, as well as supporting the escape of virus-infected cells from cytotoxic T lymphocyte (CTL)–mediated immune responses.

scholarly journals Loss of ferroportin induces memory impairment by promoting ferroptosis in Alzheimer’s disease

2021 ◽  
Author(s):  
Wen-Dai Bao ◽  
Pei Pang ◽  
Xiao-Ting Zhou ◽  
Fan Hu ◽  
Wan Xiong ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Memory Impairment ◽  
Iron Homeostasis ◽  
Critical Role ◽  
Gene Set Enrichment Analysis ◽  
Molecular Characteristics ◽  
Intracellular Iron

AbstractIron homeostasis disturbance has been implicated in Alzheimer’s disease (AD), and excess iron exacerbates oxidative damage and cognitive defects. Ferroptosis is a nonapoptotic form of cell death dependent upon intracellular iron. However, the involvement of ferroptosis in the pathogenesis of AD remains elusive. Here, we report that ferroportin1 (Fpn), the only identified mammalian nonheme iron exporter, was downregulated in the brains of APPswe/PS1dE9 mice as an Alzheimer’s mouse model and Alzheimer’s patients. Genetic deletion of Fpn in principal neurons of the neocortex and hippocampus by breeding Fpnfl/fl mice with NEX-Cre mice led to AD-like hippocampal atrophy and memory deficits. Interestingly, the canonical morphological and molecular characteristics of ferroptosis were observed in both Fpnfl/fl/NEXcre and AD mice. Gene set enrichment analysis (GSEA) of ferroptosis-related RNA-seq data showed that the differentially expressed genes were highly enriched in gene sets associated with AD. Furthermore, administration of specific inhibitors of ferroptosis effectively reduced the neuronal death and memory impairments induced by Aβ aggregation in vitro and in vivo. In addition, restoring Fpn ameliorated ferroptosis and memory impairment in APPswe/PS1dE9 mice. Our study demonstrates the critical role of Fpn and ferroptosis in the progression of AD, thus provides promising therapeutic approaches for this disease.

scholarly journals Transcriptional regulation by iron of the gene for the transferrin receptor.

1986 ◽  
Vol 6 (1) ◽  
pp. 236-240 ◽  
Author(s):  
K Rao ◽  
J B Harford ◽  
T Rouault ◽  
A McClelland ◽  
F H Ruddle ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
K562 Cells ◽  
Iron Chelator ◽  
Transcriptional Level ◽  
Transferrin Receptors ◽  
Intracellular Iron ◽  
Human Transferrin Receptor ◽  
Diferric Transferrin ◽  
Permeable Iron

Treatment of K562 cells with desferrioxamine, a permeable iron chelator, led to an increase in the number of transferrin receptors. Increasing intracellular iron levels by treatment of cells with either human diferric transferrin or hemin lowered the level of the transferrin receptors. By using a cDNA clone of the human transferrin receptor, we showed that the changes in the levels of the receptor by iron were accompanied by alterations in the levels of the mRNA for the receptor. The rapidity of these changes indicated that the mRNA had a very short half-life. By using an in vitro transcriptional assay with isolated nuclei, we obtained evidence that this regulation occurred at the transcriptional level.

Overexpression of mitochondrial ferritin causes cytosolic iron depletion and changes cellular iron homeostasis

Blood ◽  
2005 ◽  
Vol 105 (5) ◽  
pp. 2161-2167 ◽  
Author(s):  
Guangjun Nie ◽  
Alex D. Sheftel ◽  
Sangwon F. Kim ◽  
Prem Ponka
Keyword(s):  
Iron Homeostasis ◽  
Rna Binding ◽  
Binding Activity ◽  
Intracellular Iron ◽  
Free Radical Damage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron ◽  
Cellular Iron Uptake ◽  
A Cell ◽  
Cellular Iron Homeostasis

AbstractCytosolic ferritin sequesters and stores iron and, consequently, protects cells against iron-mediated free radical damage. However, the function of the newly discovered mitochondrial ferritin (MtFt) is unknown. To examine the role of MtFt in cellular iron metabolism, we established a cell line that stably overexpresses mouse MtFt under the control of a tetracycline-responsive promoter. The overexpression of MtFt caused a dose-dependent iron deficiency in the cytosol that was revealed by increased RNA-binding activity of iron regulatory proteins (IRPs) along with an increase in transferrin receptor levels and decrease in cytosolic ferritin. Consequently, the induction of MtFt resulted in a dramatic increase in cellular iron uptake from transferrin, most of which was incorporated into MtFt. The induction of MtFt caused a shift of iron from cytosolic ferritin to MtFt. In addition, iron inserted into MtFt was less available for chelation than that in cytosolic ferritin and the expression of MtFt was associated with decreased mitochondrial and cytosolic aconitase activities, the latter being consistent with the increase in IRP-binding activity. In conclusion, our results indicate that overexpression of MtFt causes a dramatic change in intracellular iron homeostasis and that shunting iron to MtFt likely limits its availability for active iron proteins.

Analyses of cellular multimerin 1 receptors: in vitro evidence of binding mediated by αΙΙbβ3 and αvβ3

2005 ◽  
Vol 94 (11) ◽  
pp. 1004-1011 ◽  
Author(s):  
Frédéric Adam ◽  
Shilun Zheng ◽  
Nilesh Joshi ◽  
David Kelton ◽  
Amin Sandhu ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Cell Types ◽  
Factor V ◽  
Cellular Activation ◽  
Fiber Assembly ◽  
Expression Studies ◽  
Additional Cell ◽  
A Cell ◽  
Rgd Site

SummaryMultimerin 1 (MMRN1) is a large, soluble, polymeric, factor V binding protein and member of the EMILIN protein family.In vivo, MMRN1 is found in platelets, megakaryocytes, endothelium and extracellular matrix fibers, but not in plasma. To address the mechanism of MMRN1 binding to activated platelets and endothelial cells, we investigated the identity of the major MMRN1 receptors on these cells using wild-type and RGE-forms of recombinant MMRN1. Ligand capture, cell adhesion, ELISA and flow cytometry analyses of platelet-MMRN1 binding, indicated that MMRN1 binds to integrins αIIbβ3 and αvβ3. Endothelial cell binding to MMRN1 was predominantly mediated by αvβ3 and did not require the MMRN1 RGD site or cellular activation. Like many other αvβ3 ligands, MMRN1 had the ability to support adhesion of additional cell types, including stimulated neutrophils. Expression studies, using a cell line capable of endothelial-like MMRN1 processing, indicated that MMRN1 adhesion to cellular receptors enhanced its extracellular matrix fiber assembly. These studies implicate integrin-mediated binding in MMRN1 attachment to cells and indicate that MMRN1 is a ligand for αIIbβ3 and αvβ3.

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