scholarly journals Deletion of a fur-Like Gene Affects Iron Homeostasis and Magnetosome Formation in Magnetospirillum gryphiswaldense

2010 ◽  
Vol 192 (16) ◽  
pp. 4192-4204 ◽  
Author(s):  
René Uebe ◽  
Birgit Voigt ◽  
Thomas Schweder ◽  
Dirk Albrecht ◽  
Emanuel Katzmann ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Iron Homeostasis ◽  
Wild Type ◽  
Intracellular Iron ◽  
Magnetospirillum Gryphiswaldense ◽  
Cellular Iron ◽  
Iron Supply ◽  
Iron Requirement ◽  
Magnetite Biomineralization ◽  
Titration Assay

ABSTRACT Magnetotactic bacteria synthesize specific organelles, the magnetosomes, which are membrane-enveloped crystals of the magnetic mineral magnetite (Fe3O4). The biomineralization of magnetite involves the uptake and intracellular accumulation of large amounts of iron. However, it is not clear how iron uptake and biomineralization are regulated and balanced with the biochemical iron requirement and intracellular homeostasis. In this study, we identified and analyzed a homologue of the ferric uptake regulator Fur in Magnetospirillum gryphiswaldense, which was able to complement a fur mutant of Escherichia coli. A fur deletion mutant of M. gryphiswaldense biomineralized fewer and slightly smaller magnetite crystals than did the wild type. Although the total cellular iron accumulation of the mutant was decreased due to reduced magnetite biomineralization, it exhibited an increased level of free intracellular iron, which was bound mostly to a ferritin-like metabolite that was found significantly increased in Mössbauer spectra of the mutant. Compared to that of the wild type, growth of the fur mutant was impaired in the presence of paraquat and under aerobic conditions. Using a Fur titration assay and proteomic analysis, we identified constituents of the Fur regulon. Whereas the expression of most known magnetosome genes was unaffected in the fur mutant, we identified 14 proteins whose expression was altered between the mutant and the wild type, including five proteins whose genes constitute putative iron uptake systems. Our data demonstrate that Fur is a regulator involved in global iron homeostasis, which also affects magnetite biomineralization, probably by balancing the competing demands for biochemical iron supply and magnetite biomineralization.

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 CBIO-10. REDUCED IRON EXPORT FUNCTIONS IN A CELL INTRINSIC MANNER TO DRIVE GLIOBLASTOMA GROWTH

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii17-ii17
Author(s):  
Katie Troike ◽  
Erin Mulkearns-Hubert ◽  
Daniel Silver ◽  
James Connor ◽  
Justin Lathia
Keyword(s):  
Tumor Cells ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Iron Status ◽  
Tumor Grade ◽  
Hfe Gene ◽  
Iron Release ◽  
Female Patients ◽  
Cellular Iron

Abstract Glioblastoma (GBM), the most common primary malignant brain tumor in adults, is characterized by invasive growth and poor prognosis. Iron is a critical regulator of many cellular processes, and GBM tumor cells have been shown to modulate expression of iron-associated proteins to enhance iron uptake from the surrounding microenvironment, driving tumor initiation and growth. While iron uptake has been the central focus of previous investigations, additional mechanisms of iron regulation, such as compensatory iron efflux, have not been explored in the context of GBM. The hemochromatosis (HFE) gene encodes a transmembrane glycoprotein that aids in iron homeostasis by limiting cellular iron release, resulting in a sequestration phenotype. We find that HFE is upregulated in GBM tumors compared to non-tumor brain and that expression of HFE increases with tumor grade. Furthermore, HFE mRNA expression is associated with significantly reduced survival specifically in female patients with GBM. Based on these findings, we hypothesize that GBM tumor cells upregulate HFE expression to augment cellular iron loading and drive proliferation, ultimately leading to reduced survival of female patients. To test this hypothesis, we generated Hfe knockdown and overexpressing mouse glioma cell lines. We observed significant alterations in the expression of several iron handling genes with Hfe knockdown or overexpression, suggesting global disruption of iron homeostasis. Additionally, we show that knockdown of Hfe in these cells increases apoptosis and leads to a significant impairment of tumor growth in vivo. These findings support the hypothesis that Hfe is a critical regulator of cellular iron status and contributes to tumor aggression. Future work will include further exploration of the mechanisms that contribute to these phenotypes as well as interactions with the tumor microenvironment. Elucidating the mechanisms by which iron effulx contributes to GBM may inform the development of next-generation targeted therapies.

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.

scholarly journals Dopamine Is a Siderophore-Like Iron Chelator That PromotesSalmonella entericaSerovar Typhimurium Virulence in Mice

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Stefanie Dichtl ◽  
Egon Demetz ◽  
David Haschka ◽  
Piotr Tymoszuk ◽  
Verena Petzer ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Iron Acquisition ◽  
Lipocalin 2 ◽  
Intracellular Iron ◽  
Content Type ◽  
Hepcidin Expression

ABSTRACTWe have recently shown that the catecholamine dopamine regulates cellular iron homeostasis in macrophages. As iron is an essential nutrient for microbes, and intracellular iron availability affects the growth of intracellular bacteria, we studied whether dopamine administration impacts the course ofSalmonellainfections. Dopamine was found to promote the growth ofSalmonellaboth in culture and within bone marrow-derived macrophages, which was dependent on increased bacterial iron acquisition. Dopamine administration to mice infected withSalmonella entericaserovar Typhimurium resulted in significantly increased bacterial burdens in liver and spleen, as well as reduced survival. The promotion of bacterial growth by dopamine was independent of the siderophore-binding host peptide lipocalin-2. Rather, dopamine enhancement of iron uptake requires both the histidine sensor kinase QseC and bacterial iron transporters, in particular SitABCD, and may also involve the increased expression of bacterial iron uptake genes. Deletion or pharmacological blockade of QseC reduced but did not abolish the growth-promoting effects of dopamine. Dopamine also modulated systemic iron homeostasis by increasing hepcidin expression and depleting macrophages of the iron exporter ferroportin, which enhanced intracellular bacterial growth.Salmonellalacking all central iron uptake pathways failed to benefit from dopamine treatment. These observations are potentially relevant to critically ill patients, in whom the pharmacological administration of catecholamines to improve circulatory performance may exacerbate the course of infection with siderophilic bacteria.IMPORTANCEHere we show that dopamine increases bacterial iron incorporation and promotesSalmonellaTyphimurium growth bothin vitroandin vivo. These observations suggest the potential hazards of pharmacological catecholamine administration in patients with bacterial sepsis but also suggest that the inhibition of bacterial iron acquisition might provide a useful approach to antimicrobial therapy.

An Anti-Apoptotic Molecule, Anamorsin, Is Essential for Erythropoiesis Through the Regulation of Cellular Labile Iron Pool

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 610-610
Author(s):  
Akira Tanimura ◽  
Yuri Hamanaka ◽  
Natsuko Fujita ◽  
Yukiko Doi ◽  
Tomohiko Ishibashi ◽  
...  
Keyword(s):  
Cell Lines ◽  
Iron Homeostasis ◽  
Fetal Liver ◽  
Liver Cells ◽  
Binding Activity ◽  
Wild Type ◽  
Labile Iron Pool ◽  
Cellular Iron ◽  
Fetal Liver Cells ◽  
Induction Of Apoptosis

Abstract Abstract 610 Introduction: Iron has crucial roles in many cellular biological processes. Cellular iron uptake and export must be tightly regulated. Insufficient iron concentrations impair the function of numerous iron proteins, whereas excess free iron can oxidize and damage the contents of cells. Anamorsin (AM, also called CIAPIN-1) is an anti-apoptotic factor, which we originally isolated as a molecule that confers factor-independent survival of hematopoietic cells. AM-deficient mice are embryonic lethal at late gestation due to the defect of definitive hematopoiesis. It is thought that AM plays a crucial role in hematopoiesis, however its precise biological mechanisms remain unclear. Recently, it was reported that the yeast AM homolog, Dre2, was implicated in cytosolic iron-sulfur (Fe/S) cluster assembly (Zhang Y., et al. Mol.Cell.Biol. 28:5569–5582, 2008). The AM carries conserved cysteine motifs (CX2CXC and twin CX2C) at its C termini, which may form iron binding sites. In this study, we have focused on the possibility that AM may be involved in the maturation of Fe/S cluster and the cellular iron homeostasis, especially, the regulation of labile iron pool (LIP) and that AM may affect the accumulation of reactive oxygen species (ROS), leading to impaired erythropoiesis. Methods and Results: To analyze the function of Fe/S protein, we established wild-type cell lines (AMWT) and AM-deficient cell lines (AMKO) from wild-type and AM-deficient fetal liver (14.5dpc) respectively by using SV40 large T antigen. Iron regulatory protein 1 (IRP1) is a well-known Fe/S protein with dual functions. In the presence of Fe/S cluster, IRP1 functions as a cytosolic aconitase. While, in the absence of Fe/S cluster, IRP1 stabilizes the transferrin receptor (TfR) mRNA by binding to the iron responsive element (IRE). We compared the aconitase activity and the IRE binding activity of IRP1 between AMWT and AMKO. The results showed that the cytosolic aconitase activity in AMKO decreased approximately 30% compared to AMWT and the IRE binding activity of IRP1 in AMKO increased 3-fold compared to AMWT. Furthermore, we compared the iron homeostasis. In the presence of iron chelator, desferrioxamine, the expression of TfR in AMWT was markedly elevated, while it was hardly elevated in AMKO. The LIP is a pool of chelatable and redox-active iron, which serves as a crossroad of cell iron metabolism. The measurement of LIP with the metal-sensitive sensor calcein acetoxymethyl ester showed that AMKO had 5-fold higher cellular LIP than AMWT. Moreover we evaluated the accumulation of ROS and the induction of apoptosis by extracellular iron uptake between AMWT and AMKO. The results showed the accumulation of ROS and the induction of apoptosis in AMKO were enhanced about twice as much as in AMWT. These enhancements could be restored by transduction of AM expressing retrovirus vector to AMKO. We also evaluated the effects of AM-deficiency on erythroid differentiation. Fetal liver cells from wild-type or AM-deficient embryos (14.5dpc) were divided into primitive and more matured erythroid populations based on their expression of CD71 and Ter119 by FACS analysis. AM-deficient fetal liver cells had a significant increase in the CD71low TER119low population, containing primitive erythroid progenitors, compared to wild-type (9.4±2.1% vs. 5.2±1.1%, P<0.05). Conversely, the CD71lowTER119highpopulation, comprised of late orthochromatophilic erythroblasts and reticulocytes, decreased in AM-deficient fetal liver cells compared to wild-type cells (2.3±0.8% vs. 7.4±1.3%, P < 0.05). Moreover we studied LIP in wild-type or AM-deficient embryo fetal liver cells. In accordance with the cell lines, the LIP in AM-deficient fetal liver cells increased 3 to 5-fold more than in wild-type fetal liver cells. The accumulation of ROS and the number of apoptotic cells also increased 2 to 5-fold in AM- deficient fetal liver cells compared to wild-type fetal liver cells. Thus, it was showed that AM deficiency impaired the iron homeostasis and conferred low sensitivity for iron concentration, resulting in the increase of LIP, the accumulation of ROS and the induction of apoptosis. Furthermore, dysregulation of cellular iron homeostasis was thought to be the cause of the embryonic lethal due to AM deficiency. Conclusion: Our current findings indicate that AM functions in cytosolic Fe/S cluster biogenesis and iron homeostasis and is essential for erythropoiesis. Disclosures: Kanakura: Shire: Consultancy.

scholarly journals Direct Activation of Genes Involved in Intracellular Iron Use by the Yeast Iron-Responsive Transcription Factor Aft2 without Its Paralog Aft1

2005 ◽  
Vol 25 (15) ◽  
pp. 6760-6771 ◽  
Author(s):  
Maïté Courel ◽  
Sylvie Lallet ◽  
Jean-Michel Camadro ◽  
Pierre-Louis Blaiseau
Keyword(s):  
Iron Homeostasis ◽  
Regulatory Elements ◽  
Intracellular Iron ◽  
Transcription Analysis ◽  
Dna Microarray Data ◽  
Cellular Iron ◽  
Surface Iron ◽  
Transcription Activators ◽  
Responsive Element ◽  
Cellular Iron Homeostasis

ABSTRACT The yeast Saccharomyces cerevisiae contains a pair of paralogous iron-responsive transcription activators, Aft1 and Aft2. Aft1 activates the cell surface iron uptake systems in iron depletion, while the role of Aft2 remains poorly understood. This study compares the functions of Aft1 and Aft2 in regulating the transcription of genes involved in iron homeostasis, with reference to the presence/absence of the paralog. Cluster analysis of DNA microarray data identified the classes of genes regulated by Aft1 or Aft2, or both. Aft2 activates the transcription of genes involved in intracellular iron use in the absence of Aft1. Northern blot analyses, combined with chromatin immunoprecipitation experiments on selected genes from each class, demonstrated that Aft2 directly activates the genes SMF3 and MRS4 involved in mitochondrial and vacuolar iron homeostasis, while Aft1 does not. Computer analysis found different cis-regulatory elements for Aft1 and Aft2, and transcription analysis using variants of the FET3 promoter indicated that Aft1 is more specific for the canonical iron-responsive element TGCACCC than is Aft2. Finally, the absence of either Aft1 or Aft2 showed an iron-dependent increase in the amount of the remaining paralog. This may provide additional control of cellular iron homeostasis.

scholarly journals Enhanced erythropoiesis in Hfe-KO mice indicates a role for Hfe in the modulation of erythroid iron homeostasis

Blood ◽  
2011 ◽  
Vol 117 (4) ◽  
pp. 1379-1389 ◽  
Author(s):  
Pedro Ramos ◽  
Ella Guy ◽  
Nan Chen ◽  
Catia C. Proenca ◽  
Sara Gardenghi ◽  
...  
Keyword(s):  
Iron Overload ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Dietary Iron ◽  
Erythroid Cells ◽  
Hepcidin Expression ◽  
Stress Erythropoiesis ◽  
Cellular Iron ◽  
Cellular Iron Uptake

Abstract In hereditary hemochromatosis, mutations in HFE lead to iron overload through abnormally low levels of hepcidin. In addition, HFE potentially modulates cellular iron uptake by interacting with transferrin receptor, a crucial protein during erythropoiesis. However, the role of HFE in this process was never explored. We hypothesize that HFE modulates erythropoiesis by affecting dietary iron absorption and erythroid iron intake. To investigate this, we used Hfe-KO mice in conditions of altered dietary iron and erythropoiesis. We show that Hfe-KO mice can overcome phlebotomy-induced anemia more rapidly than wild-type mice (even when iron loaded). Second, we evaluated mice combining the hemochromatosis and β-thalassemia phenotypes. Our results suggest that lack of Hfe is advantageous in conditions of increased erythropoietic activity because of augmented iron mobilization driven by deficient hepcidin response. Lastly, we demonstrate that Hfe is expressed in erythroid cells and impairs iron uptake, whereas its absence exclusively from the hematopoietic compartment is sufficient to accelerate recovery from phlebotomy. In summary, we demonstrate that Hfe influences erythropoiesis by 2 distinct mechanisms: limiting hepcidin expression under conditions of simultaneous iron overload and stress erythropoiesis, and impairing transferrin-bound iron uptake by erythroid cells. Moreover, our results provide novel suggestions to improve the treatment of hemochromatosis.

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