Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: UNIPROT:P02794 (ferritin)
17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies suggest that disturbances of amino acid metabolism and cellular iron regulation are important mechanisms underlying manganese (Mn) neurotoxicity, although the targets underlying these disturbances are poorly defined. Using the AF5 neural-derived cell line, which displays GABAergic properties, we showed that Mn significantly increased glutamate release to 174%-214% of that of the control and that the effects of Mn exposure on the metabolism of glutamate, glutamine, alanine, and GABA resembled the effects of fluorocitrate, an inhibitor of aconitase, but not the effects of other toxicants including paraquat, rotenone, or 3-nitropropionic acid. Consistent with this, Mn inhibited aconitase activity in AF5 cells, resulting in a 90% increase in intracellular citrate; an in vitro assay revealed that m-aconitase was significantly more sensitive to inhibition by Mn than was c-aconitase. RNA mobility shift assay and Western blot showed that Mn treatment caused c-aconitase to be converted to iron regulatory protein 1 (IRP1) and increased the abundance of IRP2, leading to reduced H-ferritin expression, increased transferrin receptor expression, and increased uptake of transferrin. To determine the relative contributions of IRP1 and IRP2 in mediating the effects of Mn on iron homeostasis, we exposed transgenic fibroblasts lacking either c-aconitase/IRP1 or IRP2 to Mn. Manganese exposure minimally altered ferritin levels in cells possessing only c-aconitase/IRP1, whereas cells possessing only IRP2 showed a robust decrease in ferritin, indicating a dominant role of IRP2 in Mn-induced alteration of iron homeostasis. Together, these results demonstrate that m-aconitase is an important target of Mn and thatMn-induced alteration of iron homeostasis is mediated predominantly through IRP2.
...
PMID:Manganese targets m-aconitase and activates iron regulatory protein 2 in AF5 GABAergic cells. 1746 37

Inherited microcytic-hypochromic anemias in rodents and zebrafish suggest the existence of corresponding human disorders. The zebrafish mutant shiraz has severe anemia and is embryonically lethal because of glutaredoxin 5 (GRLX5) deletion, insufficient biogenesis of mitochondrial iron-sulfur (Fe/S) clusters, and deregulated iron-regulatory protein 1 (IRP1) activity. This leads to stabilization of transferrin receptor 1 (TfR) RNA, repression of ferritin, and ALA-synthase 2 (ALAS2) translation with impaired heme synthesis. We report the first case of GLRX5 deficiency in a middle-aged anemic male with iron overload and a low number of ringed sideroblasts. Anemia was worsened by blood transfusions but partially reversed by iron chelation. The patient had a homozygous (c.294A>G) mutation that interferes with intron 1 splicing and drastically reduces GLRX5 RNA. As in shiraz, aconitase and H-ferritin levels were low and TfR level was high in the patient's cells, compatible with increased IRP1 binding. Based on the biochemical and clinical phenotype, we hypothesize that IRP2, less degraded by low heme, contributes to the repression of the erythroblasts ferritin and ALAS2, increasing mitochondrial iron. Iron chelation, redistributing iron to the cytosol, might relieve IRP2 excess, improving heme synthesis and anemia. GLRX5 function is highly conserved, but at variance with zebrafish, its defect in humans leads to anemia and iron overload.
...
PMID:The human counterpart of zebrafish shiraz shows sideroblastic-like microcytic anemia and iron overload. 1748 48

Frataxin is a ubiquitous mitochondrial iron-binding protein involved in the biosynthesis of Fe/S clusters and heme. Its deficiency causes Friedreich's ataxia, a severe neurodegenerative disease. Mitochondrial ferritin is another major iron-binding protein, abundant in the testis and in sideroblasts from patients with sideroblastic anemia. We previously showed that its expression rescued the defects caused by frataxin deficiency in the yeast. To verify if this occurs also in mammals, we silenced frataxin in HeLa cells. This caused a reduction of growth, inhibition of the activity of aconitase and superoxide dismutase-2 and reduction of cytosolic ferritins without alteration of mitochondrial iron content. None of these effects were evident when silencing was done in cells expressing mitochondrial ferritin. These data indicate that frataxin has some roles in controlling the balance between different mitochondrial iron pools that are partially in common with those of mitochondrial ferritin.
...
PMID:The effects of frataxin silencing in HeLa cells are rescued by the expression of human mitochondrial ferritin. 1816 53

Iron is an essential metal for all living organisms. However, iron homeostasis needs to be tightly controlled since iron can mediate the production of reactive oxygen species, which can damage cell components and compromise the integrity and/or cause DNA mutations, ultimately leading to cancer. In eukaryotes, iron-regulatory protein 1 (IRP1) plays a central role in the control of intracellular iron homeostasis. This occurs by interaction of IRP1 with iron-responsive element regions at 5' of ferritin mRNA and 3' of transferrin mRNA which, respectively, represses translation and increases mRNA stability. We have expressed IRP1 using the plasmid pT7-His-hIRP1, which codifies for human IRP1 attached to an NH2-terminal 6-His tag. IRP1 was expressed in Escherichia coli using the strategy of co-expressing chaperonins GroES and GroEL, in order to circumvent inclusion body formation and increase the yield of soluble protein. The protein co-expressed with these chaperonins was obtained mostly in the soluble form, which greatly increased the efficiency of protein purification. Metal affinity and FPLC ion exchange chromatography were used in order to obtain highly purified IRP1. Purified protein was biologically active, as assessed by electrophoretic mobility shift assay, and could be converted to the cytoplasmic aconitase form. These results corroborate previous studies, which suggest the use of folding catalysts as a powerful strategy to increase protein solubility when expressing heterologous proteins in E. coli.
...
PMID:Increased expression and purification of soluble iron-regulatory protein 1 from Escherichia coli co-expressing chaperonins GroES and GroEL. 1829 88

In mammals, two homologous cytosolic regulatory proteins, iron regulatory protein 1 (also known as IRP1 and Aco1) and iron regulatory protein 2 (also known as IRP2 and Ireb2), sense cytosolic iron levels and posttranscriptionally regulate iron metabolism genes, including transferrin receptor 1 (TfR1) and ferritin H and L subunits, by binding to iron-responsive elements (IREs) within target transcripts. Mice that lack IRP2 develop microcytic anemia and neurodegeneration associated with functional cellular iron depletion caused by low TfR1 and high ferritin expression. IRP1 knockout (IRP1(-/-)) animals do not significantly misregulate iron metabolism, partly because IRP1 is an iron-sulfur protein that functions mainly as a cytosolic aconitase in mammalian tissues and IRP2 activity increases to compensate for loss of the IRE binding form of IRP1. The neurodegenerative disease of IRP2(-/-) animals progresses slowly as the animals age. In this study, we fed IRP2(-/-) mice a diet supplemented with a stable nitroxide, Tempol, and showed that the progression of neuromuscular impairment was markedly attenuated. In cell lines derived from IRP2(-/-) animals, and in the cerebellum, brainstem, and forebrain of animals maintained on the Tempol diet, IRP1 was converted from a cytosolic aconitase to an IRE binding protein that stabilized the TfR1 transcript and repressed ferritin synthesis. We suggest that Tempol protected IRP2(-/-) mice by disassembling the cytosolic iron-sulfur cluster of IRP1 and activating IRE binding activity, which stabilized the TfR1 transcript, repressed ferritin synthesis, and partially restored normal cellular iron homeostasis in the brain.
...
PMID:Tempol-mediated activation of latent iron regulatory protein activity prevents symptoms of neurodegenerative disease in IRP2 knockout mice. 1868 2

Defects in frataxin result in Friedreich ataxia, a genetic disease characterized by early onset of neurodegeneration, cardiomyopathy, and diabetes. Frataxin is a conserved mitochondrial protein that controls iron needed for iron-sulfur cluster assembly and heme synthesis and also detoxifies excess iron. Studies in vitro have shown that either monomeric or oligomeric frataxin delivers iron to other proteins, whereas ferritin-like frataxin particles convert redox-active iron to an inert mineral. We have investigated how these different forms of frataxin are regulated in vivo. In Saccharomyces cerevisiae, only monomeric yeast frataxin (Yfh1) was detected in unstressed cells when mitochondrial iron uptake was maintained at a steady, low nanomolar level. Increments in mitochondrial iron uptake induced stepwise assembly of Yfh1 species ranging from trimer to > or = 24-mer, independent of interactions between Yfh1 and its major iron-binding partners, Isu1/Nfs1 or aconitase. The rate-limiting step in Yfh1 assembly was a structural transition that preceded conversion of monomer to trimer. This step was induced, independently or synergistically, by mitochondrial iron increments, overexpression of wild type Yfh1 monomer, mutations that stabilize Yfh1 trimer, or heat stress. Faster assembly kinetics correlated with reduced oxidative damage and higher levels of aconitase activity, respiratory capacity, and cell survival. However, deregulation of Yfh1 assembly resulted in Yfh1 aggregation, aconitase sequestration, and mitochondrial DNA depletion. The data suggest that Yfh1 assembly responds to dynamic changes in mitochondrial iron uptake or stress exposure in a highly controlled fashion and that this may enable frataxin to simultaneously promote respiratory function and stress tolerance.
...
PMID:Assembly of the iron-binding protein frataxin in Saccharomyces cerevisiae responds to dynamic changes in mitochondrial iron influx and stress level. 1878 75

The intracellular fate of iron acquired by bacteria during siderophore-mediated assimilation is poorly understood. We investigated this question in the pathogenic enterobacterium Erwinia chrysanthemi. This bacterium produces two siderophores, chrysobactin and achromobactin, during plant infection. We analyzed the distribution of iron into cytosolic proteins in bacterial cells supplied with 59Fe-chrysobactin using native gel electrophoresis. A parental strain and mutants deficient in bacterioferritin (bfr), miniferritin (dps), ferritin (ftnA), bacterioferredoxin (bfd), or iron-sulfur cluster assembly machinery (sufABCDSE) were studied. In the parental strain, we observed two rapidly 59Fe-labeled protein signals identified as bacterioferritin and an iron pool associated to the protein chain-elongation process. In the presence of increased 59Fe-chrysobactin concentrations, we detected mini-ferritin-bound iron. Iron incorporation into bacterioferritin was severely reduced in nonpolar sufA, sufB, sufD, sufS, and sufE mutants but not in a sufC background. Iron recycling from bacterioferritin did not occur in bfd and sufC mutants. Iron depletion caused a loss of aconitase activity, whereas ferric chrysobactin supplementation stimulated the production of active aconitase in parental cells and in bfr and bfd mutants. Aconitase activity in sufA, sufB, sufD, sufS, and sufE mutant strains was 10 times lower than that in parental cells. In the sufC mutant, it was twice as low as that in the parental strain. Defects observed in the mutants were not caused by altered ferric chrysobactin transport. Our data demonstrate a functional link between bacterioferritin, bacterioferredoxin, and the Suf protein machinery resulting in optimal bacterial growth and a balanced distribution of iron between essential metalloproteins.
...
PMID:Siderophore-controlled iron assimilation in the enterobacterium Erwinia chrysanthemi: evidence for the involvement of bacterioferritin and the Suf iron-sulfur cluster assembly machinery. 1899 Jun 91

Parkinson's disease (PD) is characterized by early glutathione depletion in the substantia nigra (SN). Among its various functions in the cell, glutathione acts as a substrate for the mitochondrial enzyme glutaredoxin 2 (Grx2). Grx2 is involved in glutathionylation of protein cysteine sulfhydryl residues in the mitochondria. Although monothiol glutathione-dependent oxidoreductases (Grxs) have previously been demonstrated to be involved in iron-sulfur (Fe-S) center biogenesis, including that in yeast, here we report data suggesting the involvement of mitochondrial Grx2, a dithiol Grx, in iron-sulfur biogenesis in a mammalian dopaminergic cell line. Given that mitochondrial dysfunction and increased cellular iron levels are two important hallmarks of PD, this suggests a novel potential mechanism by which glutathione depletion may affect these processes in dopaminergic neurons. We report that depletion of glutathione as substrate results in a dose-dependent Grx2 inhibition and decreased iron incorporation into a mitochondrial complex I (CI) and aconitase (m-aconitase). Mitochondrial Grx2 inhibition through siRNA results in a corresponding decrease in CI and m-aconitase activities. It also results in significant increases in iron-regulatory protein (IRP) binding, likely as a consequence of conversion of Fe-S-containing cellular aconitase to its non-Fe-S-containing IRP1 form. This is accompanied by increased transferrin receptor, decreased ferritin, and subsequent increases in mitochondrial iron levels. This suggests that glutathione depletion may affect important pathologic cellular events associated with PD through its effects on Grx2 activity and mitochondrial Fe-S biogenesis.
...
PMID:A disruption in iron-sulfur center biogenesis via inhibition of mitochondrial dithiol glutaredoxin 2 may contribute to mitochondrial and cellular iron dysregulation in mammalian glutathione-depleted dopaminergic cells: implications for Parkinson's disease. 1929 Jul 77

Mrs3p and Mrs4p (Mrs3/4p) are yeast mitochondrial iron carrier proteins that play important roles in ISC (iron-sulphur cluster) and haem biosynthesis. At low iron conditions, mitochondrial and cytoplasmic ISC protein maturation is correlated with MRS3/4 expression. Zebrafish mitoferrin1 (mfrn1), one of two MRS3/4 orthologues, is essential for erythropoiesis, but little is known about the ubiquitously expressed paralogue mfrn2. In the present study we identified a single mitoferrin gene (dmfrn) in the genome of Drosophila melanogaster, which is probably an orthologue of mfrn2. Overexpression of dmfrn in the Drosophila l(2)mbn cell line (mbn-dmfrn) resulted in decreased binding between IRP-1A (iron regulatory protein 1A) and stem-loop RNA structures referred to as IREs (iron responsive elements). mbn-dmfrn cell lines also had increased cytoplasmic aconitase activity and slightly decreased iron content. In contrast, iron loading results in decreased IRP-1A-IRE binding, but increased cellular iron content, in experimental mbn-dmfrn and control cell lines. Iron loading also increases cytoplasmic aconitase activity in all cell lines, but with slightly higher activity observed in mbn-dmfrn cells. From this we concluded that dmfrn overexpression stimulates cytoplasmic ISC protein maturation, as has been reported for MRS3/4 overexpression. Compared with control cell lines, mbn-dmfrn cells had higher Fer1HCH (ferritin 1 heavy chain homologue) transcript and protein levels. RNA interference of the putative Drosophila orthologue of human ABCB7, a mitochondrial transporter involved in cytoplasmic ISC protein maturation, restored Fer1HCH transcript levels of iron-treated mbn-dmfrn cells to those of control cells grown in normal medium. These results suggest that dmfrn overexpression in l(2)mbn cells causes an 'overestimation' of the cellular iron content, and that regulation of Fer1HCH transcript abundance probably depends on cytoplasmic ISC protein maturation.
...
PMID:Overexpression of Drosophila mitoferrin in l(2)mbn cells results in dysregulation of Fer1HCH expression. 1945 95

In mammals, iron regulatory proteins (IRPs) 1 and 2 posttranscriptionally regulate expression of genes involved in iron metabolism, including transferrin receptor 1, the ferritin (Ft) H and L subunits, and ferroportin by binding mRNA motifs called iron responsive elements (IREs). IRP1 is a bifunctional protein that mostly exists in a non-IRE-binding, [4Fe-4S] cluster aconitase form, whereas IRP2, which does not assemble an Fe-S cluster, spontaneously binds IREs. Although both IRPs fulfill a trans-regulatory function, only mice lacking IRP2 misregulate iron metabolism. NO stimulates the IRE-binding activity of IRP1 by targeting its Fe-S cluster. IRP2 has also been reported to sense NO, but the intrinsic function of IRP1 and IRP2 in NO-mediated regulation of cellular iron metabolism is controversial. In this study, we exposed bone marrow macrophages from Irp1(-/-) and Irp2(-/-) mice to NO and showed that the generated apo-IRP1 was entirely responsible for the posttranscriptional regulation of transferrin receptor 1, H-Ft, L-Ft, and ferroportin. The powerful action of NO on IRP1 also remedies the defects of iron storage found in IRP2-null bone marrow macrophages by efficiently reducing Ft overexpression. We also found that NO-dependent IRP1 activation, resulting in increased iron uptake and reduced iron sequestration and export, maintains enough intracellular iron to fuel the Fe-S cluster biosynthetic pathway for efficient restoration of the citric acid cycle aconitase in mitochondria. Thus, IRP1 is the dominant sensor and transducer of NO for posttranscriptional regulation of iron metabolism and participates in Fe-S cluster repair after exposure to NO.
...
PMID:Iron regulatory protein 1 outcompetes iron regulatory protein 2 in regulating cellular iron homeostasis in response to nitric oxide. 2156 47


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---