Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We postulated that patients with hereditary hemochromatosis (HH) absorb increased quantities of lead, as do iron-deficient subjects. To test this hypothesis, whole blood lead concentration ([blood Pb]) was quantified by atomic absorption spectrometry in HH homozygotes (n = 44), obligate heterozygotes (n = 19), normal control subjects (n = 33), and abnormal controls, with transfusion-induced iron overload (n = 8). HH homozygotes had higher [blood Pb] than did normal control subjects (5.6 +/- 0.6 microgram/dl vs 3.6 +/- 0.5 microgram/dl; p < 0.005); significantly increased mean [blood Pb] was observed in both male and female homozygotes. In heterozygotes, the mean [blood Pb] 4.1 +/- 0.5 microgram/dl) was intermediate between that of homozygotes and normal control subjects. The mean [blood Pb] of subjects with transfusion-induced iron overload (22 +/- 0.6 microgram/dl) did not differ significantly from that of normal controls. The findings in homozygotes could to be related to age, serum ferritin concentration, presence or absence of iron loading, or the extent of therapeutic phlebotomy. Lead exposure in all of our subjects was due primarily to ambient sources. Analysis of our data, when using a mathematical biokinetic model of human lead metabolism, suggests that the most likely explanation for our findings is that homozygotes (and, to a lesser extent, heterozygotes) absorb increased quantities of lead, a conclusion that corresponds to the increased absorption of iron and cobalt previously documented in homozygotes.
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PMID:Blood lead concentrations in hereditary hemochromatosis. 805 76

The present study characterizes the transport of nontransferrin (non-Tf) iron by K562 cells. Accumulation of radiolabel by cells incubated with 55Fe-nitrilotriacetate (NTA) is a saturable process that is time and temperature dependent (Ea approximately 20 kcal/mol). Initial rate analysis of iron influx yields values of Vmax = 855 fmol/min/10(6) cells and apparent Km = 0.54 microM. NHCL4 and chloroquine, agents that block cellular acquisition of iron from Tf, do not interfere with assimilation from FeNTA, demonstrating that uptake is truly independent of the Tf-mediated pathway. Furthermore, the inactivation of this transport mechanism by limited proteolytic digestion on ice indicates that specific cell surface proteins are involved. The extent of radiolabel incorporation into heme and ferritin is the same regardless of whether K562 cells acquire iron from 55FeNTA via the cell surface mechanism or from 55Fe-Tf via receptor-mediated endocytosis. Unlike other Tf-independent iron transport pathways that have been described, the K562 cell transport mechanism is not inhibited by divalent cations such as Ni2+, Co2+, or Mn2+. Uptake from 55FeNTA can be blocked by Cu2+ but at concentrations > 1500-fold molar excess. However, Cd2+ is a fairly specific inhibitor of 55Fe uptake by K562 cells (IC50 approximately 50 microM). Additionally, the K562 cell transport mechanism is not Ca2+ dependent and does not appear to be regulated by extracellular iron salts, in contrast to features noted for non-Tf iron uptake by fibroblasts (Sturrock, A., Alexander, J., Lamb, J., Craven, C. M., and Kaplan, J. (1991) J. Biol. Chem. 265, 3139-3145; Kaplan, J., Jordan, I., and Sturrock, A. (1991) J. Biol. Chem. 266, 2997-3004). These unique characteristics of the K562 cell uptake mechanism suggest that multiple transport systems function in Tf-independent iron assimilation.
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PMID:Characterization of transferrin-independent iron transport in K562 cells. Unique properties provide evidence for multiple pathways of iron uptake. 847 96

We studied uptake of iron from Fe(III)-diethylenetriamine pentaacetate (DTPA) in isolated rat hepatocytes. This uptake is specific with an affinity of 600 nM and shows an optimum pH of 6. The specificity is indicated by inhibition by ferric citrate and diferric transferrin. Iron uptake from Fe(III)-DTPA is completely inhibited by trypsinization of the cell surface, by strong impermeant ferric chelators (DTPA, apo-transferrin, polymer-conjugated desferrioxamine), both hexacyanoferrates, copper and zinc, and partly by dipyridyl, manganese, cobalt, N-ethylmaleimide, and citrate. The lysosomotropic agent chloroquin inhibits weakly; proton pump inhibitors are without effect. Ascorbate and Tiron both effectively stimulate the uptake and also mobilize iron from DTPA in vitro. Approximately 75% of the freshly acquired intracellular iron is found in ferritin even after uptake at lowered temperature (16 degrees C). We conclude that a rate-limiting mobilization of iron from the DTPA chelate by a cell-surface activity is required before iron can actually enter the cell. This can be enhanced by mediators of iron release, but does not seem to require reduction of iron. The use of DTPA as chelator offers the possibility of studying this putative activity because the Fe(III)-DTPA chelate is stable in the presence of transferrin or desferroxamine, in contrast to ferric citrate or Fe(NTA)2.
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PMID:Uptake of iron by isolated rat hepatocytes from a hydrophilic impermeant ferric chelate, Fe(III)-DTPA. 861 Oct 22

The uptake of 59Fe ascorbate by suspensions of human enterocytes prepared from endoscopically derived duodenal biopsies was studied, with each subject's serum ferritin concentration determined at the time of endoscopy. Iron uptake was greatest at 37 degrees C. Uptake increased from pH 5.5 to 7.3, before being totally inhibited at pH 9.0. However, ferrous ion concentration, determined by 3-(2-Pyridyl)-5,6-bis(4-phenyl sulfonic acid)-1,2,4-triazine, was greatest at pH 5.5 and fell over this pH range. The rate of uptake was significantly greater by enterocytes isolated from individuals with a low serum ferritin (< 22 ng/L) compared with those with normal serum ferritin (> 22 ng/L). Vmax +/- (SEM) was 78.7 +/- 8.5 pmol Fe/(micrograms DNA.min) in the normal group (n = 12) and 141 +/- 17.2 pmol Fe/(micrograms DNA.min) in the low ferritin group (n = 4, P < 0.008). Corresponding Km values were 52.5 +/- 11.7 and 66.7 +/- 5.1 mumol/L, respectively (P < 0.91). Zinc, lead, cobalt and manganese added to the incubation buffer significantly lowered iron uptake into cells (unselected patients). The concentrations of each metal required to halve the uptake rate from 50 mumol/L iron (IC50) were 85 +/- 5 mumol/L (Zn), 570 +/- 170 mumol/L (Pb), 1.1 +/- 0.1 mmol/L (Co), and 3.8 +/- 0.7 mmol/L (Mn). The results demonstrate that enterocytes isolated by this method show the characteristics of iron uptake seen in animal studies. We suggest that these cells will be useful in the study of iron uptake in humans.
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PMID:Iron uptake by isolated human enterocyte suspensions in vitro is dependent on body iron stores and inhibited by other metal cations. 904 May 63

The ferritin IRE, a highly conserved (96-99% in vertebrates) mRNA translation regulatory element in animal mRNA, was studied by molecular modeling (using MC-SYM and DOCKING) and by NMR spectroscopy. Cobalt(III) hexammine was used to model hydrated Mg2+. IRE isoforms in other mRNAs regulate mRNA translation or stability; all IREs bind IRPs (iron regulatory proteins). A G.C base pair, conserved in ferritin IREs, spans an internal loop/bulge in the middle of an A-helix and, combined with a dynamic G.U base pair, formed a pocket suitable for Co(III) hexammine binding. On the basis of the effects of Co(III) hexammine on the 1H NMR spectrum and results of automatic docking into the IRE model, the IRE bound Co(III) hexammine at the pocket in the major groove; Mg2+ may bind to the IRE at the same site on the basis of an analogy to Co(III) hexammine and on the Mg2+ inhibition of Cu-(phen)2 cleavage at the site. Distortion of the IRE helix by the internal loop/bulge near a conserved unpaired C required for IRP binding and adjacent to an IRP cross-linking site suggests a role for the pocket in ferritin IRE/IRP interactions.
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PMID:Iron regulatory element and internal loop/bulge structure for ferritin mRNA studied by cobalt(III) hexammine binding, molecular modeling, and NMR spectroscopy. 948 20

Bacterial ferritin of Azotobacter vinelandii (AvBF) is directly able to pick electrons up for iron release from or transfer them for storage to a platinum electrode in the absence of mediator or other reducer. The ferritin containing the structure of heme-Co2+ in part shows weakened activity to electrode and decreases the rate of iron release greatly. A reversible reduction process of the ferritin is observed by the spectral change regularly ranging from 310 to 260 nm under mixed gases containing 98% H2 and 2% to O2. The activity of nitrogen fixation from the whole cell of A. vinelandii increases greatly by H2 reduction with potentials ranging from -397 to -425 mV vs. NHE, indicating two important roles of H2-uptake reaction of the ferritin in increasing activity of nitrogen fixation and in supplying iron to synthesize nitrogenase.
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PMID:Studies on the heme and H2-uptake reaction from Azotobacter vinelandii bacterial ferritin. 1022 74

An apparatus consisting of two pumps, a mixer, a ferritin reactor, and a spectrophotometer was constructed to study the ability to trap various heavy metal ions (M2+) and the dynamics of a reconstituted ferritin reactor in flowing seawater. Reconstituted pig spleen ferritin (PSFr) is assembled from apo-protein shell to form a reconstituted iron core. The main components of the PSFr are its core, which contains an Fe2+:Pi stoichiometry of 6.0 +/- 0.5, reconstituted from pig spleen apoferritin (apo PSF), Fe2+, inorganic phosphate (Pi), and O2 (0.6 atm). The Fe3+-Pi clusters within the PSFr core exhibit resistance to salt ranging from 1% to 6% NaCl. The ferritin reactor consists of PSFr and an oscillating bag. Using the reactor, M2+ ions such as Cd2+, Zn2+, Co2+, and Mn2+ are directly trapped by the ferritin. We found a 1:2 +/- 0.2 stoichiometry of the trapped M2+ to the released iron as measured by chemical analysis or atomic absorption spectrometry; nontransient elements such as Na+, K+, Ca2+, etc., were scarcely trapped by the reactor. This study provides basic conditions for establishing a ferritin reactor and a convenient means for monitoring the pollution of heavy metal ions in seawater.
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PMID:Construction of a ferritin reactor: an efficient means for trapping various heavy metal ions in flowing seawater. 1119 68

Iron regulatory protein 2 (IRP2) is a mammalian cytosolic iron-sensing protein that regulates expression of iron metabolism proteins, including ferritin and transferrin receptor 1. IRP2 is ubiquitinated and degraded by the proteasome in iron-replete cells but is relatively stable in iron-depleted cells. Recent work has shown that IRP2 contains a unique 73-amino-acid domain that binds iron in vitro and undergoes iron-dependent oxidation and cleavage (J. Biol. Chem. 278 (2003), 14857). Several cysteines in the 73-amino-acid domain function as an in vitro iron-binding site. To assess the role of these cysteines in cellular iron- dependent degradation of IRP2, we mutagenized these cysteines in various combinations in the context of full-length protein and generated cell lines in which recombinant IRP2 expression was inducible. Iron-dependent degradation of IRP2 mutagenized at any or all of the cysteines of the putative degradation domain in cells was comparable to wild-type (WT). Both WT and cysteine mutant protein were stabilized in 3% oxygen. Treatment with sodium nitroprusside (SNP), an NO+ donor, caused a decrease in cellular IRP2 concentrations, but the SNP effect was abrogated by simultaneous addition of the iron chelator desferal and was not affected by cysteine mutations. Inhibition of endogenous heme synthesis with succinylacetone significantly inhibited iron- dependent degradation of IRP2. Addition of cobalt chloride inhibited degradation of both WT and mutagenized IRP2. Thus, we could not discern a role for the recently defined in vitro cysteine-dependent iron-binding site of IRP2 in cellular physiology. The early molecular events in iron-dependent degradation of IRP2 remain to be elucidated.
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PMID:The role of endogenous heme synthesis and degradation domain cysteines in cellular iron-dependent degradation of IRP2. 1297 33

Heme oxygenase-1 (HO-1), a stress-responsive enzyme that catabolizes heme into carbon monoxide (CO), biliverdin, and iron, has previously been shown to protect grafts from ischemia/reperfusion injury and rejection. Here we investigated the protective potential of HO-1 in 5 models of immune-mediated liver injury. We found that up-regulation of endogenous HO-1 by cobalt-protoporphyrin-IX (CoPP) protected mice from apoptotic liver damage induced by anti-CD95 antibody (Ab) or d-galactosamine in combination with either anti-CD3 Ab, lipopolysaccharide (LPS), or tumor necrosis factor alpha (TNF-alpha). HO-1 induction prevented apoptotic liver injury, measured by inhibition of caspase 3 activation, although it did not protect mice from caspase-3-independent necrotic liver damage caused by concanavalin A (Con A) administration. In addition, overexpression of HO-1 by adenoviral gene transfer resulted in protection from apoptotic liver injury, whereas inhibition of HO-1 enzymatic activity by tin-protoporphyrin-IX (SnPP) abrogated the protective effect. HO-1-mediated protection seems to target parenchymal liver cells directly because CoPP treatment protected isolated primary hepatocytes from anti-CD95-induced apoptosis in vitro. Furthermore, depletion of Kupffer cells (KCs) did not interfere with the protective effect in vivo. Exogenous CO administration or treatment with the CO-releasing agent methylene chloride mimicked the protective effect of HO-1, whereas treatment with exogenous biliverdin or overexpression of ferritin by recombinant adenoviral gene transfer did not. In conclusion, HO-1 is a potent protective factor for cytokine- and CD95-mediated apoptotic liver damage. Induction of HO-1 might be of a therapeutic modality for inflammatory liver diseases.
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PMID:Heme oxygenase-1 and its reaction product, carbon monoxide, prevent inflammation-related apoptotic liver damage in mice. 1572 11

Induction of the heme-degrading enzyme heme oxygenase-1 (HO-1) has been shown to be beneficial in terms of improvement of liver allograft survival and prevention of CD95-mediated apoptosis in the liver. In the present study, we investigated the effects of HO-1, and its products carbon monoxide (CO), biliverdin (BV), and iron/ferritin, in a mouse model of inflammatory liver damage inducible by lipopolysaccharide (LPS) in mice sensitized with the hepatocyte-specific transcription inhibitor D-galactosamine (GalN). Our results show that HO-1 induction by cobalt-protoporphyrin-IX (CoPP) reduced cytokine expression, protected mice from liver injury, and prolonged survival. While in contrast to ferritin overexpression, single administration of the CO donor methylene chloride (MC) or of BV also protected mice from liver damage, only coadministration of both HO products prolonged survival and reduced the expression of cytokines, e.g., tumor necrosis factor (TNF) and interferon gamma (IFN-gamma). In conclusion, HO-1-induced prolongation of survival, but not the protection from liver damage, seems to be dependent on down-regulation of cytokine synthesis.
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PMID:Cooperative effect of biliverdin and carbon monoxide on survival of mice in immune-mediated liver injury. 1572 11


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