Iron-binding Protein Ferritin Research Articles

P74 Lenalidomide in elderly patients with mantle cell lymphoma

The wasp Campoletis sonorensis injects a polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. CsPDV protects the wasp egg and larvae by selectively disabling the host's cellular immune response, and by altering host physiology, growth, and development. Among the changes in host physiology brought about by CsPDV infection is a rapid, and specific decline in the translation of fat body mRNAs encoding selected major plasma proteins. Translational inhibition of the synthesis of all storage protein monomers, p82 (Riboflavin binding hexamer), and p74/p76 (arylphorin), occurs upon infection with CsPDV. Moreover, the prewandering peak of the plasma enzyme juvenile hormone esterase (JHE) was blocked by CsPDV injection. Northern blotting of fat body mRNA demonstrated that transcript levels of storage proteins were not affected by infection. Plasma titers of the iron binding proteins transferrin (p72) and ferritin (p24/26), and of the plasma juvenile hormone binding protein (p25) were not changed by CsPDV infection. That storage protein and JHE synthesis are translationally suppressed, while the synthesis of other plasma proteins continues apace, suggests that CsPDV infection may lead to translational discrimination among available mRNAs in CsPDV infected fat bodies. The effect of this translational discrimination is to shunt host resources away from larval growth and adult development, which presumably makes them available to the developing endoparasitoid.

Fenton chemistry and oxidative stress mediate the toxicity of the beta-amyloid peptide in a Drosophila model of Alzheimer's disease.

The mechanism by which aggregates of the β-amyloid peptide (Aβ) mediate their toxicity is uncertain. We show here that the expression of the 42-amino-acid isoform of Aβ (Aβ1–42) changes the expression of genes involved in oxidative stress in a Drosophila model of Alzheimer’s disease. A subsequent genetic screen confirmed the importance of oxidative stress and a molecular dissection of the steps in the cellular metabolism of reactive oxygen species revealed that the iron-binding protein ferritin and the H2O2 scavenger catalase are the most potent suppressors of the toxicity of wild-type and Arctic (E22G) Aβ1–42. Likewise, treatment with the iron-binding compound clioquinol increased the lifespan of flies expressing Arctic Aβ1–42. The effect of iron appears to be mediated by oxidative stress as ferritin heavy chain co-expression reduced carbonyl levels in Aβ1–42 flies by 65% and restored the survival and locomotion function to normal. This was achieved despite the presence of elevated levels of the Aβ1–42. Taken together, our data show that oxidative stress, probably mediated by the hydroxyl radical and generated by the Fenton reaction, is essential for Aβ1–42 toxicity in vivo and provide strong support for Alzheimer’s disease therapies based on metal chelation.

Expression profile of the iron-binding proteins transferrin and ferritin heavy chain subunit in the bumblebee Bombus ignitus

The iron-binding proteins, transferrin and ferritin, are involved in the processes of transport and storage in iron metabolism. Their expression is induced in response to iron overload. Here, we show the expression profile of transferrin (Bi-Tf) and the ferritin heavy chain subunit (Bi-FerHCH) of the bumblebee Bombus ignitus in response to iron overload. Bi-Tf exhibits fat body-specific expression, whereas Bi-FerHCH is ubiquitously expressed and upregulated in various tissues, though in a similar manner, by iron overload. We also demonstrate their expression regulation via reduction of Bi-Tf or Bi-FerHCH levels in the fat body via RNA interference (RNAi). Under uniform conditions in which FeCl(3) was overloaded, the RNAi-induced Bi-Tf knock-down B. ignitus worker bees showed upregulated expression of Bi-FerHCH, and reciprocally, Bi-FerHCH RNAi knockdowns showed upregulated Bi-Tf expression in the fat body. This result indicates that, in case of the loss of Bi-Tf or Bi-FerHCH, the expression of Bi-FerHCH or Bi-Tf, respectively, is upregulated in response to iron overload.

Ferritin nanoparticles as magnetic resonance reporter gene

Dynamic imaging of gene expression in live animals is among the exciting challenges of molecular imaging. To achieve that, one of the approaches is to use reporter genes that encode for the synthesis of easily detectable products. Such reporter genes can be designed to be expressed under the control of the regulatory elements included in a promoter region of a gene of interest, thus allowing the use of the same reporter gene for the detection of multiple genes. The most commonly used reporter genes include the firefly light-generating enzyme luciferase and the green fluorescent protein detectable by bioluminescence and fluorescence optical imaging, respectively. Over the last years a number of studies demonstrated the ability to use the iron-binding protein ferritin as a reporter gene that allows the detection of gene expression by magnetic resonance imaging (MRI). MRI provides high spatial resolution and soft tissue contrast for deep tissues along with a large arsenal of functional and anatomical contrast mechanisms that can be correlated with gene expression, and can potentially be translated into clinical use.

Ferric Carboxymaltose

Ferric carboxymaltose (Ferinject(R)), a novel iron complex that consists of a ferric hydroxide core stabilized by a carbohydrate shell, allows for controlled delivery of iron to target tissues. Administered intravenously, it is effective in the treatment of iron-deficiency anaemia, delivering a replenishment dose of up to 1000 mg of iron during a minimum administration time of </=15 minutes. Results of several randomized trials have shown that intravenously administered ferric carboxymaltose rapidly improves haemoglobin levels and replenishes depleted iron stores in various populations of patients with iron-deficiency anaemia, including those with inflammatory bowel disease, heavy uterine bleeding, postpartum iron-deficiency anaemia or chronic kidney disease. It was well tolerated in clinical trials. Ferric carboxymaltose is, therefore, an effective option in the treatment of iron-deficiency anaemia in patients for whom oral iron preparations are ineffective or cannot be administered. Ferric carboxymaltose is a macromolecular ferric hydroxide carbohydrate complex, which allows for controlled delivery of iron within the cells of the reticuloendothelial system and subsequent delivery to the iron-binding proteins ferritin and transferrin, with minimal risk of release of large amounts of ionic iron in the serum. Intravenous administration of ferric carboxymaltose results in transient elevations in serum iron, serum ferritin and transferrin saturation, and, ultimately, in the correction of haemoglobin levels and replenishment of depleted iron stores. The total iron concentration in the serum increased rapidly in a dose-dependent manner after intravenous administration of ferric carboxymaltose. Ferric carboxymaltose is rapidly cleared from the circulation and is distributed primarily to the bone marrow ( approximately 80%) and also to the liver and spleen. Repeated weekly administration of ferric carboxymaltose does not result in accumulation of transferrin iron in patients with iron-deficiency anaemia. Intravenously administered ferric carboxymaltose was effective in the treatment of iron-deficiency anaemia in several 6- to 12-week, randomized, open-label, controlled, multicentre trials in various patient populations, including those with inflammatory bowel disease, heavy uterine bleeding or postpartum iron-deficiency anaemia, and those with chronic kidney disease not undergoing or undergoing haemodialysis. In most trials, patients received either ferric carboxymaltose equivalent to an iron dose of </=1000 mg (or 15 mg/kg in those weighing <66 kg) administered over </=15 minutes (subsequent doses administered at 1-week intervals) or oral ferrous sulfate at a dose equivalent to 65 mg iron three times daily or 100 mg iron twice daily. In one trial, patients with chronic kidney disease undergoing haemodialysis received 200 mg of iron intravenously either as ferric carboxymaltose or iron sucrose administered into the haemodialysis line two to three times weekly. In all trials, ferric carboxymaltose was administered until each patient had received his or her calculated total iron replacement dose. Haemoglobin-related outcomes improved in patients with iron-deficiency anaemia receiving ferric carboxymaltose. Treatment with ferric carboxymaltose was associated with rapid and sustained increases from baseline in haemoglobin levels. Ferric carboxymaltose was considered to be as least as effective as ferrous sulfate with regard to changes from baseline in haemoglobin levels or the proportion of patients achieving a haematopoietic response at various timepoints. In general, improvements in haemoglobin levels were more rapid with ferric carboxymaltose than with ferrous sulfate. In patients with chronic kidney disease undergoing haemodialysis, ferric carboxymaltose was at least as effective as iron sucrose. Ferric carboxymaltose also replenished depleted iron stores and improved health-related quality-of-life (HR-QOL) in patients with iron-deficiency anaemia. Recipients of ferric carboxymaltose demonstrated improvements from baseline in serum ferritin levels and transferrin saturation, as well as improvements from baseline in HR-QOL assessment scores. Ferric carboxymaltose was at least as effective as ferrous sulfate with regard to endpoints related to serum ferritin levels, transferrin saturation and HR-QOL. Ferric carboxymaltose was well tolerated in clinical trials in patients with iron-deficiency anaemia, with most drug-related adverse events considered to be mild to moderate in severity. Commonly reported drug-related adverse events include headache, dizziness, nausea, abdominal pain, constipation, diarrhoea, rash and injection-site reactions. The incidence of drug-related adverse events in patients receiving intravenous ferric carboxymaltose was generally similar to that in patients receiving oral ferrous sulfate. In general, rash and local injection-site reactions were more common with ferric carboxymaltose, whereas gastrointestinal adverse events were more frequent with ferrous sulfate. In patients with chronic kidney disease undergoing haemodialysis, a lower proportion of ferric carboxymaltose than iron sucrose recipients experienced at least one drug-related adverse event.

Cystic fibrosis: ironing out the problem of infection?

the study by moreau-marquis et al. (3) in this issue of AJP-Lung advances our understanding of lung disease in cystic fibrosis (CF). Their findings are important because they may largely explain the peculiar propensity to early Pseudomonas aeruginosa infection that characterizes this most common of lethal genetic diseases. Moreau-Marquis et al. (3) demonstrate that immortalized human CF airway epithelial cells cocultured with P. aeruginosa promote the formation of antibiotic-resistant biofilms. Their series of experiments demonstrate that this is due to abnormal accumulation and loss of iron by CF epithelial cells and that biofilm formation can be prevented by either iron chelation therapy or by increasing normal cell membrane cystic fibrosis transmembrane regulator (CFTR) expression using the novel compound Corr4a. The observations of Moreau-Marquis et al. (3) confirm what has been clinically suspected in CF with respect to iron promotion of infection with P. aeruginosa. Previous studies have demonstrated that the airways of CF patients contain increased amounts of total iron and the iron-binding protein ferritin as well as a relationship between airway iron content and quantitative P. aeruginosa load assessed by colony-forming units per milliliter of sputum (5). This study also found an increase in iron in sputum in CF patients who had not previously been infected with P. aeruginosa, suggesting that elevated airway iron content may predate P. aeruginosa acquisition. Further evidence to support a problem with iron trafficking comes from the CF G551D mouse model. The teeth of these mice exhibit abnormal iron transport in pigment ameloblasts compared with wild-type mice, resulting in unusually white dentition (7). The study by Moreau-Marquis et al. (3) lends biological rationale to these earlier observations and brings two key questions into focus. First, what is the underlying link between abnormal or absent CFTR and cell iron homeostasis? Second, how does this impact on the CF host and P. aeruginosa interaction?

Potential role of ferritin heavy chain in oxidative stress and apoptosis in human mesothelial and mesothelioma cells: implications for asbestos-induced oncogenesis

Exposure to asbestos is a known etiological factor in malignant mesothelioma (MM). However, in vitro cell culture studies have provided paradoxical evidence that asbestos exposure to mesothelial cells causes cytotoxicity or apoptosis rather than malignant transformation. Although it has been shown that the iron associated with asbestos participates in the cell toxicity and probably MM pathogenesis via generation of reactive oxygen species (ROS), the molecular mechanisms largely remain unknown. Here, we demonstrate that ferritin heavy chain (FHC), a core subunit of iron-binding protein ferritin, works as an anti-apoptotic protein against toxic asbestos and oxidative stress in human mesothelial cells and MM cells. We found that FHC was induced in asbestos-exposed MeT-5A human mesothelial cells. The mesothelial cell line stably expressing FHC generated less amount of hydrogen peroxide (H2O2), one of the main ROS, after asbestos exposure and was more resistant to apoptosis induced by H2O2 compared with the cells transfected with the empty vector. Next, we investigated biological roles of FHC in human MM cell. We found that NCI-H2052, a human MM cell line, had a higher expression of endogenous FHC than MeT-5A and used the cell to address FHC function in MM. NCI-H2052 showed reduced H2O2 production and an apoptosis-resistant phenotype compared with MeT-5A. Suppression of the over-expressed FHC by using FHC small interfering RNA rendered the MM cells sensitive to apoptosis, suggesting the contribution of FHC to apoptosis resistance of the MM cells. Our findings highlight the potential role of FHC in the pathogenesis of asbestos-induced mesothelioma.

Burkholderia cenocepacia utilizes ferritin as an iron source

Burkholderia cenocepacia is a member of the Burkholderia cepacia complex, a group of genetically similar species that inhabit a number of environmental niches, including the lungs of patients with cystic fibrosis (CF). To colonize the lung, this bacterium requires a source of iron to satisfy its nutritional requirements for this important metal. Because of the high potential for damage in lung tissue resulting from oxygen-iron interactions, this metal is sequestered by a number of mechanisms that render it potentially unavailable to invading micro-organisms. Such mechanisms include the intracellular and extracellular presence of the iron-binding protein ferritin. Ferritin has a highly stable macromolecular structure and may contain up to 4500 iron atoms per molecule. To date, there has been no known report of a pathogenic bacterial species that directly utilizes iron sequestered by this macromolecule. To examine the ability of ferritin to support growth of B. cenocepacia J2315, iron-deficient media were supplemented with different concentrations of ferritin and the growth kinetics characterized over a 40 h period. The results indicated that B. cenocepacia J2315 utilizes iron bound by ferritin. Further studies examining the mechanisms of iron uptake from ferritin indicated that iron utilization results from a proteolytic degradation of this otherwise stable macromolecular structure. Since it is known that the ferritin concentration is significantly higher in the CF lung than in healthy lungs, this novel iron-acquisition mechanism may contribute to infection by B. cenocepacia in people with CF.

Endosperm-Specific Co-Expression of Recombinant Soybean Ferritin and Aspergillus Phytase in Maize Results in Significant Increases in the Levels of Bioavailable Iron

We have generated transgenic maize plants expressing Aspergillus phytase either alone or in combination with the iron-binding protein ferritin. Our aim was to produce grains with increased amounts of bioavailable iron in the endosperm. Maize seeds expressing recombinant phytase showed enzymatic activities of up to 3 IU per gram of seed. In flour paste prepared from these seeds, up to 95% of the endogenous phytic acid was degraded, with a concomitant increase in the amount of available phosphate. In seeds expressing ferritin in addition to phytase, the total iron content was significantly increased. To evaluate the impact of the recombinant proteins on iron absorption in the human gut, we used an in vitro digestion/Caco-2 cell model. We found that phytase in the maize seeds was associated with increased cellular iron uptake, and that the rate of iron uptake correlated with the level of phytase expression regardless of the total iron content of the seeds. We also investigated iron bioavailability under more complex meal conditions by adding ascorbic acid, which promotes iron uptake, to all samples. This resulted in a further increase in iron absorption, but the effects of phytase and ascorbic acid were not additive. We conclude that the expression of recombinant ferritin and phytase could help to increase iron availability and enhance the absorption of iron, particularly in cereal-based diets that lack other nutritional components.

Markers of Iron Overload Are Poor Prognostic Factors in Stem Cell Transplantation.

Transfusional iron overload is common in survivors of acute leukemia and hematopoietic stem cell transplantation and might cause long-term liver dysfunction. Routine evaluation for iron overload in such patients is recommended because excess iron can be readily removed from the body via phlebotomy or chelation. Iron overload might be associated with worse survival after stem cell transplantation in these diseases. We were interested in determining whether levels of the iron binding protein ferritin or the serum transferrin receptor (TfR) were predictive for survival. In a prospective study, we examined the correlation between iron parameters at the time of transplantation and overall survival. Serum ferritin, transferrin saturation, and TfR were measured before preparative regimen on patients who underwent hematopoietic stem cell transplantation between 1999 and 2004 for the diagnosis of aplastic anemia, MDS or acute leukemia (n=79). We used the number of transfusions before transplantation as a measure of iron load. Among these iron markers, serum ferritin correlated the most with the number of transfusions, regardless of remission status. High ferritin (>1,500 ng/ml), low TfR (≤4 μg/ml) and low TfR/log ferritin ratio (≤2) were associated with shorter survival (p=0.005, 0.04, and 0.001 respectively)(Figure 1). Among acute leukemia patients in remission, there was no difference in overall survival between patients with high or low iron markers. Markers of iron excess (serum ferritin >1,500 ng/ml, TfR/log ferritin ratio ≤2) at the time of stem cell transplantation is associated with shorter survival in MDS, aplastic anemia and acute leukemia with active disease. These results demonstrate that knowledge of patient ferritin and TfR levels can aid in risk stratification. The results also suggest that patients with high levels of ferritin may benefit from iron chelation before treatment. [Display omitted]

Iron and the Risk of Infection

During bacterial infection, pathogen and host compete for iron (Fe). The inflammatory response associated with infection shifts Fe from the circulation into storage, resulting in hypoferremia and iron-deficient erythropoiesis, and ultimately contributing to the anemia of inflammation. In this article, we review the mechanisms of Fe acquisition and sequestration. Bacteria employ both membrane-bound transferrin receptors and high-affinity iron-binding proteins called siderophores to acquire Fe. Humans utilize the iron-binding proteins lactoferrin, transferrin, and ferritin to move Fe away from sites of infection and into storage. Synthesis and action of these proteins are regulated by inflammatory cytokines. Iron overload leads to inhibition of IFN-gamma, TNF-alpha, IL-12, and nitric oxide formation as well as impairment of macrophage, neutrophil, and T-cell function. Injection of Fe into mice and rats markedly increases the virulence of several pathogens. Studies in hemodialysis patients have documented an association between infection and increased ferritin concentration as a surrogate marker for Fe overload. Humans respond to infection with inflammatory cytokine-induced hypoferremia. This association, as well as the growing literature linking Fe to both impaired immunity and heightened microbial virulence, calls into question the value of Fe supplementation during inflammation and infection.

BIOAVAILABILITY OF IRON FROM SPINACH USING AN IN VITRO/HUMAN CACO-2 CELL BIOASSAY MODEL

Spinach (Spinacia oleracea) cv Whitney was tested for iron bioavailabilty using an in vitro human intestinal cell culture ferritin bioassay technique previously developed. Spinach was cultured in a growth chamber for 33 days, harvested, and freeze-dried. Total iron in the samples was an average of 71 micrograms/g dry weight. Spinach was digested in vitro (pepsin and 0.1 M HCl followed by pancreatin and 0.1 M NaHCO3) with and without the addition of supplemental ascorbic acid. Caco-2 cell cultures were used to determine iron bioavailability from the spinach mixtures. Production of the iron-binding protein ferritin in the Caco-2 cells showed the supplemental ascorbic acid doubled bioavailability of iron from spinach. The data show fresh spinach is a poor source of iron, and emphasize the importance of evaluation of whole meals rather than single food items. The data support the usefulness of the in vitro/Caco-2 cell ferritin bioassay model for prescreening of space flight diets for bioavailable iron.

Induction of heat shock protein 32 (Hsp32) in the rat cochlea following hyperthermia

The genes for heat shock proteins (Hsps) can be upregulated in response to cellular trauma, resulting in enhanced cell survival and protection. Hsp32, also known as heme oxygenase 1, catalyzes the degradation of heme to produce carbon monoxide and bilirubin, which play a variety of cytoprotective functions at physiological concentrations, and iron, which is rapidly sequestered by the iron-binding protein ferritin. In the present study we examined the expression and localization of Hsp32 in the rat cochlea after heat shock using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunocytochemistry. Low levels of constitutive Hsp32 expression were observed in the normal rat cochlea by RT-PCR and Western blot. Hsp32 mRNA (messenger RNA) was present at higher levels in a subfraction containing sensorineural epithelium and lateral wall than in a subfraction containing modiolus. Western blot revealed that Hsp32 protein levels increase in the rat cochlea following heat shock. Immunocytochemistry showed scattered staining of outer hair cells in the organ of Corti of normal untreated rats. Following heat shock Hsp32 is upregulated in outer hair cells and the cells of the stria vascularis. These results suggest a potential role for Hsp32 as a component of the oxidative stress response pathway in the rat cochlea.

Genetic or Pharmacological Iron Chelation Prevents MPTP-Induced Neurotoxicity In Vivo: A Novel Therapy for Parkinson's Disease

Studies on postmortem brains from Parkinson's patients reveal elevated iron in the substantia nigra (SN). Selective cell death in this brain region is associated with oxidative stress, which may be exacerbated by the presence of excess iron. Whether iron plays a causative role in cell death, however, is controversial. Here, we explore the effects of iron chelation via either transgenic expression of the iron binding protein ferritin or oral administration of the bioavailable metal chelator clioquinol (CQ) on susceptibility to the Parkinson's-inducing agent 1-methyl-4-phenyl-1,2,3,6-tetrapyridine (MPTP). Reduction in reactive iron by either genetic or pharmacological means was found to be well tolerated in animals in our studies and to result in protection against the toxin, suggesting that iron chelation may be an effective therapy for prevention and treatment of the disease.

Effect of altered thyroid hormone status on rat brain ferritin H and ferritin L mRNA during postnatal development

The iron binding protein ferritin is a heterogeneous mix of 24 heavy (H) and light (L) subunits. The H subunit is associated with iron utilization, while the L subunit is responsible for iron storage. Examination of the developmental pattern of mRNA abundance in rat brain revealed that ferritin L mRNA is highest at birth and declines during the first postnatal week. A similar decline was seen in ferritin H mRNA, but was followed by an increase in ferritin H mRNA in the second postnatal week which continued through postnatal day 21. The pattern of H mRNA regulation is similar to that in previous reports of total ferritin protein in the developing rat brain and is consistent with the fact that brain ferritin is predominately ferritin H. The effect of thyroid hormone on the developmental regulation of ferritin mRNAs was examined by the subcutaneous injection of a single dose of exogenous thyroxine (T 4; 2 μg/g) on postnatal day 1. Hypothyroidism was induced in pregnant dams with propylthiouracil (PTU; 0.05% in drinking water) from gestational day 7. Northern analysis from postnatal days 2–21 showed that T 4 increased ferritin H mRNA throughout development, while ferritin L mRNA was decreased compared to age-matched controls. PTU treatment decreased ferritin H and increased L mRNA in the later stages (days 14–21) of development. Given the distinct functions of ferritin H and L this suggests a role for thyroid hormone in the ability of the brain to regulate stored vs. utilizable iron during critical periods of development.

Elevated non-transferrin bound iron in the lungs of patients with Pneumocystis carinii pneumonia.

The aim of the present work was to determine the concentrations of iron and iron-binding proteins in the lungs of patients suffering from Pneumocystis carinii (PCP), which is crucial for justifying the treatment with iron-chelating agents in this disease. Bronchoalveolar lavage was performed in 10 HIV patients with PCP and five healthy controls. Total iron and iron-binding proteins (transferrin, ferritin and lactoferrin) were measured in acellular bronchoalveolar lavage fluid (BALF) in both groups. Iron was determined by atomic absorption spectrometry; transferrin and lactoferrin were measured using specific enzyme-linked immunosorbent assays (ELISA); and ferritin concentration was quantified by automated immunonephelometry. Our findings in patients with PCP demonstrated a six- to seven-fold increase of total iron levels and an eight-fold increase of ferritin in bronchoalveolar lavage fluid when compared with controls. No significant differences were found in transferrin or lactoferrin levels. Moreover, our results suggest that this iron is non-transferrin bound. Non-transferrin bound iron is increased in the lower respiratory tracts of PCP patients. This finding would lend experiment support to the use of iron-chelating agents in this disease.

Regional distribution of iron, transferrin, ferritin, and oxidatively-modified proteins in young and aged Fischer 344 rat brains

Iron dysregulation in the brain is thought to contribute to the oxidative damage seen in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. A role for iron in the oxidative stress thought to contribute to normal ageing is less certain. To better characterize the role of iron in normal ageing, the concentrations of iron, transferrin, ferritin, and protein carbonyl groups are measured in nine separate regions of Fischer 344 rats. The largest (approximately 30%) age-related increases in brain iron concentration are seen in the temporal cortex, medial septum, and cerebellum. Ferritin concentration in these same brain regions increases 50 to 250% with age, while protein carbonyl concentration is only −27 to +4% of young rats. These results indicate that an increase in the major iron-binding protein ferritin compensates for any age-related increase in iron concentration, and suggest that the increased ferritin is cytoprotective, serving to prevent the accumulation of protein carbonyl groups (a principal product of metal-catalysed oxidation of proteins).

Polydnavirus infection inhibits translation of specific growth-associated host proteins

The wasp Campoletis sonorensis injects a polydnavirus (CsPDV) along with its egg during parasitization of Heliothis virescens larvae. CsPDV protects the wasp egg and larvae by selectively disabling the host's cellular immune response, and by altering host physiology, growth, and development. Among the changes in host physiology brought about by CsPDV infection is a rapid, and specific decline in the translation of fat body mRNAs encoding selected major plasma proteins. Translational inhibition of the synthesis of all storage protein monomers, p82 (Riboflavin binding hexamer), and p74/p76 (arylphorin), occurs upon infection with CsPDV. Moreover, the prewandering peak of the plasma enzyme juvenile hormone esterase (JHE) was blocked by CsPDV injection. Northern blotting of fat body mRNA demonstrated that transcript levels of storage proteins were not affected by infection. Plasma titers of the iron binding proteins transferrin (p72) and ferritin (p24/26), and of the plasma juvenile hormone binding protein (p25) were not changed by CsPDV infection. That storage protein and JHE synthesis are translationally suppressed, while the synthesis of other plasma proteins continues apace, suggests that CsPDV infection may lead to translational discrimination among available mRNAs in CsPDV infected fat bodies. The effect of this translational discrimination is to shunt host resources away from larval growth and adult development, which presumably makes them available to the developing endoparasitoid.

Accumulation of waterborne iron and expression of ferritin and transferrin in early developmental stages of brown trout (Salmo trutta)

Fertilized eggs, yolk-sac larvae and start-fed fry of brown trout (Salmo trutta) were exposed to various doses of waterborne iron. The iron levels of the intact eggs showed a dose-dependent increase following the treat-ment, while the levels of the embryos within the egg membranes did not differ significantly between the treated groups and the controls. After 4 days of exposure to 59Fe, only 5% of the accumulated tracer was located in the embryos. Correspondingly, the iron content of the yolk-sac larvae was not significantly influenced by the ambient iron levels. In contrast, the start-fed fry appeared to be highly susceptible to waterborne iron. The accumulation of iron in the fry was suggested to increase with the development of the gills. The bioconcentration factor (the ratio of tissue-to-water concentrations of iron) declined with increasing iron exposure levels. mRNAs encoding the iron-binding proteins ferritin and transferrin were identified by reverse transcription polymerase chain reaction (RT-PCR) in the developing embryos 2 weeks after fertilization. Western blot analysis demonstrated the transferrin protein to be expressed in both the yolk-sac larvae and the start-fed fry, whereas no ferritin was detected in the early developmental stages of brown trout.

Ferritin heavy chain is a progesterone-inducible marker in the uterus during pregnancy.

The female sex steroid, progesterone, plays a central role in mammalian pregnancy by regulating crucial events in the uterus such as transformation of endometrium for implantation and maintenance of pregnancy. The hormone acts through its specific nuclear receptor and modulates the functions of target cells by controlling the synthesis of specific proteins. The identity of genes that are regulated by progesterone in the uterus during various phases of pregnancy, however, remains largely unknown. In this study, we employed a differential gene-screening method to identify the gene encoding ferritin heavy chain (FHC), a component of the multisubunit iron-binding protein ferritin, as being regulated by progesterone in the uterus. We observed that uterine expression of the FHC messenger RNAs (mRNAs) rose dramatically at the onset of pregnancy, coincident with the surge of progesterone. FHC expression continued at this elevated level throughout gestation when the progesterone concentration remained high. At term, FHC expression declined sharply as the progesterone concentration dropped. We localized FHC proteins exclusively in uterine stromal cells, a major site of action of progesterone during pregnancy. Administration of mifepristone, an antiprogestin, during the early stages of pregnancy abolished both FHC mRNA and protein expression, clearly suggesting a primary role of progesterone in the regulation of this gene. Consistent with this scenario, administration of progesterone to ovariectomized animals after a brief estrogen priming led to a marked (25-fold) induction of FHC mRNA in the uterus, whereas estrogen, dexamethasone, or dihydrotestosterone had no effect. Based on these results, we propose that FHC is a novel and useful marker to study progesterone-regulated events in the uterus during pregnancy.