Parenteral vs. oral iron: influence on hepcidin signaling pathways through analysis of Hfe/Tfr2-null mice

2014 ◽  
Vol 306 (2) ◽  
pp. G132-G139 ◽  
Author(s):  
Cameron J. McDonald ◽  
Daniel F. Wallace ◽  
Lesa Ostini ◽  
V. Nathan Subramaniam
Keyword(s):  
Iron Homeostasis ◽  
Regulatory System ◽  
Cell Types ◽  
Deficiency Anemia ◽  
Systematic Analysis ◽  
Cellular Iron ◽  
Morphogenetic Protein ◽  
Smad Signaling Pathway ◽  
Associated Proteins ◽  
Different Cell Types

Treatment for iron deficiency anemia can involve iron supplementation via dietary or parenteral routes that result in different cellular iron distributions. The effect of the administered iron on the iron regulatory system and hepcidin in the liver has not been well studied. Hepcidin, the liver-expressed central iron-regulatory peptide, is itself regulated through the bone morphogenetic protein (BMP)/SMAD signaling pathway. Specifically, Bmp6 expression is upregulated in response to iron and induces hepcidin through phosphorylation of Smad1/5/8. The hemochromatosis-associated proteins Hfe and transferrin receptor 2 (Tfr2) are known upstream regulators of hepcidin, although their precise roles are still unclear. To investigate the mechanisms of this regulation and the roles of the Hfe and Tfr2, we subjected wild-type, Hfe−/−, Tfr2−/−, and Hfe−/−/ Tfr2−/− mice to iron loading via dietary or parenteral routes. Systematic analysis demonstrated that Tfr2 is required for effective upregulation of Bmp6 in response to hepatocyte iron, but not nonparenchymal iron. Hfe is not required for Bmp6 upregulation, regardless of iron localization, but rather, is required for efficient downstream transmission of the regulatory signal. Our results demonstrate that Hfe and Tfr2 play separate roles in the regulatory responses to iron compartmentalized in different cell types and further elucidates the regulatory mechanisms controlling iron homeostasis.

A Convenient and Efficient Centrifugation Assay for Comparing Cell Adhesion Strength on Uncharted Surfaces

2020 ◽  
Vol 10 (4) ◽  
pp. 462-468
Author(s):  
Xuan Zhou ◽  
Xin Zhou ◽  
Yichen Du ◽  
Xiaohua Shi ◽  
Pan You ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Strength ◽  
Population Level ◽  
Cell Types ◽  
Laboratory Equipment ◽  
Substrate Adhesion ◽  
Associated Proteins ◽  
Cell Affinity ◽  
Cell Substrate Adhesion ◽  
Different Cell Types

Regulating cell-substrate adhesion is of fundamental importance in biomaterial design and development. While an increasing number of approaches are being developed to quantify cell adhesion strength, only a fraction of these techniques provide measurements that are simple and sensitive at the living cell population level. In our previous study, the expression of adhesion-associated proteins in fibroblasts was found to change on ion-implanted silicone rubber; however, the actual effects of the modified surfaces on cellular mechanical properties remain to be probed. Here, we proposed a convenient method to compare the cell adhesion strength on various surfaces, for multiple adhesion periods and with different cell types. This method requires only common laboratory equipment. In addition, we introduced a new parameter, ECS50, which is appropriate for screening optimum centrifugal conditions when the cell affinity of the surface as a control is initially unknown. This parameter is helpful for further exploration of cell affinity on all the biomaterials of interest. The results demonstrate that this centrifugation assay is simple, efficient and adaptable in investigating the overall adhesion strength of living cells under various conditions, and therefore, it is a valid way to develop adhesion-controlled biointerface materials in the future.

scholarly journals Skeletal muscle hemojuvelin is dispensable for systemic iron homeostasis

Blood ◽  
2011 ◽  
Vol 117 (23) ◽  
pp. 6319-6325 ◽  
Author(s):  
Wenjie Chen ◽  
Franklin W. Huang ◽  
Tomasa Barrientos de Renshaw ◽  
Nancy C. Andrews
Keyword(s):  
Skeletal Muscle ◽  
Iron Homeostasis ◽  
Iron Absorption ◽  
Conditional Knockout ◽  
Dietary Iron ◽  
Iron Release ◽  
Hepcidin Expression ◽  
Morphogenetic Protein ◽  
Smad Signaling Pathway ◽  
Very High

Abstract Hepcidin, a hormone produced mainly by the liver, has been shown to inhibit both intestinal iron absorption and iron release from macrophages. Hemojuvelin, a glycophosphatidyl inositol–linked membrane protein, acts as a bone morphogenetic protein coreceptor to activate hepcidin expression through a SMAD signaling pathway in hepatocytes. In the present study, we show in mice that loss of hemojuvelin specifically in the liver leads to decreased liver hepcidin production and increased tissue and serum iron levels. Although it does not have any known function outside of the liver, hemojuvelin is expressed at very high levels in cardiac and skeletal muscle. To explore possible roles for hemojuvelin in skeletal muscle, we analyzed conditional knockout mice that lack muscle hemojuvelin. The mutant animals had no apparent phenotypic abnormalities. We found that systemic iron homeostasis and liver hepcidin expression were not affected by loss of hemojuvelin in skeletal muscle regardless of dietary iron content. We conclude that, in spite of its expression pattern, hemojuvelin is primarily important in the liver.

scholarly journals TAPping into the treasures of tubulin using novel protein production methods

2018 ◽  
Vol 62 (6) ◽  
pp. 781-792
Author(s):  
Nuo Yu ◽  
Niels Galjart
Keyword(s):  
Mammalian Cells ◽  
Gene Families ◽  
Cell Types ◽  
Cellular Functions ◽  
Tubulin Isotypes ◽  
Associated Proteins ◽  
Cytoskeletal Elements ◽  
Different Cell Types ◽  
Β Tubulin

Microtubules are cytoskeletal elements with important cellular functions, whose dynamic behaviour and properties are in part regulated by microtubule-associated proteins (MAPs). The building block of microtubules is tubulin, a heterodimer of α- and β-tubulin subunits. Longitudinal interactions between tubulin dimers facilitate a head-to-tail arrangement of dimers into protofilaments, while lateral interactions allow the formation of a hollow microtubule tube that mostly contains 13 protofilaments. Highly homologous α- and β-tubulin isotypes exist, which are encoded by multi-gene families. In vitro studies on microtubules and MAPs have largely relied on brain-derived tubulin preparations. However, these consist of an unknown mix of tubulin isotypes with undefined post-translational modifications. This has blocked studies on the functions of tubulin isotypes and the effects of tubulin mutations found in human neurological disorders. Fortunately, various methodologies to produce recombinant mammalian tubulins have become available in the last years, allowing researchers to overcome this barrier. In addition, affinity-based purification of tagged tubulins and identification of tubulin-associated proteins (TAPs) by mass spectrometry has revealed the ‘tubulome’ of mammalian cells. Future experiments with recombinant tubulins should allow a detailed description of how tubulin isotype influences basic microtubule behaviour, and how MAPs and TAPs impinge on tubulin isotypes and microtubule-based processes in different cell types.

scholarly journals Regulation of TMPRSS6 by BMP6 and iron in human cells and mice

Blood ◽  
2011 ◽  
Vol 118 (3) ◽  
pp. 747-756 ◽  
Author(s):  
Delphine Meynard ◽  
Valentina Vaja ◽  
Chia Chi Sun ◽  
Elena Corradini ◽  
Shanzhuo Chen ◽  
...  
Keyword(s):  
Neutralizing Antibody ◽  
Negative Regulator ◽  
Deficiency Anemia ◽  
Hepcidin Expression ◽  
Protein Levels ◽  
Morphogenetic Protein ◽  
Smad Signaling Pathway ◽  
Feedback Inhibitor ◽  
Inhibitor Of Dna Binding

Abstract Mutations in transmembrane protease, serine 6 (TMPRSS6), encoding matriptase-2, are responsible for the familial anemia disorder iron-refractory iron deficiency anemia (IRIDA). Patients with IRIDA have inappropriately elevated levels of the iron regulatory hormone hepcidin, suggesting that TMPRSS6 is involved in negatively regulating hepcidin expression. Hepcidin is positively regulated by iron via the bone morphogenetic protein (BMP)-SMAD signaling pathway. In this study, we investigated whether BMP6 and iron also regulate TMPRSS6 expression. Here we demonstrate that, in vitro, treatment with BMP6 stimulates TMPRSS6 expression at the mRNA and protein levels and leads to an increase in matriptase-2 activity. Moreover, we identify that inhibitor of DNA binding 1 is the key element of the BMP-SMAD pathway to regulate TMPRSS6 expression in response to BMP6 treatment. Finally, we show that, in mice, Tmprss6 mRNA expression is stimulated by chronic iron treatment or BMP6 injection and is blocked by injection of neutralizing antibody against BMP6. Our results indicate that BMP6 and iron not only induce hepcidin expression but also induce TMPRSS6, a negative regulator of hepcidin expression. Modulation of TMPRSS6 expression could serve as a negative feedback inhibitor to avoid excessive hepcidin increases by iron to help maintain tight homeostatic balance of systemic iron levels.

scholarly journals Molecular mechanisms of normal iron homeostasis

Hematology ◽  
2009 ◽  
Vol 2009 (1) ◽  
pp. 207-214 ◽  
Author(s):  
An-Sheng Zhang ◽  
Caroline A. Enns
Keyword(s):  
Iron Homeostasis ◽  
Molecular Mechanisms ◽  
Iron Absorption ◽  
Hypoxia Inducible Factor ◽  
Bmp Signaling ◽  
Control Mechanisms ◽  
Iron Regulatory Proteins ◽  
Hepcidin Expression ◽  
Cellular Iron ◽  
Morphogenetic Protein

Abstract Humans possess elegant control mechanisms to maintain iron homeostasis by coordinately regulating iron absorption, iron recycling, and mobilization of stored iron. Dietary iron absorption is regulated locally by hypoxia inducible factor (HIF) signaling and iron-regulatory proteins (IRPs) in enterocytes and systematically by hepatic hepcidin, the central iron regulatory hormone. Hepcidin not only controls the rate of iron absorption but also determines iron mobilization from stores through negatively modulating the function of ferroportin, the only identified cellular iron exporter to date. The regulation of hepatic hepcidin is accomplished by the coordinated activity of multiple proteins through different signaling pathways. Recent studies have greatly expanded the knowledge in the understanding of hepcidin expression and regulation by the bone morphogenetic protein (BMP) signaling, the erythroid factors, and inflammation. In this review, we mainly focus on the roles of recently identified proteins in the regulation of iron homeostasis.

scholarly journals Subcellular dynamics studies reveal how tissue-specific distribution patterns of iron are established in developing wheat grains

2021 ◽  
Author(s):  
Sadia Sheraz ◽  
Yongfang Wan ◽  
Eudri Venter ◽  
Shailender K Verma ◽  
Qing Xiong ◽  
...  
Keyword(s):  
Iron Homeostasis ◽  
Distribution Patterns ◽  
Cell Types ◽  
Specific Gene ◽  
Tissue Specific ◽  
Iron Trafficking ◽  
Specific Distribution ◽  
Novel Approach ◽  
In Transit ◽  
Different Cell Types

AbstractUnderstanding iron trafficking in plants is key to enhancing the nutritional quality of crops. Due to the difficulty of imaging iron in transit, little is known about iron translocation and distribution in developing seeds. A novel approach, combining 57Fe isotope labelling and NanoSIMS, was used to visualize iron translocation dynamics at the subcellular level in wheat grain, Triticum aestivum L. We were able to track the main route of iron from maternal tissues to the embryo through different cell types. Further evidence for this route was provided by genetically diverting iron into storage vacuoles, as confirmed by histological staining and TEM-EDS. Virtually all iron was found in intracellular bodies, indicating symplastic rather than apoplastic transport. Aleurone cells contained a new type of iron body, highly enriched in 57Fe, and most likely represents iron-nicotianamine being delivered to phytate globoids. Correlation with tissue-specific gene expression provides an updated model of iron homeostasis in cereal grains with relevance for future biofortification efforts.

The Role of Hepcidin in Health And Disease

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. SCI-43-SCI-43
Author(s):  
Martina U. Muckenthaler
Keyword(s):  
Iron Deficiency ◽  
Iron Homeostasis ◽  
Conflicts Of Interest ◽  
Transferrin Saturation ◽  
Regulatory System ◽  
Peptide Hormone ◽  
Cell Types ◽  
Iron Transfer ◽  
Health And Disease

Imbalances of iron homeostasis account for some of the most common human diseases. Pathologies result from both, iron deficiency or overload and frequently affect the hepcidin/ferroportin regulatory system that balances systemic iron metabolism. The small hepatic peptide hormone hepcidin orchestrates systemic iron fluxes and controls plasma iron levels by binding to the iron exporter ferroportin on the surface of iron releasing cells, triggering its degradation and hence reducing iron transfer to transferrin. Hepcidin thus maintains transferrin saturation at physiological levels assuring adequate iron supplies to all cell types. My presentation will focus on mechanisms that control hepcidin and ferroportin expression as well as on pathologies that arise when this key regulatory circuitry underlying systemic iron homeostasis is disrupted. Disclosures No relevant conflicts of interest to declare.

scholarly journals Conditional Derepression of Ferritin Synthesis in Cells Expressing a Constitutive IRP1 Mutant

2002 ◽  
Vol 22 (13) ◽  
pp. 4638-4651 ◽  
Author(s):  
Jian Wang ◽  
Kostas Pantopoulos
Keyword(s):  
Iron Homeostasis ◽  
Regulatory Protein ◽  
Mrna Translation ◽  
Cell Types ◽  
Mrna Levels ◽  
Iron Sulfur Cluster ◽  
Cellular Iron ◽  
Ferritin Synthesis ◽  
Significant Enrichment ◽  
In Cells

ABSTRACT Iron regulatory protein 1 (IRP1), a major posttranscriptional regulator of cellular iron and energy metabolism, is controlled by an iron-sulfur cluster switch. Cysteine-437 is critical for coordinating the cluster, and its replacement yields mutants that do not respond to iron perturbations and constitutively bind to cognate mRNA iron-responsive elements (IREs). The expression of IRP1C437S in cells has been associated with aberrations in iron homeostasis and toxicity. We have established clones of human lung (H1299) and breast (MCF7) cancer cells that express high levels of IRP1C437S in a tetracycline-inducible manner. As expected, IRP1C437S stabilizes transferrin receptor mRNA and inhibits translation of ferritin mRNA in both cell types by binding to their respective IREs. However, H1299 transfectants grown at high densities are able to overcome the IRP1C437S-mediated inhibition in ferritin synthesis. The mechanism involves neither alteration in ferritin mRNA levels nor utilization of alternative transcription start sites to eliminate the IRE or relocate it in less inhibitory downstream positions. The derepression of ferritin mRNA translation occurs under conditions where global protein synthesis appears to be impaired, as judged by a significant enrichment in the expression of the underphosphorylated form of the translational regulator 4E-BP1. Collectively, these data document an example where ferritin mRNA translation evades control of the IRE-IRP system. The physiological implications of this response are reflected in protection against iron-mediated toxicity, oxidative stress, and apoptosis.

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