scholarly journals The role of hepatic transferrin receptor 2 in the regulation of iron homeostasis in the body

2014 ◽  
Vol 5 ◽  
Author(s):  
Christal A. Worthen ◽  
Caroline A. Enns
Keyword(s):  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
The Body ◽  
Transferrin Receptor 2

scholarly journals Normal systemic iron homeostasis in mice with macrophage-specific deletion of transferrin receptor 2

2016 ◽  
Vol 310 (3) ◽  
pp. G171-G180 ◽  
Author(s):  
Gautam Rishi ◽  
Eriza S. Secondes ◽  
Daniel F. Wallace ◽  
V. Nathan Subramaniam
Keyword(s):  
Iron Metabolism ◽  
Knockout Mice ◽  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Essential Element ◽  
Cellular Growth ◽  
Hepatic Expression ◽  
Specific Deletion ◽  
Transferrin Receptor 2

Iron is an essential element, since it is a component of many macromolecules involved in diverse physiological and cellular functions, including oxygen transport, cellular growth, and metabolism. Systemic iron homeostasis is predominantly regulated by the liver through the iron regulatory hormone hepcidin. Hepcidin expression is itself regulated by a number of proteins, including transferrin receptor 2 (TFR2). TFR2 has been shown to be expressed in the liver, bone marrow, macrophages, and peripheral blood mononuclear cells. Studies from our laboratory have shown that mice with a hepatocyte-specific deletion of Tfr2 recapitulate the hemochromatosis phenotype of the global Tfr2 knockout mice, suggesting that the hepatic expression of TFR2 is important in systemic iron homeostasis. It is unclear how TFR2 in macrophages contributes to the regulation of iron metabolism. We examined the role of TFR2 in macrophages by analysis of transgenic mice lacking Tfr2 in macrophages by crossing Tfr2 f/f mice with LysM-Cre mice. Mice were fed an iron-rich diet or injected with lipopolysaccharide to examine the role of macrophage Tfr2 in iron- or inflammation-mediated regulation of hepcidin. Body iron homeostasis was unaffected in the knockout mice, suggesting that macrophage TFR2 is not required for the regulation of systemic iron metabolism. However, peritoneal macrophages of knockout mice had significantly lower levels of ferroportin mRNA and protein, suggesting that TFR2 may be involved in regulating ferroportin levels in macrophages. These studies further elucidate the role of TFR2 in the regulation of iron homeostasis and its role in regulation of ferroportin and thus macrophage iron homeostasis.

scholarly journals Transferrin Receptor 2: Evidence for Ligand-induced Stabilization and Redirection to a Recycling Pathway

2007 ◽  
Vol 18 (3) ◽  
pp. 743-754 ◽  
Author(s):  
Martha B. Johnson ◽  
Juxing Chen ◽  
Nicholas Murchison ◽  
Frank A. Green ◽  
Caroline A. Enns
Keyword(s):  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Mutational Analysis ◽  
Direct Role ◽  
Recycling Endosomes ◽  
Late Endosomes ◽  
Transferrin Receptor 1 ◽  
Diferric Transferrin ◽  
Transferrin Receptor 2

Transferrin receptor 2 (TfR2) is a homologue of transferrin receptor 1 (TfR1), the protein that delivers iron to cells through receptor-mediated endocytosis of diferric transferrin (Fe2Tf). TfR2 also binds Fe2Tf, but it seems to function primarily in the regulation of systemic iron homeostasis. In contrast to TfR1, the trafficking of TfR2 within the cell has not been extensively characterized. Previously, we showed that Fe2Tf increases TfR2 stability, suggesting that trafficking of TfR2 may be regulated by interaction with its ligand. In the present study, therefore, we sought to identify the mode of TfR2 degradation, to characterize TfR2 trafficking, and to determine how Fe2Tf stabilizes TfR2. Stabilization of TfR2 by bafilomycin implies that TfR2 traffics to the lysosome for degradation. Confocal microscopy reveals that treatment of cells with Fe2Tf increases the fraction of TfR2 localizing to recycling endosomes and decreases the fraction of TfR2 localizing to late endosomes. Mutational analysis of TfR2 shows that the mutation G679A, which blocks TfR2 binding to Fe2Tf, increases the rate of receptor turnover and prevents stabilization by Fe2Tf, indicating a direct role of Fe2Tf in TfR2 stabilization. The mutation Y23A in the cytoplasmic domain of TfR2 inhibits its internalization and degradation, implicating YQRV as an endocytic motif.

scholarly journals Erythrocytes: Central Actors in Multiple Scenes of Atherosclerosis

2021 ◽  
Vol 22 (11) ◽  
pp. 5843
Author(s):  
Chloé Turpin ◽  
Aurélie Catan ◽  
Olivier Meilhac ◽  
Emmanuel Bourdon ◽  
François Canonne-Hergaux ◽  
...  
Keyword(s):  
Iron Homeostasis ◽  
The Body ◽  
Diabetic Patients ◽  
Special Focus ◽  
Plaque Progression ◽  
Cell Dysfunction ◽  
Circulating Cells ◽  
The Impact ◽  
Progression Of Atherosclerosis

The development and progression of atherosclerosis (ATH) involves lipid accumulation, oxidative stress and both vascular and blood cell dysfunction. Erythrocytes, the main circulating cells in the body, exert determinant roles in the gas transport between tissues. Erythrocytes have long been considered as simple bystanders in cardiovascular diseases, including ATH. This review highlights recent knowledge concerning the role of erythrocytes being more than just passive gas carriers, as potent contributors to atherosclerotic plaque progression. Erythrocyte physiology and ATH pathology is first described. Then, a specific chapter delineates the numerous links between erythrocytes and atherogenesis. In particular, we discuss the impact of extravasated erythrocytes in plaque iron homeostasis with potential pathological consequences. Hyperglycaemia is recognised as a significant aggravating contributor to the development of ATH. Then, a special focus is made on glycoxidative modifications of erythrocytes and their role in ATH. This chapter includes recent data proposing glycoxidised erythrocytes as putative contributors to enhanced atherothrombosis in diabetic patients.

scholarly journals Variability of the Transferrin Receptor 2 Gene in AMD

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Daniel Wysokinski ◽  
Janusz Blasiak ◽  
Mariola Dorecka ◽  
Marta Kowalska ◽  
Jacek Robaszkiewicz ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Risk Factors ◽  
Transferrin Receptor ◽  
Fenton Reaction ◽  
Iron Homeostasis ◽  
Critical Role ◽  
Age Related Macular Degeneration ◽  
Age Related ◽  
Its Gene ◽  
Transferrin Receptor 2

Oxidative stress is a major factor in the pathogenesis of age-related macular degeneration (AMD). Iron may catalyze the Fenton reaction resulting in overproduction of reactive oxygen species. Transferrin receptor 2 plays a critical role in iron homeostasis and variability in its gene may influence oxidative stress and AMD occurrence. To verify this hypothesis we assessed the association between polymorphisms of theTFR2gene and AMD. A total of 493 AMD patients and 171 matched controls were genotyped for the two polymorphisms of theTFR2gene: c.1892C>T (rs2075674) and c.−258+123T>C (rs4434553). We also assessed the modulation of some AMD risk factors by these polymorphisms. The CC and TT genotypes of the c.1892C>T were associated with AMD occurrence but the latter only in obese patients. The other polymorphism was not associated with AMD occurrence, but the CC genotype was correlated with an increasing AMD frequency in subjects withBMI<26. The TT genotype and the T allele of this polymorphism decreased AMD occurrence in subjects above 72 years, whereas the TC genotype and the C allele increased occurrence of AMD in this group. The c.1892C>T and c.−258+123T>C polymorphisms of theTRF2gene may be associated with AMD occurrence, either directly or by modulation of risk factors.

scholarly journals The Role of the Liver in Iron Homeostasis and What Goes Wrong?

2021 ◽  
Vol 5 (2) ◽  
pp. 26-33
Author(s):  
Ernesto Robalino Gonzaga ◽  
Irene Riestra Guiance ◽  
Richard Henriquez ◽  
Gerri Mortimore ◽  
Jan Freeman
Keyword(s):  
Iron Overload ◽  
Iron Homeostasis ◽  
The Body ◽  
Body Tissues ◽  
Hepatic Iron Overload ◽  
Common Causes ◽  
Physiologic Function ◽  
Normal Cellular Function ◽  
Synthesis Of Hormones

Iron is an essential mineral that is vital for growth development, normal cellular function, synthesis of hormones and connective tissue, and most importantly, serves as a component of hemoglobin to carry oxygen to body tissues. The body finely regulates the amount of circulating and stored iron within the body to maintain concentration levels within range for optimal physiologic function. Without iron, the ability for cells to participate in electron transport and energy metabolism decreases. Furthermore, hemoglobin synthesis is altered, which leads to anemia and decreased oxygen delivery to tissue. Problems arise when there is too little or too much iron. This review explores the role of the liver in iron physiology, iron overload and discusses the most common causes of primary and secondary hepatic iron overload.

scholarly journals Gender biased neuroprotective effect of Transferrin Receptor 2 deletion in multiple models of Parkinson’s disease

2020 ◽  
Author(s):  
Chiara Milanese ◽  
Sylvia Gabriels ◽  
Sander Barnhoorn ◽  
Silvia Cerri ◽  
Ayse Ulusoy ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Substantia Nigra ◽  
Iron Overload ◽  
Transferrin Receptor ◽  
Dopaminergic Neurons ◽  
Iron Homeostasis ◽  
Alpha Synuclein ◽  
Substantia Nigra Pars Compacta ◽  
Transferrin Receptor 2

AbstractAlterations in the metabolism of iron and its accumulation in the substantia nigra pars compacta accompany the pathogenesis of Parkinson’s disease (PD). Changes in iron homeostasis also occur during aging, which constitutes a PD major risk factor. As such, mitigation of iron overload via chelation strategies has been considered a plausible disease modifying approach. Iron chelation, however, is imperfect because of general undesired side effects and lack of specificity; more effective approaches would rely on targeting distinctive pathways responsible for iron overload in brain regions relevant to PD and, in particular, the substantia nigra. We have previously demonstrated that the Transferrin/Transferrin Receptor 2 (TfR2) iron import mechanism functions in nigral dopaminergic neurons, is perturbed in PD models and patients, and therefore constitutes a potential therapeutic target to halt iron accumulation. To validate this hypothesis, we generated mice with targeted deletion of TfR2 in dopaminergic neurons. In these animals, we modeled PD with multiple approaches, based either on neurotoxin exposure or alpha-synuclein proteotoxic mechanisms. We found that TfR2 deletion can provide neuroprotection against dopaminergic degeneration, and against PD- and aging-related iron overload. The effects, however, were significantly more pronounced in females rather than in males. Our data indicate that the TfR2 iron import pathway represents an amenable strategy to hamper PD progression. Data also suggest, however, that therapeutic strategies targeting TfR2 should consider a potential sexual dimorphism in neuroprotective response.

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.

scholarly journals The Functional Versatility of Transferrin Receptor 2 and Its Therapeutic Value

2018 ◽  
Vol 11 (4) ◽  
pp. 115 ◽  
Author(s):  
Antonella Roetto ◽  
Mariarosa Mezzanotte ◽  
Rosa Pellegrino
Keyword(s):  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Iron Regulation ◽  
Role Taking ◽  
Therapeutic Value ◽  
Living Organisms ◽  
Type 3 ◽  
Functional Versatility ◽  
Transferrin Receptor 2

Iron homeostasis is a tightly regulated process in all living organisms because this metal is essential for cellular metabolism, but could be extremely toxic when present in excess. In mammals, there is a complex pathway devoted to iron regulation, whose key protein is hepcidin (Hepc), which is a powerful iron absorption inhibitor mainly produced by the liver. Transferrin receptor 2 (Tfr2) is one of the hepcidin regulators, and mutations in TFR2 gene are responsible for type 3 hereditary hemochromatosis (HFE3), a genetically heterogeneous disease characterized by systemic iron overload. It has been recently pointed out that Hepc production and iron regulation could be exerted also in tissues other than liver, and that Tfr2 has an extrahepatic role in iron metabolism as well. This review summarizes all the most recent data on Tfr2 extrahepatic role, taking into account the putative distinct roles of the two main Tfr2 isoforms, Tfr2α and Tfr2β. Representing Hepc modulation an effective approach to correct iron balance impairment in common human diseases, and with Tfr2 being one of its regulators, it would be worthwhile to envisage Tfr2 as a therapeutic target.

scholarly journals Role of Dietary Flavonoids in Iron Homeostasis

2019 ◽  
Vol 12 (3) ◽  
pp. 119 ◽  
Author(s):  
Marija Lesjak ◽  
Surjit K. S. Srai
Keyword(s):  
Iron Metabolism ◽  
Iron Homeostasis ◽  
Iron Absorption ◽  
Therapeutic Potential ◽  
State Of The Art ◽  
Iron Status ◽  
Dietary Factors ◽  
The Body ◽  
Dietary Flavonoids

Balancing systemic iron levels within narrow limits is critical for human health, as both iron deficiency and overload lead to serious disorders. There are no known physiologically controlled pathways to eliminate iron from the body and therefore iron homeostasis is maintained by modifying dietary iron absorption. Several dietary factors, such as flavonoids, are known to greatly affect iron absorption. Recent evidence suggests that flavonoids can affect iron status by regulating expression and activity of proteins involved the systemic regulation of iron metabolism and iron absorption. We provide an overview of the links between different dietary flavonoids and iron homeostasis together with the mechanism of flavonoids effect on iron metabolism. In addition, we also discuss the clinical relevance of state-of-the-art knowledge regarding therapeutic potential that flavonoids may have for conditions that are low in iron such as anaemia or iron overload diseases.

Diferric transferrin regulates transferrin receptor 2 protein stability

Blood ◽  
2004 ◽  
Vol 104 (13) ◽  
pp. 4287-4293 ◽  
Author(s):  
Martha B. Johnson ◽  
Caroline A. Enns
Keyword(s):  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Transmembrane Protein ◽  
Hereditary Hemochromatosis ◽  
Pcr Analysis ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Diferric Transferrin ◽  
In Cells ◽  
Transferrin Receptor 2

Abstract Transferrin receptor 2 (TfR2) is a type 2 transmembrane protein expressed in hepatocytes that binds iron-bound transferrin (Tf). Mutations in TfR2 cause one form of hereditary hemochromatosis, a disease in which excessive absorption of dietary iron can lead to liver cirrhosis, diabetes, arthritis, and heart failure. The function of TfR2 in iron homeostasis is unknown. We have studied the regulation of TfR2 in HepG2 cells. Western blot analysis shows that TfR2 increases in a time- and dose-dependent manner after diferric Tf is added to the culture medium. In cells exposed to diferric Tf, the amount of TfR2 returns to control levels within 8 hours after the removal of diferric Tf from the medium. However, TfR2 does not increase when non–Tf-bound iron (FeNTA) or apo Tf is added to the medium. The response to diferric Tf appears to be hepatocyte specific. Real-time quantitative reverse transcription–polymerase chain reaction (qRT-PCR) analysis shows that TfR2 mRNA levels do not change in cells exposed to diferric Tf. Rather, the increase in TfR2 is attributed to an increase in the half-life of TfR2 protein in cells exposed to diferric Tf. Our results support a role for TfR2 in monitoring iron levels by sensing changes in the concentration of diferric Tf.

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