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Clara Camaschella - One of the best experts on this subject based on the ideXlab platform.
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Targeting Transferrin Receptor 2: A Novel Erythropoiesis-Stimulating Approach in a Model of Anemia of Chronic Kidney Disease
Blood, 2019Co-Authors: Violante Olivari, Laura Silvestri, Clara Camaschella, Maria Rosa Lidonnici, Mariateresa Pettinato, Giuliana Ferrari, Antonella NaiAbstract:Introduction Anemia is a common and invalidating complication of chronic kidney disease (CKD) mainly due to the impaired erythropoietin (EPO) production that parallels the progression of kidney failure. The current treatment, based on erythropoiesis-stimulating agents (ESA), is far from optimal, because of potential off-target side effects. The same holds true for HIF-stabilizers tested in phase 3 clinical trials. For this reason, the identification of agents that selectively boost erythropoiesis would be of great benefit. Transferrin Receptor 2 (TFR2) is a protein expressed in hepatocytes, where it modulates iron homeostasis activating hepcidin production, and in erythroid cells, where it acts as a partner of erythropoietin (EPO) Receptor decreasing EPO signaling. Tfr2 deletion in the liver causes iron overload due to low hepcidin levels, while its deletion in erythroid compartment enhances erythropoiesis through increased EPO sensitivity. Aim The study aims at exploring whether erythroid TFR2 is a potential therapeutic target in anemia of CKD, characterized by reduced EPO production and function. Methods CKD was induced by feeding animals an adenine-rich diet for 8 weeks. The protocol was applied to both wild-type animals, to set-up the system, and to mice with genetic bone marrow Tfr2 deletion (Tfr2BMKO). Complete blood count (CBC) and serum urea were evaluated every 2 weeks during the entire protocol. At the end of the 8 weeks animals were sacrificed and a complete phenotypic analysis of hematological parameters, renal damage and iron homeostasis was performed. Results Wild-type mice fed the adenine diet showed renal damage and inflammation, anemia and iron restriction, recapitulating the main features of human CKD. Renal damage and iron restriction were similar between Tfr2BMKO and control mice, excluding a differential effect of the diet on the two genotypes. Tfr2BMKO mice maintained higher red blood cell count relative to controls for the entire timespan. Hemoglobin levels were higher in Tfr2BMKO mice for 6 weeks, while reached levels of controls at 8 weeks. Based on these findings we conclude that BM Tfr2deletion, increasing EPO sensitivity of erythroid cells, improves erythropoiesis and anemia until iron levels remains adequate. Conclusions We confirm that the adenine-induced murine model of CKD can be a suitable tool for the study of the pathophysiology of renal anemia and for the identification and validation of novel potential therapeutic approaches. More importantly, our results suggest that targeting Tfr2 could become a novel approach to ameliorate anemia of CKD. Given the TFR2 restricted expression, its inactivation would enhance EPO responsiveness selectively in erythroid cells, minimizing the risk of side effects. Targeting erythroid Tfr2 might be considered a novel "erythropoiesis-stimulating approach", likely applicable to other forms of anemia due to insufficient EPO stimulation and response. Disclosures Camaschella: Celgene: Consultancy; Vifor Iron Core: Consultancy; Novartis: Consultancy.
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Transferrin Receptor 2 is a potential novel therapeutic target for β-thalassemia: evidence from a murine model.
Blood, 2018Co-Authors: Irene Artuso, Laura Silvestri, Clara Camaschella, Maria Rosa Lidonnici, Sandro Altamura, Giacomo Mandelli, Mariateresa Pettinato, Martina U. Muckenthaler, Giuliana Ferrari, Antonella NaiAbstract:β-thalassemias are genetic disorders characterized by anemia, ineffective erythropoiesis, and iron overload. Current treatment of severe cases is based on blood transfusion and iron chelation or allogeneic bone marrow (BM) transplantation. Novel approaches are explored for nontransfusion-dependent patients (thalassemia intermedia) who develop anemia and iron overload. Here, we investigated the erythropoietin (EPO) Receptor partner, Transferrin Receptor 2 (TFR2), as a novel potential therapeutic target. We generated a murine model of thalassemia intermedia specifically lacking BM Tfr2: because their erythroid cells are more susceptible to EPO stimulation, mice show improved erythropoiesis and red blood cell morphology as well as partial correction of anemia and iron overload. The beneficial effects become attenuated over time, possibly due to insufficient iron availability to sustain the enhanced erythropoiesis. Germ line deletion of Tfr2, including haploinsufficiency, had a similar effect in the thalassemic model. Because targeting TFR2 enhances EPO-mediated effects exclusively in cells expressing both Receptors, this approach may have advantages over erythropoiesis-stimulating agents in the treatment of other anemias.
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Transferrin Receptor 2 mutations in patients with juvenile hemochromatosis phenotype
American journal of hematology, 2015Co-Authors: Giulia Ravasi, Laura Silvestri, Marco Rausa, Raffaella Mariani, Sara Pelucchi, Cristina Arosio, Federico Greni, Irene Pelloni, Pedro Pineda, Clara CamaschellaAbstract:Artículo de publicación IS
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Regulation of cell surface Transferrin Receptor-2 by iron-dependent cleavage and release of a soluble form
Haematologica, 2015Co-Authors: Alessia Pagani, Antonella Nai, Clara Camaschella, Marco Rausa, Maud Vieillevoye, Meriem Ladli, Catherine Lacombe, Patrick Mayeux, Frédérique Verdier, Laura SilvestriAbstract:Transferrin Receptor-2 is a transmembrane protein whose expression is restricted to hepatocytes and erythroid cells. Transferrin Receptor-2 has a regulatory function in iron homeostasis, since its inactivation causes systemic iron overload. Hepatic Transferrin Receptor-2 participates in iron sensing and is involved in hepcidin activation, although the mechanism remains unclear. Erythroid Transferrin Receptor-2 associates with and stabilizes erythropoietin Receptors on the erythroblast surface and is essential to control erythrocyte production in iron deficiency. We identified a soluble form of Transferrin Receptor-2 in the media of transfected cells and showed that cultured human erythroid cells release an endogenous soluble form. Soluble Transferrin Receptor-2 originates from a cleavage of the cell surface protein, which is inhibited by diferric Transferrin in a dose-dependent manner. Accordingly, the shedding of the Transferrin Receptor-2 variant G679A, mutated in the Arginine-Glycine-Aspartic acid motif and unable to bind diferric Transferrin, is not modulated by the ligand. This observation links the process of Transferrin Receptor-2 removal from the plasma membrane to iron homeostasis. Soluble Transferrin Receptor-2 does not affect the binding of erythropoietin to erythropoietin Receptor or the consequent signaling and partially inhibits hepcidin promoter activation only in vitro. Whether it is a component of the signals released by erythropoiesis in iron deficiency remains to be investigated. Our results indicate that membrane Transferrin Receptor-2, a sensor of circulating iron, is released from the cell membrane in iron deficiency.
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The erythroid function of Transferrin Receptor 2 revealed by Tmprss6 inactivation in different models of Transferrin Receptor 2 knockout mice.
Haematologica, 2014Co-Authors: Antonella Nai, Alessia Pagani, Laura Silvestri, Marco Rausa, Rosa Maria Pellegrino, Martina Boero, Giuseppe Saglio, Antonella Roetto, Clara CamaschellaAbstract:Transferrin Receptor 2 (TFR2) is a transmembrane glycoprotein expressed in the liver and in the erythroid compartment, mutated in a form of hereditary hemochromatosis. Hepatic TFR2, together with HFE, activates the transcription of the iron-regulator hepcidin, while erythroid TFR2 is a member of the erythropoietin Receptor complex. The TMPRSS6 gene, encoding the liver-expressed serine protease matriptase-2, is the main inhibitor of hepcidin and inactivation of TMPRSS6 leads to iron deficiency with high hepcidin levels. Here we evaluate the phenotype resulting from the genetic loss of Tmprss6 in Tfr2 total (Tfr2−/−) and liver-specific (Tfr2LCKO) knockout mice. Tmprss6−/−Tfr2−/− and Tmprss6−/−Tfr2LCKO mice have increased hepcidin levels and show iron-deficiency anemia like Tmprss6−/−mice. However, while Tmprss6−/−Tfr2LCKO are phenotypically identical to Tmprss6−/− mice, Tmprss6−/−Tfr2−/− mice have increased red blood cell count and more severe microcytosis than Tmprss6−/− mice. In addition hepcidin expression in Tmprss6−/−Tfr2−/− mice is higher than in the wild-type animals, but lower than in Tmprss6−/− mice, suggesting partial inhibition of the hepcidin activating pathway. Our results prove that hepatic TFR2 acts upstream of TMPRSS6. In addition Tfr2 deletion causes a relative erythrocytosis in iron-deficient mice, which likely attenuates the effect of over-expression of hepcidin in Tmprss6−/− mice. Since liver-specific deletion of Tfr2 in Tmprss6−/− mice does not modify the erythrocyte count, we speculate that loss of Tfr2 in the erythroid compartment accounts for the hematologic phenotype of Tmprss6−/−Tfr2−/− mice. We propose that TFR2 is a limiting factor for erythropoiesis, particularly in conditions of iron restriction.
Caroline A. Enns - One of the best experts on this subject based on the ideXlab platform.
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Extrahepatic deficiency of Transferrin Receptor 2 is associated with increased erythropoiesis independent of iron overload.
The Journal of biological chemistry, 2020Co-Authors: Aaron M. Wortham, An Sheng Zhang, Devorah C. Goldman, Juxjing Chen, William H. Fleming, Caroline A. EnnsAbstract:Transferrin Receptor 2 (TFR2) is a transmembrane protein expressed mainly in hepatocytes and in developing erythroid cells and is an important focal point in systemic iron regulation. Loss of TFR2 function results in a rare form of the iron-overload disease hereditary hemochromatosis. Although TFR2 in the liver has been shown to be important for regulating iron homeostasis in the body, TFR2's function in erythroid progenitors remains controversial. In this report, we analyzed TFR2-deficient mice in the presence or absence of iron overload to distinguish between the effects caused by a high iron load and those caused by loss of TFR2 function. Analysis of bone marrow from TFR2-deficient mice revealed a reduction in the early burst-forming unit-erythroid and an expansion of late-stage erythroblasts that was independent of iron overload. Spleens of TFR2-deficient mice displayed an increase in colony-forming unit-erythroid progenitors and in all erythroblast populations regardless of iron overload. This expansion of the erythroid compartment coincided with increased erythroferrone (ERFE) expression and serum erythropoietin (EPO) levels. Rescue of hepatic TFR2 expression normalized hepcidin expression and the total cell count of the bone marrow and spleen, but it had no effect on erythroid progenitor frequency. On the basis of these results, we propose a model of TFR2's function in murine erythropoiesis, indicating that deficiency in this Receptor is associated with increased erythroid development and expression of EPO and ERFE in extrahepatic tissues independent of TFR's role in the liver.
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CD81 Promotes Both the Degradation of Transferrin Receptor 2 (TfR2) and the Tfr2-mediated Maintenance of Hepcidin Expression *
The Journal of biological chemistry, 2015Co-Authors: Juxing Chen, Caroline A. EnnsAbstract:Mutations in Transferrin Receptor 2 (TfR2) cause a rare form of the hereditary hemochromatosis, resulting in iron overload predominantly in the liver. TfR2 is primarily expressed in hepatocytes and is hypothesized to sense iron levels in the blood to positively regulate the expression of hepcidin through activation of the BMP signaling pathway. Hepcidin is a peptide hormone that negatively regulates iron egress from cells and thus limits intestinal iron uptake. In this study, a yeast two-hybrid approach using the cytoplasmic domain of TfR2 identified CD81 as an interacting protein. CD81 is an abundant tetraspanin in the liver. Co-precipitations of CD81 with different TfR2 constructs demonstrated that both the cytoplasmic and ecto-transmembrane domains of TfR2 interact with CD81. Knockdown of CD81 using siRNA significantly increased TfR2 levels by increasing the half-life of TfR2, indicating that CD81 promotes degradation of TfR2. Previous studies showed that CD81 is targeted for degradation by GRAIL, an ubiquitin E3 ligase. Knockdown of GRAIL in Hep3B-TfR2 cells increased TfR2 levels, consistent with inhibition of CD81 ubiquitination. These results suggest that down-regulation of CD81 by GRAIL targets TfR2 for degradation. Surprisingly, knockdown of CD81 decreased hepcidin expression, implying that the TfR2/CD81 complex is involved in the maintenance of hepcidin mRNA. Moreover, knockdown of CD81 did not affect the stimulation of hepcidin expression by BMP6 but increased both the expression of ID1 and SMAD7, direct targets of BMP signaling pathway, and the phosphorylation of ERK1/2, indicating that the CD81 regulates hepcidin expression differently from the BMP and ERK1/2 signaling pathways.
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The role of hepatic Transferrin Receptor 2 in the regulation of iron homeostasis in the body.
Frontiers in pharmacology, 2014Co-Authors: Christal Worthen, Caroline A. EnnsAbstract:Fine-tuning of body iron is required to prevent diseases such as iron-overload and anemia. The putative iron sensor, Transferrin Receptor 2 (TfR2), is expressed in the liver and mutations in this protein result in the iron-overload disease Type III hereditary hemochromatosis (HH). With the loss of functional TfR2, the liver produces about 2-fold less of the peptide hormone hepcidin, which is responsible for negatively regulating iron uptake from the diet. This reduction in hepcidin expression leads to the slow accumulation of iron in the liver, heart, joints, and pancreas and subsequent cirrhosis, heart disease, arthritis, and diabetes. TfR2 can bind iron-loaded Transferrin (Tf) in the bloodstream, and hepatocytes treated with Tf respond with a 2-fold increase in hepcidin expression through stimulation of the bone morphogenetic protein (BMP)-signaling pathway. Loss of functional TfR2 or its binding partner, the original HH protein, results in a loss of this Transferrin-sensitivity. While much is known about the trafficking and regulation of TfR2, the mechanism of its Transferrin-sensitivity through the BMP-signaling pathway is still not known.
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n linked glycosylation is required for Transferrin induced stabilization of Transferrin Receptor 2 but not for Transferrin binding or trafficking to the cell surface
Biochemistry, 2013Co-Authors: Ningning Zhao, Caroline A. EnnsAbstract:Transferrin Receptor 2 (TfR2) is a member of the Transferrin Receptor-like family of proteins. Mutations in TfR2 can lead to a rare form of the iron overload disease, hereditary hemochromatosis. TfR2 is proposed to sense body iron levels and increase the level of expression of the iron regulatory hormone, hepcidin. Human TfR2 (hTfR2) contains four potential Asn-linked (N-linked) glycosylation sites on its ectodomain. The importance of glycosylation in TfR2 function has not been elucidated. In this study, by employing site-directed mutagenesis to remove glycosylation sites of hTfR2 individually or in combination, we found that hTfR2 was glycosylated at Asn 240, 339, and 754, while the consensus sequence for N-linked glycosylation at Asn 540 was not utilized. Cell surface protein biotinylation and biotin-labeled Tf indicated that in the absence of N-linked oligosaccharides, hTfR2 still moved to the plasma membrane and bound its ligand, holo-Tf. However, without N-linked glycosylation, hTfR2 did not form the...
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N-linked glycosylation is required for Transferrin-induced stabilization of Transferrin Receptor 2, but not for Transferrin binding or trafficking to the cell surface.
Biochemistry, 2013Co-Authors: Ningning Zhao, Caroline A. EnnsAbstract:Transferrin Receptor 2 (TfR2) is a member of the Transferrin Receptor-like family of proteins. Mutations in TfR2 can lead to a rare form of the iron overload disease, hereditary hemochromatosis. TfR2 is proposed to sense body iron levels and increase the level of expression of the iron regulatory hormone, hepcidin. Human TfR2 (hTfR2) contains four potential Asn-linked (N-linked) glycosylation sites on its ectodomain. The importance of glycosylation in TfR2 function has not been elucidated. In this study, by employing site-directed mutagenesis to remove glycosylation sites of hTfR2 individually or in combination, we found that hTfR2 was glycosylated at Asn 240, 339, and 754, while the consensus sequence for N-linked glycosylation at Asn 540 was not utilized. Cell surface protein biotinylation and biotin-labeled Tf indicated that in the absence of N-linked oligosaccharides, hTfR2 still moved to the plasma membrane and bound its ligand, holo-Tf. However, without N-linked glycosylation, hTfR2 did not form the intersubunit disulfide bonds as efficiently as the wild type (WT). Moreover, the unglycosylated form of hTfR2 could not be stabilized by holo-Tf. We further provide evidence that the unglycosylated hTfR2 behaved in manner different from that of the WT in response to holo-Tf treatment. Thus, the putative iron-sensing function of TfR2 could not be achieved in the absence of N-linked oligosaccharides. On the basis of our analyses, we conclude that unlike TfR1, N-linked glycosylation is dispensable for the cell surface expression and holo-Tf binding, but it is required for efficient intersubunit disulfide bond formation and holo-Tf-induced stabilization of TfR2.
V. Nathan Subramaniam - One of the best experts on this subject based on the ideXlab platform.
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Gender biased neuroprotective effect of Transferrin Receptor 2 deletion in multiple models of Parkinson’s disease
Cell Death & Differentiation, 2020Co-Authors: Chiara Milanese, Daniel F. Wallace, Sylvia Gabriels, Sander Barnhoorn, Silvia Cerri, Ayse Ulusoy, S. V. Gornati, Fabio Blandini, Donato A. Di Monte, V. Nathan SubramaniamAbstract:Alterations 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.
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Gender biased neuroprotective effect of Transferrin Receptor 2 deletion in multiple models of Parkinson's disease.
Cell death and differentiation, 2020Co-Authors: Chiara Milanese, Daniel F. Wallace, Sylvia Gabriels, Sander Barnhoorn, Silvia Cerri, Ayse Ulusoy, S. V. Gornati, Fabio Blandini, Donato A. Di Monte, V. Nathan SubramaniamAbstract:Alterations 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.
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Hematopoietic deletion of Transferrin Receptor 2 in mice leads to a block in erythroid differentiation during iron-deficient anemia
American journal of hematology, 2016Co-Authors: Gautam Rishi, Daniel F. Wallace, Eriza S Secondes, V. Nathan SubramaniamAbstract:Iron metabolism and erythropoiesis are inherently interlinked physiological processes. Regulation of iron metabolism is mediated by the iron-regulatory hormone hepcidin. Hepcidin limits the amount of iron released into the blood by binding to and causing the internalization of the iron exporter, ferroportin. A number of molecules and physiological stimuli, including erythropoiesis, are known to regulate hepcidin. An increase in erythropoietic demand decreases hepcidin, resulting in increased bioavailable iron in the blood. Transferrin Receptor 2 (TFR2) is involved in the systemic regulation of iron metabolism. Patients and mice with mutations in TFR2 develop hemochromatosis due to inappropriate hepcidin levels relative to body iron. Recent studies from our laboratory and others have suggested an additional role for TFR2 in response to iron-restricted erythropoiesis. These studies used mouse models with perturbed systemic iron metabolism: anemic mice lacking matriptase-2 and Tfr2, or bone marrow transplants from iron-loaded Tfr2 null mice. We developed a novel transgenic mouse model which lacks Tfr2 in the hematopoietic compartment, enabling the delineation of the role of Tfr2 in erythroid development without interfering with its role in systemic iron metabolism. We show that in the absence of hematopoietic Tfr2 immature polychromatic erythroblasts accumulate with a concordant reduction in the percentage of mature erythroid cells in the spleen and bone marrow of anemic mice. These results demonstrate that erythroid Tfr2 is essential for an appropriate erythropoietic response in iron-deficient anemia. These findings may be of relevance in clinical situations in which an immediate and efficient erythropoietic response is required. Am. J. Hematol. 91:812-818, 2016. © 2016 Wiley Periodicals, Inc.
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Normal systemic iron homeostasis in mice with macrophage-specific deletion of Transferrin Receptor 2
American journal of physiology. Gastrointestinal and liver physiology, 2015Co-Authors: Gautam Rishi, Daniel F. Wallace, Eriza S Secondes, V. Nathan SubramaniamAbstract: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.
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An Essential Role For Transferrin Receptor 2 In Erythropoiesis During Iron Restriction
Blood, 2013Co-Authors: Daniel F. Wallace, Eriza S Secondes, Gautam Rishi, L Ostini, Cameron J Mcdonald, John D Hooper, Gloria Velasco, Andrew J. Ramsay, Carlos López-otín, V. Nathan SubramaniamAbstract:Iron deficiency and iron overload are common clinical conditions that impact on the health and wellbeing of up to 30% of the world’s population. Understanding mechanisms regulating iron homeostasis will provide improved strategies for treating these disorders. The liver-expressed proteins matriptase-2 (encoded by TMPRSS6 ), HFE and Transferrin Receptor 2 (TFR2) play important and opposing roles in systemic iron homeostasis by regulating expression of the iron regulatory hormone hepcidin. Mutations in TMPRSS6 lead to iron refractory iron deficiency anemia, whereas mutations in HFE and TFR2 lead to the iron overload disorder hereditary hemochromatosis. To elucidate the competing roles of these hepcidin regulators, we created mice lacking matriptase-2, Hfe and Tfr2. Tmprss6 -/-/ Hfe -/-/ Tfr2 -/- mice had iron deficiency anemia resulting from hepatic hepcidin over-expression and activation of Smad1/5/8, indicating that matriptase-2 predominates over Hfe and Tfr2 in hepcidin regulation. Surprisingly, this anemia was more severe than in the Tmprss6 -/- mice, demonstrated by more extensive alopecia, lower hematocrit and significant extramedullary erythropoiesis in the spleen. There was increased expression of erythroid-specific genes in the spleens of Tmprss6 -/-/ Hfe -/-/ Tfr2 -/- mice, consistent with the extramedullary erythropoiesis. Expression of Tfr2 but not Hfe in the spleen was increased in the Tmprss6 -/- mice compared to wild type and correlated with the expression of erythroid genes, suggesting that Tfr2 is expressed in erythroid cells. Further analysis of gene expression in the bone marrow suggests that the loss of Tfr2 in the erythroid cells of Tmprss6 -/-/ Hfe -/-/ Tfr2 -/- mice causes a delay in the differentiation process leading to a more severe phenotype. In conclusion, our results indicate that Hfe and Tfr2 act upstream of matriptase-2 in hepcidin regulation or in a way that is overridden when matriptase-2 is deleted. These results indicate that inhibition of matriptase-2 would be useful in the treatment of iron overload conditions such as hereditary hemochromatosis. We have also identified a novel role for Tfr2 in erythroid differentiation that is separate from its canonical role as a regulator of iron homeostasis in the liver. This important role of Tfr2 in erythropoiesis only becomes apparent during conditions of iron restriction. Our results provide novel insights into mechanisms regulating and linking iron homeostasis and erythropoiesis. Disclosures: No relevant conflicts of interest to declare.
Daniel F. Wallace - One of the best experts on this subject based on the ideXlab platform.
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Gender biased neuroprotective effect of Transferrin Receptor 2 deletion in multiple models of Parkinson’s disease
Cell Death & Differentiation, 2020Co-Authors: Chiara Milanese, Daniel F. Wallace, Sylvia Gabriels, Sander Barnhoorn, Silvia Cerri, Ayse Ulusoy, S. V. Gornati, Fabio Blandini, Donato A. Di Monte, V. Nathan SubramaniamAbstract:Alterations 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.
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Gender biased neuroprotective effect of Transferrin Receptor 2 deletion in multiple models of Parkinson's disease.
Cell death and differentiation, 2020Co-Authors: Chiara Milanese, Daniel F. Wallace, Sylvia Gabriels, Sander Barnhoorn, Silvia Cerri, Ayse Ulusoy, S. V. Gornati, Fabio Blandini, Donato A. Di Monte, V. Nathan SubramaniamAbstract:Alterations 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.
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hematopoietic deletion of Transferrin Receptor 2 in mice leads to a block in erythroid differentiation during iron deficient anemia
American Journal of Hematology, 2016Co-Authors: Daniel F. Wallace, Eriza S Secondes, Gautam Rishi, Nathan V SubramaniamAbstract:Iron metabolism and erythropoiesis are inherently interlinked physiological processes. Regulation of iron metabolism is mediated by the iron-regulatory hormone hepcidin. Hepcidin limits the amount of iron released into the blood by binding to and causing the internalization of the iron exporter, ferroportin. A number of molecules and physiological stimuli, including erythropoiesis, are known to regulate hepcidin. An increase in erythropoietic demand decreases hepcidin, resulting in increased bioavailable iron in the blood. Transferrin Receptor 2 (TFR2) is involved in the systemic regulation of iron metabolism. Patients and mice with mutations in TFR2 develop hemochromatosis due to inappropriate hepcidin levels relative to body iron. Recent studies from our laboratory and others have suggested an additional role for TFR2 in response to iron-restricted erythropoiesis. These studies used mouse models with perturbed systemic iron metabolism: anemic mice lacking matriptase-2 and Tfr2, or bone marrow transplants from iron-loaded Tfr2 null mice. We developed a novel transgenic mouse model which lacks Tfr2 in the hematopoietic compartment, enabling the delineation of the role of Tfr2 in erythroid development without interfering with its role in systemic iron metabolism. We show that in the absence of hematopoietic Tfr2 immature polychromatic erythroblasts accumulate with a concordant reduction in the percentage of mature erythroid cells in the spleen and bone marrow of anemic mice. These results demonstrate that erythroid Tfr2 is essential for an appropriate erythropoietic response in iron-deficient anemia. These findings may be of relevance in clinical situations in which an immediate and efficient erythropoietic response is required.
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Hematopoietic deletion of Transferrin Receptor 2 in mice leads to a block in erythroid differentiation during iron-deficient anemia
American journal of hematology, 2016Co-Authors: Gautam Rishi, Daniel F. Wallace, Eriza S Secondes, V. Nathan SubramaniamAbstract:Iron metabolism and erythropoiesis are inherently interlinked physiological processes. Regulation of iron metabolism is mediated by the iron-regulatory hormone hepcidin. Hepcidin limits the amount of iron released into the blood by binding to and causing the internalization of the iron exporter, ferroportin. A number of molecules and physiological stimuli, including erythropoiesis, are known to regulate hepcidin. An increase in erythropoietic demand decreases hepcidin, resulting in increased bioavailable iron in the blood. Transferrin Receptor 2 (TFR2) is involved in the systemic regulation of iron metabolism. Patients and mice with mutations in TFR2 develop hemochromatosis due to inappropriate hepcidin levels relative to body iron. Recent studies from our laboratory and others have suggested an additional role for TFR2 in response to iron-restricted erythropoiesis. These studies used mouse models with perturbed systemic iron metabolism: anemic mice lacking matriptase-2 and Tfr2, or bone marrow transplants from iron-loaded Tfr2 null mice. We developed a novel transgenic mouse model which lacks Tfr2 in the hematopoietic compartment, enabling the delineation of the role of Tfr2 in erythroid development without interfering with its role in systemic iron metabolism. We show that in the absence of hematopoietic Tfr2 immature polychromatic erythroblasts accumulate with a concordant reduction in the percentage of mature erythroid cells in the spleen and bone marrow of anemic mice. These results demonstrate that erythroid Tfr2 is essential for an appropriate erythropoietic response in iron-deficient anemia. These findings may be of relevance in clinical situations in which an immediate and efficient erythropoietic response is required. Am. J. Hematol. 91:812-818, 2016. © 2016 Wiley Periodicals, Inc.
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Normal systemic iron homeostasis in mice with macrophage-specific deletion of Transferrin Receptor 2
2016Co-Authors: Gautam Rishi, Daniel F. Wallace, Eriza S Secondes, V N SubramaniamAbstract: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 Tfr2f/f mice with LysMCre 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. © 2016 the American Physiological Society.
Antonella Roetto - One of the best experts on this subject based on the ideXlab platform.
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Transferrin Receptor 2 controls bone mass and pathological bone formation via BMP and Wnt signaling.
Nature metabolism, 2019Co-Authors: Martina Rauner, Rosa Maria Pellegrino, Antonella Roetto, Ulrike Baschant, Sandra Rother, Juliane Salbach-hirsch, Heike Weidner, Vera Hintze, Graeme M. Campbell, Andreas PetzoldAbstract:Transferrin Receptor 2 (Tfr2) is mainly expressed in the liver and controls iron homeostasis. Here, we identify Tfr2 as a regulator of bone homeostasis that inhibits bone formation. Mice lacking Tfr2 display increased bone mass and mineralization independent of iron homeostasis and hepatic Tfr2. Bone marrow transplantation experiments and studies of cell-specific Tfr2 knockout mice demonstrate that Tfr2 impairs BMP-p38MAPK signaling and decreases expression of the Wnt inhibitor sclerostin specifically in osteoblasts. Reactivation of MAPK or overexpression of sclerostin rescues skeletal abnormalities in Tfr2 knockout mice. We further show that the extracellular domain of Tfr2 binds BMPs and inhibits BMP-2-induced heterotopic ossification by acting as a decoy Receptor. These data indicate that Tfr2 limits bone formation by modulating BMP signaling, possibly through direct interaction with BMP either as a Receptor or as a co-Receptor in a complex with other BMP Receptors. Finally, the Tfr2 extracellular domain may be effective in the treatment of conditions associated with pathological bone formation.
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The Functional Versatility of Transferrin Receptor 2 and Its Therapeutic Value.
Pharmaceuticals (Basel Switzerland), 2018Co-Authors: Antonella Roetto, Mariarosa Mezzanotte, Rosa Maria PellegrinoAbstract: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.
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Transferrin Receptor 2 Dependent Alterations of Brain Iron Metabolism Affect Anxiety Circuits in the Mouse.
Scientific reports, 2016Co-Authors: Rosa Maria Pellegrino, Martina Boero, Giuseppe Saglio, Mariarosa Mezzanotte, Enrica Boda, Francesca Montarolo, Annalisa Buffo, Antonella RoettoAbstract:The Transferrin Receptor 2 (Tfr2) modulates systemic iron metabolism through the regulation of iron regulator Hepcidin (Hepc) and Tfr2 inactivation causes systemic iron overload. Based on data demonstrating Tfr2 expression in brain, we analysed Tfr2-KO mice in order to examine the molecular, histological and behavioural consequences of Tfr2 silencing in this tissue. Tfr2 abrogation caused an accumulation of iron in specific districts in the nervous tissue that was not accompanied by a brain Hepc response. Moreover, Tfr2-KO mice presented a selective overactivation of neurons in the limbic circuit and the emergence of an anxious-like behaviour. Furthermore, microglial cells showed a particular sensitivity to iron perturbation. We conclude that Tfr2 is a key regulator of brain iron homeostasis and propose a role for Tfr2 alpha in the regulation of anxiety circuits.
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The erythroid function of Transferrin Receptor 2 revealed by Tmprss6 inactivation in different models of Transferrin Receptor 2 knockout mice.
Haematologica, 2014Co-Authors: Antonella Nai, Alessia Pagani, Laura Silvestri, Marco Rausa, Rosa Maria Pellegrino, Martina Boero, Giuseppe Saglio, Antonella Roetto, Clara CamaschellaAbstract:Transferrin Receptor 2 (TFR2) is a transmembrane glycoprotein expressed in the liver and in the erythroid compartment, mutated in a form of hereditary hemochromatosis. Hepatic TFR2, together with HFE, activates the transcription of the iron-regulator hepcidin, while erythroid TFR2 is a member of the erythropoietin Receptor complex. The TMPRSS6 gene, encoding the liver-expressed serine protease matriptase-2, is the main inhibitor of hepcidin and inactivation of TMPRSS6 leads to iron deficiency with high hepcidin levels. Here we evaluate the phenotype resulting from the genetic loss of Tmprss6 in Tfr2 total (Tfr2−/−) and liver-specific (Tfr2LCKO) knockout mice. Tmprss6−/−Tfr2−/− and Tmprss6−/−Tfr2LCKO mice have increased hepcidin levels and show iron-deficiency anemia like Tmprss6−/−mice. However, while Tmprss6−/−Tfr2LCKO are phenotypically identical to Tmprss6−/− mice, Tmprss6−/−Tfr2−/− mice have increased red blood cell count and more severe microcytosis than Tmprss6−/− mice. In addition hepcidin expression in Tmprss6−/−Tfr2−/− mice is higher than in the wild-type animals, but lower than in Tmprss6−/− mice, suggesting partial inhibition of the hepcidin activating pathway. Our results prove that hepatic TFR2 acts upstream of TMPRSS6. In addition Tfr2 deletion causes a relative erythrocytosis in iron-deficient mice, which likely attenuates the effect of over-expression of hepcidin in Tmprss6−/− mice. Since liver-specific deletion of Tfr2 in Tmprss6−/− mice does not modify the erythrocyte count, we speculate that loss of Tfr2 in the erythroid compartment accounts for the hematologic phenotype of Tmprss6−/−Tfr2−/− mice. We propose that TFR2 is a limiting factor for erythropoiesis, particularly in conditions of iron restriction.
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Transferrin Receptor 2 and hfe regulate furin expression via mitogen activated protein kinase extracellular signal regulated kinase mapk erk signaling implications for Transferrin dependent hepcidin regulation
Haematologica, 2010Co-Authors: Maura Poli, Laura Silvestri, Antonella Roetto, Sara Luscieti, Valentina Gandini, Federica Maccarinelli, Dario Finazzi, Paolo ArosioAbstract:Background Impaired regulation of hepcidin in response to iron is the cause of genetic hemochromatosis associated with defects of HFE and Transferrin Receptor 2. However, the role of these proteins in the regulation of hepcidin expression is unclear.Design and Methods Hepcidin expression, SMAD and extracellular signal-regulated kinase (Erk) phosphorylation and furin expression were analyzed in hepatic HepG2 cells in which HFE and Transferrin Receptor 2 were down-regulated or expressed, or furin activity specifically inhibited. Furin expression was also analyzed in the liver of Transferrin Receptor 2 null mice.Results We showed that the silencing of HFE and Transferrin Receptor 2 reduced both Erk phosphorylation and furin expression, that the exogenous expression of the two enhanced the induction of phosphoErk1/2 and furin by holoTransferrin, but that this did not occur when the pathogenic HFE mutant C282Y was expressed. Furin, phosphoErk1/2 and phosphoSMAD1/5/8 were down-regulated also in Transferrin Receptor 2-null mice. Treatment of HepG2 cells with an inhibitor of furin activity caused a strong suppression of hepcidin mRNA, probably due to the inhibition of bone morphogenic protein maturation.Conclusions The data indicate that Transferrin Receptor 2 and HFE are involved in holoTransferrin-dependent signaling for the regulation of furin which involved Erk phosphorylation. Furin in turn may control hepcidin expression.