scholarly journals WDR45 Contributes to Iron Accumulation Through Dysregulation of Neuronal Iron Homeostasis

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 1188-1188
Author(s):  
Luisa Aring ◽  
Eun-kyeong Choi ◽  
Young-Ah Seo
Keyword(s):  
Iron Overload ◽  
Iron Homeostasis ◽  
Iron Acquisition ◽  
Neuronal Cells ◽  
Iron Accumulation ◽  
Autophagic Flux ◽  
Brain Iron ◽  
Divalent Metal Transporter 1 ◽  
Iron Storage ◽  
Cellular Iron

Abstract Objectives Neurodegeneration with brain iron accumulation (NBIA) is a clinically and genetically heterogeneous group of neurodegenerative diseases characterized by an abnormal accumulation of brain iron and progressive degeneration of the nervous system. β-propeller protein-associated neurodegeneration (BPAN) (OMIM #300,894) is a recently identified subtype of NBIA. BPAN is caused by de novo mutations in the WD repeat domain 45 (WDR45) gene. WDR45 deficiency in BPAN patients and animal models has shown defects in autophagic flux, suggesting a role for WDR45 in autophagy. How WDR45 deficiency leads to brain iron overload remains unclear. The goal of the present study is to identify the pathogenic mechanisms of WDR45 deficiency that cause iron overload and neurodegeneration. Methods To elucidate the role of WDR45 in dopaminergic neuronal cells, we generated a WDR45-knockout (KO) SH-SY5Y cell line by CRISPR/Cas9-mediated genome editing. To identify mechanisms underlying iron homeostasis and transport, we examined two cellular iron acquisition pathways in these cells using radioactive isotope 59Fe: 1) the canonical transferrin-bound iron (TBI) uptake pathway and 2) the nontransferrin-bound iron (NTBI) pathway. Results Loss of WDR45 increased total iron levels with a concomitant increase in the iron storage protein ferritin in neuronal cells. Specifically, WDR45-KO cells preferentially took up NTBI compared to wild-type cells. Concordant with these functional data, the level of divalent metal transporter-1 (DMT1) expression was upregulated in WDR45-KO cells, providing a causal link to iron overload in WDR45 deficiency. In addition, loss of WDR45 led to defects in autophagic flux and impaired ferritinophagy, a lysosomal process that promotes ferritin degradation, suggesting that iron overload is driven by impaired ferritinophagy. Interestingly, WDR45 deficiency increased iron accumulation in the mitochondria, impaired mitochondrial function, and in turn, elevated reactive oxygen species generation. Conclusions Our study provides the first evidence that WDR45 deficiency alters cellular iron acquisition pathways thereby leading to iron accumulation in neuronal cells. These findings will serve as a basis for developing therapeutic strategies for patients with NBIA. Funding Sources NIH, NBIA Disorder Association.

scholarly journals Nitric oxide–mediated regulation of ferroportin-1 controls macrophage iron homeostasis and immune function in Salmonella infection

2013 ◽  
Vol 210 (5) ◽  
pp. 855-873 ◽  
Author(s):  
Manfred Nairz ◽  
Ulrike Schleicher ◽  
Andrea Schroll ◽  
Thomas Sonnweber ◽  
Igor Theurl ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Iron Homeostasis ◽  
Molecular Mechanisms ◽  
Iron Acquisition ◽  
Iron Chelator ◽  
Related Factor ◽  
Cellular Iron ◽  
Splenic Macrophages ◽  
Ferroportin 1 ◽  
Pathogen Control

Nitric oxide (NO) generated by inducible NO synthase 2 (NOS2) affects cellular iron homeostasis, but the underlying molecular mechanisms and implications for NOS2-dependent pathogen control are incompletely understood. In this study, we found that NO up-regulated the expression of ferroportin-1 (Fpn1), the major cellular iron exporter, in mouse and human cells. Nos2−/− macrophages displayed increased iron content due to reduced Fpn1 expression and allowed for an enhanced iron acquisition by the intracellular bacterium Salmonella typhimurium. Nos2 gene disruption or inhibition of NOS2 activity led to an accumulation of iron in the spleen and splenic macrophages. Lack of NO formation resulted in impaired nuclear factor erythroid 2-related factor-2 (Nrf2) expression, resulting in reduced Fpn1 transcription and diminished cellular iron egress. After infection of Nos2−/− macrophages or mice with S. typhimurium, the increased iron accumulation was paralleled by a reduced cytokine (TNF, IL-12, and IFN-γ) expression and impaired pathogen control, all of which were restored upon administration of the iron chelator deferasirox or hyperexpression of Fpn1 or Nrf2. Thus, the accumulation of iron in Nos2−/− macrophages counteracts a proinflammatory host immune response, and the protective effect of NO appears to partially result from its ability to prevent iron overload in macrophages

scholarly journals Iron Overload in the Face of Anemia

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. SCI-38-SCI-38
Author(s):  
Yatrik Shah
Keyword(s):  
Transcription Factors ◽  
Sickle Cell Disease ◽  
Iron Overload ◽  
Sickle Cell ◽  
Iron Absorption ◽  
Conflicts Of Interest ◽  
Iron Accumulation ◽  
Cell Disease ◽  
Divalent Metal Transporter 1 ◽  
Tissue Iron

Abstract Several distinct congenital disorders can lead to tissue-iron overload with anemia including β-thalassemia and sickle cell disease. We show that intestinal absorption of iron is highly increased and significantly contributes to tissue iron accumulation in these disorders. The present work describes a novel pathway by which oxygen sensing transcription factors are highly upregulated in iron overload anemias and are subsequently essential for the increase intestinal iron absorption. Oxygen signaling is mediated through well-conserved hypoxia driven transcription factors, hypoxia-inducible factor (HIF)1a and HIF2a. In the intestine, HIF2a directly activates divalent metal transporter 1 (DMT1), duodenal ferric reductase (DcytB), and Fpn1, which are iron transporters critical for adaptive changes in iron absorption. We demonstrate that HIF2a and its downstream target gene, DMT1 are essential for iron accumulation in mouse models of β-thalassemia and sickle cell disease. Furthermore, studies of thalassemic mouse model with established iron overload demonstrated that loss of intestinal HIF2a and DMT1 signaling led to decreased tissue iron accumulation in the livers. Interestingly, disrupting intestinal HIF2a not only improves tissue iron accumulation, but a marked improvement of anemia was also observed. These novel findings suggests that inhibition of HIF2a signaling pathway could be a novel and robust treatment strategy for several conditions that cause iron overload with anemia. Disclosures No relevant conflicts of interest to declare.

scholarly journals Cryo-EM structures and functional characterization of homo- and heteropolymers of human ferritin variants

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jose Irimia-Dominguez ◽  
Chen Sun ◽  
Kunpeng Li ◽  
Barry B. Muhoberac ◽  
Grace I. Hallinan ◽  
...  
Keyword(s):  
Iron Homeostasis ◽  
Functional Characterization ◽  
Protein Solubility ◽  
Cell Types ◽  
Brain Iron ◽  
Iron Storage ◽  
Human Ferritin ◽  
And Function ◽  
Brain Iron Metabolism

AbstractThe role of abnormal brain iron metabolism in neurodegenerative diseases is still insufficiently understood. Here, we investigate the molecular basis of the neurodegenerative disease hereditary ferritinopathy (HF), in which dysregulation of brain iron homeostasis is the primary cause of neurodegeneration. We mutagenized ferritin’s three-fold pores (3FPs), i.e. the main entry route for iron, to investigate ferritin’s iron management when iron must traverse the protein shell through the disrupted four-fold pores (4FPs) generated by mutations in the ferritin light chain (FtL) gene in HF. We assessed the structure and properties of ferritins using cryo-electron microscopy and a range of functional analyses in vitro. Loss of 3FP function did not alter ferritin structure but led to a decrease in protein solubility and iron storage. Abnormal 4FPs acted as alternate routes for iron entry and exit in the absence of functional 3FPs, further reducing ferritin iron-storage capacity. Importantly, even a small number of MtFtL subunits significantly compromises ferritin solubility and function, providing a rationale for the presence of ferritin aggregates in cell types expressing different levels of FtLs in patients with HF. These findings led us to discuss whether modifying pores could be used as a pharmacological target in HF.

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 Enhanced erythropoiesis in Hfe-KO mice indicates a role for Hfe in the modulation of erythroid iron homeostasis

Blood ◽  
2011 ◽  
Vol 117 (4) ◽  
pp. 1379-1389 ◽  
Author(s):  
Pedro Ramos ◽  
Ella Guy ◽  
Nan Chen ◽  
Catia C. Proenca ◽  
Sara Gardenghi ◽  
...  
Keyword(s):  
Iron Overload ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Dietary Iron ◽  
Erythroid Cells ◽  
Hepcidin Expression ◽  
Stress Erythropoiesis ◽  
Cellular Iron ◽  
Cellular Iron Uptake

Abstract In hereditary hemochromatosis, mutations in HFE lead to iron overload through abnormally low levels of hepcidin. In addition, HFE potentially modulates cellular iron uptake by interacting with transferrin receptor, a crucial protein during erythropoiesis. However, the role of HFE in this process was never explored. We hypothesize that HFE modulates erythropoiesis by affecting dietary iron absorption and erythroid iron intake. To investigate this, we used Hfe-KO mice in conditions of altered dietary iron and erythropoiesis. We show that Hfe-KO mice can overcome phlebotomy-induced anemia more rapidly than wild-type mice (even when iron loaded). Second, we evaluated mice combining the hemochromatosis and β-thalassemia phenotypes. Our results suggest that lack of Hfe is advantageous in conditions of increased erythropoietic activity because of augmented iron mobilization driven by deficient hepcidin response. Lastly, we demonstrate that Hfe is expressed in erythroid cells and impairs iron uptake, whereas its absence exclusively from the hematopoietic compartment is sufficient to accelerate recovery from phlebotomy. In summary, we demonstrate that Hfe influences erythropoiesis by 2 distinct mechanisms: limiting hepcidin expression under conditions of simultaneous iron overload and stress erythropoiesis, and impairing transferrin-bound iron uptake by erythroid cells. Moreover, our results provide novel suggestions to improve the treatment of hemochromatosis.

Deregulation of proteins involved in iron metabolism in hepcidin-deficient mice

Blood ◽  
2005 ◽  
Vol 105 (12) ◽  
pp. 4861-4864 ◽  
Author(s):  
Lydie Viatte ◽  
Jeanne-Claire Lesbordes-Brion ◽  
Dan-Qing Lou ◽  
Myriam Bennoun ◽  
Gaël Nicolas ◽  
...  
Keyword(s):  
Iron Overload ◽  
Iron Homeostasis ◽  
Genetic Disorder ◽  
Divalent Metal Transporter 1 ◽  
Divalent Metal Transporter ◽  
Metal Transporter ◽  
The Common ◽  
Related Proteins ◽  
Deficient Mice

Abstract Evidence is accumulating that hepcidin, a liver regulatory peptide, could be the common pathogenetic denominator of all forms of iron overload syndromes including HFE-related hemochromatosis, the most prevalent genetic disorder characterized by inappropriate iron absorption. To understand the mechanisms whereby hepcidin controls iron homeostasis in vivo, we have analyzed the level of iron-related proteins by Western blot and immunohistochemistry in hepcidin-deficient mice, a mouse model of severe hemochromatosis. These mice showed important increased levels of duodenal cytochrome b (Dcytb), divalent metal transporter 1 (DMT1), and ferroportin compared with control mice. Interestingly, the level of ferroportin was coordinately up-regulated in the duodenum, the spleen, and the liver (predominantly in the Kupffer cells). Finally, we also evidenced a decrease of ceruloplasmin in the liver of hepcidin-deficient mice. We hypothesized that the deregulation of these proteins might be central in the pathogenesis of iron overload, providing key therapeutic targets for iron disorders. (Blood. 2005;105:4861-4864)

scholarly journals Iron overload is accompanied by mitochondrial and lysosomal dysfunction in WDR45 mutant cells

Brain ◽  
2018 ◽  
Vol 141 (10) ◽  
pp. 3052-3064 ◽  
Author(s):  
Philip Seibler ◽  
Lena F Burbulla ◽  
Marija Dulovic ◽  
Simone Zittel ◽  
Johanne Heine ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Iron Overload ◽  
Iron Homeostasis ◽  
De Novo ◽  
Induced Pluripotent Stem Cell ◽  
Patient Specific ◽  
Autophagic Flux ◽  
De Novo Mutations ◽  
Animal Cells ◽  
Mutant Cells

Abstract Beta-propeller protein-associated neurodegeneration is a subtype of monogenic neurodegeneration with brain iron accumulation caused by de novo mutations in WDR45. The WDR45 protein functions as a beta-propeller scaffold and plays a putative role in autophagy through its interaction with phospholipids and autophagy-related proteins. Loss of WDR45 function due to disease-causing mutations has been linked to defects in autophagic flux in patient and animal cells. However, the role of WDR45 in iron homeostasis remains elusive. Here we studied patient-specific WDR45 mutant fibroblasts and induced pluripotent stem cell-derived midbrain neurons. Our data demonstrated that loss of WDR45 increased cellular iron levels and oxidative stress, accompanied by mitochondrial abnormalities, autophagic defects, and diminished lysosomal function. Restoring WDR45 levels partially rescued oxidative stress and the susceptibility to iron treatment, and activation of autophagy reduced the observed iron overload in WDR45 mutant cells. Our data suggest that iron-containing macromolecules and organelles cannot effectively be degraded through the lysosomal pathway due to loss of WDR45 function.

scholarly journals Inflaming the Brain with Iron

Antioxidants ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 61
Author(s):  
Pamela J. Urrutia ◽  
Daniel A. Bórquez ◽  
Marco Tulio Núñez
Keyword(s):  
Nitric Oxide ◽  
Iron Homeostasis ◽  
Regulatory Protein ◽  
Iron Accumulation ◽  
Cellular Iron ◽  
Bidirectional Relationship ◽  
Inflammatory Phenotype ◽  
Related Proteins ◽  
Cellular Iron Homeostasis ◽  
The Brain

Iron accumulation and neuroinflammation are pathological conditions found in several neurodegenerative diseases, including Alzheimer’s disease (AD) and Parkinson’s disease (PD). Iron and inflammation are intertwined in a bidirectional relationship, where iron modifies the inflammatory phenotype of microglia and infiltrating macrophages, and in turn, these cells secrete diffusible mediators that reshape neuronal iron homeostasis and regulate iron entry into the brain. Secreted inflammatory mediators include cytokines and reactive oxygen/nitrogen species (ROS/RNS), notably hepcidin and nitric oxide (·NO). Hepcidin is a small cationic peptide with a central role in regulating systemic iron homeostasis. Also present in the cerebrospinal fluid (CSF), hepcidin can reduce iron export from neurons and decreases iron entry through the blood–brain barrier (BBB) by binding to the iron exporter ferroportin 1 (Fpn1). Likewise, ·NO selectively converts cytosolic aconitase (c-aconitase) into the iron regulatory protein 1 (IRP1), which regulates cellular iron homeostasis through its binding to iron response elements (IRE) located in the mRNAs of iron-related proteins. Nitric oxide-activated IRP1 can impair cellular iron homeostasis during neuroinflammation, triggering iron accumulation, especially in the mitochondria, leading to neuronal death. In this review, we will summarize findings that connect neuroinflammation and iron accumulation, which support their causal association in the neurodegenerative processes observed in AD and PD.

Defective palmitoylation of transferrin receptor triggers iron overload in Friedreich's ataxia fibroblasts

Blood ◽  
2021 ◽  
Author(s):  
Floriane Petit ◽  
Anthony Drecourt ◽  
Michaël Dussiot ◽  
Coralie Zangarelli ◽  
Olivier Hermine ◽  
...  
Keyword(s):  
Iron Overload ◽  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Mitochondrial Protein ◽  
Friedreich’S Ataxia ◽  
Friedreich's Ataxia ◽  
Gene Encoding ◽  
Iron Sulfur Cluster ◽  
The Road ◽  
Cellular Iron

Friedreich's ataxia (FRDA) is a frequent autosomal recessive disease caused by a GAA repeat expansion in the FXN gene encoding frataxin, a mitochondrial protein involved in iron-sulfur cluster (ISC) biogenesis. Resulting frataxin deficiency affects ISC-containing proteins and causes iron to accumulate in the brain and heart of FRDA patients. Here we report on abnormal cellular iron homeostasis in FRDA fibroblasts inducing a massive iron overload in the cytosol and mitochondria. We observe membrane transferrin receptor 1 (TfR1) accumulation, increased TfR1 endocytosis, and delayed transferrin recycling, ascribing this to impaired TfR1 palmitoylation. Frataxin deficiency is shown to reduce coenzyme A (CoA) availability for TfR1 palmitoylation. Finally, we demonstrate that artesunate, CoA, and dichloroacetate improve TfR1 palmitoylation and decrease iron overload, paving the road for evidence-based therapeutic strategies at the actionable level of TfR1 palmitoylation in FRDA.

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