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1.
Biometals ; 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-35167013

RESUMO

The mammalian multicopper ferroxidases (MCFs) ceruloplasmin (CP), hephaestin (HEPH) and zyklopen (ZP) comprise a family of conserved enzymes that are essential for body iron homeostasis. Each of these enzymes contains six biosynthetically incorporated copper atoms which act as intermediate electron acceptors, and the oxidation of iron is associated with the four electron reduction of dioxygen to generate two water molecules. CP occurs in both a secreted and GPI-linked (membrane-bound) form, while HEPH and ZP each contain a single C-terminal transmembrane domain. These enzymes function to ensure the efficient oxidation of iron so that it can be effectively released from tissues via the iron export protein ferroportin and subsequently bound to the iron carrier protein transferrin in the blood. CP is particularly important in facilitating iron release from the liver and central nervous system, HEPH is the major MCF in the small intestine and is critical for dietary iron absorption, and ZP is important for normal hair development. CP and HEPH (and possibly ZP) function in multiple tissues. These proteins also play other (non-iron-related) physiological roles, but many of these are ill-defined. In addition to disrupting iron homeostasis, MCF dysfunction perturbs neurological and immune function, alters cancer susceptibility, and causes hair loss, but, despite their importance, how MCFs co-ordinately maintain body iron homeostasis and perform other functions remains incompletely understood.

2.
J Nutr ; 151(9): 2541-2550, 2021 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-34114013

RESUMO

BACKGROUND: The ferroxidase zyklopen (Zp) has been implicated in the placental transfer of iron to the fetus. However, the evidence for this is largely circumstantial. OBJECTIVES: This study aimed to determine whether Zp is essential for placental iron transfer. METHODS: A model was established using 8- to 12-wk-old pregnant C57BL/6 mice on standard rodent chow in which Zp was knocked out in the fetus and fetal components of the placenta. Zp was also disrupted in the entire placenta using global Zp knockout mice. Inductively coupled plasma MS was used to measure total fetal iron, an indicator of the amount of iron transferred by the placenta to the fetus, at embryonic day 18.5 of gestation. Iron transporter expression in the placenta was measured by Western blotting, and the expression of Hamp1, the gene encoding the iron regulatory hormone hepcidin, was determined in fetal liver by real-time PCR. RESULTS: There was no change in the amount of iron transferred to the fetus when Zp was disrupted in either the fetal component of the placenta or the entire placenta. No compensatory changes in the expression of the iron transport proteins transferrin receptor 1 or ferroportin were observed, nor was there any change in fetal liver Hamp1 mRNA. Hephl1, the gene encoding Zp, was expressed mainly in the maternal decidua of the placenta and not in the nutrient-transporting syncytiotrophoblast. Disruption of Zp in the whole placenta resulted in a 26% increase in placental size (P < 0.01). CONCLUSIONS: Our data indicate that Zp is not essential for the efficient transfer of iron to the fetus in mice and is localized predominantly in the maternal decidua. The increase in placental size observed when Zp is knocked out in the entire placenta suggests that this protein may play a role in placental development.


Assuntos
Ceruloplasmina , Placenta , Animais , Ceruloplasmina/genética , Feminino , Feto/metabolismo , Ferro/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Placenta/metabolismo , Placentação , Gravidez
3.
Cell Mol Gastroenterol Hepatol ; 11(1): 199-220, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-32866618

RESUMO

BACKGROUND & AIMS: Liver fibrosis is a multifactorial trait that develops in response to chronic liver injury. Our aim was to characterize the genetic architecture of carbon tetrachloride (CCl4)-induced liver fibrosis using the Hybrid Mouse Diversity Panel, a panel of more than 100 genetically distinct mouse strains optimized for genome-wide association studies and systems genetics. METHODS: Chronic liver injury was induced by CCl4 injections twice weekly for 6 weeks. Four hundred thirty-seven mice received CCl4 and 256 received vehicle, after which animals were euthanized for liver histology and gene expression. Using automated digital image analysis, we quantified fibrosis as the collagen proportionate area of the whole section, excluding normal collagen. RESULTS: We discovered broad variation in fibrosis among the Hybrid Mouse Diversity Panel strains, demonstrating a significant genetic influence. Genome-wide association analyses revealed significant and suggestive loci underlying susceptibility to fibrosis, some of which overlapped with loci identified in mouse crosses and human population studies. Liver global gene expression was assessed by RNA sequencing across the strains, and candidate genes were identified using differential expression and expression quantitative trait locus analyses. Gene set enrichment analyses identified the underlying pathways, of which stellate cell involvement was prominent, and coexpression network modeling identified modules associated with fibrosis. CONCLUSIONS: Our results provide a rich resource for the design of experiments to understand mechanisms underlying fibrosis and for rational strain selection when testing antifibrotic drugs.


Assuntos
Tetracloreto de Carbono/toxicidade , Redes Reguladoras de Genes/efeitos dos fármacos , Predisposição Genética para Doença , Cirrose Hepática/induzido quimicamente , Fígado/patologia , Animais , Tetracloreto de Carbono/administração & dosagem , Modelos Animais de Doenças , Estudo de Associação Genômica Ampla , Humanos , Injeções Intraperitoneais , Fígado/efeitos dos fármacos , Cirrose Hepática/genética , Cirrose Hepática/patologia , Masculino , Camundongos , Locos de Características Quantitativas
4.
Mol Metab ; 30: 30-47, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31767179

RESUMO

OBJECTIVE: Lipocalin-2 (LCN2) is a secreted protein involved in innate immunity and has also been associated with several cardiometabolic traits in both mouse and human studies. However, the causal relationship of LCN2 to these traits is unclear, and most studies have examined only males. METHODS: Using adeno-associated viral vectors we expressed LCN2 in either adipose or liver in a tissue specific manner on the background of a whole-body Lcn2 knockout or wildtype mice. Metabolic phenotypes including body weight, body composition, plasma and liver lipids, glucose homeostasis, insulin resistance, mitochondrial phenotyping, and metabolic cage studies were monitored. RESULTS: We studied the genetics of LCN2 expression and associated clinical traits in both males and females in a panel of 100 inbred strains of mice (HMDP). The natural variation in Lcn2 expression across the HMDP exhibits high heritability, and genetic mapping suggests that it is regulated in part by Lipin1 gene variation. The correlation analyses revealed striking tissue dependent sex differences in obesity, insulin resistance, hepatic steatosis, and dyslipidemia. To understand the causal relationships, we examined the effects of expression of LCN2 selectively in liver or adipose. On a Lcn2-null background, LCN2 expression in white adipose promoted metabolic disturbances in females but not males. It acted in an autocrine/paracrine manner, resulting in mitochondrial dysfunction and an upregulation of inflammatory and fibrotic genes. On the other hand, on a null background, expression of LCN2 in liver had no discernible impact on the traits examined despite increasing the levels of circulating LCN2 more than adipose LCN2 expression. The mechanisms underlying the sex-specific action of LCN2 are unclear, but our results indicate that adipose LCN2 negatively regulates its receptor, LRP2 (or megalin), and its repressor, ERα, in a female-specific manner and that the effects of LCN2 on metabolic traits are mediated in part by LRP2. CONCLUSIONS: Following up on our population-based studies, we demonstrate that LCN2 acts in a highly sex- and tissue-specific manner in mice. Our results have important implications for human studies, emphasizing the importance of sex and the tissue source of LCN2.


Assuntos
Tecido Adiposo/metabolismo , Lipocalina-2/metabolismo , Adiposidade , Animais , Composição Corporal , Peso Corporal , Feminino , Glucose/análise , Homeostase , Resistência à Insulina , Lipídeos/análise , Lipocalina-2/genética , Lipocalina-2/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Camundongos Knockout , Obesidade/metabolismo , Fatores Sexuais
5.
PLoS Genet ; 15(5): e1008143, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-31125343

RESUMO

Maintenance of the correct redox status of iron is functionally important for critical biological processes. Multicopper ferroxidases play an important role in oxidizing ferrous iron, released from the cells, into ferric iron, which is subsequently distributed by transferrin. Two well-characterized ferroxidases, ceruloplasmin (CP) and hephaestin (HEPH) facilitate this reaction in different tissues. Recently, a novel ferroxidase, Hephaestin like 1 (HEPHL1), also known as zyklopen, was identified. Here we report a child with compound heterozygous mutations in HEPHL1 (NM_001098672) who presented with abnormal hair (pili torti and trichorrhexis nodosa) and cognitive dysfunction. The maternal missense mutation affected mRNA splicing, leading to skipping of exon 5 and causing an in-frame deletion of 85 amino acids (c.809_1063del; p.Leu271_ala355del). The paternal mutation (c.3176T>C; p.Met1059Thr) changed a highly conserved methionine that is part of a typical type I copper binding site in HEPHL1. We demonstrated that HEPHL1 has ferroxidase activity and that the patient's two mutations exhibited loss of this ferroxidase activity. Consistent with these findings, the patient's fibroblasts accumulated intracellular iron and exhibited reduced activity of the copper-dependent enzyme, lysyl oxidase. These results suggest that the patient's biallelic variants are loss-of-function mutations. Hence, we generated a Hephl1 knockout mouse model that was viable and had curly whiskers, consistent with the hair phenotype in our patient. These results enhance our understanding of the function of HEPHL1 and implicate altered ferroxidase activity in hair growth and hair disorders.


Assuntos
Oxirredutases/genética , Oxirredutases/metabolismo , Adulto , Alelos , Animais , Sítios de Ligação , Ceruloplasmina/metabolismo , Pré-Escolar , Cobre/metabolismo , Feminino , Regulação da Expressão Gênica/genética , Variação Genética/genética , Células HEK293 , Cabelo , Humanos , Ferro/metabolismo , Masculino , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Oxirredução , Fenótipo
6.
BMC Genomics ; 20(1): 9, 2019 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-30616562

RESUMO

BACKGROUND: 3' RNA sequencing provides an alternative to whole transcript analysis. However, we do not know a priori the relative advantage of each method. Thus, a comprehensive comparison between the whole transcript and the 3' method is needed to determine their relative merits. To this end, we used two commercially available library preparation kits, the KAPA Stranded mRNA-Seq kit (traditional method) and the Lexogen QuantSeq 3' mRNA-Seq kit (3' method), to prepare libraries from mouse liver RNA. We then sequenced and analyzed the libraries to determine the advantages and disadvantages of these two approaches. RESULTS: We found that the traditional whole transcript method and the 3' RNA-Seq method had similar levels of reproducibility. As expected, the whole transcript method assigned more reads to longer transcripts, while the 3' method assigned roughly equal numbers of reads to transcripts regardless of their lengths. We found that the 3' RNA-Seq method detected more short transcripts than the whole transcript method. With regard to differential expression analysis, we found that the whole transcript method detected more differentially expressed genes, regardless of the level of sequencing depth. CONCLUSIONS: The 3' RNA-Seq method was better able to detect short transcripts, while the whole transcript RNA-Seq was able to detect more differentially expressed genes. Thus, both approaches have relative advantages and should be selected based on the goals of the experiment.


Assuntos
Regiões 3' não Traduzidas/genética , Sequenciamento de Nucleotídeos em Larga Escala , RNA Mensageiro/genética , Análise de Sequência de RNA/métodos , Animais , Perfilação da Expressão Gênica , Camundongos , Transcriptoma/genética , Sequenciamento Completo do Exoma/métodos
7.
Cell Mol Gastroenterol Hepatol ; 6(4): 405-427, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30182051

RESUMO

Background & Aims: Multicopper ferroxidases (MCFs) facilitate intestinal iron absorption and systemic iron recycling, likely by a mechanism involving the oxidization of Fe2+ from the iron exporter ferroportin 1 for delivery to the circulating Fe3+ carrier transferrin. Hephaestin (HEPH), the only MCF known to be expressed in enterocytes, aids in the basolateral transfer of dietary iron to the blood. Mice lacking HEPH in the whole body (Heph-/- ) or intestine alone (Hephint/int ) exhibit defects in dietary iron absorption but still survive and grow. Circulating ceruloplasmin (CP) is the only other known MCF likely to interact with enterocytes. Our aim was to assess the effects of combined deletion of HEPH and CP on intestinal iron absorption and homeostasis in mice. Methods: Mice lacking both HEPH and CP (Heph-/-Cp-/- ) and mice with whole-body knockout of CP and intestine-specific deletion of HEPH (Hephint/intCp-/- ) were generated and phenotyped. Results: Heph-/-Cp-/- mice were severely anemic and had low serum iron, but they exhibited marked iron loading in duodenal enterocytes, the liver, heart, pancreas, and other tissues. Hephint/intCp-/- mice were moderately anemic (similar to Cp-/- mice) but were iron loaded only in the duodenum and liver, as in Hephint/int and Cp-/- mice, respectively. Both double knockout models absorbed iron in radiolabeled intestinal iron absorption studies, but the iron was inappropriately distributed, with an abnormally high percentage retained in the liver. Conclusions: These studies indicate that HEPH and CP, and likely MCFs in general, are not essential for intestinal iron absorption but are required for proper systemic iron distribution. They also point to important extra-intestinal roles for HEPH in maintaining whole-body iron homeostasis.


Assuntos
Ceruloplasmina/deficiência , Ferro/metabolismo , Proteínas de Membrana/deficiência , Absorção Fisiológica , Anemia/patologia , Animais , Animais Lactentes , Tamanho Corporal , Peso Corporal , Proteínas de Transporte de Cátions/metabolismo , Ceruloplasmina/metabolismo , Modelos Animais de Doenças , Duodeno/metabolismo , Enterócitos/metabolismo , Feminino , Ligadura , Masculino , Proteínas de Membrana/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Especificidade de Órgãos , Fenótipo
8.
Redox Biol ; 17: 432-439, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29883959

RESUMO

Little is known about the iron efflux from the pancreas, but it is likely that multicopper ferroxidases (MCFs) are involved in this process. We thus used hephaestin (Heph) and ceruloplasmin (Cp) single-knockout mice and Heph/Cp double-knockout mice to investigate the roles of MCFs in pancreatic iron homeostasis. We found that both HEPH and CP were expressed in the mouse pancreas, and that ablation of either MCF had limited effect on the pancreatic iron levels. However, ablation of both MCFs together led to extensive pancreatic iron deposition and severe oxidative damage. Perls' Prussian blue staining revealed that this iron deposition was predominantly in the exocrine pancreas, while the islets were spared. Consistent with these results, plasma lipase and trypsin were elevated in Heph/Cp knockout mice, indicating damage to the exocrine pancreas, while insulin secretion was not affected. These data indicate that HEPH and CP play mutually compensatory roles in facilitating iron efflux from the exocrine pancreas, and show that MCFs are able to protect the pancreas against iron-induced oxidative damage.


Assuntos
Ceruloplasmina/genética , Ferro/metabolismo , Proteínas de Membrana/genética , Estresse Oxidativo/genética , Animais , Ceruloplasmina/metabolismo , Homeostase/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Knockout , Oxirredução , Oxirredutases/genética , Oxirredutases/metabolismo , Pâncreas Exócrino/metabolismo , Pâncreas Exócrino/patologia
9.
Sci Rep ; 6: 39470, 2016 12 19.
Artigo em Inglês | MEDLINE | ID: mdl-27991585

RESUMO

Multicopper ferroxidases (MCFs) play an important role in cellular iron homeostasis. However, the role of MCFs in renal metabolism remains unclear. We used Hephaestin (Heph) and Ceruloplasmin (Cp) single or double (Heph/Cp) knockout (KO) mice to study the roles of MCFs in the kidney. Renal iron levels and the expression of iron metabolism genes were examined. The non-heme iron content both in the renal cortex and medulla of Heph/Cp KO mice was significantly increased. Perls' Prussian blue staining showed iron accumulation on the apical side of renal tubular cells in Heph/Cp KO mice. A significant increase in ferritin protein expression was also observed in the renal medulla and cortex of Heph/Cp KO mice. Both DMT1 and TfR1 protein expression were significantly decreased in the renal medulla of Heph/Cp KO mice, while the expression of DMT1 protein was significantly increased in the renal cortex of these animals. Significant increase in proteinuria and total urinary iron was observed in the double knockout mice, and this was associated with compromised structural integrity. These results suggest that KO of both the HEPH and CP genes leads to kidney iron deposition and toxicity, MCFs could protect kidney against a damage from iron excess.


Assuntos
Ceruloplasmina/genética , Ceruloplasmina/metabolismo , Ferro/metabolismo , Rim/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Animais , Cobre/química , Ferritinas/metabolismo , Ferrocianetos , Genótipo , Homeostase , Córtex Renal , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout
10.
J Nutr ; 145(5): 1003-9, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25788583

RESUMO

BACKGROUND: Iron accumulation in the central nervous system (CNS) is a common feature of many neurodegenerative diseases. Multicopper ferroxidases (MCFs) play an important role in cellular iron metabolism. However, the role of MCFs in the CNS in health and disease remains poorly characterized. OBJECTIVE: The aim was to study the role of hephaestin (HEPH) and ceruloplasmin (CP) in CNS iron metabolism and homeostasis. METHODS: Iron concentrations and L-ferritin protein levels of selected brain regions were determined in global hephaestin knockout (Heph KO), global ceruloplasmin knockout (Cp KO), and wild-type (WT) male mice at 6-7 mo of age. Gene expression of divalent metal transporter 1 (Dmt1), ferroportin 1 (Fpn1), Heph, Cp, and transferrin receptor 1 (Tfrc) and HEPH protein level was quantitated in the same brain regions. RESULTS: Iron and L-ferritin protein levels were significantly increased in Heph KO mouse brain cortex (iron: 30%, P < 0.05; L-ferritin: 200%, P < 0.05), hippocampus (iron: 80%, P < 0.05; L-ferritin: 300%, P < 0.05), brainstem (iron: 20%, P < 0.05; L-ferritin: 150%, P < 0.05), and cerebellum (iron: 20%, P < 0.05; L-ferritin: 100%, P < 0.05) regions than in WT and Cp KO mouse brain regions at 6 mo of age. Expression of the Heph gene was significantly increased in the Cp KO mouse cortex (100%; P < 0.01), hippocampus (350%; P < 0.001), brainstem (30%; P < 0.01), and cerebellum (150%; P < 0.001) than in WT controls, and Cp gene expression was significantly decreased in the Heph KO mouse hippocampus (20%; P < 0.05) than in WT control mice at 6 mo of age. CONCLUSIONS: Ablation of HEPH or CP results in disordered brain iron homeostasis in mice. Heph KO may provide a novel model for neurodegenerative disorders.


Assuntos
Encéfalo/metabolismo , Ceruloplasmina/metabolismo , Regulação da Expressão Gênica , Homeostase , Ferro/metabolismo , Proteínas de Membrana/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Animais , Tronco Encefálico/metabolismo , Proteínas de Transporte de Cátions/genética , Proteínas de Transporte de Cátions/metabolismo , Cerebelo/metabolismo , Córtex Cerebral/metabolismo , Ceruloplasmina/genética , Hipocampo/metabolismo , Masculino , Proteínas de Membrana/genética , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Receptores da Transferrina/genética , Receptores da Transferrina/metabolismo
11.
PLoS One ; 9(6): e98792, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24896847

RESUMO

Hephaestin is a vertebrate multicopper ferroxidase important for the transfer of dietary iron from intestinal cells to the blood. Hephaestin is mutated in the sex-linked anemia mouse, resulting in iron deficiency. However, sex-linked anemia mice still retain some hephaestin ferroxidase activity. They survive, breed, and their anemia improves with age. To gain a better understanding of the role of hephaestin in iron homeostasis, we used the Cre-lox system to generate knockout mouse models with whole body or intestine-specific (Villin promoter) ablation of hephaestin. Both types of mice were viable, indicating that hephaestin is not essential and that other mechanisms, multicopper ferroxidase-dependent or not, must compensate for hephaestin deficiency. The knockout strains, however, both developed a microcytic, hypochromic anemia, suggesting severe iron deficiency and confirming that hephaestin plays an important role in body iron acquisition. Consistent with this, the knockout mice accumulated iron in duodenal enterocytes and had reduced intestinal iron absorption. In addition, the similarities of the phenotypes of the whole body and intestine-specific hephaestin knockout mice clarify the important role of hephaestin specifically in intestinal enterocytes in maintaining whole body iron homeostasis. These mouse models will serve as valuable tools to study the role of hephaestin and associated proteins in iron transport in the small intestine and other tissues.


Assuntos
Absorção Intestinal , Mucosa Intestinal/metabolismo , Ferro/metabolismo , Proteínas de Membrana/metabolismo , Animais , Peso Corporal , Feminino , Genótipo , Absorção Intestinal/genética , Masculino , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Fenótipo
12.
J Trace Elem Med Biol ; 26(2-3): 115-9, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22575541

RESUMO

Intestinal iron absorption is a critical process for maintaining body iron levels within the optimal physiological range. Iron in the diet is found in a wide variety of forms, but the absorption of non-heme iron is best understood. Most of this iron is moved across the enterocyte brush border membrane by the iron transporter divalent metal-ion transporter 1, a process enhanced by the prior reduction of the iron by duodenal cytochrome B and possibly other reductases. Enterocyte iron is exported to the blood via ferroportin 1 on the basolateral membrane. This transporter acts in partnership with the ferroxidase hephaestin that oxidizes exported ferrous iron to facilitate its binding to plasma transferrin. Iron absorption is controlled by a complex network of systemic and local influences. The liver-derived peptide hepcidin binds to ferroportin, leading to its internalization and a reduction in absorption. Hepcidin expression in turn responds to body iron demands and the BMP-SMAD signaling pathway plays a key role in this process. The levels of iron and oxygen in the enterocyte also exert important influences on iron absorption. Disturbances in the regulation of iron absorption are responsible for both iron loading and iron deficiency disorders in humans.


Assuntos
Absorção Intestinal/fisiologia , Ferro/metabolismo , Animais , Transporte Biológico/fisiologia , Enterócitos/metabolismo , Humanos
13.
Biometals ; 25(4): 687-95, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22350470

RESUMO

Discovered over a decade ago, hephaestin (Heph) has been implicated as a ferroxidase (FOX) vital for intestinal iron absorption. Stringent structural or kinetic data derived from purified, native protein is however lacking, leading to the hypothesis that an alternate, undiscovered form of Heph could exist in mammalian enterocytes. This possibility was tested using laboratory rodent and cell culture models. Cytosolic and membrane fractions were obtained from rat enterocytes and purity of the fractions was assessed. Western blot analyses revealed Heph in cytosol obtained by three different methods, ruling out the possibility of a method-induced artifact being the major contributor to this observation. Absence of two different membrane-proteins, ferroportin 1 and Menke's copper ATPase in cytosol, and the absence of lipids in representative cytosolic samples tested by thin layer chromatography, eliminated significant membrane contamination of cytosol. Further, immunohisto- and immunocyto-chemical analyses identified Heph in rat enterocytes and in two intestinal epithelial cell lines, IEC-6 and Caco-2, intracellularly. Additionally, cytosolic Heph increased upon iron-deprivation but more important, decreased significantly upon copper-deprivation, mimicking the response of membrane-bound Heph. Moreover, FOX activity was present in rat cytosol, and was partly inhibited by anti-Heph antibody. Finally, lack of immunodetectable ceruloplasmin (Cp) by western blot precluded Cp as an underlying cause of this activity. These data demonstrate that rat enterocytes contain a soluble/cytosolic form of Heph possibly contributing to the observed FOX activity.


Assuntos
Ceruloplasmina/metabolismo , Citosol/enzimologia , Enterócitos/enzimologia , Proteínas de Membrana/metabolismo , Animais , Western Blotting , Células Cultivadas , Cromatografia em Camada Delgada , Imuno-Histoquímica , Ratos
14.
Proc Natl Acad Sci U S A ; 109(9): 3564-9, 2012 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-22331876

RESUMO

Hephaestin (Heph), a membrane-bound multicopper ferroxidase (FOX) expressed in duodenal enterocytes, is required for optimal iron absorption. However, sex-linked anemia (sla) mice harboring a 194-amino acid deletion in the Heph protein are able to absorb dietary iron despite reduced expression and mislocalization of the mutant protein. Thus Heph may not be essential, and mice are able to compensate for the loss of its activity. The current studies were undertaken to search for undiscovered FOXs in rodent enterocytes. An experimental approach was developed to investigate intestinal FOXs in which separate membrane and cytosolic fractions were prepared and FOX activity was measured by a spectrophotometric transferrin-coupled assay. Unexpectedly, FOX activity was noted in membrane and cytosolic fractions of rat enterocytes. Different experimental approaches demonstrated that cytosolic FOX activity was not caused by contamination with membrane Heph or a method-induced artifact. Cytosolic FOX activity was abolished by SDS and heat (78 °C), suggesting protein-mediated iron oxidation, and was also sensitive to Triton X-100. Furthermore, cytosolic FOX activity increased ∼30% in iron-deficient rats (compared with controls) but was unchanged in copper-deficient rats (in contrast to the reported dramatic reduction of Heph expression and activity during copper deficiency). Additional studies done in sla, Heph-knockout, and ceruloplasmin-knockout mice proved that cytosolic FOX activity could not be fully explained by Heph or ceruloplasmin. Therefore rodent enterocytes contain a previously undescribed soluble cytosolic FOX that may function in transepithelial iron transport and complement membrane-bound Heph.


Assuntos
Ceruloplasmina/isolamento & purificação , Enterócitos/enzimologia , Anemia Ferropriva/genética , Animais , Fracionamento Celular , Membrana Celular/enzimologia , Ceruloplasmina/deficiência , Ceruloplasmina/metabolismo , Citosol/enzimologia , Duodeno/citologia , Duodeno/enzimologia , Ferrozina/análise , Distúrbios do Metabolismo do Ferro/metabolismo , Jejuno/citologia , Jejuno/enzimologia , Masculino , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Proteínas de Membrana/isolamento & purificação , Proteínas de Membrana/metabolismo , Proteínas de Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Doenças Neurodegenerativas/metabolismo , Oxirredução , Ratos , Ratos Sprague-Dawley , Solubilidade
15.
J Nutr ; 140(10): 1728-35, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20685892

RESUMO

We previously detected a membrane-bound, copper-containing oxidase that may be involved in iron efflux in BeWo cells, a human placental cell line. We have now identified a gene encoding a predicted multicopper ferroxidase (MCF) with a putative C-terminal membrane-spanning sequence and high sequence identity to hephaestin (Heph) and ceruloplasmin (Cp), the other known vertebrate MCF. Molecular modeling revealed conservation of all type I, II, and III copper-binding sites as well as a putative iron-binding site. Protein expression was observed in multiple diverse mouse tissues, including placenta and mammary gland, and the expression pattern was distinct from that of Cp and Heph. The protein possessed ferroxidase activity, and protein levels decreased in cellular copper deficiency. Knockdown with small interfering RNA in BeWo cells indicates that this gene represents the previously detected oxidase. We propose calling this new member of the MCF family "zyklopen."


Assuntos
Ceruloplasmina/química , Ceruloplasmina/genética , Cobre/análise , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Células CACO-2 , Linhagem Celular , Linhagem Celular Tumoral , Ceruloplasmina/análise , Cobre/metabolismo , Feminino , Expressão Gênica , Humanos , Ferro/metabolismo , Glândulas Mamárias Animais/enzimologia , Proteínas de Membrana/química , Proteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Modelos Moleculares , Especificidade de Órgãos , Oxirredutases atuantes sobre Doadores de Grupo CH-NH/metabolismo , Fragmentos de Peptídeos/química , Placenta/enzimologia , Gravidez , RNA Interferente Pequeno/farmacologia , Ratos , Homologia de Sequência
16.
J Nutr ; 132(11 Suppl): 3482S-3489S, 2002 11.
Artigo em Inglês | MEDLINE | ID: mdl-12421874

RESUMO

Flavonoids, such as daidzein and genistein, present in dietary plants like soybean, have unique chemical properties with biological activity relevant to cancer. Many flavonoids and polyphenols, including resveratrol in red wine and epigallocatechin gallate in green tea, are known antioxidants. Some of these compounds have estrogenic (and antiestrogenic) activity and are commonly referred to as phytoestrogens. A yeast-based estrogen receptor (ER) reporter assay has been used to measure the ability of flavonoids to bind to ER and activate estrogen responsive genes. Recently, estrogenic compounds were also shown to trigger rapid, nongenomic effects. The molecular mechanisms, however, have not been completely detailed and little information exists regarding their relevance to cancer progression. As a preliminary step toward elucidating rapid phytoestrogen action on breast cancer cells, we investigated the effect of 17-beta estradiol (E2), genistein, daidzein and resveratrol on the activation status of signaling proteins that regulate cell survival and invasion, the cell properties underlying breast cancer progression. The effect of these estrogenic compounds on the activation, via phosphorylation, of Akt/protein kinase B (Akt) and focal adhesion kinase (FAK) were analyzed in ER-positive and -negative human breast cancer cell lines. E2, genistein and daidzein increased whereas resveratrol decreased both Akt and FAK phosphorylation in nonmetastatic ER-positive T47D cells. In metastatic ER-negative MDA-MB-231 cells, all estrogenic compounds tested increased Akt and FAK phosphorylation. The inhibitory action of resveratrol on cell survival and proliferation is ER dependent. Therefore, all estrogenic compounds tested, including resveratrol, may exert supplementary ER-independent nongenomic effects on cell survival and migration in breast cancer cells.


Assuntos
Neoplasias da Mama/patologia , Divisão Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Flavonoides/farmacologia , Neoplasias da Mama/química , Ativação Enzimática/efeitos dos fármacos , Estradiol/farmacologia , Receptor alfa de Estrogênio , Receptor beta de Estrogênio , Estrogênios não Esteroides/farmacologia , Quinase 1 de Adesão Focal , Proteína-Tirosina Quinases de Adesão Focal , Genisteína/farmacologia , Humanos , Isoflavonas/farmacologia , Fosforilação , Fitoestrógenos , Preparações de Plantas , Proteínas Tirosina Quinases/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-akt , Receptores de Estrogênio/análise , Resveratrol , Estilbenos/farmacologia , Células Tumorais Cultivadas
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