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1.
Biochim Biophys Acta Gen Subj ; 1865(2): 129799, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33232799

RESUMO

BACKGROUND: The bone morphogenetic protein 6 (BMP6) is a crucial inducer of hepcidin, the peptide hormone that regulates the iron availability in our body. Hepcidin expression is influenced by hepatic heparan sulfate (HS) and by heparin administration, suggesting BMP6 interaction with heparin/HS. The BMP2/4 subfamily has been deeply characterized to have a N-terminal heparin/HS binding domain (HBD), whose basic residues contact the sulfate groups on heparin and HS. Such detailed characterization is still required for other, structurally different BMPs, including BMP6. METHODS: BMP6 peptides encompassing potential HBDs were analysed on heparin-functionalized plates and microcantilevers, and on membrane HS expressing CHO-K1 cells. Monomeric wild-type BMP6 and mutants were produced, substituting the basic residues with non-charged ones, and their affinity to the heparin-column was measured. The BMP6-heparin interaction was also predicted at atomic level by in silico molecular dynamics. RESULTS: N-terminal and C-terminal BMP6 peptides showed high heparin affinity in solid-phase assays. The mutation of the two sites (R5L, R6S, R7L and K126N, K127N, R129S) abolished the heparin-binding activity of the recombinant monomeric BMP6. Monomeric BMP6 and peptides specifically bound to membrane HS of CHO-K1 cells through the same domains. Molecular dynamic studies supported the role of the two HBDs, suggesting a cooperative behaviour. CONCLUSIONS: In BMP6, N-terminal (R5, R6, R7) and C-terminal (K126, K127, R129) domains mediate the interaction with heparin and HS. GENERAL SIGNIFICANCE: This study provides the molecular mechanism supporting the use of heparin to sequester BMP6 and inhibit hepcidin expression, a novel clinical approach for high-hepcidin iron disorders.


Assuntos
Proteína Morfogenética Óssea 6/metabolismo , Heparina/metabolismo , Heparitina Sulfato/metabolismo , Animais , Sítios de Ligação , Proteína Morfogenética Óssea 6/química , Células CHO , Cricetulus , Células Hep G2 , Hepcidinas/metabolismo , Humanos , Modelos Moleculares , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas
4.
J Biol Chem ; 294(36): 13292-13303, 2019 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-31315930

RESUMO

Hepcidin is a liver-derived peptide hormone that controls systemic iron homeostasis. Its expression is regulated by the bone morphogenetic protein 6 (BMP6)/SMAD1/5/8 pathway and by the proinflammatory cytokine interleukin 6 (IL6). Proteoglycans that function as receptors of these signaling proteins in the liver are commonly decorated by heparan sulfate, but the potential role of hepatic heparan sulfate in hepcidin expression and iron homeostasis is unclear. Here, we show that modulation of hepatic heparan sulfate significantly alters hepcidin expression and iron metabolism both in vitro and in vivo Specifically, enzymatic removal of heparan sulfate from primary human hepatocytes, CRISPR/Cas9 manipulation of heparan sulfate biosynthesis in human hepatoma cells, or pharmacological manipulation of heparan sulfate-protein interactions using sodium chlorate or surfen dramatically reduced baseline and BMP6/SMAD1/5/8-dependent hepcidin expression. Moreover inactivation of the heparan sulfate biosynthetic gene N-deacetylase and N-sulfotransferase 1 (Ndst1) in murine hepatocytes (Ndst1f/fAlbCre+) reduced hepatic hepcidin expression and caused a redistribution of systemic iron, leading to iron accumulation in the liver and serum of mice. Manipulation of heparan sulfate had a similar effect on IL6-dependent hepcidin expression in vitro and suppressed IL6-mediated iron redistribution induced by lipopolysaccharide in vivo These results provide compelling evidence that hepatocyte heparan sulfate plays a key role in regulating hepcidin expression and iron homeostasis in mice and in human hepatocytes.


Assuntos
Heparitina Sulfato/metabolismo , Hepatócitos/metabolismo , Hepcidinas/genética , Homeostase , Ferro/metabolismo , Animais , Linhagem Celular , Perfilação da Expressão Gênica , Hepcidinas/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos , Regiões Promotoras Genéticas/genética
5.
Molecules ; 22(4)2017 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-28397746

RESUMO

The peptide hormone hepcidin is a key controller of systemic iron homeostasis, and its expression in the liver is mainly regulated by bone morphogenetic proteins (BMPs), which are heparin binding proteins. In fact, heparins are strong suppressors of hepcidin expression in hepatic cell lines that act by inhibiting the phosphorylation of SMAD1/5/8 proteins elicited by the BMPs. The inhibitory effect of heparins has been demonstrated in cells and in mice, where subcutaneous injections of non-anticoagulant heparins inhibited liver hepcidin expression and increased iron bioavailability. The chemical characteristics for high anti-hepcidin activity in vitro and in vivo include the 2O-and 6O-sulfation and a molecular weight above 7 kDa. The most potent heparins have been found to be the super-sulfated ones, active in hepcidin suppression with a molecular weight as low as 4 kDa. Moreover, the alteration of endogenous heparan sulfates has been found to cause a reduction in hepcidin expression in vitro and in vivo, indicating that heparins act by interfering with the interaction between BMPs and components of the complex involved in the activation of the BMP/SMAD1/5/8 pathway. This review summarizes recent findings on the anti-hepcidin activity of heparins and their possible use for the treatment of anemia caused by hepcidin excess, including the anemia of chronic diseases.


Assuntos
Anemia/tratamento farmacológico , Anemia/metabolismo , Heparina/farmacologia , Heparina/uso terapêutico , Hepcidinas/antagonistas & inibidores , Anemia/etiologia , Animais , Proteína Morfogenética Óssea 6/metabolismo , Proteínas Morfogenéticas Ósseas/metabolismo , Expressão Gênica , Heparitina Sulfato/metabolismo , Hepcidinas/genética , Hepcidinas/metabolismo , Homeostase , Humanos , Ferro/metabolismo , Fígado/metabolismo , Ligação Proteica
6.
Protein Eng Des Sel ; 30(2): 77-84, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27980120

RESUMO

Hepcidin is a liver-synthesized hormone that plays a central role in the regulation of systemic iron homeostasis. To produce a new tool for its functional properties the cDNA coding for camel hepcidin-25 was cloned at the 5'end of human FTH sequence into the pASK-IBA43plus vector for expression in Escherichia coli The recombinant fusion hepcidin-ferritin-H subunit was isolated as an insoluble iron-containing protein. When alone it did not refold in a 24-mer ferritin molecule, but it did when renatured together with H- or L-ferritin chains. We obtained stable ferritin shells exposing about 4 hepcidin peptides per 24-mer shell. The molecules were then reduced and re-oxidized in a controlled manner to allow the formation of the proper hepcidin disulfide bridges. The functionality of the exposed hepcidin was confirmed by its ability to specifically bind the mouse macrophage cell line J774 that express ferroportin and to promote ferroportin degradation. This chimeric protein may be useful for studying the hepcidin-ferroportin interaction in cells and also as drug-delivery agent.


Assuntos
Apoferritinas/química , Apoferritinas/metabolismo , Hepcidinas/genética , Multimerização Proteica , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Sequência de Aminoácidos , Animais , Apoferritinas/biossíntese , Apoferritinas/genética , Camelus , Proteínas de Transporte de Cátions/metabolismo , Linhagem Celular , Humanos , Ferro/metabolismo , Camundongos , Oxirredução , Estrutura Quaternária de Proteína , Transporte Proteico , Proteólise , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/genética , Solubilidade
7.
Biochim Biophys Acta ; 1850(6): 1267-73, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25749565

RESUMO

BACKGROUND: Three functional ferritin genes have been identified so far in mammals, and they encode the cytosolic Heavy (FTH) and Light chain (FTL) and the mitochondrial ferritin. The expression of a transcript by a fourth ferritin-like gene (Ferritin-Heavy-Polypeptide-Like-17, FTHL17) on the X chromosome was reported in mouse spermatogonia and in early embryonic cells. METHODS: The intronless human FTHL17 gene encodes a protein with 64% identity to human FTH with substitution of key residues of the ferroxidase center. The gene was cloned into vectors for expression in Escherichia coli and mammalian cells, linked to a flag-tag. RESULTS: The recombinant FTHL17 from E. coli purified as an assembled 24-mer ferritin devoid of ferroxidase activity and with a reduced physical stability. When transiently expressed in mammalian cells the flag-FTHL17 assembled in ferritin shells that showed reduced stability to denaturants compared with flag H and L ferritins. Immunocytochemistry with anti-flag antibody decorated the nuclei of flag-FTHL17 transfected COS cells, but not those of the cells transfected with flag-FTH or flag-FTL. CONCLUSIONS: We concluded that FTHL17 encodes a ferritin-like protein without ferroxidase activity. Its restricted embryonic expression and partial nuclear localization suggest that this novel ferritin type may have functions other than iron storage. GENERAL SIGNIFICANCE: The work confirms the presence of a fourth functional human ferritin gene with properties distinct from the canonical cytosolic ones.


Assuntos
Apoferritinas/metabolismo , Núcleo Celular/metabolismo , Sequência de Aminoácidos , Animais , Apoferritinas/química , Apoferritinas/genética , Células COS , Diferenciação Celular , Chlorocebus aethiops , Células-Tronco Embrionárias/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Células Hep G2 , Humanos , Camundongos , Dados de Sequência Molecular , Estrutura Molecular , Desnaturação Proteica , Estabilidade Proteica , Proteínas Recombinantes/metabolismo , Transfecção
8.
Front Pharmacol ; 6: 316, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26955355

RESUMO

Heparins are efficient inhibitors of hepcidin expression even in vivo, where they induce an increase of systemic iron availability. Heparins seem to act by interfering with BMP6 signaling pathways that control the expression of liver hepcidin, causing the suppression of SMAD1/5/8 phosphorylation. The anti-hepcidin activity persists also when the heparin anticoagulant property is abolished or reduced by chemical reactions of oxidation/reduction (glycol-split, Gs-Heparins) or by high sulfation (SS-Heparins), but the structural characteristics needed to optimize this inhibitory activity have not been studied in detail. To this aim we analyzed three different heparins (Mucosal Heparin, the Glycol split RO-82, the partially desulfated glycol-split RO-68 and the oversulfated SSLMWH) and separated them in fractions of molecular weight in the range 4-16 kD. Since the distribution of the negative charges in heparins contributes to the activity, we produced 2-O- and 6-O-desulfated heparins. These derivatives were analyzed for the capacity to inhibit hepcidin expression in hepatic HepG2 cells and in mice. The two approaches produced consistent results and showed that the anti-hepcidin activity strongly decreases with molecular weight below 7 kD, with high N-acetylation and after 2-O and 6-O desulfation. The high sulfation and high molecular weight properties for efficient anti-hepcidin activity suggest that heparin is involved in multiple binding sites.

9.
Biochem Pharmacol ; 92(3): 467-75, 2014 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-25241290

RESUMO

Hepcidin is a peptide hormone that controls systemic iron availability and is upregulated by iron and inflammation. Heparins have been shown to be efficient hepcidin inhibitors both in vitro and in vivo, even when their anticoagulant activity has been abolished by chemical reactions of oxidation/reduction (glycol-split). We analyzed a modified heparin type, characterized by a high, almost saturated, sulfation degree and low molecular weight. It inhibited hepcidin expression in hepatic HepG2 cells, and when used in mice, it readily suppressed liver hepcidin mRNA and serum hepcidin, with a significant decrease of spleen iron. This occurred also in inflammation-model, LPS-treated animals, and after heparin chronic 10-day treatments. The heparin had low/absent anticoagulant activity, as tested for factor-Xa and -IIA, APTT and anti Xa. It reduced triglyceride levels in the mice. This heparin acts faster and is more potent than the glycol split-heparins, probably because of its smaller molecular weight and higher sulfation degree. This modified heparin has potential applications for the treatment of diseases with high hepcidin levels.


Assuntos
Anticoagulantes/farmacologia , Heparina/química , Heparina/farmacologia , Hepcidinas/antagonistas & inibidores , Animais , Anticoagulantes/química , Fator Xa/metabolismo , Inibidores do Fator Xa/farmacologia , Células Hep G2/efeitos dos fármacos , Heparina de Baixo Peso Molecular/química , Heparina de Baixo Peso Molecular/farmacologia , Hepcidinas/metabolismo , Humanos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Camundongos Endogâmicos C57BL , Protrombina/metabolismo , Relação Estrutura-Atividade , Sulfatos/química , Triglicerídeos/metabolismo
10.
Front Pharmacol ; 5: 86, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24808863

RESUMO

The discovery of hepcidin clarified the basic mechanism of the control of systemic iron homeostasis. Hepcidin is mainly produced by the liver as a propeptide and processed by furin into the mature active peptide. Hepcidin binds ferroportin, the only cellular iron exporter, causing the internalization and degradation of both. Thus hepcidin blocks iron export from the key cells for dietary iron absorption (enterocytes), recycling of hemoglobin iron (the macrophages) and the release of storage iron from hepatocytes, resulting in the reduction of systemic iron availability. The BMP/HJV/SMAD pathway is the major regulator of hepcidin expression that responds to iron status. Also inflammation stimulates hepcidin via the IL6/STAT3 pathway with a support of an active BMP/HJV/SMAD pathway. In some pathological conditions hepcidin level is inadequately elevated and reduces iron availability in the body, resulting in anemia. These conditions occur in the genetic iron refractory iron deficiency anemia and the common anemia of chronic disease (ACD) or anemia of inflammation. Currently, there is no definite treatment for ACD. Erythropoiesis-stimulating agents and intravenous iron have been proposed in some cases but they are scarcely effective and may have adverse effects. Alternative approaches aimed to a pharmacological control of hepcidin expression have been attempted, targeting different regulatory steps. They include hepcidin sequestering agents (antibodies, anticalins, and aptamers), inhibitors of BMP/SMAD or of IL6/STAT3 pathway or of hepcidin transduction (siRNA/shRNA) or ferroportin stabilizers. In this review we summarized the biochemical interactions of the proteins involved in the BMP/HJV/SMAD pathway and its natural inhibitors, the murine and rat models with high hepcidin levels currently available and finally the progresses in the development of hepcidin antagonists, with particular attention to the role of heparins and heparin sulfate proteoglycans in hepcidin expression and modulation of the BMP6/SMAD pathway.

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