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1
Lobreaux, S., S. J. Yewdall, J. F. Briat et P. M. Harrison. « Amino-acid sequence and predicted three-dimensional structure of pea seed (Pisum sativum) ferritin ». Biochemical Journal 288, no 3 (15 décembre 1992) : 931–39. http://dx.doi.org/10.1042/bj2880931.
Texte intégralRésumé :
The iron storage protein, ferritin, is widely distributed in the living kingdom. Here the complete cDNA and derived amino-acid sequence of pea seed ferritin are described, together with its predicted secondary structure, namely a four-helix-bundle fold similar to those of mammalian ferritins, with a fifth short helix at the C-terminus. An N-terminal extension of 71 residues contains a transit peptide (first 47 residues) responsible for plastid targetting as in other plant ferritins, and this is cleaved before assembly. The second part of the extension (24 residues) belongs to the mature subunit; it is cleaved during germination. The amino-acid sequence of pea seed ferritin is aligned with those of other ferritins (49% amino-acid identity with H-chains and 40% with L-chains of human liver ferritin in the aligned region). A three-dimensional model has been constructed by fitting the aligned sequence to the coordinates of human H-chains, with appropriate modifications. A folded conformation with an 11-residue helix is predicted for the N-terminal extension. As in mammalian ferritins, 24 subunits assemble into a hollow shell. In pea seed ferritin, its N-terminal extension is exposed on the outside surface of the shell. Within each pea subunit is a ferroxidase centre resembling those of human ferritin H-chains except for a replacement of Glu-62 by His. The channel at the 4-fold-symmetry axes defined by E-helices, is predicted to be hydrophilic in plant ferritins, whereas it is hydrophobic in mammalian ferritins.
2
Morikawa, K., F. Oseko et S. Morikawa. « H- and L-rich ferritins suppress antibody production, but not proliferation, of human B lymphocytes in vitro ». Blood 83, no 3 (1 février 1994) : 737–43. http://dx.doi.org/10.1182/blood.v83.3.737.737.
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Abstract The effect of human spleen(L-rich) and heart(H-rich) ferritins on the proliferation and differentiation of human B lymphocytes was studied in comparison with that of holo- and apo-transferrins. Ferritins rich in H and L chain, as well as the transferrins, did not inhibit the proliferative response of resting and activated B cells stimulated with polyclonal B-cell mitogen, Staphylococcus aureus Cowan strain I. In contrast, the ferritins, but not the transferrins, clearly suppressed the antibody production by B blasts in T-cell-independent as well as T- cell-dependent system. Kinetic study showed that inhibitory action of ferritins on immunoglobulin (Ig) production was caused at an early stage of B-cell differentiation. The cytoplasmic Ig-containing cells decreased in proportion to the reduction of Ig secretion. The evidence that ferritin inhibited Ig synthesis of Epstein-Barr virus-transformed human B-lymphoblastoid cell line also supported the idea that the effect of ferritin was directed toward the antibody-producing B lymphocytes. The molecular analysis showed that the inhibitory effect of ferritin was regulated at the transcriptional level of the Ig generation signal. Our results suggest that H- and L-rich ferritins exert their inhibitory action on the differentiation of B cells maturing into Ig-producing cells.
3
Morikawa, K., F. Oseko et S. Morikawa. « H- and L-rich ferritins suppress antibody production, but not proliferation, of human B lymphocytes in vitro ». Blood 83, no 3 (1 février 1994) : 737–43. http://dx.doi.org/10.1182/blood.v83.3.737.bloodjournal833737.
Texte intégralRésumé :
The effect of human spleen(L-rich) and heart(H-rich) ferritins on the proliferation and differentiation of human B lymphocytes was studied in comparison with that of holo- and apo-transferrins. Ferritins rich in H and L chain, as well as the transferrins, did not inhibit the proliferative response of resting and activated B cells stimulated with polyclonal B-cell mitogen, Staphylococcus aureus Cowan strain I. In contrast, the ferritins, but not the transferrins, clearly suppressed the antibody production by B blasts in T-cell-independent as well as T- cell-dependent system. Kinetic study showed that inhibitory action of ferritins on immunoglobulin (Ig) production was caused at an early stage of B-cell differentiation. The cytoplasmic Ig-containing cells decreased in proportion to the reduction of Ig secretion. The evidence that ferritin inhibited Ig synthesis of Epstein-Barr virus-transformed human B-lymphoblastoid cell line also supported the idea that the effect of ferritin was directed toward the antibody-producing B lymphocytes. The molecular analysis showed that the inhibitory effect of ferritin was regulated at the transcriptional level of the Ig generation signal. Our results suggest that H- and L-rich ferritins exert their inhibitory action on the differentiation of B cells maturing into Ig-producing cells.
4
Ebrahimi, Kourosh Honarmand, Eckhard Bill, Peter-Leon Hagedoorn et Wilfred R. Hagen. « Spectroscopic evidence for the role of a site of the di-iron catalytic center of ferritins in tuning the kinetics of Fe(ii) oxidation ». Molecular BioSystems 12, no 12 (2016) : 3576–88. http://dx.doi.org/10.1039/c6mb00235h.
Texte intégralRésumé :
Spectroscopic studies of human H-type ferritin in comparison with an archaeal ferritin from Pyrococcus furiosus reveal how kinetics of a common mechanism of Fe(ii) oxidation is tuned differently in these two ferritins.
5
CORSI, Barbara, Federica PERRONE, Monique BOURGEOIS, Carole BEAUMONT, C. Maria PANZERI, Anna COZZI, Romina SANGREGORIO et al. « Transient overexpression of human H- and L-ferritin chains in COS cells ». Biochemical Journal 330, no 1 (15 février 1998) : 315–20. http://dx.doi.org/10.1042/bj3300315.
Texte intégralRésumé :
The understanding of the in vitro mechanisms of ferritin iron incorporation has greatly increased in recent years with the studies of recombinant and mutant ferritins. However, little is known about how this protein functions in vivo, mainly because of the lack of cellular models in which ferritin expression can be modulated independently from iron. To this aim, primate fibroblastoid COS-7 cells were transiently transfected with cDNAs for human ferritin H- and L-chains under simian virus 40 promoter and analysed within 66 h. Ferritin accumulation reached levels 300-500-fold higher than background, with about 40% of the cells being transfected. Thus ferritin concentration in individual cells was increased up to 1000-fold over controls with no evident signs of toxicity. The exogenous ferritin subunits were correctly assembled into homopolymers, but did not affect either the size or the subunit composition of the endogenous heteropolymeric fraction of ferritin, which remained essentially unchanged in the transfected and non-transfected cells. After 18 h of incubation with [59Fe]ferric-nitrilotriacetate, cellular iron incorporation was similar in the transfected and non-transfected cells and most of the protein-bound radioactivity was associated with ferritin heteropolymers, while H- and L-homopolymers remained iron-free. Cell co-transfection with cDNAs for H- and L-chains produced ferritin heteropolymers that also did not increase cellular iron incorporation. It is concluded that transient transfection of COS cells induces a high level of expression of ferritin subunits that do not co-assemble with the endogenous ferritins and have no evident activity in iron incorporation/metabolism.
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Fargion, S., AL Fracanzani, B. Brando, P. Arosio, S. Levi et G. Fiorelli. « Specific binding sites for H-ferritin on human lymphocytes : modulation during cellular proliferation and potential implication in cell growth control ». Blood 78, no 4 (15 août 1991) : 1056–61. http://dx.doi.org/10.1182/blood.v78.4.1056.1056.
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Abstract Interactions between human recombinant H- and L-ferritins and human lymphocytes were studied in vitro by direct binding assays and by flow cytometry. L-ferritin did not cause detectable specific binding, whereas H-ferritin showed a specific and saturable binding that increased markedly in phytohemagglutinin (PHA)-stimulated cells. This ferritin bound up to 30% of CD4+ and CD8+ T-lymphocytes and most B cells, indicating that expression of ferritin binding sites is not related to cell lineage or function. Dual-color flow cytometry experiments showed that ferritin binding sites were present on cells expressing the proliferation markers HLA-DR, MLR3, interleukin 2 (IL- 2), and transferrin receptors (Tf-R). In addition, after PHA induction, the time course of the expression of H-ferritin binding sites was similar to those of the above proliferation markers. Ferritin binding sites were observed in lymphocytes at all cell cycle phases, including the early S-phase. H-Ferritin at nanomolar and picomolar concentrations had an inhibitory effect on PHA-induced blastogenesis. We propose that H-ferritin binding sites behave like proliferation markers, with the unusual function of downregulating proliferation.
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Fargion, S., AL Fracanzani, B. Brando, P. Arosio, S. Levi et G. Fiorelli. « Specific binding sites for H-ferritin on human lymphocytes : modulation during cellular proliferation and potential implication in cell growth control ». Blood 78, no 4 (15 août 1991) : 1056–61. http://dx.doi.org/10.1182/blood.v78.4.1056.bloodjournal7841056.
Texte intégralRésumé :
Interactions between human recombinant H- and L-ferritins and human lymphocytes were studied in vitro by direct binding assays and by flow cytometry. L-ferritin did not cause detectable specific binding, whereas H-ferritin showed a specific and saturable binding that increased markedly in phytohemagglutinin (PHA)-stimulated cells. This ferritin bound up to 30% of CD4+ and CD8+ T-lymphocytes and most B cells, indicating that expression of ferritin binding sites is not related to cell lineage or function. Dual-color flow cytometry experiments showed that ferritin binding sites were present on cells expressing the proliferation markers HLA-DR, MLR3, interleukin 2 (IL- 2), and transferrin receptors (Tf-R). In addition, after PHA induction, the time course of the expression of H-ferritin binding sites was similar to those of the above proliferation markers. Ferritin binding sites were observed in lymphocytes at all cell cycle phases, including the early S-phase. H-Ferritin at nanomolar and picomolar concentrations had an inhibitory effect on PHA-induced blastogenesis. We propose that H-ferritin binding sites behave like proliferation markers, with the unusual function of downregulating proliferation.
8
Bauminger, E. R., A. Treffry, A. J. Hudson, D. Hechel, N. W. Hodson, S. C. Andrews, S. Levi et al. « Iron incorporation into ferritins : evidence for the transfer of monomeric Fe(III) between ferritin molecules and for the formation of an unusual mineral in the ferritin of Escherichia coli ». Biochemical Journal 302, no 3 (15 septembre 1994) : 813–20. http://dx.doi.org/10.1042/bj3020813.
Texte intégralRésumé :
Iron that has been oxidized by H-chain ferritin can be transferred into other ferritin molecules before it is incorporated into mature ferrihydrite iron cores. Iron(III) dimers are formed at the ferroxidase centres of ferritin H chains at an early stage of Fe(II) oxidation. Mössbauer spectroscopic data now show that the iron is transferred as monomeric species arising from dimer dissociation and that it binds to the iron core of the acceptor ferritin. Human H-chain ferritin variants containing altered threefold channels can act as acceptors, as can the ferritin of Escherichia coli (Ec-FTN). A human H-chain ferritin variant with a substituted tyrosine (rHuHF-Y34F) can act as a donor of Fe(III). Since an Fe(III)-tyrosinate (first identified in bullfrog H-chain ferritin) is absent from variant rHuHF-Y34F, the Fe(III) transferred is not derived from this tyrosinate complex. Mössbauer parameters of the small iron cores formed within Ec-FTN are significantly different from those of mammalian ferritins. Analysis of the spectra suggests that they are derived from both ferrihydrite and non-ferrihydrite components. This provides further evidence that the ferritin protein shell can influence the structure of its iron core.
9
Arosio, Paolo, Fernando Carmona, Raffaella Gozzelino, Federica Maccarinelli et Maura Poli. « The importance of eukaryotic ferritins in iron handling and cytoprotection ». Biochemical Journal 472, no 1 (30 octobre 2015) : 1–15. http://dx.doi.org/10.1042/bj20150787.
Texte intégralRésumé :
Ferritins, the main intracellular iron storage proteins, have been studied for over 60 years, mainly focusing on the mammalian ones. This allowed the elucidation of the structure of these proteins and the mechanisms regulating their iron incorporation and mineralization. However, ferritin is present in most, although not all, eukaryotic cells, comprising monocellular and multicellular invertebrates and vertebrates. The aim of this review is to provide an update on the general properties of ferritins that are common to various eukaryotic phyla (except plants), and to give an overview on the structure, function and regulation of ferritins. An update on the animal models that were used to characterize H, L and mitochondrial ferritins is also provided. The data show that ferritin structure is highly conserved among different phyla. It exerts an important cytoprotective function against oxidative damage and plays a role in innate immunity, where it also contributes to prevent parenchymal tissue from the cytotoxicity of pro-inflammatory agonists released by the activation of the immune response activation. Less clear are the properties of the secretory ferritins expressed by insects and molluscs, which may be important for understanding the role played by serum ferritin in mammals.
10
Fargion, S., P. Arosio, AL Fracanzani, V. Cislaghi, S. Levi, A. Cozzi, A. Piperno et G. Fiorelli. « Characteristics and expression of binding sites specific for ferritin H- chain on human cell lines ». Blood 71, no 3 (1 mars 1988) : 753–57. http://dx.doi.org/10.1182/blood.v71.3.753.753.
Texte intégralRésumé :
Abstract Purified recombinant human ferritin composed solely of H subunit was radiolabeled and incubated with proerythroleukemic K562 human cells. A specific binding was detected, and it could be displaced only by ferritins, natural or recombinant, containing large proportion of the H subunit. The specific ferritin H-chain binding was saturable, and cells showed 17,000 to 23,000 binding sites per cell. The affinity constant measured at 37 degrees C was of 3 x 10(8) M-1. Treatment with pronase eliminated the specific binding. The binding sites were expressed in a high number during the cellular exponential phase of growth and progressively decreased to disappear when cells reached the plateau phase. Treatment of the cells with desferrioxamine increased recombinant H-ferritin binding, while iron had little effect. K562 cells induced to differentiate by hemin failed to bind ferritin H. Ferritin H-chain binding capacity is present on various cell lines such as HL60, lung cancer, and hepatoma cells. Analysis of the binding sites by western blotting showed a peptide with apparent mol wt of about 100 kd.
11
Fargion, S., P. Arosio, AL Fracanzani, V. Cislaghi, S. Levi, A. Cozzi, A. Piperno et G. Fiorelli. « Characteristics and expression of binding sites specific for ferritin H- chain on human cell lines ». Blood 71, no 3 (1 mars 1988) : 753–57. http://dx.doi.org/10.1182/blood.v71.3.753.bloodjournal713753.
Texte intégralRésumé :
Purified recombinant human ferritin composed solely of H subunit was radiolabeled and incubated with proerythroleukemic K562 human cells. A specific binding was detected, and it could be displaced only by ferritins, natural or recombinant, containing large proportion of the H subunit. The specific ferritin H-chain binding was saturable, and cells showed 17,000 to 23,000 binding sites per cell. The affinity constant measured at 37 degrees C was of 3 x 10(8) M-1. Treatment with pronase eliminated the specific binding. The binding sites were expressed in a high number during the cellular exponential phase of growth and progressively decreased to disappear when cells reached the plateau phase. Treatment of the cells with desferrioxamine increased recombinant H-ferritin binding, while iron had little effect. K562 cells induced to differentiate by hemin failed to bind ferritin H. Ferritin H-chain binding capacity is present on various cell lines such as HL60, lung cancer, and hepatoma cells. Analysis of the binding sites by western blotting showed a peptide with apparent mol wt of about 100 kd.
12
Van Wuytswinkel, O., G. Savino et J. F. Briat. « Purification and characterization of recombinant pea-seed ferritins expressed in Escherichia coli : influence of N-terminus deletions on protein solubility and core formation in vitro ». Biochemical Journal 305, no 1 (1 janvier 1995) : 253–61. http://dx.doi.org/10.1042/bj3050253.
Texte intégralRésumé :
Plant ferritin subunits are synthesized as precursor molecules; the transit peptide (TP) in their NH2 extremity, responsible for plastid targeting, is cleaved during translocation to this compartment. In addition, the N-terminus of the mature subunit contains a plant-specific sequence named extension peptide (EP) [Ragland, Briat, Gagnon, Laulhère, Massenet, and Theil, E.C. (1990) J. Biol. Chem. 265, 18339-18344], the function of which is unknown. A novel pea-seed ferritin cDNA, with a consensus ferroxidase centre conserved within H-type animal ferritins has been characterized. This pea-seed ferritin cDNA has been engineered using oligonucleotide-directed mutagenesis to produce DNA fragments (1) corresponding to the wild-type (WT) ferritin precursor, (2) with the TP deleted, (3) with both the TP and the plant specific EP sequences deleted and (4) containing the TP but with the EP deleted. These four DNA fragments have been cloned in an Escherichia coli expression vector to produce the corresponding recombinant pea-seed ferritins. Expression at 37 degrees C led to the accumulation of recombinant pea-seed ferritins in inclusion bodies, whatever the construct introduced in E. coli. Expression at 25 degrees C in the presence of sorbitol and betaine allowed soluble proteins to accumulate when constructs with the TP deleted were used; under this condition, E. coli cells transformed with constructs containing the TP were unable to accumulate recombinant protein. Recombinant ferritins purified from inclusion bodies were found to be assembled only when the TP was deleted; however assembled ferritin under this condition had a ferroxidase activity undetectable at acid pH. On the other hand, soluble recombinant ferritins with the TP deleted and expressed at 25 degrees C were purified as 24-mers containing an average of 40-50 iron atoms per molecule. Despite the conservation in the plant ferritin subunit of a consensus ferroxidase centre, the iron uptake activity in vitro at pH 6.8 was found to be lower than that of the recombinant human H-ferritin, though it was much more active than the recombinant human L-ferritin. The recombinant ferritin with both the TP and the EP deleted (r delta TP/EP) assembled correctly as a 24-mer; it has slightly higher ferroxidase activity and decreased solubility compared with the wild-type protein with the TP deleted (r delta TP). In addition, on denaturation by urea followed by renaturation by dialysis the r delta TP/EP protein showed a 25% increase in core-formation in vitro compared with the r delta TP protein.(ABSTRACT TRUNCATED AT 400 WORDS)
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Kim, Kyung-Suk, Hyang-Ran Mun et Jung-Hoo Lee. « Iron cores of tadpole ferritin : native, reconstituted and recombinant H-chain ferritins ». Inorganica Chimica Acta 298, no 1 (janvier 2000) : 107–11. http://dx.doi.org/10.1016/s0020-1693(99)00423-5.
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and L Monteiro Rodrigues, eds, Catarina Rosado. « Proceedings - CBIOS Science Sessions 2020 ». Biomedical and Biopharmaceutical Research Journal 17, no 2 (novembre 2020) : 1–7. http://dx.doi.org/10.19277/bbr.17.2.245.
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Science Sessions 2020 Catarina Rosado and L Monteiro Rodrigues, eds. Vinicius Cuña, Universidade Lusófona de Humanidades e Tecnologias `````````````````````````````````` p.2 Oxygen Ozone Therapy - Tool in Veterinary Medicine Oxigênio Ozônio Terapia - Ferramenta na Medicina Veterinária Elisabete Silva, Faculdade de Ciências da Universidade de Lisboa p.2 Eco-friendly mon-biocide-releasing antifouling coatings for biofouling prevention Revestimentos antivegetativos monocidas amigos do ambiente para a prevenção de biofouling Amélia Pilar Rauter, Centro de Química Estrutural, Faculdade de Ciências; Universidade de Lisboa, p.3 Departamento de Química e Bioquímica, CiênciasULisboa. The sustainable chemistry of sugars: New antibacterial with a new mechanism of action A química sustentável dos açúcares: Novos antibacterianos com um novo mecanismo de ação Sofia Ramos, CBIOS Lusófona’s Research Center for Biosciences and Health Technologies p.4 Expression profile of cellular redox and calcium signaling-related genes: role in breast cancer progression Perfil de expressão de genes redox celulares e de sinalização de cálcio: papel na progressão do cancro da mama Ana Coutinho, Departamento de Química e Bioquímica. Faculdade de Ciências da Universidade de Lisboa p.4 Studying the conformational plasticity of KcsA potassium channel by homo-FRET Estudo da plasticidade conformacional do canal de potássio KcsA por homo-FRET Andreia Valente, Centro de Química Estrutural da Faculdade de Ciências da Universidade de Lisboa` p.5 Targeted cancer therapy using ruthenium compounds Terapia específica do cancro usando compostos de ruténio Sérgio Faloni Andrade, CBIOS Lusófona’s Research Center for Biosciences and Health Technologies p.5 Natural products and their potential to treat gastrointestinal inflammatory and ulcerative diseases Produtos naturais e o seu potencial para tratar doenças inflamatórias e ulcerativas gastrointestinais Cláudia Nunes, LAQV, Requimte, FFUP p.6 Fat nanoparticles: a diet towards targeted nano delivery Nanopartículas de gordura: uma dieta orientada para a nanodeficiência Cíntia Ferreira-Pêgo, CBIOS Lusófona’s Research Center for Biosciences and Health Technologies p.6 Mediterranean diet adherence, eating behavior and body shape concerns in Portuguese university students Adesão à dieta mediterrânica, comportamento alimentar e preocupações com a forma do corpo em estudantes universitários portugueses João Gregório, CBIOS Lusófona's Research Center for Biosciences and Health Technologies p. 7 "Pharmacists' guide to the future: challenges and opportunities for research and development of pharmacy services" "Guia dos farmacêuticos para o futuro: desafios e oportunidades para a investigação e desenvolvimento dos serviços de farmácia" Andreia Valença, Universidade Lusófona de Humanidades e Tecnologias p. 7 TIM2: a new membrane receiver for ferritin-H in the retina of murganho TIM2: um novo receptor de membrana para a ferritina-H na retina de murganho
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Kwon, Mun-Gyeong, Ji-Min Jeong, Ju-Won Kim et Chan-Il Park. « Molecular cloning and expression analysis of a ferritin H subunit from rock bream, Oplegnathus fasciatus ». Journal of fish pathology 26, no 3 (31 décembre 2013) : 295–301. http://dx.doi.org/10.7847/jfp.2013.26.3.295.
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Cozzi, Anna, Paolo Santambrogio, Daniela Privitera, Vania Broccoli, Luisa Ida Rotundo, Barbara Garavaglia, Rudolf Benz et al. « Human L-ferritin deficiency is characterized by idiopathic generalized seizures and atypical restless leg syndrome ». Journal of Experimental Medicine 210, no 9 (12 août 2013) : 1779–91. http://dx.doi.org/10.1084/jem.20130315.
Texte intégralRésumé :
The ubiquitously expressed iron storage protein ferritin plays a central role in maintaining cellular iron homeostasis. Cytosolic ferritins are composed of heavy (H) and light (L) subunits that co-assemble into a hollow spherical shell with an internal cavity where iron is stored. The ferroxidase activity of the ferritin H chain is critical to store iron in its Fe3+ oxidation state, while the L chain shows iron nucleation properties. We describe a unique case of a 23-yr-old female patient affected by a homozygous loss of function mutation in the L-ferritin gene, idiopathic generalized seizures, and atypical restless leg syndrome (RLS). We show that L chain ferritin is undetectable in primary fibroblasts from the patient, and thus ferritin consists only of H chains. Increased iron incorporation into the FtH homopolymer leads to reduced cellular iron availability, diminished levels of cytosolic catalase, SOD1 protein levels, enhanced ROS production and higher levels of oxidized proteins. Importantly, key phenotypic features observed in fibroblasts are also mirrored in reprogrammed neurons from the patient’s fibroblasts. Our results demonstrate for the first time the pathophysiological consequences of L-ferritin deficiency in a human and help to define the concept for a new disease entity hallmarked by idiopathic generalized seizure and atypical RLS.
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Treffry, A., E. R. Bauminger, D. Hechel, N. W. Hodson, I. Nowik, S. J. Yewdall et P. M. Harrison. « Defining the roles of the threefold channels in iron uptake, iron oxidation and iron-core formation in ferritin : a study aided by site-directed mutagenesis ». Biochemical Journal 296, no 3 (15 décembre 1993) : 721–28. http://dx.doi.org/10.1042/bj2960721.
Texte intégralRésumé :
This paper aims to define the role of the threefold intersubunit channels in iron uptake and sequestration processes in the iron-storage protein, ferritin. Iron uptake, measured as loss of availability of Fe(II) to ferrozine (due to oxidation), has been studied in recombinant human H-chain ferritins bearing amino acid substitutions in the threefold channels or ferroxidase centres. Similar measurements with recombinant horse L-chain ferritin are compared. It is concluded that significant Fe(II) oxidation occurs only at the H-chain ferroxidase centres and not in the threefold channels, although this route is used by Fe(II) for entry. Investigations by Mössbauer and u.v.-difference spectroscopy show that part of the iron oxidized by H-chain ferritin returns to the threefold channels as Fe(III). This monomeric Fe(III) can be displaced by addition of Tb(III). Fe(III) also moves into the cavity for formation of the iron-core mineral, ferrihydrite. Iron incorporated into ferrihydrite becomes kinetically inert.
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Pozzi, Cecilia, Flavio Di Pisa, Caterina Bernacchioni, Silvia Ciambellotti, Paola Turano et Stefano Mangani. « Iron binding to human heavy-chain ferritin ». Acta Crystallographica Section D Biological Crystallography 71, no 9 (25 août 2015) : 1909–20. http://dx.doi.org/10.1107/s1399004715013073.
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Maxi-ferritins are ubiquitous iron-storage proteins with a common cage architecture made up of 24 identical subunits of five α-helices that drive iron biomineralization through catalytic iron(II) oxidation occurring at oxidoreductase sites (OS). Structures of iron-bound human H ferritin were solved at high resolution by freezing ferritin crystals at different time intervals after exposure to a ferrous salt. Multiple binding sites were identified that define the iron path from the entry ion channels to the oxidoreductase sites. Similar data are available for another vertebrate ferritin: the M protein fromRana catesbeiana. A comparative analysis of the iron sites in the two proteins identifies new reaction intermediates and underlines clear differences in the pattern of ligands that define the additional iron sites that precede the oxidoreductase binding sites along this path. Stopped-flow kinetics assays revealed that human H ferritin has different levels of activity compared with itsR. catesbeianacounterpart. The role of the different pattern of transient iron-binding sites in the OS is discussed with respect to the observed differences in activity across the species.
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SANTAMBROGIO, Paolo, Patrizia PINTO, Sonia LEVI, Anna COZZI, Ermanna ROVIDA, Alberto ALBERTINI, Peter ARTYMIUK, Pauline M. HARRISON et Paolo AROSIO. « Effects of modifications near the 2-, 3- and 4-fold symmetry axes on human ferritin renaturation ». Biochemical Journal 322, no 2 (1 mars 1997) : 461–68. http://dx.doi.org/10.1042/bj3220461.
Texte intégralRésumé :
Ferritin is a protein of 24 subunits which assemble into a shell with 432 point symmetry. It can be denatured reversibly in acidic guanidine hydrochloride, with the formation of poorly populated renaturation intermediates. In order to increase the accumulation of intermediates and to study the mechanism of ferritin renaturation, we analysed variants of the human ferritin H-chain altered at the N-terminus (Δ1–13), near the 4-fold axis (Leu-169→Arg), the 3-fold axis (Asp-131→Ile+Glu-134→Phe) or the 2-fold axis (Ile-85→Cys). We also carried out specific chemical modifications of Cys-130 (near the 3-fold axis) and Cys-85 (near the 2-fold axis). Renaturation of the modified ferritins yielded assembly intermediates that differed in size and physical properties. Alterations of residues around the 2-, 4- and 3-fold axes produced subunit monomers, dimers and higher oligomers respectively. All these intermediates could be induced to assemble into ferritin 24-mers by concentrating them or by co-renaturing them with wild-type H-ferritin. The results support the hypothesis that the symmetric subunit dimers are the building blocks of ferritin assembly, and are consistent with a reassembly pathway involving the coalescence of dimers, probably around the 4-fold axis, followed by stepwise addition of dimers until the 24-mer cage is completed. In addition they show that assembly interactions are responsible for the large hysteresis of folding and unfolding plots. The implications of the studies for in vivoheteropolymer formation in vertebrates, which have two types of ferritin chain (H and L), are discussed.
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LEVI, Sonia, Paolo SANTAMBROGIO, Barbara CORSI, Anna COZZI et Paolo AROSIO. « Evidence that residues exposed on the three-fold channels have active roles in the mechanism of ferritin iron incorporation ». Biochemical Journal 317, no 2 (15 juillet 1996) : 467–73. http://dx.doi.org/10.1042/bj3170467.
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Iron is thought to enter the ferritin cavity via the three-fold channel, which is lined in its narrowest part by the residues Asp-131 and Glu-134. We describe here variants of human ferritins with active and inactive ferroxidase centres having Asp-131 and Glu-134 substituted with Ala and Ala or with Ile and Phe respectively. The two types of substitution had similar effects on ferritin functionality: (i) they decreased the amount of iron incorporated from Fe(II) solutions and decreased ferroxidase activity by about 50%; (ii) they inhibited iron incorporation from Fe(III) citrate in the presence of ascorbate; (iii) they resulted in loss of Fe and Tb binding sites; and (iv) they resulted in a marked decrease in the inhibition of iron oxidation by Tb (but not by Zn). In addition, it was found that substitution with Ala of Cys-130 and His-118, both of which face the three-fold channel, decreased the capacity of H-ferritin to bind terbium and to incorporate iron from Fe(III) citrate in the presence of ascorbate. The results indicate that: (i) the three-fold channels are the major sites of iron transfer into the cavity of H- and L-ferritins; (ii) at least two metal binding sites are located on the channels which play an active role in capturing and transferring iron into the cavity; and (iii) the permeability of the channel is apparently not affected by the hydrophilicity of its narrowest part. In addition, it is proposed that iron incorporation from Fe(III) citrate complexes in the presence of ascorbate is a reliable, and possibly more physiological, approach to the study of ferritin functionality.
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Lucignano, Rosanna, Alessandro Pratesi, Paola Imbimbo, Daria Maria Monti, Delia Picone, Luigi Messori, Giarita Ferraro et Antonello Merlino. « Evaluation of Auranofin Loading within Ferritin Nanocages ». International Journal of Molecular Sciences 23, no 22 (16 novembre 2022) : 14162. http://dx.doi.org/10.3390/ijms232214162.
Texte intégralRésumé :
Auranofin (AF), a gold(I) compound that is currently used for the treatment of rheumatoid arthritis and is in clinical trials for its promising anticancer activity, was encapsulated within the human H-chain and the horse spleen ferritin nanocages using the alkaline disassembly/reassembly protocol. The aim of the work was to highlight possible differences in their drug loading capacity and efficacy. The drug-loaded ferritins were characterized via UV-vis absorption spectroscopy and inductively coupled plasma-atomic emission spectroscopy to assess AF encapsulation and to define the exact amount of gold atoms trapped in the Ft cavity. The crystal structures allowed us to define the nature of AF interaction with both ferritins and to identify the gold binding sites. Moreover, the biological characterization let us to obtain preliminary information on the cytotoxic effect of AF when bound to the human H-chain.
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Bou-Abdallah, Fadi, John Paliakkara, Galina Melman et Artem Melman. « Reductive Mobilization of Iron from Intact Ferritin : Mechanisms and Physiological Implication ». Pharmaceuticals 11, no 4 (5 novembre 2018) : 120. http://dx.doi.org/10.3390/ph11040120.
Texte intégralRésumé :
Ferritins are highly conserved supramolecular protein nanostructures composed of two different subunit types, H (heavy) and L (light). The two subunits co-assemble into a 24-subunit heteropolymer, with tissue specific distributions, to form shell-like protein structures within which thousands of iron atoms are stored as a soluble inorganic ferric iron core. In-vitro (or in cell free systems), the mechanisms of iron(II) oxidation and formation of the mineral core have been extensively investigated, although it is still unclear how iron is loaded into the protein in-vivo. In contrast, there is a wide spread belief that the major pathway of iron mobilization from ferritin involves a lysosomal proteolytic degradation of ferritin, and the dissolution of the iron mineral core. However, it is still unclear whether other auxiliary iron mobilization mechanisms, involving physiological reducing agents and/or cellular reductases, contribute to the release of iron from ferritin. In vitro iron mobilization from ferritin can be achieved using different reducing agents, capable of easily reducing the ferritin iron core, to produce soluble ferrous ions that are subsequently chelated by strong iron(II)-chelating agents. Here, we review our current understanding of iron mobilization from ferritin by various reducing agents, and report on recent results from our laboratory, in support of a mechanism that involves a one-electron transfer through the protein shell to the iron mineral core. The physiological significance of the iron reductive mobilization from ferritin by the non-enzymatic FMN/NAD(P)H system is also discussed.
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Massover, William H., Sonia Levi, Alessandra Luzzago, Paola Tateo et Paolo Arosio. « Ultrastructure of Two Mutants in the H-Subunit of Recombinant Human Ferritin : Ordered Arrays Indicate Altered Surface Properties ». Proceedings, annual meeting, Electron Microscopy Society of America 48, no 1 (12 août 1990) : 288–89. http://dx.doi.org/10.1017/s0424820100180197.
Texte intégralRésumé :
Two major types of polypeptide subunits, H and L, coassemble (n = 24) as heteropolymers to form molecules of the iron-storage protein, ferritin [1]. The significance of the H-type subunits for molecular structure and function remains unclear. The present study has examined the ultrastructure of recombinant human ferritins which are homopolymers of wild-type or mutant H-subunits [2]. Both mutations change the aminoacid sequence along the outer surface of the molecule; 9Cd has a single substitution of glycine for the lysine at position 86, and Ml has a duplication of 18 aminoacids [2].Recombinant ferritins were overexpressed in E. coli. and purified as described by Levi et al [2]. Samples (0.1-0.5 mg/ml) were deposited onto a thin carbon film stripped from freshly cleaved mica and carried on 400 mesh grids; these specimen carriers had been made hydrophilic by glow discharge treatment. After negative staining with 2% sodium silicotungstate (pH 7.0), the specimens were dried and examined at lOOkV with a JEOL 100CX electron microscope.
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Collawn, James F., Henry Donato et Wayne W. Fish. « Evidence that H-enriched human placental ferritin is structurally similar to L-enriched ferritins of other tissues ». Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology 871, no 3 (juin 1986) : 235–42. http://dx.doi.org/10.1016/0167-4838(86)90204-9.
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Scindia, Yogesh, Ewa Wlazlo, Elizabeth Ghias, Valentina Voi, Sylvia Cechova, Joseph Leeds et Sundararaman Swaminathan. « Therapeutic Benefit of Regulating Iron Metabolism in Spontaneous Lupus Nephritis ». Journal of Immunology 204, no 1_Supplement (1 mai 2020) : 236.7. http://dx.doi.org/10.4049/jimmunol.204.supp.236.7.
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Abstract Background Lupus nephritis (LN) is an end-organ complication of Systemic lupus erythematosus and is more common in premenopausal women. Hepcidin, the master regulator of iron homeostasis, modulates inflammation and is negatively regulated by estrogen. Therefore, we hypothesized that exogenous hepcidin may reduce the severity and delay the onset of LN. Methods Pre-nephritic 8-week-old or nephritic 16-week-old MRL/lpr female mice were injected Hepcidin (50ug, i.p) or vehicle twice a week and markers of renal injury and inflammation were examined at 18 and 20 weeks of age. The direct effect of hepcidin on macrophages was studied in-vitro. Results Hepcidin reduced intrarenal iron accumulation, and increased H-ferritin. This was associated with reduced renal inflammation and immune cell infiltration, which collectively mitigated microalbuminuria and tubular injury, independent of immune complex deposits and autoantibodies. The increase in H-ferritin, was associated with a reduced number of renal Ki-67+-F4/80+ macrophages. In-vitro, hepcidin induced H-ferritin in macrophages and reduced labile (Fe2+) iron. H-ferritinhi macrophages proliferated less upon Mcsf-1 stimulation and secreted less IL-1b, and IL-6 upon TLR-3 activation. Hepcidin reduced microalbuminuria when administered to nephritic, 16-week-old mice without worsening lupus-associated anemia. Conclusions We have identified that hepcidin targets iron homeostasis and reduces cardinal pathogenic features of LN. Importantly, Hepcidin treatment ameliorates kidney disease in mice with established proteinuria. Thus, our data highlight that targeting cellular iron metabolism with hepcidin represents a promising and a new therapeutic strategy in LN.
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Waidner, Barbara, Stefan Greiner, Stefan Odenbreit, Holger Kavermann, Jyoti Velayudhan, Frank Stähler, Johannes Guhl et al. « Essential Role of Ferritin Pfr in Helicobacter pylori Iron Metabolism and Gastric Colonization ». Infection and Immunity 70, no 7 (juillet 2002) : 3923–29. http://dx.doi.org/10.1128/iai.70.7.3923-3929.2002.
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ABSTRACT The reactivity of the essential element iron necessitates a concerted expression of ferritins, which mediate iron storage in a nonreactive state. Here we have further established the role of the Helicobacter pylori ferritin Pfr in iron metabolism and gastric colonization. Iron stored in Pfr enabled H. pylori to multiply under severe iron starvation and protected the bacteria from acid-amplified iron toxicity, as inactivation of the pfr gene restricted growth of H. pylori under these conditions. The lowered total iron content in the pfr mutant, which is probably caused by decreased iron uptake rates, was also reflected by an increased resistance to superoxide stress. Iron induction of Pfr synthesis was clearly diminished in an H. pylori feoB mutant, which lacked high-affinity ferrous iron transport, confirming that Pfr expression is mediated by changes in the cytoplasmic iron pool and not by extracellular iron. This is well in agreement with the recent discovery that iron induces Pfr synthesis by abolishing Fur-mediated repression of pfr transcription, which was further confirmed here by the observation that iron inhibited the in vitro binding of recombinant H. pylori Fur to the pfr promoter region. The functions of H. pylori Pfr in iron metabolism are essential for survival in the gastric mucosa, as the pfr mutant was unable to colonize in a Mongolian gerbil-based animal model. In summary, the pfr phenotypes observed give new insights into prokaryotic ferritin functions and indicate that iron storage and homeostasis are of extraordinary importance for H. pylori to survive in its hostile natural environment.
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SANTAMBROGIO, Paolo, Sonia LEVI, Anna COZZI, Barbara CORSI et Paolo AROSIO. « Evidence that the specificity of iron incorporation into homopolymers of human ferritin L- and H-chains is conferred by the nucleation and ferroxidase centres ». Biochemical Journal 314, no 1 (15 février 1996) : 139–44. http://dx.doi.org/10.1042/bj3140139.
Texte intégralRésumé :
Mammalian ferritins are iron-storage proteins made of 24 subunits of two types: the H- and L-chains. L-chains, in contrast with H-chains, lack detectable ferroxidase activity. When ferritins were subjected to iron loading in vitro with increments near the saturation limit of 4000 Fe atoms per molecule, the homopolymers of human H-chains formed insoluble aggregates, caused by non-specific iron hydrolysis, whereas the homopolymers of L-chains remained soluble and incorporated most of the available iron. To analyse the molecular reasons for the difference, Glu-57 and Glu-60, which are conserved and exposed on the cavity of L-chains, were substituted with His, as in H-chains. The double substitution made the L-homopolymers as sensitive as the H-homopolymers to the iron-induced aggregation, whereas the opposite substitution in the H-chain increased homopolymer resistance to the aggregation only marginally. Millimolar concentrations of citrate and phosphate increased iron incorporation in H-homopolymers by reducing non-specific iron hydrolysis, but inhibited that in L-homopolymers by sequestering available iron. The data indicate that the specific iron incorporation into L-homopolymers is mainly due to the iron-nucleation capacity of Glu-57, Glu-60 and other carboxyl groups exposed on the cavity; in contrast, the specificity of iron incorporation into H-homopolymers is related to its ferroxidase activity, which determines rapid Fe(III) accumulation inside the cavity. The finding that ferroxidase centres are essential for the incorporation of iron in the presence of likely candidates of cellular iron transport, such as phosphate and citrate, confirms their importance in ferritin function in vivo.
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Ruscitti, P., P. Di Benedetto, O. Berardicurti, N. Panzera, F. Sensini, P. Cipriani et R. Giacomelli. « FRI0006 ASSESSING PRO-INFLAMMATORY PROPERTIES OF H-FERRITIN BY EX VIVO AND IN VITRO OBSERVATIONS ». Annals of the Rheumatic Diseases 79, Suppl 1 (juin 2020) : 574.2–574. http://dx.doi.org/10.1136/annrheumdis-2020-eular.3473.
Texte intégralRésumé :
Background:The concept of ‘hyperferritinemic syndrome’ has recently been proposed, suggesting high levels of ferritin as pathogenic pro-inflammatory mediator [1] Ferritin is an intracellular iron storage protein, comprising 24 subunits, heavy (H) and light (L) based on molecular weight. The H-/L subunits ratio may be different in tissues, since the ferritin enriched in L subunits (L-ferritin) and the ferritin enriched in H subunits (H-ferritin) may be observed in different tissues, according to pathophysiologic status [1].Objectives:We aimed to assess the presence of H- and L-ferritin as well as of CD68/H-ferritin and CD68/L-ferritin in bone marrow (BM) biopsies of adult macrophage activation syndrome (MAS) patients. In the same patients, we matched the findings of BM biopsies with sera to identify the main represented subunits of ferritin. Furthermore, we evaluated effects of ferritin, L-ferritin, and H-ferritin on human monocytes, assessing pro- and anti-inflammatory cytokines, and expression of NLRP3 inflammasome. Finally, we checked the ability of monocytes, which were treated with ferritin, to stimulate or not the proliferation of peripheral blood mononuclear cells (PBMCs).Methods:Immunofluorescence analysis was performed to investigate the tissue presence of L- and H-ferritin in BM biopsies as well as of CD68/H-ferritin and CD68/L-ferritin. Liquid chromatography mass spectrometry (LC-MS/MS) based proteomics was performed to identify L- and H-ferritin in sera proteins. Human monocytes were cultured with M-CSF for 7 days and, after that, treated with ferritin, H-ferritin, and L-ferritin at 10nM, for 120 and 240 minutes. After stimulation, IL-1β, IL-6, IL-10, IL-12, IFN-γ, TGF-β, TNF, and VEGF were assessed by RT-PCR and, in case of positive finding, evaluated by western blot. NLRP3 inflammasome was also assessed. Finally, the proliferation of PBMCs when co-cultured with ferritin-treated monocytes was tested by a specific proliferation assay.Results:Immunofluorescence showed an increased H-ferritin expression in the BMs of MAS patients, whereas L-ferritin did not. Conversely, LC-MS/MS identified that the L-ferritin was the dominant form, after stringent probability matching.In vitro, H-Ferritin induced a significant increased expression of IL-1β, IL-6, IL-12, and TNF after 240 minutes. Ferritin also induced a significant increased expression of IL-1β, IL-6, IL-12, and TNF after 240 minutes. Effects on pro-inflammatory cytokines were more marked with H-ferritin than ferritin. Conversely, no significant effects were retrieved analysing IFN-γ, IL-10, TGF-β, and VEGF after 240 minutes, after ferritin and H-ferritin stimulation. Furthermore, both ferritin and H-ferritin induced a direct effect on NLRP3 inflammasome. Finally, monocytes, which were treated with H-ferritin, stimulated the proliferation of co-cultured PBMCs.Conclusion:In our work, results showed the presence of H-ferritin and CD68/H-ferritin cells in BM biopsies of MAS patients, by immunofluorescence. Conversely, LC-MS/MS identified L-ferritin in sera proteins of those patients. Furthermore, pro-inflammatory effects of ferritin and, particularly, of H-ferritin on human monocytes were observedin vitro, increasing pro-inflammatory cytokines and NLRP3 inflammosome. Finally, H-ferritin-treated monocytes stimulated the proliferation of co-cultured PBMCs.References:[1]Rosario C, et al. BMC Med 2013; 11:185.Disclosure of Interests:Piero Ruscitti Grant/research support from: Pfizer, Speakers bureau: BMS, MSD, Ely Lilly, SOBI, Paola Di Benedetto Grant/research support from: Paola Di Benedetto received grant from Dompè outside this work., Onorina Berardicurti: None declared, Noemi Panzera: None declared, Federica Sensini: None declared, Paola Cipriani Grant/research support from: Actelion, Pfizer, Speakers bureau: Actelion, Pfizer, Roberto Giacomelli Grant/research support from: Actelion, Pfizer, Speakers bureau: Abbvie, Roche, Actelion, BMS, MSD, Ely Lilly, SOBI, Pfizer
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Levi, Sonia, Domenico Girelli, Federica Perrone, Marcella Pasti, Carole Beaumont, Roberto Corrocher, Alberto Albertini et Paolo Arosio. « Analysis of Ferritins in Lymphoblastoid Cell Lines and in the Lens of Subjects With Hereditary Hyperferritinemia-Cataract Syndrome ». Blood 91, no 11 (1 juin 1998) : 4180–87. http://dx.doi.org/10.1182/blood.v91.11.4180.
Texte intégralRésumé :
Abstract Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal and dominant disease caused by heterogeneous mutations in the iron responsive element (IRE) of the 5′ untranslated flanking region of ferritin L-chain mRNA, which reduce the binding to the trans iron regulatory proteins and make L-chain synthesis constitutively upregulated. In the several families identified so far, the serum and tissue L-ferritin levels are fivefold to 20-fold higher than in nonaffected control subjects, iron metabolism is apparently normal, and the only relevant clinical symptom is early onset, bilateral cataract. Some pathogenetic aspects of HHCS remain obscure, with particular reference to the isoferritins produced by HHCS cells, as well as the mechanism of cataract formation. We analyzed lymphoblastoid cell lines obtained from two nonaffected control subjects and from HHCS patients carrying the substitution A40G (Paris-1), G41C (Verona-1), and the deletion of the residues 10-38 (Verona-2) in the IRE structure. Enzyme-linked immunosorbent assays specific for the H- and L-type ferritins showed that L-ferritin levels were up to 20-fold higher in HHCS than in control cells and were not affected by iron supplementation or chelation. Sequential immunoprecipitation experiments of metabolically-labeled cells with specific antibodies indicated that in HHCS cells about half of the L-chain was assembled in L-chain homopolymers, which did not incorporate iron, and the other half was assembled in isoferritins with a high proportion of L-chain. In control cells, all ferritin was assembled in functional heteropolymers with equivalent proportion of H- and L-chains. Cellular and ferritin iron uptake was slightly higher in HHCS than control cells. In addition, we analyzed the lens recovered from cataract surgery of a HHCS patient. We found it to contain about 10-fold more L-ferritin than control lens. The ferritin was fully soluble with a low iron content. It was purified and partially characterized. Our data indicate that: (1) in HHCS cells a large proportion of L-ferritin accumulates as nonfunctional L-chain 24 homopolymers; (2) the concomitant fivefold to 10-fold expansion of ferritin heteropolymers, with a shift to L-chain–rich isoferritins, does not have major effects on cellular iron metabolism; (3) L-chain accumulation occurs also in the lens, where it may induce cataract formation by altering the delicate equilibrium between other water-soluble proteins (ie, crystallins) and/or the antioxidant properties.
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Levi, Sonia, Domenico Girelli, Federica Perrone, Marcella Pasti, Carole Beaumont, Roberto Corrocher, Alberto Albertini et Paolo Arosio. « Analysis of Ferritins in Lymphoblastoid Cell Lines and in the Lens of Subjects With Hereditary Hyperferritinemia-Cataract Syndrome ». Blood 91, no 11 (1 juin 1998) : 4180–87. http://dx.doi.org/10.1182/blood.v91.11.4180.411k38_4180_4187.
Texte intégralRésumé :
Hereditary hyperferritinemia-cataract syndrome (HHCS) is an autosomal and dominant disease caused by heterogeneous mutations in the iron responsive element (IRE) of the 5′ untranslated flanking region of ferritin L-chain mRNA, which reduce the binding to the trans iron regulatory proteins and make L-chain synthesis constitutively upregulated. In the several families identified so far, the serum and tissue L-ferritin levels are fivefold to 20-fold higher than in nonaffected control subjects, iron metabolism is apparently normal, and the only relevant clinical symptom is early onset, bilateral cataract. Some pathogenetic aspects of HHCS remain obscure, with particular reference to the isoferritins produced by HHCS cells, as well as the mechanism of cataract formation. We analyzed lymphoblastoid cell lines obtained from two nonaffected control subjects and from HHCS patients carrying the substitution A40G (Paris-1), G41C (Verona-1), and the deletion of the residues 10-38 (Verona-2) in the IRE structure. Enzyme-linked immunosorbent assays specific for the H- and L-type ferritins showed that L-ferritin levels were up to 20-fold higher in HHCS than in control cells and were not affected by iron supplementation or chelation. Sequential immunoprecipitation experiments of metabolically-labeled cells with specific antibodies indicated that in HHCS cells about half of the L-chain was assembled in L-chain homopolymers, which did not incorporate iron, and the other half was assembled in isoferritins with a high proportion of L-chain. In control cells, all ferritin was assembled in functional heteropolymers with equivalent proportion of H- and L-chains. Cellular and ferritin iron uptake was slightly higher in HHCS than control cells. In addition, we analyzed the lens recovered from cataract surgery of a HHCS patient. We found it to contain about 10-fold more L-ferritin than control lens. The ferritin was fully soluble with a low iron content. It was purified and partially characterized. Our data indicate that: (1) in HHCS cells a large proportion of L-ferritin accumulates as nonfunctional L-chain 24 homopolymers; (2) the concomitant fivefold to 10-fold expansion of ferritin heteropolymers, with a shift to L-chain–rich isoferritins, does not have major effects on cellular iron metabolism; (3) L-chain accumulation occurs also in the lens, where it may induce cataract formation by altering the delicate equilibrium between other water-soluble proteins (ie, crystallins) and/or the antioxidant properties.
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Fisher, J., K. Devraj, J. Ingram, B. Slagle-Webb, A. B. Madhankumar, X. Liu, M. Klinger, I. A. Simpson et J. R. Connor. « Ferritin : a novel mechanism for delivery of iron to the brain and other organs ». American Journal of Physiology-Cell Physiology 293, no 2 (août 2007) : C641—C649. http://dx.doi.org/10.1152/ajpcell.00599.2006.
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Traditionally, transferrin has been considered the primary mechanism for cellular iron delivery, despite suggestive evidence for additional iron delivery mechanisms. In this study we examined ferritin, considered an iron storage protein, as a possible delivery protein. Ferritin consists of H- and L-subunits, and we demonstrated iron uptake by ferritin into multiple organs and that the uptake of iron is greater when the iron is delivered via H-ferritin compared with L-ferritin. The delivery of iron via H-ferritin but not L-ferritin was significantly decreased in mice with compromised iron storage compared with control, indicating that a feedback mechanism exists for H-ferritin iron delivery. To further evaluate the mechanism of ferritin iron delivery into the brain, we used a cell culture model of the blood-brain barrier to demonstrate that ferritin is transported across endothelial cells. There are receptors that prefer H-ferritin on the endothelial cells in culture and on rat brain microvasculature. These studies identify H-ferritin as an iron transport protein and suggest the presence of an H-ferritin receptor for mediating iron delivery. The relative amount of iron that could be delivered via H-ferritin could make this protein a predominant player in cellular iron delivery.
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PARTHASARATHY, Narayanan, Suzy V. TORTI et Frank M. TORTI. « Ferritin binds to light chain of human H-kininogen and inhibits kallikrein-mediated bradykinin release ». Biochemical Journal 365, no 1 (1 juillet 2002) : 279–86. http://dx.doi.org/10.1042/bj20011637.
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Ferritin is an iron-storage protein that exists in both intracellular and extracellular compartments. We have previously identified H-kininogen (high-molecular-weight kininogen) as a ferritin-binding protein [Torti and Torti (1998) J. Biol. Chem. 273, 13630–13635]. H-Kininogen is a precursor of the potent pro-inflammatory peptide bradykinin, which is released from H-kininogen following cleavage of H-kininogen by the serine protease kallikrein. In this report, we demonstrate that binding of ferritin to H-kininogen occurs via the modified light chain of H-kininogen, and that ferritin binds preferentially to activated H-kininogen. We further demonstrate that binding of ferritin to H-kininogen retards the proteolytic cleavage of H-kininogen by kallikrein and its subsequent release of bradykinin fromH-kininogen. Ferritin does not interfere with the ability of kallikrein to digest a synthetic substrate, suggesting that ferritin specifically impedes the ability of kallikrein to digest H-kininogen, perhaps by steric hindrance. Based on these results, we propose a model of sequential H-kininogen cleavage and ferritin binding. These results are consistent with the hypothesis that the binding of ferritin to H-kininogen may serve to modulate bradykinin release.
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Langlois, Michel R., Marie-Elise Martin, Johan R. Boelaert, Carole Beaumont, Youri E. Taes, Marc L. De Buyzere, Dirk R. Bernard, Hugo M. Neels et Joris R. Delanghe. « The Haptoglobin 2-2 Phenotype Affects Serum Markers of Iron Status in Healthy Males ». Clinical Chemistry 46, no 10 (1 octobre 2000) : 1619–25. http://dx.doi.org/10.1093/clinchem/46.10.1619.
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Abstract Background: Human iron status is influenced by environmental and genetic factors. We hypothesized that the genetic polymorphism of haptoglobin (Hp), a hemoglobin-binding plasma protein, could affect iron status. Methods: Reference values of serum iron status markers were compared according to Hp phenotypes (Hp 1-1, Hp 2-1, Hp 2-2; determined by starch gel electrophoresis) in 717 healthy adults. Iron storage was investigated in peripheral blood monocyte-macrophages by measuring cytosolic L- and H-ferritins and by in vitro uptake of radiolabeled (125I) hemoglobin-haptoglobin complexes. Results: In males but not in females, the Hp 2-2 phenotype was associated with higher serum iron (P <0.05), transferrin saturation (P <0.05), and ferritin (P <0.01) concentrations than Hp 1-1 and 2-1, whereas soluble transferrin receptor concentrations were lower (P <0.05). Moreover, serum ferritin correlated with monocyte L-ferritin content (r = 0.699), which was also highest in the male Hp 2-2 subgroup (P <0.01). In vitro, monocyte-macrophages took up a small fraction of 125I-labeled hemoglobin complexed to Hp 2-2 but not to Hp 1-1 or 2-1. Conclusions: The Hp 2-2 phenotype affects serum iron status markers in healthy males and is associated with higher L-ferritin concentrations in monocyte-macrophages because of a yet undescribed iron delocalization pathway, selectively occurring in Hp 2-2 subjects.
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Holmes, David. « Novel protective role of H-Ferritin ». Nature Reviews Nephrology 9, no 11 (1 octobre 2013) : 625. http://dx.doi.org/10.1038/nrneph.2013.193.
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Lo, James, et Robert AR Hurta. « Transforming growth factor β1 selectively regulates ferritin gene expression in malignant H-ras-transformed fibrosarcoma cell lines ». Biochemistry and Cell Biology 78, no 4 (3 avril 2000) : 527–35. http://dx.doi.org/10.1139/o00-062.
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Transforming growth factor β1 is an important growth regulator in many cell types, usually exerting a negative effect on cellular growth. Inhibition of DNA synthesis and cell proliferation is frequently lost during malignant transformation, and in some cases, tumor cell proliferation is actually stimulated by TGF-β1. The present study demonstrates a novel link between alterations in TGF-β1 regulation during malignant conversion, and the expression of ferritin, an important activity involved in a number of biological functions including iron homeostasis and cell-growth control. A series of H-ras-transformed mouse 10 T 1/2 cell lines, exhibiting increasing malignant potential, was investigated for possible TGF-β1-mediated changes in ferritin gene expression. Selective induction of gene expression was observed, since only H-ras-transformed cells with malignant potential exhibited marked elevations in ferritin gene expression, in particular, alterations in H-ferritin gene expression. The regulation of H-ferritin gene expression in response to TGF-β 1 did not involve alterations in transcription, but occurred through mechanisms of post-transcriptional stabilization of the H-ferritin mRNA. Additionally, evidence was obtained for a cycloheximide-sensitive regulator of H-ferritin gene expression, since the presence of this protein synthesis inhibitor increased H-ferritin message levels, and in combination with TGF-β1, cooperated in an additive manner to augment H-ferritin gene expression. These results show for the first time that TGF-β1 can regulate ferritin gene expression in malignant H-ras transformed cells, and suggest a mechanism for growth factor stimulation of malignant cells, in which early alterations in the control of H-ferritin gene expression are important.Key words: TGF-β1, ferritin gene expression, malignant transformation.
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Mackenzie, Elizabeth L., et Yoshiaki Tsuji. « Elevated intracellular calcium increases ferritin H expression through an NFAT-independent post-transcriptional mechanism involving mRNA stabilization ». Biochemical Journal 411, no 1 (13 mars 2008) : 107–13. http://dx.doi.org/10.1042/bj20071544.
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An increase in intracellular Ca2+ is one of the initiating events in T-cell activation. A calcium-mediated signalling cascade in T-cells involves activation of calcineurin and the dephosphorylation and translocation of NFAT (nuclear factor of activated T-cells), resulting in the transcriptional activation of target genes such as IL-2 (interleukin-2). In the present study, we found that increased intracellular calcium leads to induction of the antioxidant protein ferritin H. We previously reported that the ferritin H gene is transcriptionally activated under oxidative stress conditions through an ARE (antioxidant-responsive element). The facts that the ferritin H ARE contains a composite AP-1 (activator protein 1) site and that NFAT collaborates with AP-1 transcription factors led us to test whether calcium-activated NFAT is involved in the ferritin H induction through the ARE. Treatment of Jurkat T-cells with the calcium ionophore, ionomycin, increased ferritin H mRNA and protein expression. Although NFAT translocated to the nucleus and bound a consensus NFAT sequence located in the IL-2 promoter after ionomycin treatment, it did not activate ferritin H transcription despite the presence of a putative NFAT-binding sequence in the ferritin H ARE. In addition, the calcineurin inhibitor cyclosporin A treatment blocked ionomycin-mediated NFAT nuclear translocation but failed to abrogate the increase in ferritin H mRNA. Analysis of mRNA stability after actinomycin D treatment revealed that ionomycin prolongs ferritin H mRNA half-life. Taken together, these results suggest that ionomycin-mediated induction of ferritin H may occur in an NFAT-independent manner but through post-transcriptional stabilization of the ferritin H mRNA.
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Cozzi, Anna, Barbara Corsi, Sonia Levi, Paolo Santambrogio, Giorgio Biasiotto et Paolo Arosio. « Analysis of the biologic functions of H- and L-ferritins in HeLa cells by transfection with siRNAs and cDNAs : evidence for a proliferative role of L-ferritin ». Blood 103, no 6 (15 mars 2004) : 2377–83. http://dx.doi.org/10.1182/blood-2003-06-1842.
Texte intégralRésumé :
Abstract We describe the use of small interfering RNAs (siRNAs) to down-regulate H- and L-ferritin levels in HeLa cells. siRNAs repressed H- and L-ferritin expression to about 20% to 25% of the background level in both stable and transient transfections. HeLa cells transfected with H- and L-ferritin cDNAs were analyzed in parallel to compare the effects of ferritin up- and down-regulation. We found that large modifications of L-ferritin levels did not affect iron availability in HeLa cells but positively affected cell proliferation rate in an iron-independent manner. The transient down-regulation of H-ferritin modified cellular iron availability and resistance to oxidative damage, as expected. In contrast, the stable suppression of H-ferritin in HeLa cell clones transfected with siRNAs did not increase cellular iron availability but made cells less resistant to iron supplementation and chelation. The results indicate that L-ferritin has no direct effects on cellular iron homeostasis in HeLa cells, while it has new, iron-unrelated functions. In addition, they suggest that H-ferritin function is to act as an iron buffer.
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PANG, Jong-Hwei S., Chia-Jung WU et Lee-Young CHAU. « Post-transcriptional regulation of H-ferritin gene expression in human monocytic THP-1 cells by protein kinase C ». Biochemical Journal 319, no 1 (1 octobre 1996) : 185–89. http://dx.doi.org/10.1042/bj3190185.
Texte intégralRésumé :
The mRNA coding for H-ferritin was highly induced in human monocytic THP-1 cells following treatment with phorbol 12-myristate 13-acetate (PMA). The induction was detected at 3 h, reached maximal levels at 12 h, and was sustained for up to 48 h subsequent to PMA exposure. PMA-induced up-regulation of H-ferritin gene expression was also observed in other leukaemic cell lines, HL60 and U937, but not in non-leukaemic cell types, including human fibroblasts, endothelial cells and smooth muscle cells. The effect of PMA could be completely blocked by the protein kinase C inhibitor, H-7. Furthermore, treatment of THP-1 cells with bacterial phospholipase C also produced a marked increase in expression of H-ferritin mRNA, suggesting the activation of protein kinase C was responsible for the accumulation of mRNA. Nuclear run-off experiments demonstrated that PMA did not increase the transcriptional rate of the H-ferritin gene. In contrast, the half-life of the H-ferritin mRNA measured in the presence of actinomycin D was greatly prolonged in PMA-treated cells. The induction of H-ferritin mRNA by PMA required no protein synthesis. Conversely, treatment of THP-1 cells with protein synthesis inhibitor, cycloheximide, resulted in a 4–5-fold increase in H-ferritin mRNA. The increase in the stability of the H-ferritin mRNA was also observed in cells treated with cycloheximide. Taken together, these results suggest that the stability of H-ferritin mRNA in THP-1 is subjected to regulation via a protein kinase C-mediated phosphorylation on existing putative protein factor(s).
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Carraway, M. S., A. J. Ghio, J. L. Taylor et C. A. Piantadosi. « Induction of ferritin and heme oxygenase-1 by endotoxin in the lung ». American Journal of Physiology-Lung Cellular and Molecular Physiology 275, no 3 (1 septembre 1998) : L583—L592. http://dx.doi.org/10.1152/ajplung.1998.275.3.l583.
Texte intégralRésumé :
Heme oxygenase (HO)-1 expression is increased by forms of oxidative stress that also induce ferritin. Even though this could result from release of iron by heme degradation, we hypothesized that ferritin expression in the lung after endotoxin [lipopolysaccharide (LPS)] would occur independently of HO-1 because iron sequestration is an important response to infection. We tested this hypothesis by instilling saline or LPS (1 mg) into lungs of rats and measuring ferritin expression, HO-1 expression and activity, and HO-1 and ferritin mRNAs at different times. Lungs were also inflation fixed for immunohistochemistry for HO-1 and ferritin. Studies were performed with and without the HO inhibitor tin protoporphyrin. Ferritin and HO-1 labeling were minimal (macrophages only) in control lungs. By 4 h after LPS instillation, ferritin staining was present in bronchial epithelium and macrophages, became diffuse at 16 h, and was nearly gone by 48–72 h. HO-1 was detectable in macrophages 4 and 16 h after LPS instillation, increased in macrophages and bronchial epithelium at 24 h, and diffusely increased in bronchial epithelium and the alveolar region at 48–72 h. Lung ferritin content increased significantly by 4 h and peaked at 16 h before declining. HO-1 protein was present by Western blot in control lung, stable at 4 h, and increased by 24 h after LPS instillation, whereas HO enzyme activity had increased by 4 h after LPS instillation. After complete inhibition of HO enzyme activity with tin protoporphyrin, ferritin increased threefold at 4 h and sixfold at 24 h after LPS instillation. HO-1 mRNA increased by 4 h and was sustained at 24 h, whereas ferritin mRNA did not change after LPS instillation. These results indicate that intratracheal LPS rapidly induces ferritin protein in the lung independently of its mRNA synthesis or HO enzyme activity. LPS induces HO-1 mRNA, which is followed by increased expression of protein.
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Yeh, Kwo-Yih, Mary Yeh et Jonathan Glass. « Glucocorticoids and dietary iron regulate postnatal intestinal heavy and light ferritin expression in rats ». American Journal of Physiology-Gastrointestinal and Liver Physiology 278, no 2 (1 février 2000) : G217—G226. http://dx.doi.org/10.1152/ajpgi.2000.278.2.g217.
Texte intégralRésumé :
To cope with increasing dietary iron exposure, the intestinal epithelium of weaning rats must control intracellular labile iron pools. Intestinal expression of heavy (H) and light (L) ferritin subunits during early weaning and after cortisone administration and/or iron feeding was investigated. Changes in H and L ferritin gene expression were determined by nuclear runoff transcriptional assay, Northern blot analysis, and metabolic labeling of protein synthesis. H ferritin mRNA levels did not change between days 12 and 15, doubled on day 18, and tripled on day 24. L ferritin mRNA was reduced by 50% on days 18 and 24. The protein level of the H and L subunits paralleled the change in mRNAs. Cortisone treatment on day 12 induced a precocious increase of H and decrease of L mRNA expression on day 15. Nuclear runoff assays showed that cortisone did not change H and reduced L ferritin gene transcription. The increased level of H mRNA by cortisone was not translated, unless the rats were fed an iron-fortified diet, which reduced iron regulatory protein activity and stimulated a three- to sixfold increase of ferritin synthesis. Thus changes in intestinal H and L ferritin expression in weaning rats are modulated by glucocorticoids and iron; the former stabilizes H mRNA and suppresses L ferritin gene transcription, and the latter derepresses translation of ferritin mRNA.
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Ferreira, Chrystophe, Paolo Santambrogio, Marie-Elise Martin, Valérie Andrieu, Gérard Feldmann, Dominique Hénin et Carole Beaumont. « H ferritin knockout mice : a model of hyperferritinemia in the absence of iron overload ». Blood 98, no 3 (1 août 2001) : 525–32. http://dx.doi.org/10.1182/blood.v98.3.525.
Texte intégralRésumé :
Abstract Ferritin, the iron-storing molecule, is made by the assembly of various proportions of 2 different H and L subunits into a 24-mer protein shell. These heteropolymers have distinct physicochemical properties, owing to the ferroxidase activity of the H subunit, which is necessary for iron uptake by the ferritin molecule, and the ability of the L subunit to facilitate iron core formation inside the protein shell. It has previously been shown that H ferritin is indispensable for normal development, since inactivation of the H ferritin gene by homologous recombination in mice is lethal at an early stage during embryonic development. Here the phenotypic analysis of the mice heterozygous for the H ferritin gene (Fth+/− mice) is reported, and differences in gene regulation between the 2 subunits are shown. The heterozygousFth+/− mice were healthy and fertile and did not present any apparent abnormalities. Although they had iron-overloaded spleens at the adult stage, this is identical to what is observed in normal Fth+/+ mice. However, these heterozygous mice had slightly elevated tissue L ferritin content and 7- to 10-fold more L ferritin in the serum than normal mice, but their serum iron remained unchanged. H ferritin synthesis from the remaining allele was not up-regulated. This probably results from subtle changes in the intracellular labile iron pool, which would stimulate L ferritin but not H ferritin synthesis. These results raise the possibility that reduced H ferritin expression might be responsible for unexplained human cases of hyperferritinemia in the absence of iron overload where the hereditary hyperferritinemia-cataract syndrome has been excluded.
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Pattanapanyasat, K., T. G. Hoy et A. Jacobs. « The response of intracellular and surface ferritin after T-cell stimulation in vitro ». Clinical Science 73, no 6 (1 décembre 1987) : 605–11. http://dx.doi.org/10.1042/cs0730605.
Texte intégralRésumé :
1. Measurements of T-lymphocyte surface ferritin using flow cytometry show that phytohaemagglutinin (PHA) stimulation causes a marked increase in the number of cells bearing spleen-type (S) and heart-type (H) ferritin on their membrane, whereas no such change occurs in non-stimulated cells. This coincides with increases in interleukin-2 receptors, transferrin receptors and HLA-DR antigen. 2. There is an increase in the intracellular concentration of both S- and H-ferritin in lymphocytes after PHA stimulation: H-ferritin increases five- to seven-fold, but S-ferritin only two- to three-fold. The maximum H/S ratio is about 15/1. However, these increases also occur in cells cultured in the absence of PHA. 3. Small amounts of both S- and H-ferritin are released into the medium, especially from stimulated cells, but the H/S ratios are lower than intracellular ratios. 4. The present findings suggest that lymphocyte stimulation followed by ferritin synthesis is accompanied by an increase in the amount of intracellular and cell surface ferritin and, possibly, the amount released from the cells.
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ORINO, Kouichi, Lori LEHMAN, Yoshiaki TSUJI, Hitoshi AYAKI, Suzy V. TORTI et Frank M. TORTI. « Ferritin and the response to oxidative stress ». Biochemical Journal 357, no 1 (25 juin 2001) : 241–47. http://dx.doi.org/10.1042/bj3570241.
Texte intégralRésumé :
Iron is required for normal cell growth and proliferation. However, excess iron is potentially harmful, as it can catalyse the formation of toxic reactive oxygen species (ROS) via Fenton chemistry. For this reason, cells have evolved highly regulated mechanisms for controlling intracellular iron levels. Chief among these is the sequestration of iron in ferritin. Ferritin is a 24 subunit protein composed of two subunit types, termed H and L. The ferritin H subunit has a potent ferroxidase activity that catalyses the oxidation of ferrous iron, whereas ferritin L plays a role in iron nucleation and protein stability. In the present study we report that increased synthesis of both subunits of ferritin occurs in HeLa cells exposed to oxidative stress. An increase in the activity of iron responsive element binding proteins in response to oxidative stress was also observed. However, this activation was transient, allowing ferritin protein induction to subsequently proceed. To assess whether ferritin induction reduced the accumulation of ROS, and to test the relative contribution of ferritin H and L subunits in this process, we prepared stable transfectants that overexpressed either ferritin H or ferritin L cDNA under control of a tetracycline-responsive promoter. We observed that overexpression of either ferritin H or ferritin L reduced the accumulation of ROS in response to oxidant challenge.
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Salatino, Alessandro, Ilenia Aversa, Anna Martina Battaglia, Alessandro Sacco, Anna Di Vito, Gianluca Santamaria, Roberta Chirillo et al. « H-Ferritin Affects Cisplatin-Induced Cytotoxicity in Ovarian Cancer Cells through the Modulation of ROS ». Oxidative Medicine and Cellular Longevity 2019 (31 octobre 2019) : 1–13. http://dx.doi.org/10.1155/2019/3461251.
Texte intégralRésumé :
Reactive oxygen species (ROS) mediates cisplatin-induced cytotoxicity in tumor cells. However, when cisplatin-induced ROS do not reach cytotoxic levels, cancer cells may develop chemoresistance. This phenomenon can be attributed to the inherited high expression of antioxidant protein network. H-Ferritin is an important member of the antioxidant system due to its ability to store iron in a nontoxic form. Altered expression of H-Ferritin has been described in ovarian cancers; however, its functional role in cisplatin-based chemoresistance of this cancer type has never been explored. Here, we investigated whether the modulation of H-Ferritin might affect cisplatin-induced cytotoxicity in ovarian cancer cells. First, we characterized OVCAR3 and OVCAR8 cells for their relative ROS and H-Ferritin baseline amounts. OVCAR3 exhibited lower ROS levels compared to OVCAR8 and greater expression of H-Ferritin. In addition, OVCAR3 showed pronounced growth potential and survival accompanied by the strong activation of pERK/pAKT and overexpression of c-Myc and cyclin E1. When exposed to different concentrations of cisplatin, OVCAR3 were less sensitive than OVCAR8. At the lowest concentration of cisplatin (6 μM), OVCAR8 underwent a consistent apoptosis along with a downregulation of H-Ferritin and a consistent increase of ROS levels; on the other hand, OVCAR3 cells were totally unresponsive, H-Ferritin was almost unaffected, and ROS amounts met a slight increase. Thus, we assessed whether the modulation of H-Ferritin levels was able to affect the cisplatin-mediated cytotoxicity in both the cell lines. H-Ferritin knockdown strengthened cisplatin-mediated ROS increase and significantly restored sensitivity to 6 μM cisplatin in resistant OVCAR3 cells. Conversely, forced overexpression of H-Ferritin significantly suppressed the cisplatin-mediated elevation of intracellular ROS subsequently leading to a reduced responsiveness in OVCAR8 cells. Overall, our findings suggest that H-Ferritin might be a key protein in cisplatin-based chemoresistance and that its inhibition may represent a potential approach for enhancing cisplatin sensitivity of resistant ovarian cancer cells.
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Smirnova, L. A., Z. I. Kravchuk et Zh M. Kozich. « H- AND L-FERRITINS IN ACUTE LEUKEMIA ». Health and Ecology Issues, no 2S (28 décembre 2011) : 81–83. http://dx.doi.org/10.51523/2708-6011.2011-8-2s-28.
Texte intégralRésumé :
We have studied H- and L-subunits of ferritin in acute leukemia. Our data makes it possible to suggest that the appearance of considerable numbers of ferritin in the serum of patients with clonal blood diseases is connected with its secretion with lymphocytes. As it is impossible to establish the reliable correlation between the dimension of the tumor in leukemia and the level of ferritin, then the ferritin secretion is hypothetically relating to its regulatory functions. We have shown that the separate testing of H- and L-forms of ferritin makes it possible to determine the content of serum ferritin. It has been established that the content of serum ferritin differs in acute leukemia at attacks and remission but it is necessary to accumulate the data for the comprehension of true diagnostic H-ferritin value. It is possible that in the nearest future hematologic syndromes in malignant tumors, i.e. clonal processes from the inflammation-associated syndromes, can be differentiated according to the content of serum ferritin.
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Bradley, Justin M., Dimitri A. Svistunenko, Jacob Pullin, Natalie Hill, Rhona K. Stuart, Brian Palenik, Michael T. Wilson, Andrew M. Hemmings, Geoffrey R. Moore et Nick E. Le Brun. « Reaction of O2with a diiron protein generates a mixed-valent Fe2+/Fe3+center and peroxide ». Proceedings of the National Academy of Sciences 116, no 6 (18 janvier 2019) : 2058–67. http://dx.doi.org/10.1073/pnas.1809913116.
Texte intégralRésumé :
The gene encoding the cyanobacterial ferritinSynFtn is up-regulated in response to copper stress. Here, we show that, whileSynFtn does not interact directly with copper, it is highly unusual in several ways. First, its catalytic diiron ferroxidase center is unlike those of all other characterized prokaryotic ferritins and instead resembles an animal H-chain ferritin center. Second, as demonstrated by kinetic, spectroscopic, and high-resolution X-ray crystallographic data, reaction of O2with the di-Fe2+center results in a direct, one-electron oxidation to a mixed-valent Fe2+/Fe3+form. Iron–O2chemistry of this type is currently unknown among the growing family of proteins that bind a diiron site within a four α-helical bundle in general and ferritins in particular. The mixed-valent form, which slowly oxidized to the more usual di-Fe3+form, is an intermediate that is continually generated during mineralization. Peroxide, rather than superoxide, is shown to be the product of O2reduction, implying that ferroxidase centers function in pairs via long-range electron transfer through the protein resulting in reduction of O2bound at only one of the centers. We show that electron transfer is mediated by the transient formation of a radical on Tyr40, which lies ∼4 Å from the diiron center. As well as demonstrating an expansion of the iron–O2chemistry known to occur in nature, these data are also highly relevant to the question of whether all ferritins mineralize iron via a common mechanism, providing unequivocal proof that they do not.
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Rogers, JT. « Ferritin translation by interleukin-6 : the role of sequences upstream of the start codons of the heavy and light subunit genes ». Blood 87, no 6 (15 mars 1996) : 2525–37. http://dx.doi.org/10.1182/blood.v87.6.2525.bloodjournal8762525.
Texte intégralRésumé :
Interleukin-1beta (IL-1beta) elevates H- and L-ferritin subunit synthesis in both human hepatoma cells (HepG2) and primary human umbilical vein endothelial cells. Ferritin induction is greater than the increase in total HepG2 protein synthesis in response to IL-1. IL-6 causes a moderate increase in L-subunit synthesis. The levels of the mRNAs for the ferritin H-subunits (H-mRNA) and light subunits (L-mRNA) remain unchanged, indicating that expression of the iron storage protein, ferritin, is regulated by translational mechanisms during inflammation. We have found a translational enhancer region in the L- ferritin mRNA 5′UTR that confers two-fold baseline and twofold IL-1- dependent translational regulation to a CAT reporter message. The L- mRNA motif is related to a 61 nucleotide (nt) G+C-rich translational enhancer within 70 nt of the H-ferritin start codon. Sequences upstream of the start codons (SUS elements) in both H-mRNA and L-mRNAs confer IL- 1beta but not IL-6-dependent translation to hybrid ferritin/CAT reporter mRNAs. The H- and L-ferritin mRNA SUS elements contain a motif similar to a consensus reported for the 5′ leaders of other acute phase response mRNAs. Transfected hybrid H-mRNA SUS/CAT mRNAs with a three nucleotide deleted version of the H-mRNA SUS displays an eightfold reduced level of translation and no longer confer IL-1beta-dependent translation.
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Percy, Maire E., Sharon J. Bauer, Susan Rainey, Donald R. C. McLachlan, Madhu S. Dhar et Jayant G. Joshi. « Localization of a new ferritin heavy chain sequence present in human brain mRNA to chromosome 11 ». Genome 38, no 3 (1 juin 1995) : 450–57. http://dx.doi.org/10.1139/g95-059.
Texte intégralRésumé :
Two types of ferritin heavy (H) chain clones have been isolated from cDNA libraries of human fetal and adult brain: one corresponds to the ferritin H chain mRNA that is abundant in liver and is called "liver-like" brain cDNA; the other contains an additional 279 nucleotide (nt) sequence in the 3′untranslated region and is called brain ferritin H chain cDNA. To map the 279-nt sequence, polymerase chain reaction (PCR) amplification was carried out using DNA from rodent × human hybrid cell lines containing single human chromosomes as templates, and oligomeric primers homologous to the 3′end of the 279-nt sequence (primer A) and to a coding sequence just 5′ to the 279-nt sequence. Significant PCR product of the size expected from analysis of the brain ferritin H chain cDNA clones and a genomic ferritin H chain clone (487 bp) was generated only from hybrid-cell DNA containing human chromosome 11. This PCR product and the "liver-like" brain cDNA (lacking the 279-nt sequence) both hybridized to chromosome 11 fragments that are known to define the well-characterized functional liver ferritin H chain gene and a putative pseudogene. Preliminary data indicate that primer A (and thus the 279-nt sequence) maps to the functional ferritin H chain gene fragments, but binding to the pseudogene has not been ruled out.Key words: gene mapping, human brain ferritin, chromosome 11.
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Xie, Changchuan, Na Zhang, Huamin Zhou, Jinquan Li, Qinxi Li, Tyler Zarubin, Sheng-Cai Lin et Jiahuai Han. « Distinct Roles of Basal Steady-State and Induced H-Ferritin in Tumor Necrosis Factor-Induced Death in L929 Cells ». Molecular and Cellular Biology 25, no 15 (1 août 2005) : 6673–81. http://dx.doi.org/10.1128/mcb.25.15.6673-6681.2005.
Texte intégralRésumé :
ABSTRACT Tumor necrosis factor (TNF) alpha is a cytokine capable of inducing caspase-dependent (apoptotic) cell death in some cells and caspase-independent (necrosis-like) cell death in others. Here, using a mutagenesis screen for genes critical in TNF-induced death in L929 cells, we have found that H-ferritin deficiency is responsible for TNF resistance in a mutant line and that, upon treatment with TNF, this line fails to elevate levels of labile iron pool (LIP), critical for TNF-induced reactive oxygen species (ROS) production and ROS-dependent cell death. Since we found that TNF-induced LIP in L929 cells is primarily furnished by intracellular storage iron, the lesser induction of LIP in H-ferritin-deficient cells results from a reduction of intracellular iron storage caused by less H-ferritin. Different from some other cell lines, the H-ferritin gene in L929 cells is not TNF inducible; however, when H-ferritin is expressed in L929 cells under a TNF-inducible system, the TNF-induced LIP and subsequent ROS production and cell death were all prevented. Thus, LIP is a common denominator of ferritin both in the enhancement of cell death by basal steady-state H-ferritin and in protection against cell death by induced H-ferritin, thereby acting as a key determinant of TNF-induced cell death.
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Ai, Li-Shaung, et Lee-Young Chau. « Post-transcriptional Regulation of H-ferritin mRNA ». Journal of Biological Chemistry 274, no 42 (15 octobre 1999) : 30209–14. http://dx.doi.org/10.1074/jbc.274.42.30209.
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