The Natural Resistance-Associated Macrophage Protein from the Protozoan ParasitePerkinsus marinusMediates Iron Uptake

Biochemistry ◽  
2011 ◽  
Vol 50 (29) ◽  
pp. 6340-6355 ◽  
Author(s):  
Zhuoer Lin ◽  
José-Antonio Fernández-Robledo ◽  
Mathieu F. M. Cellier ◽  
Gerardo R. Vasta
Keyword(s):  
Iron Uptake ◽  
Natural Resistance ◽  
Macrophage Protein

Solute carrier 11a1 (Slc11a1; formerly Nramp1) regulates metabolism and release of iron acquired by phagocytic, but not transferrin-receptor-mediated, iron uptake

2002 ◽  
Vol 363 (1) ◽  
pp. 89-94 ◽  
Author(s):  
Victoriano MULERO ◽  
Susan SEARLE ◽  
Jenefer M. BLACKWELL ◽  
Jeremy H. BROCK
Keyword(s):  
Iron Uptake ◽  
Interferon Γ ◽  
Natural Resistance ◽  
Null Alleles ◽  
Iron Release ◽  
Wild Type ◽  
Bivalent Cation ◽  
Insoluble Form ◽  
Solute Carrier ◽  
Macrophage Protein

Solute carrier 11a1 (Slc11a1; formerly Nramp1; where Nramp stands for natural-resistance-associated macrophage protein) is a proton/bivalent cation antiporter that localizes to late endosomes/lysosomes and controls resistance to pathogens. In the present study the role of Slc11a1 in iron turnover is examined in macrophages transfected with Slc11a1Gly169 (wild-type) or Slc11a1Asp169 (mutant = functional null) alleles. Following direct acquisition of transferrin (Tf)-bound iron via the Tf receptor, iron uptake and release was equivalent in wild-type and mutant macrophages and was not influenced by interferon-γ/lipopolysaccharide activation. Following phagocytosis of [59Fe]Tf—anti-Tf immune complexes, iron uptake was equivalent and up-regulated similarly with activation, but intracellular distribution was markedly different. In wild-type macrophages most iron was in the soluble (60%) rather than insoluble (12%) fraction, with 28% ferritin (Ft)-bound. With activation, the soluble component increased to 82% at the expense of Ft-bound iron (< 5%). In mutant macrophages, 40–50% of iron was in insoluble form, 50–60% was soluble and < 5% was Ft-bound. Western-blot analysis confirmed failure of mutant macrophages to degrade complexes 24h after phagocytic uptake. Confocal microscopy showed that complexes were within lysosome-associated membrane protein 1-positive vesicles in wild-type and mutant macrophages at 30min and 24h, implying failure in the degradative process in mature phagosomes in mutant macrophages. NO-mediated iron release was 2.4-fold higher in activated wild-type macrophages compared with mutant macrophages. Overall, our data suggest that iron acquired by phagocytosis and degradation is retained within the phagosomal compartment in wild-type macrophages, and that NO triggers iron release by direct secretion of phagosomal contents rather than via the cytoplasm.

Heterologous expression, functional characterization and localization of two isoforms of the monkey iron transporter Nramp2

2000 ◽  
Vol 349 (1) ◽  
pp. 289-297 ◽  
Author(s):  
Li ZHANG ◽  
Timothy LEE ◽  
Yue WANG ◽  
Tuck W. SOONG
Keyword(s):  
Amino Acid ◽  
Subcellular Localization ◽  
Tissue Distribution ◽  
Iron Uptake ◽  
Functional Characterization ◽  
Amino Acid Level ◽  
Natural Resistance ◽  
C Terminus ◽  
Macrophage Protein ◽  
Responsive Element

Natural resistance-associated macrophage protein 2 (Nramp2) has been suggested to be involved in transferrin-independent iron uptake. Two isoforms of the Nramp2 gene generated by alternative splicing of the 3ʹ exons were identified in mouse, rat and human, but it is unclear if they perform distinct functions. To rationalize our previous work, which indicated an increase in iron deposition in a Parkinsonian monkey brain, two monkey Nramp2 isoforms were isolated for a comparative study to assess their relative iron-uptake abilities, tissue distribution and subcellular localization. The monkey Nramp2 isoforms, 2a and 2b, exhibit approx. 98% identity at the amino acid level when compared with the human homologues. The Nramp2a transcript contains a canonical iron-responsive element (IRE), whereas that of Nramp2b lacks the IRE motif in the 3ʹ untranslated region. By reverse transcriptase (RT)-PCR, the mRNAs of both isoforms were detected in all tissues examined. The amino acid differences at the C-terminus neither affected the protein expression levels in HEK-293T and COS-7 cells nor altered the subcellular localization and tissue distribution of the isoforms. Similar levels of iron uptake were detected in the HEK-293T cells transfected with either the Nramp2a or 2b gene, and a reduction of iron from the ferric (Fe3+) to the ferrous (Fe2+) state is necessary before transport can take place. However, this transferrin-independent uptake of iron into the cells is not a Ca2+-dependent process.

scholarly journals Typhoid Fever and Genetic Polymorphisms at the Natural Resistance–Associated Macrophage Protein 1

2001 ◽  
Vol 183 (7) ◽  
pp. 1156-1160 ◽  
Author(s):  
Sarah J. Dunstan ◽  
Vo An Ho ◽  
Chau Minh Duc ◽  
Mai Ngoc Lanh ◽  
Cao Xuan Thanh Phuong ◽  
...  
Keyword(s):  
Typhoid Fever ◽  
Genetic Polymorphisms ◽  
Natural Resistance ◽  
Macrophage Protein

scholarly journals Mycobacterium tuberculosis Expresses a Novel Ph-Dependent Divalent Cation Transporter Belonging to the Nramp Family

1999 ◽  
Vol 190 (5) ◽  
pp. 717-724 ◽  
Author(s):  
Daniel Agranoff ◽  
Irene M. Monahan ◽  
Joseph A. Mangan ◽  
Philip D. Butcher ◽  
Sanjeev Krishna
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Metal Ion ◽  
Divalent Cations ◽  
Natural Resistance ◽  
Xenopus Laevis Oocytes ◽  
Mrna Levels ◽  
Susceptibility To Infection ◽  
Reverse Transcription Pcr ◽  
Acidic Extracellular Ph ◽  
Macrophage Protein

Mammalian natural resistance–associated macrophage protein (Nramp) homologues are important determinants of susceptibility to infection by diverse intracellular pathogens including mycobacteria. Eukaryotic Nramp homologues transport divalent cations such as Fe2+, Mn2+, Zn2+, and Cu2+. Mycobacterium tuberculosis and Mycobacterium bovis (bacillus Calmette-Guérin [BCG]) also encode an Nramp homologue (Mramp). RNA encoding Mramp induces ∼20-fold increases in 65Zn2+ and 55Fe2+ uptake when injected into Xenopus laevis oocytes. Transport is dependent on acidic extracellular pH and is maximal between pH 5.5 and 6.5. Mramp-mediated 65Zn2+ and 55Fe2+ transport is abolished by an excess of Mn2+ and Cu2+, confirming that Mramp interacts with a broad range of divalent transition metal cations. Using semiquantitative reverse transcription PCR, we show that Mramp mRNA levels in M. tuberculosis are upregulated in response to increases in ambient Fe2+ and Cu2+ between &lt;1 and 5 μM concentrations and that this upregulation occurs in parallel with mRNA for y39, a putative metal-transporting P-type ATPase. Using a quantitative ratiometric PCR technique, we demonstrate a fourfold decrease in Mramp/y39 mRNA ratios from organisms grown in 5–70 μM Cu2+. M. bovis BCG cultured axenically and within THP-1 cells also expresses mRNA encoding Mramp. Mramp exemplifies a novel prokaryotic class of metal ion transporter. Within phagosomes, Mramp and Nramp1 may compete for the same divalent cations, with implications for intracellular survival of mycobacteria.

Transcriptional control of Nramp1: a paradigm for the repressive action of c-Myc

2004 ◽  
Vol 32 (6) ◽  
pp. 1084-1086 ◽  
Author(s):  
A.S. Lapham ◽  
E.S. Phillips ◽  
C.H. Barton
Keyword(s):  
Transcriptional Control ◽  
Cell Activation ◽  
Zinc Finger Protein ◽  
Specific Binding ◽  
Divalent Cations ◽  
Natural Resistance ◽  
Finger Protein ◽  
Late Endosomes ◽  
Solute Carrier ◽  
Macrophage Protein

Slc11a1/Nramp1 (solute carrier family 11 member a1/murine natural resistance-associated macrophage protein 1 gene) encodes a divalent cation transporter that resides within lysosomes/late endosomes of macrophages. Nramp1 modulates the cellular distribution of divalent cations in response to cell activation by intracellular pathogens. Nramp1 expression is repressed and activated by the proto-oncogene c-Myc and Miz-1 (c-Myc-interacting zinc finger protein 1) respectively. Here we demonstrate, using a c-Myc mutant (V394D, Val394→Asp) that is incapable of binding Miz-1, that c-Myc repression of Nramp1 transcription is dependent on its interaction with Miz-1. An oligo pull-down assay demonstrates specific binding of recombinant Miz-1 to the Nramp1 Miz-1-binding site or initiator element(s), and Miz-1-dependent c-Myc recruitment.

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