Natural-resistance-associated macrophage protein 1 is an H+/bivalent cation antiporter

2001 ◽  
Vol 354 (3) ◽  
pp. 511-519 ◽  
Author(s):  
Tapasree GOSWAMI ◽  
Arin BHATTACHARJEE ◽  
Paul BABAL ◽  
Susan SEARLE ◽  
Elizabeth MOORE ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Proton Gradient ◽  
Natural Resistance ◽  
Bivalent Cation ◽  
Bivalent Cations ◽  
Carbonyl Cyanide ◽  
Endosomal Membranes ◽  
Data Points ◽  
Macrophage Protein

In mammals, natural-resistance-associated macrophage protein 1 (Nramp1) regulates macrophage activation and is associated with infectious and autoimmune diseases. Nramp2 is associated with anaemia. Both belong to a highly conserved eukaryote/prokaryote protein family. We used Xenopus oocytes to demonstrate that, like Nramp2, Nramp1 is a bivalent cation (Fe2+, Zn2+ and Mn2+) transporter. Strikingly, however, where Nramp2 is a symporter of H+ and metal ions, Nramp1 is a highly pH-dependent antiporter that fluxes metal ions in either direction against a proton gradient. At pH9.0, oocytes injected with cRNA from wild-type murine Nramp1 with a glycine residue at position 169 (Nramp1G169; P = 3.22×10-6) and human NRAMP1 (P = 3.87×10-5) showed significantly enhanced uptake of radiolabelled Zn2+ compared with water-injected controls. At pH5.5, Nramp1G169 (P = 1.34×10-13) and NRAMP1 (P = 1.09×10-6) oocytes showed significant efflux of Zn2+. Zn2+ transport was abolished when the proton gradient was dissipated using carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Using pre-acidified oocytes, currents of 130±57 nA were evoked by 100µM Zn2+ at pH7.5, and 139±47 nA by 100µM Fe2+ at pH7.0, in Nramp1G169 oocytes; currents of 254±49 nA and 242±26 nA were evoked, respectively, in NRAMP1 oocytes. Steady-state currents evoked by increasing concentrations of Zn2+ were saturable, with apparent affinity constants of approx. 614nM for Nramp1G169 and approx. 562nM for NRAMP1 oocytes, and a curvilinear voltage dependence of transporter activity (i.e. the data points approximate to a curve that approaches a linear asymptote). In the present study we propose a new model for metal ion homoeostasis in macrophages. Under normal physiological conditions, Nramp2, localized to early endosomal membranes, delivers extracellularly acquired bivalent cations into the cytosol. Nramp1, localized to late endosomal/lysosomal membranes, delivers bivalent cations from the cytosol into this acidic compartment where they may directly affect antimicrobial activity.

scholarly journals The Nramp orthologue of Cryptococcus neoformans is a pH-dependent transporter of manganese, iron, cobalt and nickel

2004 ◽  
Vol 385 (1) ◽  
pp. 225-232 ◽  
Author(s):  
Daniel AGRANOFF ◽  
Lauren COLLINS ◽  
David KEHRES ◽  
Tom HARRISON ◽  
Michael MAGUIRE ◽  
...  
Keyword(s):  
Cryptococcus Neoformans ◽  
Metal Ion ◽  
Ph Dependence ◽  
Opportunistic Pathogen ◽  
Membrane Topology ◽  
Natural Resistance ◽  
Xenopus Laevis Oocytes ◽  
Bivalent Cation ◽  
Gradient Based ◽  
Macrophage Protein

Cryptococcus neoformans is an important human opportunistic pathogen and a facultative intracellular parasite, particularly in HIV-infected individuals. Little is known about metal ion transport in this organism. C. neoformans encodes a single member of the Nramp (natural resistance-associated macrophage protein) family of bivalent cation transporters, known as Cramp, which we have cloned and expressed in Xenopus laevis oocytes and Spodoptera frugiperda Sf 21 insect cells. Cramp induces saturable transport of a broad range of bivalent transition series cations, including Mn2+, Fe2+, Co2+ and Ni2+. Maximal cation transport occurs at pH 5.5–6.0, consistent with the proton gradient-based energetics of other Nramp orthologues. Mn2+ transport is diminished in the presence of 140 mM Na+, compatible with a Na+ slippage mechanism proposed for the Saccharomyces cerevisiae Nramp orthologue Smf1p. Cramp resembles Smf1p with respect to predicted membrane topology, substrate specificity and pH dependence, but differs in terms of its apparent affinity for Mn2+ and negligible inhibition by Zn2+. Cramp is the first Nramp orthologue from a fungal pathogen to be functionally characterized. Insights afforded by these findings will allow the formulation of new hypotheses regarding the role of metal ions in the pathophysiology of cryptococcosis.

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 <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.

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.

scholarly journals Natural-resistance-associated macrophage protein 1 is an H+/bivalent cation antiporter

2001 ◽  
Vol 354 (3) ◽  
pp. 511 ◽  
Author(s):  
Tapasree GOSWAMI ◽  
Arin BHATTACHARJEE ◽  
Paul BABAL ◽  
Susan SEARLE ◽  
Elizabeth MOORE ◽  
...  
Keyword(s):  
Natural Resistance ◽  
Bivalent Cation ◽  
Macrophage Protein

scholarly journals Manganese is a Physiologically Relevant TORC1 Activator in Yeast and Mammals.

2021 ◽  
Author(s):  
Raffaele Nicastro ◽  
Helene Gaillard ◽  
Laura Zarzuela ◽  
Elisabet Fernandez-Garcia ◽  
Mercedes Tome ◽  
...  
Keyword(s):  
Metal Ion ◽  
Human Diseases ◽  
Natural Resistance ◽  
Homeostatic Process ◽  
Downstream Effectors ◽  
Mtorc1 Signaling ◽  
The Family ◽  
Macrophage Protein

The essential biometal manganese (Mn) functions as a cofactor for several enzymatic activities that are critical for the prevention of human diseases. Whether intracellular Mn levels may also modulate signaling events has so far remained largely unexplored. The target of rapamycin complex 1 (TORC1, mTORC1 in mammals) is a conserved protein kinase complex that requires metal co-factors to phosphorylate its downstream effectors as part of a central, homeostatic process that coordinates cell growth and metabolism in response to nutrient and/or growth factor availability. Using genetic and biochemical approaches, we show here that TORC1 activity is exquisitely sensitive to stimulation by Mn both in vivo and in vitro. Mn-mediated control of TORC1 depends on Smf1 and Smf2, two members of the family of natural resistance-associated macrophage protein (NRAMP) metal ion transporters, the turnover of which is subjected to feedback control by TORC1 activity. Notably, increased Mn levels and consequent activation of TORC1 cause retrograde dysregulation and antagonize the rapamycin-induced gene expression and autophagy programs in yeast. Because Mn also activates mTORC1 signaling in aminoacid starved human cells, our data indicate that intracellular Mn levels may constitute an evolutionary conserved physiological cue that modulates eukaryotic TORC1/mTORC1 signaling. Our findings therefore reveal a hitherto elusive connection between intracellular Mn levels, mTORC1 activity, and human diseases.

Genetic analysis of SLC11A1 polymorphisms in multiple sclerosis patients

2004 ◽  
Vol 10 (6) ◽  
pp. 618-620 ◽  
Author(s):  
Manuel Comabella ◽  
Laura Altet ◽  
Francesc Peris ◽  
Pablo Villoslada ◽  
Armand Sánchez ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Natural Resistance ◽  
Bivalent Cation ◽  
Slc11a1 Gene ◽  
Late Endosomes ◽  
Solute Carrier ◽  
Macrophage Protein ◽  
Multiple Sclerosis Patients ◽  
Control Study

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. SLC11A1 regulates macrophage functions that are of potential importance in the induction and/or maintenance of autoimmune diseases such as rheumatoid arthritis, type 1 diabetes and Crohn’s disease. We investigated SLC11A1 gene as a candidate gene for genetic susceptibility to multiple sclerosis (MS) in our population. Four SLC11A1 gene polymorphisms (5?GT repeat, D543N, 1729 -55del4 and 1729 -271del4) were analysed in a case-control study of 195 patients with MS and 125 control subjects. We found no evidence of association between SLC11A1 polymorphisms and MS susceptibility in the Spanish population.

scholarly journals Metal ions suppress the abnormal taste behavior of the Drosophila mutant malvolio.

1998 ◽  
Vol 201 (1) ◽  
pp. 115-120
Author(s):  
S Orgad ◽  
H Nelson ◽  
D Segal ◽  
N Nelson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Signal Transduction ◽  
Metal Ions ◽  
Metal Ion ◽  
Adult Stage ◽  
Taste Perception ◽  
Natural Resistance ◽  
Ion Transporters ◽  
Normal Taste ◽  
Drosophila Mutant

A mutation in the malvolio (mvl) gene affects taste behavior in Drosophila melanogaster. The malvolio gene encodes a protein (MVL) that exhibits homology to the mammalian natural resistance-associated macrophage proteins. It is also homologous to the Smf1 protein from Saccharomyces cerevisiae, which we have recently demonstrated to function as a Mn2+/Zn2+ transporter. We proposed that the Drosophila and mammalian proteins, like the yeast SMF1 gene product, are metal-ion transporters. To test this hypothesis, malvolio mutant flies were allowed to develop, from egg to adulthood, on a medium containing elevated concentrations of metal ions. Mutant flies that were reared in the presence of 10 mmol l-1 MnCl2 or FeCl2 developed into adults with recovered taste behavior. CaCl2 or MgCl2 had no effect on the mutant's taste perception. ZnCl2 inhibited the effect of MnCl2 when both ions were supplied together. Similar suppression of the abnormal taste behavior was observed when mvl mutants were fed MnCl2 or FeCl2 only at the adult stage. Furthermore, exposure of adult mutant flies to these ions in the testing plate for only 2 h was sufficient to restore normal taste behavior. The suppression of the defective taste behavior suggests that MVL functions as a Mn2+/Fe2+ transporter and that Mn2+ and/or Fe2+ are involved in the signal transduction of taste perception in Drosophila adults.

scholarly journals Bioinformatics and Transcriptional Study of the Nramp Gene in the Extreme Acidophile Acidithiobacillus ferrooxidans Strain DC

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 544 ◽  
Author(s):  
Bo Miao ◽  
Li Shen ◽  
Xueduan Liu ◽  
Weimin Zeng ◽  
Xueling Wu
Keyword(s):  
Acidithiobacillus Ferrooxidans ◽  
Metal Ion ◽  
Cytoplasmic Membrane ◽  
Ferrous Ion ◽  
Natural Resistance ◽  
Online Tools ◽  
The Family ◽  
Bioinformatics Software ◽  
Macrophage Protein ◽  
High Concentrations

The family of Nramp (natural resistance-associated macrophage protein) metal ion transporter functions in diverse organisms from bacteria to humans. Acidithiobacillus ferrooxidans (At. ferrooxidans) is a Gram-negative bacterium that lives at pH 2 in high concentrations of soluble ferrous ion (600 mM). The AFE_2126 protein of At. ferrooxidans of the Dachang Copper Mine (DC) was analyzed by bioinformatics software or online tools, showing that it was highly homologous to the Nramp family, and its subcellular localization was predicted to locate in the cytoplasmic membrane. Transcriptional study revealed that AFE_2126 was expressed by Fe2+-limiting conditions in At. ferrooxidans DC. It can be concluded that the AFE_2126 protein may function in ferrous ion transport into the cells. Based on the ΔpH of the cytoplasmic membrane between the periplasm (pH 3.5) and the cytoplasm (pH 6.5), it can be concluded that Fe2+ is transported in the direction identical to that of the H+ gradient. This study indirectly confirmed that the function of Nramp in At. ferrooxidans DC can transport divalent iron ions.

Recent progress in structure–function analyses of Nramp proton-dependent metal-ion transportersThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Membrane Proteins in Health and Disease.

2006 ◽  
Vol 84 (6) ◽  
pp. 960-978 ◽  
Author(s):  
P. Courville ◽  
R. Chaloupka ◽  
M.F.M. Cellier
Keyword(s):  
Structure Function ◽  
Metal Ion ◽  
Hypochromic Anemia ◽  
Experimental Models ◽  
Natural Resistance ◽  
Bacterial Cells ◽  
Divalent Metal Ions ◽  
Recycling Endosomes ◽  
Transmembrane Segments ◽  
Macrophage Protein

The natural resistance-associated macrophage protein (Nramp) homologs form a family of proton-coupled transporters that facilitate the cellular absorption of divalent metal ions (Me2+, including Mn2+, Fe2+, Co2+, and Cd2+). The Nramp, or solute carrier 11 (SLC11), family is conserved in eukaryotes and bacteria. Humans and rodents express 2 parologous genes that are associated with iron disorders and immune diseases. The NRAMP1 (SLC11A1) protein is specific to professional phagocytes and extrudes Me2+ from the phagosome to defend against ingested microbes; polymorphisms in the NRAMP1 gene are associated with various immune diseases. Several isoforms of NRAMP2 (SLC11A2, DMT1, DCT1) are expressed ubiquitously in recycling endosomes or specifically at the apical membrane of epithelial cells in intestine and kidneys, and can contribute to iron overload, whereas mutations impairing NRAMP2 function cause a form of congenital microcytic hypochromic anemia. Structure–function studies, using various experimental models, and mutagenesis approaches have begun to reveal the overall transmembrane organization of Nramp, some of the transmembrane segments (TMS) that are functionally important, and an unusual mechanism coupling Me2+ and proton H+ transport. The approaches used include functional complementation of yeast knockout strains, electrophysiology analyses in Xenopus oocytes, and transport assays that use mammalian and bacterial cells and direct and indirect measurements of SLC11 transporter properties. These complementary studies enabled the identification of TMS1and 6 as crucial structural segments for Me2+ and H+ symport, and will help develop a deeper understanding of the Nramp transport mechanism and its contribution to Me2+ homeostasis in human health and diseases.

scholarly journals Effect of bivalent cations on the adenosine triphosphatase of actomyosin and its modification by tropomyosin and troponin

1969 ◽  
Vol 111 (5) ◽  
pp. 777-783 ◽  
Author(s):  
M. C. Schaub ◽  
M. Ermini
Keyword(s):  
Ionic Strength ◽  
Metal Ions ◽  
Metal Ion ◽  
Adenosine Triphosphatase ◽  
Ionic Radius ◽  
Unique Feature ◽  
Optimum Concentration ◽  
Adenosine Triphosphatase Activity ◽  
Bivalent Cations ◽  
Low Ionic Strength

1. After removal of tropomyosin and troponin from the ‘natural’ actomyosin complex, the adenosine triphosphatase activity of the resulting ‘desensitized’ actomyosin is stimulated to the same extent by various bivalent cations with an ionic radius in the range 0·65–0·99å when tested at optimum concentration of the metal ion in the presence of 2·5mm-ATP at low ionic strength and pH7·6. Under identical conditions the adenosine triphosphatase activity of myosin alone is stimulated to an appreciable extent only by Ca2+ (ionic radius 0·99å). 2. Tropomyosin narrows the range of size of the stimulatory cations by inhibiting specifically the adenosine triphosphatase activity of ‘desensitized’ actomyosin when stimulated by Ca2+ or the slightly smaller Cd2+ (ionic radius 0·97å). Tropomyosin has no effect on the adenosine triphosphatase activity of ‘desensitized’ actomyosin when stimulated by the smaller cations, nor on the Ca2+-activated adenosine triphosphatase activity of myosin alone. 3. The adenosine triphosphatase activity of the ‘natural’ actomyosin system (containing tropomyosin and troponin) stimulated by the smallest cation, Mg2+ (ionic radius 0·65å), is low when the system is deprived of Ca2+ but high in the presence of small amounts of Ca2+. This sensitivity to Ca2+ seems to be a unique feature of the Mg2+-stimulated system. 4. The changes in specificity of the myosin adenosine triphosphatase activity in its requirement for bivalent cations caused by interaction with actin, tropomyosin and troponin primarily concern the size of the metal ions. The effects on enzymic properties of myofibrils due to tropomyosin and troponin can be demonstrated at low and at physiological ionic strength.

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