title: Nramp1 locus encodes a 65 kDa interferon-gamma-inducible protein in murine macrophages.
abstract: The murine Nramp1 (natural-resistance-associated macrophage protein) locus, formerly known as Ity/Lsh/Bcg, was isolated previously on the basis of chromosomal location, and as conferring natural resistance to infection against intracellular macrophage pathogens. The gene encodes a transporter molecule of unknown function. We have prepared polyclonal antisera against the C-terminal 35 amino acids of murine Nramp1. This serum is reactive towards a 65 kDa protein, expressed in murine macrophage cells from resistant or susceptible mice stimulated with interferon-gamma and lipopolysaccharide, but not in non-macrophage cells. Evidence indicates that Nramp1 is localized in a subcellular membrane rather than at the cell surface. This evidence includes: the identification of conserved endocytic targeting motifs following inspection of human and murine Nramp sequences; the enrichment of Nramp1, following magnetic selection of phagolysosomal vesicles from activated macrophages that were allowed to phagocytose magnetic, IgG-coated beads; confocal microscopy. These studies place Nramp1 on a membrane in close proximity to obligate intracellular pathogens. A link between Nramp1 and divalent-cation transport is suggested by sequence similarity with yeast SMF1. Evidence showing modulation of Nramp1 protein levels by iron chelation provides a direct link with Nramp1 function and divalent-cation metabolism.
authors.affiliation: University of Southampton, Biochemistry and Molecular Biology Division, School of Biological Sciences, Bassett Crescent East, Southampton SO16 7PX, U.K.
authors.forename: P G
authors.initials: PG
authors.lastname: Atkinson
authors.forename: J M
authors.initials: JM
authors.lastname: Blackwell
authors.forename: C H
authors.initials: CH
authors.lastname: Barton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D027682:Cation Transport Proteins; D006801:Humans; D007106:Immune Sera; D007371:Interferon-gamma / Q000494:pharmacology*; D007502:Iron Chelating Agents / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D051379:Mice; D017628:Microglia / Q000378:metabolism; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D000099173:Natural Resistance-associated Macrophage Protein 1
chemical_list: D002352:Carrier Proteins; D027682:Cation Transport Proteins; D007106:Immune Sera; D007371:Interferon-gamma; D007502:Iron Chelating Agents; D008565:Membrane Proteins; D000099173:Natural Resistance-associated Macrophage Protein 1