title: Function and mechanism of action of Dictyostelium Nramp1 (Slc11a1) in bacterial infection.
abstract: Dictyostelium amoebae are professional phagocytes, which ingest bacteria as the principal source of food. We have cloned the Dictyostelium homologue of human natural resistance-associated membrane protein 1 (Nramp1) [solute carrier family 11 member 1 (Slc11a1)], an endo-lysosomal membrane protein that confers on macrophages resistance to infection by a variety of intracellular bacteria and protozoa. The Dictyostelium Nramp1 gene encodes a protein of 53 kDa with 11 putative transmembrane domains. The Nramp1 gene is transcribed during the growth-phase and downregulated to barely detectable levels upon starvation. To gain insights into their intracellular localization, we fused Nramp1 or the vatB subunit of the V-H(+)ATPase with green fluorescent protein and expressed in cells. Green fluorescent protein-vatB was inserted in membranes of all acidic compartments and the contractile vacuole network and decorated macropinosomes and phagosomes. Green fluorescent protein-Nramp1 decorated macropinosomes and phagosomes, in addition to intracellular vesicular compartments positive for endosomal SNARE protein Vti1 or vacuolin, a marker of the exocytic pathway. Nramp1 disruption generated mutants that were more permissive hosts than wild-type cells for intracellular growth of Legionella pneumophila and Micobacterium avium. Nramp1 overexpression protected cells from L. pneumophila infection. Evidence is provided that Nramp1 transports metal cations out of the phagolysosome in an ATP-dependent process and that L. pneumophila and M. avium use different mechanisms to neutralize Nramp1 activity.
authors.affiliation: Department of Clinical and Biological Sciences, University of Turin, Orbassano, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Peracino
authors.forename: Carina
authors.initials: C
authors.lastname: Wagner
authors.forename: Alessandra
authors.initials: A
authors.lastname: Balest
authors.forename: Alessandra
authors.initials: A
authors.lastname: Balbo
authors.forename: Barbara
authors.initials: B
authors.lastname: Pergolizzi
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
authors.forename: Michael
authors.initials: M
authors.lastname: Steinert
authors.forename: Salvatore
authors.initials: S
authors.lastname: Bozzaro
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000254:growth & development*; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000235:genetics / Q000382:microbiology / Q000502:physiology*; D004926:Escherichia coli / Q000254:growth & development; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000378:metabolism; D007875:Legionella / Q000254:growth & development; D008247:Lysosomes / Q000378:metabolism; D008969:Molecular Sequence Data; D009162:Mycobacterium avium / Q000254:growth & development; D010587:Phagocytosis; D010588:Phagosomes / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D000099173:Natural Resistance-associated Macrophage Protein 1
chemical_list: D027682:Cation Transport Proteins; D049452:Green Fluorescent Proteins; D007501:Iron; D000099173:Natural Resistance-associated Macrophage Protein 1