Dictyostelium Nramp1, which is structurally and functionally similar tomammalian DMT1 transporter, mediates phagosomal iron efflux

Simona Buracco, Barbara Peracino, Raffaella Cinquetti, Elena Signoretto, Alessandra Vollero, Francesca Imperiali, Michela Castagna, Elena Bossi, Salvatore Bozzaro

Research output: Contribution to journalArticle

Abstract

The Nramp (Slc11) protein family is widespread in bacteria and eukaryotes, and mediates transport of divalent metals across cellular membranes. The social amoeba Dictyostelium discoideum has two Nramp proteins. Nramp1, like its mammalian ortholog (SLC11A1), is recruited to phagosomal and macropinosomal membranes, and confers resistance to pathogenic bacteria. Nramp2 is located exclusively in the contractile vacuole membrane and controls, synergistically with Nramp1, iron homeostasis. It has long been debated whether mammalian Nramp1 mediates iron import or export from phagosomes. By selectively loading the iron-chelating fluorochrome calcein inmacropinosomes, we show that Dictyostelium Nramp1 mediates iron efflux from macropinosomes in vivo. To gain insight in ion selectivity and the transport mechanism, the proteins were expressed in Xenopus oocytes. Using a novel assay with calcein, and electrophysiological and radiochemical assays, we show that Nramp1, similar to rat DMT1 (also known as SLC11A2), transports Fe2+ and manganese, not Fe3+ or copper. Metal ion transport is electrogenic and proton dependent. By contrast, Nramp2 transports only Fe2+ in a non-electrogenic and proton-independent way. These differences reflect evolutionary divergence of the prototypical Nramp2 protein sequence compared to the archetypical Nramp1 and DMT1 proteins.

Original languageEnglish
Pages (from-to)3304-3316
Number of pages13
JournalJournal of Cell Science
Volume128
Issue number17
DOIs
Publication statusPublished - 2015

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Keywords

  • Bacterial infection
  • DMT1
  • Iron homeostasis
  • Macropinocytosis
  • Nramp1
  • Nramp2

ASJC Scopus subject areas

  • Cell Biology

Cite this

Buracco, S., Peracino, B., Cinquetti, R., Signoretto, E., Vollero, A., Imperiali, F., Castagna, M., Bossi, E., & Bozzaro, S. (2015). Dictyostelium Nramp1, which is structurally and functionally similar tomammalian DMT1 transporter, mediates phagosomal iron efflux. Journal of Cell Science, 128(17), 3304-3316. https://doi.org/10.1242/jcs.173153