SMF-1, SMF-2 and SMF-3 DMT1 orthologues regulate and are regulated differentially by manganese levels in C. elegans

PLoS One. 2009 Nov 18;4(11):e7792. doi: 10.1371/journal.pone.0007792.

Abstract

Manganese (Mn) is an essential metal that can exert toxic effects at high concentrations, eventually leading to Parkinsonism. A major transporter of Mn in mammals is the divalent-metal transporter (DMT1). We characterize here DMT1-like proteins in the nematode C. elegans, which regulate and are regulated by Mn and iron (Fe) content. We identified three new DMT1-like genes in C. elegans: smf-1, smf-2 and smf-3. All three can functionally substitute for loss of their yeast orthologues in S. cerevisiae. In the worm, deletion of smf-1 or smf-3 led to an increased Mn tolerance, while loss of smf-2 led to increased Mn sensitivity. smf mRNA levels measured by QRT-PCR were up-regulated upon low Mn and down-regulated upon high Mn exposures. Translational GFP-fusions revealed that SMF-1 and SMF-3 strongly localize to partially overlapping apical regions of the gut epithelium, suggesting a differential role for SMF-1 and SMF-3 in Mn nutritional intake. Conversely, SMF-2 was detected in the marginal pharyngeal epithelium, possibly involved in metal-sensing. Analysis of metal content upon Mn exposure in smf mutants revealed that SMF-3 is required for normal Mn uptake, while smf-1 was dispensable. Higher smf-2 mRNA levels correlated with higher Fe content, supporting a role for SMF-2 in Fe uptake. In smf-1 and smf-3 but not in smf-2 mutants, increased Mn exposure led to decreased Fe levels, suggesting that both metals compete for transport by SMF-2. Finally, SMF-3 was post-translationally and reversibly down-regulated following Mn-exposure. In sum, we unraveled a complex interplay of transcriptional and post-translational regulations of 3 DMT1-like transporters in two adjacent tissues, which regulate metal-content in C. elegans.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Animals, Genetically Modified
  • Biological Transport
  • Caenorhabditis elegans
  • Caenorhabditis elegans Proteins / metabolism*
  • Cation Transport Proteins / genetics*
  • Cation Transport Proteins / metabolism*
  • Cloning, Molecular
  • Gene Deletion
  • Gene Expression Regulation*
  • Iron / chemistry
  • Manganese / chemistry
  • Manganese / metabolism*
  • Metals / chemistry
  • Molecular Sequence Data
  • Saccharomyces cerevisiae / metabolism
  • Sequence Homology, Amino Acid

Substances

  • Caenorhabditis elegans Proteins
  • Cation Transport Proteins
  • Metals
  • smf-1 protein, C elegans
  • smf-2 protein, C elegans
  • smf-3 protein, C elegans
  • solute carrier family 11- (proton-coupled divalent metal ion transporters), member 2
  • Manganese
  • Iron