Title: SMF-1, SMF-2 and SMF-3 DMT1 orthologues regulate and are regulated differentially by manganese levels in C. elegans.
Authors: Au, Catherine; Benedetto, Alexandre; Anderson, Joel; Labrousse, Arnaud; Erikson, Keith; Ewbank, Jonathan J; Aschner, Michael
Published In PLoS One, (2009 Nov 18)
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.
PubMed ID: 19924247
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