title: SMF-1, SMF-2 and SMF-3 DMT1 orthologues regulate and are regulated differentially by manganese levels in C. elegans.
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.
authors.affiliation: Department of Pediatrics, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Au
authors.forename: Alexandre
authors.initials: A
authors.lastname: Benedetto
authors.forename: Joel
authors.initials: J
authors.lastname: Anderson
authors.forename: Arnaud
authors.initials: A
authors.lastname: Labrousse
authors.forename: Keith
authors.initials: K
authors.lastname: Erikson
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Ewbank
authors.forename: Michael
authors.initials: M
authors.lastname: Aschner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001692:Biological Transport; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D017353:Gene Deletion; D005786:Gene Expression Regulation; D007501:Iron / Q000737:chemistry; D008345:Manganese / Q000737:chemistry / Q000378:metabolism*; D008670:Metals / Q000737:chemistry; D008969:Molecular Sequence Data; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D029742:Caenorhabditis elegans Proteins; D027682:Cation Transport Proteins; D007501:Iron; D008345:Manganese; D008670:Metals; D000099236:Solute Carrier Family 11, Member 2; C548880:smf-1 protein, C elegans; C548881:smf-2 protein, C elegans; C548882:smf-3 protein, C elegans