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

Catherine Au (1, 2) , Alexandre Benedetto (1, 3, 4) , Joel Anderson (5) , Arnaud Labrousse (6, 7) , Keith Erikson (5) , Jonathan J Ewbank (7) , Michael Aschner (1, 2, 3)

1 Department of Pediatrics
2 Center for Molecular Toxicology
3 Children's Hospital
4 London Centre for Nanotechnology
5 Department of Nutrition
6 IPBS - Institut de pharmacologie et de biologie structurale
7 CIML - Centre d'Immunologie de Marseille - Luminy

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.

Mots clés: Gastrointestinal tract; Toxicity; Saccharomyces cerevisiae; Intracellular membranes; Cell membranes; Manganese; Caenorhabditis elegans; Vertebrates

Domaines: Ecotoxicologie; Biochimie, Biologie Moléculaire

Catherine Au, Alexandre Benedetto, Joel Anderson, Arnaud Labrousse, Keith Erikson, et al.. SMF-1, SMF-2 and SMF-3 DMT1 orthologues regulate and are regulated differentially by manganese levels in C. elegans. PLoS ONE, 2009, 4 (11), pp.e7792. ⟨10.1371/journal.pone.0007792⟩. ⟨hal-00439893⟩