title: Expression of divalent metal transporter 1 in primary hippocampal neurons: reconsidering its role in non-transferrin-bound iron influx.
abstract: The divalent metal transporter 1 (DMT1) is the best characterized Fe²⁺ transporter involved in cellular iron uptake in mammals. Four possible isoforms have been identified as a result of alternative promoter (DMT1-1A and DMT1-1B) and alternative splicing involving the C-terminus and producing transcripts with or without an iron responsive element [DMT1-IRE⁺ and DMT1-IRE⁻, respectively]. Despite the general importance of DMT1 in controlling iron homeostasis, the distribution and the role of the transporter in the CNS is still controversial. In this study, we characterize the expression of DMT1 in hippocampal neurons and astrocytes. We found that the main isoform endogenously expressed is DMT1-1B/IRE⁺, which shows cytoplasmic distribution, colocalization with late endosome/lysosome markers and iron regulation, as expected from the presence of an iron responsive element. Our results also show that DMT1-1B/IRE⁺ isoform does not sustain iron entry, even after its neuronal over-expression. Overall, our results argue against a physiological role of the endogenous DMT1 in neuronal iron uptake but do not exclude that, under pathological conditions, the expression of other DMT1 isoforms might contribute to iron overload.
authors: San Raffaele Scientific Institute, Division of Neuroscience, Milano, Italy.
authors: Ilaria
authors: I
authors: Pelizzoni
authors: Daniele
authors: D
authors: Zacchetti
authors: Craig P
authors: CP
authors: Smith
authors: Fabio
authors: F
authors: Grohovaz
authors: Franca
authors: F
authors: Codazzi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism*; D002458:Cell Fractionation / Q000379:methods; D002478:Cells, Cultured; D003676:Deferoxamine / Q000494:pharmacology; D004386:Duodenum / Q000166:cytology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology*; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism*; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D011990:Receptors, Transferrin / Q000378:metabolism; D017262:Siderophores / Q000494:pharmacology; D014162:Transfection / Q000379:methods; D014168:Transferrin / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism; D014741:Video Recording; D000099236:Solute Carrier Family 11, Member 2; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D027682:Cation Transport Proteins; D003676:Deferoxamine; D049452:Green Fluorescent Proteins; D007501:Iron; D051907:Lysosomal Membrane Proteins; D012333:RNA, Messenger; D011990:Receptors, Transferrin; D017262:Siderophores; D014168:Transferrin; D033921:Vesicular Transport Proteins; D000099236:Solute Carrier Family 11, Member 2; C489117:Lamp1 protein, rat; D052118:Lysosomal-Associated Membrane Protein 1; C545564:Tfrc protein, rat; C093846:early endosome antigen 1; C485184:enhanced green fluorescent protein