title: Retromer-mediated direct sorting is required for proper endosomal recycling of the mammalian iron transporter DMT1.
abstract: Endosomal recycling of the mammalian iron transporter DMT1 is assumed to be important for efficient and rapid uptake of iron across the endosomal membrane in the transferrin cycle. Here, we show that the retromer, a complex that mediates retrograde transport of transmembrane cargoes from endosomes to the trans-Golgi network, is required for endosomal recycling of DMT1-II, an alternative splicing isoform of DMT1. Bacterially expressed Vps26-Vsp29-Vsp35 trimer, a retromer cargo recognition complex, specifically binds to the cytoplasmic tail domain of DMT1-II in vitro. In particular, this binding is dependent on a specific hydrophobic motif of DMT1-II, which is required for its endosomal recycling. DMT1-II colocalizes with the Vps35 subunit of the retromer in TfR-positive endosomes. Depletion of the retromer by siRNA against Vps35 leads to mis-sorting of DMT1-II to LAMP2-positive structures, and expression of siRNA-resistant Vps35 can rescue this effect. These findings demonstrate that the retromer recognizes the recycling signal of DMT1-II and ensures its proper endosomal recycling.
authors.affiliation: Department of Molecular Genetics, Kawasaki Medical School, 577 Matsushima, Kurashiki, Okayama 701-0192, Japan. mtabuchi1125@gmail.com
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Tabuchi
authors.forename: Izumi
authors.initials: I
authors.lastname: Yanatori
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kawai
authors.forename: Fumio
authors.initials: F
authors.lastname: Kishi
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D011992:Endosomes / Q000378:metabolism*; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008969:Molecular Sequence Data; D021381:Protein Transport / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism; D000099236:Solute Carrier Family 11, Member 2
chemical_list: D027682:Cation Transport Proteins; D033921:Vesicular Transport Proteins; D000099236:Solute Carrier Family 11, Member 2; C419573:VPS35 protein, human