title: The DnaJ-domain protein RME-8 functions in endosomal trafficking.
abstract: Through a proteomic analysis of clathrin-coated vesicles from rat liver we identified the mammalian homolog of receptor-mediated endocytosis 8 (RME-8), a DnaJ domain-containing protein originally identified in a screen for endocytic defects in Caenorhabditis elegans. Mammalian RME-8 has a broad tissue distribution, and affinity selection assays reveal the ubiquitous chaperone Hsc70, which regulates protein conformation at diverse membrane sites as the major binding partner for its DnaJ domain. RME-8 is tightly associated with microsomal membranes and co-localizes with markers of the endosomal system. Small interfering RNA-mediated knock down of RME-8 has no influence on transferrin endocytosis but causes a reduction in epidermal growth factor internalization. Interestingly, and consistent with a localization to endosomes, knock down of RME-8 also leads to alterations in the trafficking of the cation-independent mannose 6-phosphate receptor and improper sorting of the lysosomal hydrolase cathepsin D. Our data demonstrate that RME-8 functions in intracellular trafficking and provides the first evidence of a functional role for a DnaJ domain-bearing co-chaperone on endosomes.
authors.affiliation: Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal QC H3A 2B4, Canada.
authors.forename: Martine
authors.initials: M
authors.lastname: Girard
authors.forename: Viviane
authors.initials: V
authors.lastname: Poupon
authors.forename: Francois
authors.initials: F
authors.lastname: Blondeau
authors.forename: Peter S
authors.initials: PS
authors.lastname: McPherson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism / Q000502:physiology*; D002402:Cathepsin D / Q000737:chemistry; D002412:Cations; D002462:Cell Membrane / Q000378:metabolism; D002469:Cell Separation; D002522:Chlorocebus aethiops; D002772:Cholera Toxin / Q000737:chemistry; D002966:Clathrin / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D005456:Fluorescent Dyes / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D050956:HSP40 Heat-Shock Proteins / Q000737:chemistry*; D006801:Humans; D008099:Liver / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008862:Microsomes, Liver / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D040901:Proteomics; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D014168:Transferrin / Q000737:chemistry / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D002412:Cations; D002966:Clathrin; D018076:DNA, Complementary; C507525:DNAJC13 protein, human; C507526:DNAJC13 protein, rat; D005456:Fluorescent Dyes; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018832:Molecular Chaperones; C439316:RME-8 protein, C elegans; D034741:RNA, Small Interfering; D017527:Receptor, IGF Type 2; D011993:Recombinant Fusion Proteins; D014168:Transferrin; D004815:Epidermal Growth Factor; D002772:Cholera Toxin; D005982:Glutathione Transferase; D002402:Cathepsin D