title: STAM proteins bind ubiquitinated proteins on the early endosome via the VHS domain and ubiquitin-interacting motif.
abstract: Conjugation with ubiquitin acts as a sorting signal for proteins in the endocytic and biosynthetic pathways at the endosome. Signal-transducing adaptor molecule (STAM) proteins, STAM1 and STAM2, are associated with hepatocyte growth factor-regulated substrate (Hrs) but their function remains unknown. Herein, we show that STAM proteins bind ubiquitin and ubiquitinated proteins and that the tandemly located VHS (Vps27/Hrs/STAM) domain and ubiquitin-interacting motif serve as the binding site(s). STAM proteins colocalize with Hrs on the early endosome. Overexpression of STAM proteins, but not their mutants lacking the ubiquitin-binding activity, causes the accumulation of ubiquitinated proteins and ligand-activated epidermal growth factor receptor on the early endosome. These results suggest that through interaction with ubiquitinated cargo proteins on the early endosome via the VHS domain and ubiquitin-interacting motif, STAM proteins participate in the sorting of cargo proteins for trafficking to the lysosome.
authors.affiliation: Department of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan. makomada@bio.titech.ac.jp
authors.forename: Emi
authors.initials: E
authors.lastname: Mizuno
authors.forename: Kensuke
authors.initials: K
authors.lastname: Kawahata
authors.forename: Masaki
authors.initials: M
authors.lastname: Kato
authors.forename: Naomi
authors.initials: N
authors.lastname: Kitamura
authors.forename: Masayuki
authors.initials: M
authors.lastname: Komada
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004705:Endocytosis / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D010750:Phosphoproteins / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D056827:Endosomal Sorting Complexes Required for Transport; D010750:Phosphoproteins; C109775:STAM protein, human; C491647:STAM2 protein, human; D025801:Ubiquitin; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D066246:ErbB Receptors