title: Differential functions of Hrs and ESCRT proteins in endocytic membrane trafficking.
abstract: A ubiquitin-binding endosomal protein machinery is responsible for sorting endocytosed membrane proteins into intraluminal vesicles of multivesicular endosomes (MVEs) for subsequent degradation in lysosomes. The Hrs-STAM complex and endosomal sorting complex required for transport (ESCRT)-I, -II and -III are central components of this machinery. Here, we have performed a systematic analysis of their importance in four trafficking pathways through endosomes. Neither Hrs, Tsg101 (ESCRT-I), Vps22/EAP30 (ESCRT-II), nor Vps24/CHMP3 (ESCRT-III) was required for ligand-mediated internalization of epidermal growth factor (EGF) receptors (EGFRs) or for recycling of cation-independent mannose 6-phosphate receptors (CI-M6PRs) from endosomes to the trans-Golgi network (TGN). In contrast, both Hrs and ESCRT subunits were equally required for degradation of both endocytosed EGF and EGFR. Whereas depletion of Hrs or Tsg101 caused enhanced recycling of endocytosed EGFRs, this was not the case with depletion of Vps22 or Vps24. Depletion of Vps24 instead caused a strong increase in the levels of CI-M6PRs and a dramatic redistribution of the Golgi and the TGN. These results indicate that, although Hrs-STAM and ESCRT-I, -II and -III have a common function in degradative protein sorting, they play differential roles in other trafficking pathways, probably reflecting their functions at distinct stages of the endocytic pathway.
authors.affiliation: Centre for Cancer Biomedicine, University of Oslo, and Department of Biochemistry, the Norwegian Radium Hospital, Rikshospitalet, Norway.
authors.forename: Camilla
authors.initials: C
authors.lastname: Raiborg
authors.forename: Lene
authors.initials: L
authors.lastname: Malerød
authors.forename: Nina M
authors.initials: NM
authors.lastname: Pedersen
authors.forename: Harald
authors.initials: H
authors.lastname: Stenmark
mesh_terms: D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D004705:Endocytosis; D056827:Endosomal Sorting Complexes Required for Transport; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D021381:Protein Transport; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D034622:RNA Interference; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics; D033921:Vesicular Transport Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D021601:trans-Golgi Network / Q000378:metabolism; D000099177:Tsg101 Protein
chemical_list: D004268:DNA-Binding Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D010750:Phosphoproteins; D021122:Protein Subunits; D011506:Proteins; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D033921:Vesicular Transport Proteins; D000099177:Tsg101 Protein; C498543:CHMP3 protein, human; C525859:SNF8 protein, human; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate