title: Endocytic down-regulation of ErbB2 is stimulated by cleavage of its C-terminus.
abstract: High ErbB2 levels are associated with cancer, and impaired endocytosis of ErbB2 could contribute to its overexpression. Therefore, knowledge about the mechanisms underlying endocytic down-regulation of ErbB2 is warranted. The C-terminus of ErbB2 can be cleaved after various stimuli, and after inhibition of HSP90 with geldanamycin this cleavage is accompanied by proteasome-dependent endocytosis of ErbB2. However, it is unknown whether C-terminal cleavage is linked to endocytosis. To study ErbB2 cleavage and endocytic trafficking, we fused yellow fluorescent protein (YFP) and cyan fluorescent protein (CFP) to the N- and C-terminus of ErbB2, respectively (YFP-ErbB2-CFP). After geldanamycin stimulation YFP-ErbB2-CFP became cleaved in nonapoptotic cells in a proteasome-dependent manner, and a markedly larger relative amount of cleaved YFP-ErbB2-CFP was observed in early endosomes than in the plasma membrane. Furthermore, cleavage took place at the plasma membrane, and cleaved ErbB2 was internalized and degraded far more efficiently than full-length ErbB2. Concordantly, a C-terminally truncated ErbB2 was also readily endocytosed and degraded in lysosomes compared with full-length ErbB2. Altogether, we suggest that geldanamycin leads to C-terminal cleavage of ErbB2, which releases the receptor from a retention mechanism and causes endocytosis and lysosomal degradation of ErbB2.
authors.affiliation: Department of Cellular and Molecular Medicine, University of Copenhagen, The Panum Institute, DK-2200 Copenhagen N, Denmark.
authors.forename: Mads
authors.initials: M
authors.lastname: Lerdrup
authors.forename: Silas
authors.initials: S
authors.lastname: Bruun
authors.forename: Michael V
authors.initials: MV
authors.lastname: Grandal
authors.forename: Kirstine
authors.initials: K
authors.lastname: Roepstorff
authors.forename: Malene M
authors.initials: MM
authors.lastname: Kristensen
authors.forename: Anette M
authors.initials: AM
authors.lastname: Hommelgaard
authors.forename: Bo
authors.initials: B
authors.lastname: van Deurs
mesh_terms: D016227:Benzoquinones / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics*; D004705:Endocytosis / Q000187:drug effects; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D050505:Mutant Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015203:Reproducibility of Results; D013329:Structure-Activity Relationship
chemical_list: D016227:Benzoquinones; D047029:Lactams, Macrocyclic; D050505:Mutant Proteins; D046988:Proteasome Endopeptidase Complex; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C001277:geldanamycin