title: Geldanamycin induces ErbB-2 degradation by proteolytic fragmentation.
abstract: Exposure of carcinoma cell lines to the antibiotic geldanamycin induces the degradation of ErbB-2, a co-receptor tyrosine kinase that is frequently overexpressed in certain tumors. Using ErbB-2 mutants expressed as chimeric receptors or green fluorescent protein fusion proteins, we report that the kinase domain of ErbB-2 is essential for geldanamycin-induced degradation. The kinase domain of the related epidermal growth factor receptor was not sensitive to this drug. The data further indicate mechanistic aspects of ErbB-2 degradation by geldanamycin. The data show that exposure to the drug induces at least one cleavage within the cytoplasmic domain of ErbB-2 producing a 135-kDa fragment and a 23-kDa fragment. The latter represents the carboxyl-terminal domain of ErbB-2, whereas the former represents the ectodomain and part of the cytoplasmic domain. Degradation of the carboxyl-terminal fragment is prevented by proteasome inhibitors, whereas degradation of the membrane-anchored 135-kDa ErbB-2 fragment is blocked by inhibitors of the endocytosis-dependent degradation pathway. Confocal microscopy studies confirm a geldanamycin-induced localization of ErbB-2 on intracellular vesicles.
authors.affiliation: Departments of Biochemistry and Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
authors.forename: O
authors.initials: O
authors.lastname: Tikhomirov
authors.forename: G
authors.initials: G
authors.lastname: Carpenter
mesh_terms: D016475:3T3 Cells; D000818:Animals; D016227:Benzoquinones; D001665:Binding Sites; D019556:COS Cells; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D006801:Humans; D047029:Lactams, Macrocyclic; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011809:Quinones / Q000494:pharmacology*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
chemical_list: D016227:Benzoquinones; D004791:Enzyme Inhibitors; D066246:ErbB Receptors; D047029:Lactams, Macrocyclic; D010446:Peptide Fragments; D011505:Protein-Tyrosine Kinases; D011809:Quinones; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C001277:geldanamycin