title: Degradation signals in ErbB-2 dictate proteasomal processing and immunogenicity and resist protection by cis glycine-alanine repeat.
abstract: ErbB-2 is ubiquitinated and degraded when dissociated from its membrane chaperone or bound by specific antibody. Reagents which induce such degradation have demonstrated antitumor activity and may impact ErbB-2 immunogenicity. To further understand ErbB-2 degradation and immunogenicity, a glycine-alanine repeat (GAr) or the reverse proline-alanine repeat (PAr) which protects certain proteins from proteasome degradation, was inserted after amino acid 5 (GAr5/PAr5) or 55 (GAr55/PAr55) of ErbB-2. When dissociated from the membrane with geldanamycin, E2-GAr5 and E2-PAr5 were not protected and still ubiquitinated and degraded by the proteasome, despite the presence of GAr. Insertional mutagenesis with GAr sequences at a.a. 55 of E2 enhanced proteasome degradation rendering E2-GAr55 and E2-PAr55 unstable on the membrane, but rescued in the cytosol by proteasome inhibitors. Immunization with E2-GAr induced antitumor immunity and CTL which lysed tumor cells expressing chimeric E2-GAr or wild-type E2 proteins, demonstrating efficient presentation through MHC I pathway. Improved understanding of the strong degradation signals in ErbB-2 may facilitate the development of anticancer agents or vaccines.
authors.affiliation: School of Medicine, Karmanos Cancer Institute, Department of Otolaryngology, Wayne State University, Detroit, Michigan 48201, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Piechocki
authors.forename: S A
authors.initials: SA
authors.lastname: Pilon
authors.forename: C
authors.initials: C
authors.lastname: Kelly
authors.forename: W Z
authors.initials: WZ
authors.lastname: Wei
mesh_terms: D000409:Alanine / Q000737:chemistry; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000494:pharmacology; D016227:Benzoquinones; D019496:Cancer Vaccines / Q000627:therapeutic use; D002462:Cell Membrane / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D015195:Drug Design; D005260:Female; D005998:Glycine / Q000737:chemistry; D006801:Humans; D016233:Immunotherapy, Active; D047029:Lactams, Macrocyclic; D008325:Mammary Neoplasms, Experimental / Q000276:immunology / Q000473:pathology / Q000628:therapy; D008565:Membrane Proteins / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D009097:Multienzyme Complexes / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D009363:Neoplasm Proteins / Q000276:immunology / Q000378:metabolism; D009368:Neoplasm Transplantation; D046988:Proteasome Endopeptidase Complex; D011809:Quinones / Q000494:pharmacology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000276:immunology; D020449:Repetitive Sequences, Amino Acid; D013045:Species Specificity; D013329:Structure-Activity Relationship; D014162:Transfection; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured / Q000276:immunology; D025801:Ubiquitin / Q000378:metabolism; D019444:Vaccines, DNA / Q000627:therapeutic use
chemical_list: D000409:Alanine; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D016227:Benzoquinones; D019496:Cancer Vaccines; D003546:Cysteine Endopeptidases; D005998:Glycine; D047029:Lactams, Macrocyclic; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D046988:Proteasome Endopeptidase Complex; D011809:Quinones; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; D000068878:Trastuzumab; D025801:Ubiquitin; D019444:Vaccines, DNA; C001277:geldanamycin