title: Peptides with dual binding specificity for HLA-A2 and HLA-E are encoded by alternatively spliced isoforms of the antioxidant enzyme peroxiredoxin 5.
abstract: Peptides with dual binding specificity for classical HLA class I and non-classical HLA-E molecules have been identified in virus-encoded proteins, but not in cellular proteins from normal or neoplastic cells. Expression screening of a melanoma cDNA library with a CTL clone recognizing an HLA-A2-restricted tumor-specific epitope encoded by mutant peroxiredoxin 5 (Prdx5), a stress-inducible peroxidase, led to the identification of two alternatively spliced isoforms of the same gene. These isoforms, which lack the catalytic cysteine fundamental for enzymatic activity, showed widespread expression in neoplastic and normal tissues but were unstable at the protein level, being detectable, following transient transfection, only after lactacystin treatment to inhibit proteasomal degradation. Isoform-specific sequences which formed, respectively, as result of exon 1 splicing to either exon 3 or 4, encoded two distinct nonapeptides (AMAPIKTHL and AMAPIKVRL, not present in the full-length protein) with anchor residues for HLA-A2 and HLA-E molecules and able to stabilize HLA-A2 and HLA-E cell surface expression. HLA-E+ targets, loaded with these peptides, were not recognized by NK cells expressing CD94/NKG2A inhibitory or CD94/NKG2C activatory receptors. However, both peptides were recognized, although with low avidity, by HLA-E-restricted CD8+ CTL. The nonapeptide AMAPIKVRL was used to elicit HLA-A2-restricted CTL clones that killed peptide-pulsed lymphoblastoid cell lines and melanoma cells expressing the corresponding Prdx5 isoform. Our results suggest that alternatively spliced isoforms of Prdx5, through the generation of HLA-E- and HLA-A2-restricted peptides may be part of immune-mediated stress response contributing to the detection and elimination of damaged normal or neoplastic cells.
authors.affiliation: Dipartimento di Oncologia Sperimentale, Immunobiologia dei Tumori Umani, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy. marialuisa.sensi@istitutotumori.mi.it
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Sensi
authors.forename: Gabriella
authors.initials: G
authors.lastname: Pietra
authors.forename: Alessandra
authors.initials: A
authors.lastname: Molla
authors.forename: Gabriella
authors.initials: G
authors.lastname: Nicolini
authors.forename: Claudia
authors.initials: C
authors.lastname: Vegetti
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bersani
authors.forename: Enrico
authors.initials: E
authors.lastname: Millo
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Weiss
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Moretta
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Mingari
authors.forename: Andrea
authors.initials: A
authors.lastname: Anichini
mesh_terms: D017398:Alternative Splicing; D020816:Amino Acid Motifs / Q000276:immunology; D000951:Antigens, Neoplasm / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000975:Antioxidants / Q000378:metabolism; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D002999:Clone Cells; D003545:Cysteine / Q000172:deficiency; D006680:HLA Antigens / Q000378:metabolism*; D015789:HLA-A2 Antigen / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007111:Immunity, Cellular; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008545:Melanoma / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018384:Oxidative Stress / Q000276:immunology; D010455:Peptides / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D054464:Peroxiredoxins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D055550:Protein Stability / Q000187:drug effects; D017384:Sequence Deletion; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology / Q000378:metabolism; D000097625:HLA-E Antigens
chemical_list: D000951:Antigens, Neoplasm; D000975:Antioxidants; D003545:Cysteine; D006680:HLA Antigens; D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D010455:Peptides; D054464:Peroxiredoxins; D020033:Protein Isoforms; D000097625:HLA-E Antigens; C515974:PRDX5 protein, human