Peptides with dual binding specificity for HLA-A2 and HLA-E are encoded by alternatively spliced isoforms of the antioxidant enzyme peroxiredoxin 5.
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.
Sensi
Marialuisa
M
Dipartimento di Oncologia Sperimentale, Immunobiologia dei Tumori Umani, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy. marialuisa.sensi@istitutotumori.mi.it
Pietra
Gabriella
G
Molla
Alessandra
A
Nicolini
Gabriella
G
Vegetti
Claudia
C
Bersani
Ilaria
I
Millo
Enrico
E
Weiss
Elizabeth
E
Moretta
Lorenzo
L
Mingari
Maria Cristina
MC
Anichini
Andrea
A
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
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