title: Final antigenic Melan-A peptides produced directly by the proteasomes are preferentially selected for presentation by HLA-A*0201 in melanoma cells.
abstract: The melanoma-associated protein Melan-A contains the immunodominant CTL epitope Melan-A(26/27-35)/HLA-A*0201 against which a high frequency of T lymphocytes has been detected in many melanoma patients. In this study we show that the in vitro degradation of a polypeptide encompassing Melan-A(26/27-35) by proteasomes produces both the final antigenic peptide and N-terminally extended intermediates. When human melanoma cells expressing the corresponding fragments were exposed to specific CTL, those expressing the minimal antigenic sequence were recognized more efficiently than those expressing the N-terminally extended intermediates. Using a tumor-reactive CTL clone, we confirmed that the recognition of melanoma cells expressing an N-terminally extended intermediate of Melan-A is inefficient. We demonstrated that the inefficient cytosolic trimming of N-terminally extended intermediates could offer a selective advantage for the preferred presentation of Melan-A peptides directly produced by the proteasomes. These results imply that both the proteasomes and postproteasomal peptidases limit the availability of antigenic peptides and that the efficiency of presentation may be affected by conditions that alter the ratio between fully and partially processed proteasomal products.
authors.affiliation: Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Ch. des Boveresses 155, CH-1066 Epalinges, Switzerland.
authors.forename: Laurence
authors.initials: L
authors.lastname: Chapatte
authors.forename: Catherine
authors.initials: C
authors.lastname: Servis
authors.forename: Danila
authors.initials: D
authors.lastname: Valmori
authors.forename: Odile
authors.initials: O
authors.lastname: Burlet-Schiltz
authors.forename: Johanna
authors.initials: J
authors.lastname: Dayer
authors.forename: Bernard
authors.initials: B
authors.lastname: Monsarrat
authors.forename: Pedro
authors.initials: P
authors.lastname: Romero
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lévy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000235:genetics / Q000276:immunology*; D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D003600:Cytosol / Q000201:enzymology; D018984:Epitopes, T-Lymphocyte / Q000235:genetics / Q000378:metabolism; D015234:HLA-A Antigens / Q000096:biosynthesis / Q000378:metabolism*; D015789:HLA-A2 Antigen; D006801:Humans; D006868:Hydrolysis; D007424:Intracellular Fluid / Q000201:enzymology; D058965:MART-1 Antigen; D008545:Melanoma / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000276:immunology* / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000235:genetics / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology / Q000276:immunology / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D018984:Epitopes, T-Lymphocyte; D015234:HLA-A Antigens; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D058965:MART-1 Antigen; C548667:MLANA protein, human; C548668:Mlana protein, mouse; D009363:Neoplasm Proteins; D010446:Peptide Fragments; D011498:Protein Precursors; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex