Amino acid identity and/or position determines the proteasomal cleavage of the HLA-A*0201-restricted peptide tumor antigen MAGE-3271-279.
The proteasome plays a crucial role in the proteolytic processing of antigens presented to T cells in the context of major histocompatibility complex class I molecules. However, the rules governing the specificity of cleavage sites are still largely unknown. We have previously shown that a cytolytic T lymphocyte-defined antigenic peptide derived from the MAGE-3 tumor-associated antigen (MAGE-3(271-279), FLWGPRALV in one-letter code) is not presented at the surface of melanoma cell lines expressing the MAGE-3 protein. By using purified proteasome and MAGE-3(271-279) peptides extended at the C terminus by 6 amino acids, we identified predominant cleavages after residues 278 and 280 but no detectable cleavage after residue Val(279), the C terminus of the antigenic peptide. In the present study, we have investigated the influence of Pro(275), Leu(278), and Glu(280) on the proteasomal digestion of MAGE-3(271-285) substituted at these positions. We show that positions 278 and 280 are major proteasomal cleavage sites because they tolerate most amino acid substitutions. In contrast, the peptide bond after Val(279) is a minor cleavage site, influenced by both distal and proximal amino acid residues.
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Ludwig Institute for Cancer Research, Lausanne Branch, University of Lausanne, Ch. Des Boveresses 155, CH-1066 Epalinges and the Institute of Biochemistry, University of Lausanne, Ch. Des Boveresses 155, CH-1066 Epalinges, Switzerland.
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Cerottini
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Romero
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Lévy
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D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015234:HLA-A Antigens / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D014407:Tumor Cells, Cultured
D000951:Antigens, Neoplasm; D015234:HLA-A Antigens; C072013:MAGEA3 protein, human; C489519:Mageb3 protein, mouse; D009097:Multienzyme Complexes; D009363:Neoplasm Proteins; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex