Final antigenic Melan-A peptides produced directly by the proteasomes are preferentially selected for presentation by HLA-A*0201 in melanoma cells

J Immunol. 2004 Nov 15;173(10):6033-40. doi: 10.4049/jimmunol.173.10.6033.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigen Presentation / genetics
  • Antigen Presentation / immunology*
  • Antigens, Neoplasm / biosynthesis*
  • Antigens, Neoplasm / genetics
  • Antigens, Neoplasm / metabolism
  • Cell Line
  • Cell Line, Tumor
  • Cytosol / enzymology
  • Epitopes, T-Lymphocyte / genetics
  • Epitopes, T-Lymphocyte / metabolism
  • HLA-A Antigens / biosynthesis
  • HLA-A Antigens / metabolism*
  • HLA-A2 Antigen
  • Humans
  • Hydrolysis
  • Intracellular Fluid / enzymology
  • MART-1 Antigen
  • Melanoma / immunology*
  • Melanoma / metabolism
  • Mice
  • Molecular Sequence Data
  • Neoplasm Proteins / biosynthesis*
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Peptide Fragments / biosynthesis*
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Peptide Hydrolases / metabolism
  • Proteasome Endopeptidase Complex / immunology*
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Precursors / genetics
  • Protein Precursors / metabolism
  • Protein Processing, Post-Translational / genetics
  • Protein Processing, Post-Translational / immunology
  • T-Lymphocytes, Cytotoxic / enzymology
  • T-Lymphocytes, Cytotoxic / immunology
  • T-Lymphocytes, Cytotoxic / metabolism


  • Antigens, Neoplasm
  • Epitopes, T-Lymphocyte
  • HLA-A Antigens
  • HLA-A*02:01 antigen
  • HLA-A2 Antigen
  • MART-1 Antigen
  • MLANA protein, human
  • Mlana protein, mouse
  • Neoplasm Proteins
  • Peptide Fragments
  • Protein Precursors
  • Peptide Hydrolases
  • Proteasome Endopeptidase Complex