title: HLA-DR antigens of autologous melanoma and B lymphoblastoid cell lines: differences in glycosylation but not protein structure.
abstract: The HLA-DR antigen expressed on the surface of the human melanoma cell line SK-MEL-37 was characterized and compared with the HLA-DR antigen from the MU B lymphoblastoid cell line originating from the same individual. The HLA-DR heavy chain from SK-MEL-37 cells had an apparent mobility on SDS-PAGE slightly slower than that isolated from MU cells. In contrast, the HLA-DR light chains and the HLA-A,-B heavy chains from the two cell lines had identical mobilities. Double-labeled tryptic peptide mapping and limited N-terminal sequencing showed that the SK-MEL-37 HLA-DR antigen, like all previously examined B lymphoblastoid cell HLA-DR antigens, was homologous to the murine I-E/C subregion antigens and that the mobility difference of the SK-MEL-37 HLA-DR heavy chain was not attributable to differences in the primary structure of the polypeptide. Treatment of the cells with tunicamycin abolished the m.w. difference, suggesting that it was due to a change in glycosylation in SK-MEL-37. This was confirmed by analysis of the glycopeptides from pronase-digested HLA-DR light and heavy chains and HLA-A,B heavy chains purified from the two cell types. The results suggest 1) there is a difference in asparagine-linked oligosaccharide processing in the two cell types, with more of the larger complex glycans synthesized in the melanoma cells than in the B lymphoblastoid cells, 2) the effect is more pronounced with HLA-DR heavy chains than with HLA-DR light chains or HLA-A,B heavy chains, and 3) the oligosaccharide size difference is not solely due to sialic acid content.
mesh_terms: D000595:Amino Acid Sequence; D000937:Antigen-Antibody Reactions; D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D011232:Chemical Precipitation; D006020:Glycopeptides / Q000378:metabolism*; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II / Q000032:analysis* / Q000276:immunology; D006801:Humans; D008213:Lymphocyte Activation; D008545:Melanoma / Q000276:immunology*; D009844:Oligosaccharides / Q000378:metabolism; D010455:Peptides / Q000032:analysis; D012795:Sialoglycoproteins / Q000378:metabolism
chemical_list: D006020:Glycopeptides; D006684:HLA-DR Antigens; D000949:Histocompatibility Antigens Class II; D009844:Oligosaccharides; D010455:Peptides; D012795:Sialoglycoproteins