A mannose 6-phosphate-containing N-linked glycopeptide derived from lysosomal acid lipase is bound to MHC class II in B lymphoblastoid cell lines.
Binding of peptides to MHC class II Ag generates ligands for TCR of Th lymphocytes. We have identified a novel class of peptides bound to MHC class II: mannose 6- phosphate (Man-6-P) containing glycopeptides from lysosomal enzymes. These species were identified in the process of characterizing mannose 6-phosphate/insulin-like growth factor II (M-6-P/IGF-II) receptor binding to the surface of B lymphoblasts. Surface iodination and Man-6-P/IGF-II receptor affinity chromatography implicated MHC class II as a carrier of Man-6-P-modified oligosaccharides. These oligosaccharides were found to be primarily associated with the bound peptide. Peptides eluted from the Man-6-P/IGF-II receptor-binding fraction of immunoaffinity-purified MHC class II from the Swei cell line contained a sequence derived from the propiece of lysosomal acid lipase. Partial sequences were also obtained for peptides from other HLA-DR alleles but none of these were attributable to known proteins. This study defines a novel approach for isolating rare glycan-modified peptides from MHC class II and demonstrates that very large secondary modifications are tolerated in peptides bound to MHC class II.
Dustin
M L
ML
Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
McCourt
D W
DW
Kornfeld
S
S
D000595:Amino Acid Sequence; D001402:B-Lymphocytes / Q000201:enzymology* / Q000276:immunology; D002236:Carbohydrate Conformation; D002460:Cell Line; D006020:Glycopeptides / Q000737:chemistry* / Q000378:metabolism; D006684:HLA-DR Antigens / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D008049:Lipase / Q000737:chemistry*; D008213:Lymphocyte Activation; D008247:Lysosomes / Q000201:enzymology*; D008360:Mannosephosphates / Q000737:chemistry* / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000276:immunology; D008969:Molecular Sequence Data; D010455:Peptides / Q000302:isolation & purification; D011485:Protein Binding / Q000276:immunology; D017527:Receptor, IGF Type 2 / Q000378:metabolism
D006020:Glycopeptides; D006684:HLA-DR Antigens; D008360:Mannosephosphates; D008562:Membrane Glycoproteins; D010455:Peptides; D017527:Receptor, IGF Type 2; C027693:mannose-6-phosphate; D008049:Lipase