title: A transporter associated with antigen-processing independent vacuolar pathway for the MHC class I-mediated presentation of endogenous transmembrane proteins.
abstract: MHC class I molecules present peptides derived from the ectodomains of endogenous transmembrane proteins; however, the processing of these Ags is incompletely understood. As model transmembrane Ags we investigated the processing of MHC-I-derived fusion proteins containing the N-terminally extended K(b)-restricted OVA epitope SIINFEKL in the extracytoplasmic domain. In TAP-deficient, nonprofessional APCs, the epitope was cleaved out of various sequence contexts and presented to T cells. Ag presentation was inhibited by acidophilic amines and inhibitors of the vacuolar proton pump, indicating processing in endosomes. Endosomal aspartic-type cathepsins, and to some extent also the trans-Golgi network protease furin, were involved in processing. Clathrin-dependent and independent internalization from the cell surface targeted MHC-I fusion proteins to early and late endosomes, where SIINFEKL/K(b) complexes were detected by immunofluorescence microscopy. Targeting of MHC-I fusion proteins to processing compartments was independent of sequence motifs in the cytoplasmic tail. Not only TAP-deficient cells, but also TAP-competent APCs used the vacuolar pathway for processing of MHC-I fusion proteins. Thus, endosomal processing of internalized endogenous transmembrane proteins represents a novel alternate pathway for the generation of MHC-I-binding peptides.
authors.affiliation: Department of Molecular Immunology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Tiwari
authors.forename: Natalio
authors.initials: N
authors.lastname: Garbi
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinheckel
authors.forename: Gerhard
authors.initials: G
authors.lastname: Moldenhauer
authors.forename: Günter J
authors.initials: GJ
authors.lastname: Hämmerling
authors.forename: Frank
authors.initials: F
authors.lastname: Momburg
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000378:metabolism; D000818:Animals; D017951:Antigen Presentation; D001224:Aspartic Acid / Q000737:chemistry; D002403:Cathepsins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004527:Egg Proteins / Q000378:metabolism; D011992:Endosomes / Q000201:enzymology* / Q000276:immunology; D045683:Furin / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D010047:Ovalbumin / Q000378:metabolism; D010446:Peptide Fragments; D010455:Peptides / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D004527:Egg Proteins; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D015778:Minor Histocompatibility Antigens; C110366:OVA-8; D010446:Peptide Fragments; D010455:Peptides; D011993:Recombinant Fusion Proteins; C486171:Tap1 protein, mouse; D001224:Aspartic Acid; D010047:Ovalbumin; D002403:Cathepsins; D000626:Aminopeptidases; C509944:ERAP1 protein, mouse; D045683:Furin