title: Discrete proteolytic intermediates in the MHC class I antigen processing pathway and MHC I-dependent peptide trimming in the ER.
abstract: The antigen processing pathway generates the peptides displayed by MHC I molecules on the cell surface. Whether these peptides are generated in the cytosol or from longer intermediates transported into the ER is unclear, because peptides other than those bound to MHC I have been difficult to find. Using a novel assay, we show that N-terminally extended antigenic analogs were associated with high-molecular weight material in the cytosol and were transported by TAP. In the ER, a nonapeptide was predominant that was converted to the final octapeptide only in presence of the appropriate MHC I molecule. The existence of extended peptides and their MHC I-dependent trimming suggest a mechanism for efficiently satisfying the distinct sequence preferences of polymorphic MHC I molecules.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA.
authors.forename: P
authors.initials: P
authors.lastname: Paz
authors.forename: N
authors.initials: N
authors.lastname: Brouwenstijn
authors.forename: R
authors.initials: R
authors.lastname: Perry
authors.forename: N
authors.initials: N
authors.lastname: Shastri
mesh_terms: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000502:physiology; D000818:Animals; D017951:Antigen Presentation; D019556:COS Cells; D003600:Cytosol / Q000378:metabolism; D010450:Endopeptidases / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008970:Molecular Weight
chemical_list: D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D015395:Histocompatibility Antigens Class I; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; D010450:Endopeptidases