title: Selective export of MHC class I molecules from the ER after their dissociation from TAP.
abstract: It has been assumed that upon dissociation from TAP, MHC class I molecules exit the ER by nonselective bulk flow. We now show that exit must occur by association with cargo receptors. Inconsistent with exit by bulk flow, loading of MHC class I molecules with high-affinity peptides triggers dissociation from TAP but has no effect on rates of ER-to-Golgi transport. Moreover, peptide-loaded MHC class I molecules accumulate at ER exit sites from which TAP molecules are excluded. Consistent with receptor-mediated exit, ER-to-Golgi transport of MHC class I molecules is independent of their cytoplasmic tails, which themselves lack ER export motifs. In addition, we show that MHC class I molecules associate with the putative cargo receptor BAP31.
authors.affiliation: Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: E T
authors.initials: ET
authors.lastname: Spiliotis
authors.forename: H
authors.initials: H
authors.lastname: Manley
authors.forename: M
authors.initials: M
authors.lastname: Osorio
authors.forename: M C
authors.initials: MC
authors.lastname: Zúñiga
authors.forename: M
authors.initials: M
authors.lastname: Edidin
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D001692:Biological Transport; D004721:Endoplasmic Reticulum / Q000276:immunology*; D006183:H-2 Antigens / Q000235:genetics / Q000276:immunology*; D064532:Histocompatibility Antigen H-2D; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D007739:L Cells; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D011506:Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: C489642:Bcap31 protein, mouse; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D064532:Histocompatibility Antigen H-2D; D015395:Histocompatibility Antigens Class I; D008565:Membrane Proteins; D011506:Proteins