Selective export of MHC class I molecules from the ER after their dissociation from TAP.
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.
Spiliotis
E T
ET
Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
Manley
H
H
Osorio
M
M
Zúñiga
M C
MC
Edidin
M
M
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
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