Effect of TAP on the generation and intracellular trafficking of peptide-receptive major histocompatibility complex class I molecules.
Using a fluorescein-conjugated antigenic peptide, peptide-receptive H-2Kb MHC class I molecules were found throughout the secretory pathways of RMA cells and peptide transporter (TAP)-deficient derivative cells (RMA/S). RMA/S cells displayed higher levels of intracellular peptide-receptive molecules, while, surprisingly, RMA cells expressed 3- to 5-fold more cell surface peptide-receptive molecules. Metabolic radiolabeling of Kb-associated oligosaccharides with [1-3H]galactose demonstrated that despite a large difference in the fraction of Kb molecules in native conformation in detergent extracts, Kb transport rates from the trans-Golgi complex to the surfaces of RMA and RMA/S cells were similar. Thus, although considerable numbers of class I alpha chains reach the RMA/S cell surface, they are a less productive source of peptide-receptive molecules than class I molecules synthesized by TAP-expressing RMA cells, suggesting paradoxically that TAP functions to increase the amount of peptide-receptive molecules at the cell surface.
Day
P M
PM
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.
Esquivel
F
F
Lukszo
J
J
Bennink
J R
JR
Yewdell
J W
JW
D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005095:Exoribonucleases; D005656:Fungal Proteins / Q000494:pharmacology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D011485:Protein Binding; D013601:T-Lymphocytes / Q000378:metabolism*; D015534:Trans-Activators / Q000494:pharmacology*
D005656:Fungal Proteins; D015395:Histocompatibility Antigens Class I; D010455:Peptides; D015534:Trans-Activators; D005095:Exoribonucleases