Slow egress of a mouse MHC class I molecule to the cell surface despite its strong association with beta 2-microglobulin.
Two H-2D region class I genes from the wild-derived mouse strain B10.GAA37 provisionally encoding the Dw16 and Lw16 molecules, respectively, were transfected into mouse L cells, and the expressed gene products were analyzed serologically by flow cytometry. As expected from nucleotide sequence comparisons, these analyses revealed that several Ld-reactive monoclonal antibodies (mAbs) recognize Lw16 and not Dw16. As detected by flow cytometry of intact L.Lw16 cells and B10.GAA37 splenocytes, and by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) of immunoprecipitates from splenocyte lysates, the alpha 2 domain-reactive mAb 30-5-7 detected less Lw16 than did the alpha 3 domain-reactive mAb 28-14-8, suggesting the existence of two populations of Lw16 molecules: 30-5-7+ 28-14-8+ and 30-5-7- 28-14-8+. Sequential immunoprecipitation studies provided further evidence for these two Lw16 subsets; furthermore, the 30-5-7- 28-14-8+ subset was found predominantly on the cell surface and in association with beta 2-microglobulin (beta 2-m). Pulse-chase studies of B10.GAA37 splenocytes revealed that Lw16, like Ld, is trafficked slowly to the cell surface, whereas Dw16 is trafficked quickly, like most other mouse K and D region class I molecules. Despite these similarities, Lw16 and Ld differ in their association with beta 2-m, in that the immunoprecipitates of Lw16 contained much higher levels of radiolabeled beta 2-m per heavy chain. Together, these studies indicate that the slower trafficking of Lw16 to the surface does not result from a weaker association with beta 2-m, suggesting that other factors, such as peptide ligand-induced assembly, and/or retention by ER-resident proteins play an important role in the trafficking of major histocompatibility (MHC) class I molecules to the cell surface.
Department of Molecular Microbiology and Immunology, University of Missouri, Columbia 65212.
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Talken
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Tummuru
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Lee
D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D006183:H-2 Antigens / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D011499:Protein Processing, Post-Translational; D001613:beta 2-Microglobulin / Q000378:metabolism*
D006183:H-2 Antigens; D001613:beta 2-Microglobulin