Calnexin expression does not enhance the generation of MHC class I-peptide complexes.
We investigated the requirement for calnexin in the biogenesis of MHC class I molecules. Mutant human cells lacking calnexin were infected with recombinant vaccinia viruses encoding mouse MHC class I molecules, Kd, Kb, Kk, Dd, Db, and Ld. Flow cytometry indicated that each of the six MHC class I allomorphs was transported to the cell surface at similar rates in calnexin-deficient cells and transfectants expressing calnexin. For Kb and Kd, the calnexin-independent biogenesis occurred regardless of whether the MHC class I molecules contained human or mouse beta 2-microglobulin. Also addressed was the effect of calnexin on the surface expression of Kb molecules bearing the immunodominant peptide from ovalbumin (OVA257-264). This was detected with a recently described monoclonal antibody specific for the Kb/peptide complex. Calnexin expression had no significant effect on the formation of Kb/peptide complexes generated from full-length OVA, cytosolic OVA257-264, or endoplasmic reticulum-targeted OVA257-264, which was expressed in the presence of the herpes simplex virus ICP47 protein to ensure detection of TAP-independent peptide-MHC class I complexes. Complementary results were obtained with TAP-independent formation of Kd/ peptide complexes. These findings indicate that calnexin is not required for the efficient assembly of MHC class I molecules with TAP-dependent or independent peptides.
Prasad
S A
SA
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, USA.
Yewdell
J W
JW
Porgador
A
A
Sadasivan
B
B
Cresswell
P
P
Bennink
J R
JR
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D000956:Antigens, Viral / Q000737:chemistry / Q000378:metabolism; D001692:Biological Transport; D002135:Calcium-Binding Proteins / Q000502:physiology*; D037281:Calnexin; D002451:Cell Compartmentation; D002478:Cells, Cultured; D006183:H-2 Antigens / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D010047:Ovalbumin / Q000276:immunology; D010455:Peptides / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D001613:beta 2-Microglobulin / Q000378:metabolism
D000071181:ATP Binding Cassette Transporter, Subfamily B, Member 2; D018528:ATP-Binding Cassette Transporters; D000956:Antigens, Viral; D002135:Calcium-Binding Proteins; D006183:H-2 Antigens; D015395:Histocompatibility Antigens Class I; D046911:Macromolecular Substances; D010455:Peptides; C073119:TAP1 protein, human; C486171:Tap1 protein, mouse; D001613:beta 2-Microglobulin; D037281:Calnexin; D010047:Ovalbumin