Evidence for a human leucocyte antigen-DM-induced structural change in human leucocyte antigen-DObeta.
Human leucocyte antigen (HLA)-DO is a non-classical major histocompatibility complex class II molecule which modulates the function of HLA-DM and the loading of antigenic peptides on molecules such as HLA-DR. The bulk of HLA-DO associates with HLA-DM and this interaction is critical for HLA-DO egress from the endoplasmic reticulum. HLA-DM assists the early steps of HLA-DO maturation presumably through the stabilization of the interactions between the N-terminal regions of the alpha and beta chains. To evaluate a possible role for HLA-DM in influencing the conformation of HLA-DO, we made use of a monoclonal antibody, Mags.DO5, that was raised against HLA-DO/DM complexes. Using transfected cells expressing mismatched heterodimers between HLA-DR and -DO chains, we found that the epitope for Mags.DO5 is located on the DObeta chain and that Mags.DO5 reactivity was increased upon cotransfection with HLA-DM. Our results suggest that HLA-DM influences the folding of HLA-DO in the endoplasmic reticulum. A mutant HLA-DO showing reduced capacity for endoplasmic reticulum egress was better recognized by Mags.DO5 in the presence of HLA-DM. On the other hand, an HLA-DO mutant capable of endoplasmic reticulum egress on its own was efficiently recognized by Mags.DO5, irrespective of the presence of HLA-DM. Taken together, our results suggest that HLA-DM acts as a private chaperone, directly assisting the folding of HLA-DO to promote egress from the endoplasmic reticulum.
Deshaies
Francis
F
Laboratoire d'Immunologie Moléculaire, Département de Microbiologie et Immunologie, Université de Montréal, Montréal, QC, Canada.
Diallo
Djibril A
DA
Fortin
Jean-Simon
JS
O'Rourke
Helen M
HM
Pezeshki
Abdul Mohammad
AM
Bellemare-Pelletier
Angélique
A
Raby
Nicola
N
Bédard
Nathalie
N
Brunet
Alexandre
A
Denzin
Lisa K
LK
Thibodeau
Jacques
J
D000911:Antibodies, Monoclonal / Q000276:immunology; D017951:Antigen Presentation / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology; D004721:Endoplasmic Reticulum / Q000276:immunology; D018985:Epitopes, B-Lymphocyte / Q000032:analysis; D006681:HLA-D Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D006367:HeLa Cells; D006801:Humans; D017510:Protein Folding; D014162:Transfection
D000911:Antibodies, Monoclonal; D018985:Epitopes, B-Lymphocyte; D006681:HLA-D Antigens; C084245:HLA-DM antigens; C046148:HLA-DO antigens