Association of ERp57 with mouse MHC class I molecules is tapasin dependent and mimics that of calreticulin and not calnexin.
Before peptide binding in the endoplasmic reticulum, the class I heavy (H) chain-beta(2)-microglobulin complexes are detected in association with TAP and two chaperones, TPN and CRT. Recent studies have shown that the thiol-dependent reductase, ERp57, is also present in this peptide-loading complex. However, it remains controversial whether the association of ERp57 with MHC class I molecules precedes their combined association with the peptide-loading complex or whether ERp57 only associates with class I molecules in the presence of TPN. Resolution of this controversy could help determine the role of ERp57 in class I folding and/or assembly. To define the mouse class I H chain structures involved in interaction with ERp57, we tested chaperone association of L(d) mutations at residues 134 and 227/229 (previously implicated in TAP association), residues 86/88 (which ablate an N-linked glycan), and residue 101 (which disrupts a disulfide bond). The association of ERp57 with each of these mutant H chains showed a complete concordance with CRT, TAP, and TPN but not with calnexin. Furthermore, ERp57 failed to associate with H chain in TPN-deficient.220 cells. These combined data demonstrate that, during the assembly of the peptide-loading complex, the association of ERp57 with mouse class I is TPN dependent and parallels that of CRT and not calnexin.
Harris
M R
MR
Department of Newborn Medicine, Children's Hospital, St. Louis, MO 63110, USA.
Lybarger
L
L
Yu
Y Y
YY
Myers
N B
NB
Hansen
T H
TH
D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D017920:Antiporters / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D037281:Calnexin; D037282:Calreticulin; D002236:Carbohydrate Conformation; D002461:Cell Line, Transformed; D003545:Cysteine / Q000235:genetics; D004220:Disulfides / Q000037:antagonists & inhibitors / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D006183:H-2 Antigens / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064532:Histocompatibility Antigen H-2D; D006801:Humans; D007136:Immunoglobulins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D007535:Isomerases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007739:L Cells; D026901:Membrane Transport Proteins; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011134:Polysaccharides / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D019704:Protein Disulfide-Isomerases; D012261:Ribonucleoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014162:Transfection
D017920:Antiporters; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D004220:Disulfides; D006183:H-2 Antigens; D006360:Heat-Shock Proteins; D064532:Histocompatibility Antigen H-2D; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D011134:Polysaccharides; D012261:Ribonucleoproteins; C107762:tapasin; D037281:Calnexin; D007535:Isomerases; C513195:Pdia3 protein, mouse; D019704:Protein Disulfide-Isomerases; C085868:PDIA3 protein, human; D003545:Cysteine