Association of ERp57 with mouse MHC class I molecules is tapasin dependent and mimics that of calreticulin and not calnexin

Michael R. Harris, Lonnie Lybarger, Yik Y.L. Yu, Nancy B. Myers, Ted H. Hansen

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Before peptide binding in the endoplasmic reticulum, the class I heavy (H) chain-β2-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 Ld 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.

Original languageEnglish (US)
Pages (from-to)6686-6692
Number of pages7
JournalJournal of Immunology
Issue number11
StatePublished - May 1 2001

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology


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