Calreticulin promotes folding of functional human leukocyte antigen class I molecules in vitro

Slobodan Culina, Grégoire Lauvau, Brigitte Gubler, Peter M. Van Endert

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


The assembly of MHC class I molecules with β2-microglobulin and peptides is assisted by the housekeeping chaperones calnexin, calreticulin, and Erp57 and the dedicated accessory protein, tapasin. Tapasin and calreticulin are essential for efficient MHC class I assembly, but their precise action during class I assembly remains to be elucidated. Previous in vitro studies have demonstrated that the lectin calreticulin interacts with monoglucosylated MHC class I heavy chains, whatever their state of assembly with light chains and peptide, and inhibits their aggregation above physiological temperature. We used a soluble single chain HLA-A2/β2- microglobulin molecule, A2SC, to study the effect of calreticulin on the peptide binding capacity of HLA class I molecules. Calreticulin inhibited the formation of A2SC aggregates both when co-expressed in insect cells and during incubations at elevated temperature. Calreticulin dramatically enhanced acquisition of peptide binding capacity when added to denatured A2SC molecules during refolding at 4 °C. However, it had no effect on the rapid loss of A2SC peptide binding capacity at physiological temperature. We conclude that calreticulin promotes the folding of HLA class I molecules to a state in which, at low temperature, they spontaneously acquire peptide binding capacity. However, it does not induce or maintain a peptide-receptive state of the class I-binding site, which is likely to be promoted by one or several other components of the class I loading complexes. By being amenable to complementation with additional proteins, the described system should be useful for identification of these components.

Original languageEnglish (US)
Pages (from-to)54210-54215
Number of pages6
JournalJournal of Biological Chemistry
Issue number52
StatePublished - Dec 24 2004
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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