Productive association between MHC class I and tapasin requires the tapasin transmembrane/cytosolic region and the tapasin C-terminal Ig-like domain

Laura C. Simone, Corey J. Georgesen, Peter D. Simone, Xiaojian Wang, Joyce C. Solheim

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

The current model of antigen assembly with major histocompatibility complex (MHC) class I molecules posits that interactions between the tapasin N-terminal immunoglobulin (Ig)-like domain and the MHC class I peptide-binding groove permit tapasin to regulate antigen selection. Much less is known regarding interactions that might involve the tapasin C-terminal Ig-like domain. Additionally, the tapasin transmembrane/cytoplasmic region enables tapasin to bridge the MHC class I molecule to the transporter associated with antigen processing (TAP). In this investigation, we made use of two tapasin mutants to determine the relative contribution of the tapasin C-terminal Ig-like domain and the tapasin transmembrane/cytoplasmic region to the assembly of MHC class I molecules. Deletion of a loop within the tapasin C-terminal Ig-like domain (Δ334-342) prevented tapasin association with the MHC class I molecule Kd. Although tapasin Δ334-342 did not increase the efficiency of Kd folding, Kd surface expression was enhanced on cells expressing this mutant relative to tapasin-deficient cells. In contrast to tapasin Δ334-342, a soluble tapasin mutant lacking the transmembrane/cytoplasmic region retained the ability to bind to Kd molecules, but did not facilitate Kd surface expression. Furthermore, when soluble tapasin and tapasin Δ334-342 were co-expressed, soluble tapasin had a dominant negative effect on the folding and surface expression of not only Kd, but also Db and Kb. In addition, our molecular modeling of the MHC class I-tapasin interface revealed novel potential interactions involving tapasin residues 334-342. Together, these findings demonstrate that the tapasin C-terminal and transmembrane/cytoplasmic regions are critical to tapasin's capacity to associate effectively with the MHC class I molecule.

Original languageEnglish (US)
Pages (from-to)628-639
Number of pages12
JournalMolecular Immunology
Volume49
Issue number4
DOIs
StatePublished - Jan 2012

Keywords

  • Antigen processing and presentation
  • K
  • MHC class I
  • Peptide-loading complex
  • Tapasin
  • Transporter associated with antigen processing

ASJC Scopus subject areas

  • Immunology
  • Molecular Biology

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