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MHC class I/beta 2-microglobulin complexes associate with TAP transporters before peptide binding
B Ortmann1, M J Androlewicz, P Cresswell
1Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06520.
Nature
|April 28, 1994
Summary
Transporters associated with antigen processing (TAP) are crucial for assembling major histocompatibility complex class I peptide complexes. TAP molecules bind to class I/beta 2-microglobulin dimers, facilitating peptide association for immune recognition.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Major histocompatibility complex (MHC) class I molecules present antigenic peptides to cytotoxic T lymphocytes.
- Peptide generation involves the proteasome, and transport into the endoplasmic reticulum (ER) is mediated by transporters associated with antigen processing (TAP).
Purpose of the Study:
- To investigate the role of TAP molecules in the assembly of MHC class I/beta 2-microglobulin (beta 2m) peptide complexes.
- To elucidate the interaction between MHC class I, beta 2m, calnexin, and TAP within the ER.
Main Methods:
- Analysis of protein-protein interactions within the ER of human B-cell lines.
- Investigating the association of MHC class I heavy chains, beta 2m, calnexin, and TAP.
Main Results:
- Free MHC class I heavy chains associate with calnexin in the ER.
- In human B-cell lines, MHC class I/beta 2m dimers associate with TAP, not calnexin.
- TAP association with MHC class I/beta 2m dimers facilitates peptide binding.
Conclusions:
- Calnexin mediates the dimerization of MHC class I and beta 2m.
- TAP molecules play a direct role in the assembly of the MHC class I peptide complex by binding to dimers and facilitating peptide association.