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Tapasin is required for efficient peptide binding to transporter associated with antigen processing
1Tumor Immunology, Lund University, Solvegatan 21, s-22362 Lund, Sweden. su-ling.li@wblab.lu.se
The Journal of Biological Chemistry
|January 15, 2000
Summary
Tapasin is crucial for efficient peptide binding to the transporter associated with antigen processing (TAP). This interaction is essential for proper major histocompatibility complex (MHC) class I assembly and function.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- The transporter associated with antigen processing (TAP) moves peptides into the endoplasmic reticulum (ER) for MHC class I assembly.
- Tapasin, a TAP complex subunit, binds TAP1 and MHC class I, and is vital for MHC class I assembly and surface expression.
Purpose of the Study:
- To investigate tapasin's role in antigenic peptide processing.
- To clarify the interaction between peptides, TAP, and MHC class I in the presence and absence of tapasin.
Main Methods:
- Utilized tapasin mutant (721.220) and tapasin-expressing (721.221) cell lines, including HLA-A2 transfectants.
- Analyzed peptide binding to TAP, peptide transport across ER membranes, and peptide-MHC class I association.
Main Results:
- Peptide binding to TAP was significantly reduced in tapasin-deficient cells (721.220) compared to tapasin-expressing cells (721.221).
- Impaired peptide-TAP interaction led to defective peptide transport in tapasin mutant cells, although the transport rate of bound peptides was not significantly altered.
- Restoration of efficient peptide-TAP interaction occurred after transfecting tapasin cDNA into 721.220 cells.
Conclusions:
- Tapasin is essential for effective peptide binding to the transporter associated with antigen processing (TAP).
- This study highlights tapasin's critical role in initiating the antigen processing pathway by facilitating peptide-TAP interactions.