TAPBPR mediates peptide dissociation from MHC class I using a leucine lever

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Tapasin and TAPBPR are chaperones involved in peptide editing of MHC I molecules.
• The exact molecular mechanisms of TAPBPR-mediated peptide editing are not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanisms of TAPBPR-mediated peptide exchange on MHC I.
• To identify key structural features of TAPBPR and MHC I involved in peptide editing.

Main Methods:

• Utilized immunopeptidomics.
• Developed novel cell-based assays for TAPBPR-mediated peptide exchange.
• Investigated structure-function relationships of TAPBPR and MHC I.

Main Results:

• Identified a critical role for the K22-D35 loop of TAPBPR in mediating peptide exchange.
• Discovered a specific leucine within this loop essential for TAPBPR-facilitated peptide dissociation from MHC I.
• Delineated the structural requirements of the MHC I F pocket for TAPBPR-dependent peptide dissociation.

Conclusions:

• Chaperone-mediated peptide editing on MHC I can vary based on the C-terminal residue accommodated in the MHC I F pocket.
• These findings offer insights into manipulating TAPBPR for enhancing tumor immunogenicity.