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Our understanding of the antigen presentation pathway has recently been enhanced with the identification that the tapasin-related protein TAPBPR is a second major histocompatibility complex (MHC) class I-specific chaperone. We sought to determine whether, like tapasin, TAPBPR can also influence MHC class I peptide selection by functioning as a peptide exchange catalyst. We show that TAPBPR can catalyse the dissociation of peptides from peptide-MHC I complexes, enhance the loading of peptide-receptive MHC I molecules, and discriminate between peptides based on affinity in vitro. In cells, the depletion of TAPBPR increased the diversity of peptides presented on MHC I molecules, suggesting that TAPBPR is involved in restricting peptide presentation. Our results suggest TAPBPR binds to MHC I in a peptide-receptive state and, like tapasin, works to enhance peptide optimisation. It is now clear there are two MHC class I specific peptide editors, tapasin and TAPBPR, intimately involved in controlling peptide presentation to the immune system.

Original publication

DOI

10.7554/elife.09617

Type

Journal article

Journal

eLife

Publication Date

06/10/2015

Volume

4

Addresses

Department of Pathology, University of Cambridge, Cambridge, United Kingdom.

Keywords

Cell Line, Humans, Peptides, Immunoglobulins, Membrane Proteins, Antigens, Histocompatibility Antigens Class I, Antigen Presentation, Protein Binding