TAPBPR alters MHC class I peptide presentation by functioning as a peptide exchange catalyst

Abstract

Our understanding of the antigen presentation pathway has recently been enhanced with the identification that the tapasin-related protein TAPBPR is a second MHC I-specific chaperone. We sought to determine whether, like tapasin, TAPBPR can also influence MHC 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.

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Identifiers

ORCID for Andy Van Hateren: orcid.org/0000-0002-3915-0239

ORCID for Patrick J. Duriez: orcid.org/0000-0003-1814-2552

ORCID for Tim Elliott: orcid.org/0000-0003-1097-0222

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