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Tapasin-related protein TAPBPR is an additional component of the MHC class I presentation pathway
Louise H. Boyle, Clemens Hermann, Jessica M. Boname, Keith M. Porter, Peysh A. Patel, Marian L. Burr, Lidia M. Duncan, Michael E. Harbour, David A. Rhodes, Karsten Skjødt, Paul J. Lehner and John Trowsdale
Proceedings of the National Academy of Sciences of the United States of America
Vol. 110, No. 9 (February 26, 2013), pp. 3465-3470
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/42583620
Page Count: 6
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Tapasin is an integral component of the peptide-loading complex (PLC) important for efficient peptide loading onto MHC class I molecules. We investigated the function of the tapasin-related protein, TAPBPR. Like tapasin, TAPBPR is widely expressed, IFN-γ-inducible, and binds to MHC class I coupled with β2-microglobulin in the endoplasmic reticulum. In contrast to tapasin, TAPBPR does not bind ERp57 or calreticulin and is not an integral component of the PLC. β2-microglobulin is essential for the association between TAPBPR and MHC class I. However, the association between TAPBPR and MHC class I occurs in the absence of a functional PLC, suggesting peptide is not required. Expression of TAPBPR decreases the rate of MHC class I maturation through the secretory pathway and prolongs the association of MHC class I on the PLC. The TAPBPR: MHC class I complex trafficks through the Golgi apparatus, demonstrating a function of TAPBPR beyond the endoplasmic reticulum/cis-Golgi. The identification of TAPBPR as an additional component of the MHC class I antigen-presentation pathway demonstrates that mechanisms controlling MHC class I expression remain incompletely understood.
Proceedings of the National Academy of Sciences of the United States of America © 2013 National Academy of Sciences