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KMID : 0624620110440060369
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BMB Reports
2011 Volume.44 No. 6 p.369 ~ p.374
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Tmp21, a novel MHC-I interacting protein, preferentially binds to β2-microglobulin-free MHC-I heavy chains
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Jun Young-Soo
Ahn Kwang-Seog
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Abstract
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MHC-I molecules play a critical role in immune surveillance against viruses by presenting peptides to cytotoxic T lymphocytes. Although the mechanisms by which MHC-I molecules assemble and acquire peptides in the ER are well characterized, how MHC-I molecules traffic to the cell surface remains poorly understood. To identify novel proteins that regulate the intracellular transport of MHC-I molecules, MHC-I-interacting proteins were isolated by affinity purification, and their identity was determined by mass spectrometry. Among the identified MHC-I-associated proteins was Tmp21, the human ortholog of yeast Emp24p, which mediates the ER-Golgi trafficking of a subset of proteins. Here, we show that Tmp21 binds to human classical and non-classical MHC-I molecules. The Tmp21-MHC-I complex lacks Β(2)-microglobulin, and the number of the complexes is increased when free MHC-I heavy chains are more abundant. Taken together, these results suggest that Tmp21 is a novel protein that preferentially binds to Β(2)-microglobulin-free MHC-I heavy chains.
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KEYWORD
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Antigen presentation, Cargo receptor, ER-associated protein degradation, MHC class I, Tmp21
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