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BACKGROUND: The human major histocompatibility complex (MHC) class lb molecule HLA-E is transcribed in most tissues but little is known about its localisation within the cell. We have recently shown that HLA-E binds signal-sequence-derived peptides from human MHC class I molecules in vitro. RESULTS: Using a newly characterised antibody recognising HLA-E, we show that HLA-E is expressed at the cell surface. We demonstrate that HLA-E surface expression is correlated with the presence of MHC class I molecules which provide suitable leader sequence peptides capable of binding to HLA-E. Further studies on the interaction of HLA-E with molecules in the endoplasmic reticulum revealed that HLA-E associates with the transporter associated with antigen processing (TAP) and calreticulin, and that HLA-E expression is TAP-dependent and tapasin-dependent. In addition, HLA-E dissociates from TAP upon binding of MHC class I leader sequence peptides. CONCLUSION: These experiments establish that surface expression of HLA-E is regulated by the binding of a restricted pool of peptides from the leader sequence of MHC class I molecules. The correlation between HLA-E and MHC class I surface expression might be relevant to the function of HLA-E. Our results also show that, although these HLA-E binding peptides are derived from signal sequences, they may be released back into the cytosol and subsequently translocated by the TAP complex and loaded onto HLA-E molecules.

Type

Journal article

Journal

Curr Biol

Publication Date

01/01/1998

Volume

8

Pages

1 - 10

Keywords

Alleles, Amino Acid Sequence, Animals, Antibodies, Monoclonal, Antiporters, Binding Sites, Cell Line, HLA Antigens, Histocompatibility Antigens Class I, Humans, Immunoglobulins, Membrane Transport Proteins, Mice, Protein Binding, Protein Sorting Signals, Saguinus, Surface Properties, Tumor Necrosis Factor Receptor Superfamily, Member 7