TAP- and tapasin-dependent HLA-E surface expression correlates with the binding of an MHC class I leader peptide.
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Braud VM, Allan DS, Wilson D, McMichael AJ
TAP- and tapasin-dependent HLA-E surface expression correlates with the binding of an MHC class I leader peptide.
Curr Biol. 1998 Jan 1;8(1):1-10. doi: 10.1016/s0960-9822(98)70014-4.
- PubMed ID
- 9427624 [ View in PubMed]
- Abstract
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.