title: Interaction of HLA-E with peptides and the peptide transporter in vitro: implications for its function in antigen presentation.
abstract: The assembly of MHC Ia molecules in the endoplasmic reticulum requires the presence of peptide ligands and beta2m and is facilitated by chaperones in an ordered sequence of molecular interactions. A crucial step in this process is the interaction of the class I alpha-chain/beta2m dimer with TAP, which is believed to ensure effective peptide loading of the empty class I molecule. We have previously demonstrated impaired intracellular transport of the class Ib molecule HLA-E in mouse myeloma cells cotransfected with the genes for HLA-E and human beta2m, which is most likely attributable to inefficient intracellular peptide loading of the HLA-E molecule. We therefore analyzed the ability of HLA-E in the transfectant cell line to bind synthetic peptides by means of their ability to enhance cell surface expression of HLA-E. Peptide binding was confirmed by testing the effect on the thermostability of soluble empty HLA-E/human beta2m dimers. Two viral peptides binding to HLA-E were thus identified, for which the exact positioning of the N terminus appeared critical for binding, whereas the contribution of the length of the C terminus seemed to be minor, allowing peptides as short as seven amino acids and up to 16 amino acids to exhibit considerable binding activity. Furthermore, we demonstrate that HLA-E interacts with TAP and that this interaction can be prolonged by the proteasome inhibitor N-acetyl-L-leucyl-L-leucyl-L-norleucinal, which reduces the intracellular peptide pool. The presented data indicate that HLA-E is capable of presenting peptide ligands similar to the repertoire of HLA class Ia molecules.
authors.affiliation: Institut für Anthropologie und Humangenetik, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Ulbrecht
authors.forename: S
authors.initials: S
authors.lastname: Modrow
authors.forename: R
authors.initials: R
authors.lastname: Srivastava
authors.forename: P A
authors.initials: PA
authors.lastname: Peterson
authors.forename: E H
authors.initials: EH
authors.lastname: Weiss
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation; D017920:Antiporters; D002352:Carrier Proteins / Q000276:immunology*; D005434:Flow Cytometry; D006680:HLA Antigens / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D006801:Humans; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000276:immunology*; D011233:Precipitin Tests; D014407:Tumor Cells, Cultured; D000097625:HLA-E Antigens
chemical_list: D017920:Antiporters; D002352:Carrier Proteins; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D010455:Peptides; D000097625:HLA-E Antigens; C107762:tapasin