title: Recognition of class I MHC by a rat Ly49 NK cell receptor is dependent on the identity of the P2 anchor amino acid of bound peptide.
abstract: Members of the rodent Ly49 receptor family control NK cell responsiveness and demonstrate allele specificity for MHC class I (MHC-I) ligands. For example, the rat Ly49i2 inhibitory NK cell receptor binds RT1-A1(c) but not other rat MHC class Ia or Ib molecules. RT1-A1(c) preferentially binds peptides with proline at the second, or P2, position, which defines it as an HLA-B7 supertype MHC-I molecule. Previously, our laboratory showed that mutations within the MHC-I supertype-defining B-pocket of RT1-A1(c) could lead to alterations in P2 anchor residues of the peptide repertoire bound by RT1-A1(c) and loss of recognition by Ly49i2. Although suggestive of peptide involvement, it was unclear whether the peptide P2 anchor residue or alteration of the RT1-A1(c) primary sequence influenced Ly49i2 recognition. Therefore, we directly investigated the role of the P2 anchor residue of RT1-A1(c)-bound peptides in Ly49i2 recognition. First, fluorescent multimers generated by refolding soluble recombinant RT1-A1(c) with individual synthetic peptides differing only at the P2 anchor residue were examined for binding to Ly49i2 NK cell transfectants. Second, cytotoxicity by Ly49i2-expressing NK cells toward RMA-S target cells expressing RT1-A1(c) bound with peptides that only differ at the P2 anchor residue was evaluated. Our results demonstrate that Ly49i2 recognizes RT1-A1(c) bound with peptides that have Pro or Val at P2, whereas little or no recognition is observed when RT1-A1(c) is complexed with peptide bearing Gln at P2. Thus, the identity of the P2 peptide anchor residue is an integral component of MHC-I recognition by Ly49i2.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Ma
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Kane
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000950:Antigens, Ly / Q000737:chemistry* / Q000378:metabolism; D002469:Cell Separation; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006649:Histocompatibility Antigens / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000276:immunology; D011487:Protein Conformation; D051381:Rats; D011971:Receptors, Immunologic / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000950:Antigens, Ly; D006649:Histocompatibility Antigens; D015395:Histocompatibility Antigens Class I; C408248:Ly49I antigen; D011971:Receptors, Immunologic; C038353:histocompatibility antigens RT, rat