The NK cell MHC class I receptor Ly49A detects mutations on H-2Dd inside and outside of the peptide binding groove.
The NK cell inhibitory receptor Ly49A recognizes the mouse MHC class I molecule H-2D(d) and participates in the recognition of missing self. Previous studies indicated that the determinant recognized by Ly49A exists in alpha1/alpha2 domain of H-2D(d). Here we have substituted polymorphic as well as conserved residues of H-2D(d) alpha1/alpha2 domain (when compared with H-2K(d), which does not interact with Ly49A). We then tested the ability of the H-2D(d) mutants to interact with Ly49A by soluble Ly49A tetramer binding and NK cell cytotoxicity inhibition assays. Individual introduction of mutations converting the H-2D(d) residue into the corresponding H-2K(d) residue (N30D, D77S, or A99F) in H-2D(d) partially abrogated the interaction between Ly49A and H-2D(d). Introduction of the three mutations into H-2D(d) completely abolished Ly49A recognition. Individual introduction of D29N or R35A mutation into the residues of H-2D(d) that are conserved among murine MHC class I severely impaired the interaction. The crystal structure of H-2D(d) reveals that D77 and A99 are located in the peptide binding groove and that N30, D29, and R35 are in the interface of the three structural domains of MHC class I: alpha1/alpha2, alpha3, and beta(2)-microglobulin. These data suggest that Ly49A can monitor mutations in MHC class I inside and outside of the peptide binding groove and imply that inhibitory MHC class I-specific receptors are sensitive to mutations in MHC class I as well as global loss of MHC class I. Our results also provide insight into the molecular basis of Ly49A to distinguish MHC class I polymorphism.
Laboratory of Molecular Medicine, Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan. nmatsu@k.u-tokyo.ac.jp
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Matsumoto
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Yokoyama
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Kojima
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Yamamoto
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology; D000818:Animals; D000950:Antigens, Ly; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D002352:Carrier Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D003601:Cytotoxicity Tests, Immunologic; D000939:Epitopes / Q000235:genetics / Q000378:metabolism; D006183:H-2 Antigens / Q000235:genetics* / Q000378:metabolism; D064532:Histocompatibility Antigen H-2D; D015979:Killer Cells, Lymphokine-Activated / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism*; D037181:Lectins, C-Type; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D055650:NK Cell Lectin-Like Receptor Subfamily A; D010446:Peptide Fragments / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D017354:Point Mutation; D011110:Polymorphism, Genetic / Q000235:genetics / Q000276:immunology; D017434:Protein Structure, Tertiary / Q000235:genetics; D011971:Receptors, Immunologic / Q000378:metabolism*; D055630:Receptors, NK Cell Lectin-Like; D014162:Transfection; D014407:Tumor Cells, Cultured
D000950:Antigens, Ly; D002352:Carrier Proteins; D000939:Epitopes; D006183:H-2 Antigens; D064532:Histocompatibility Antigen H-2D; C527088:Klra1 protein, mouse; D037181:Lectins, C-Type; D008565:Membrane Proteins; D055650:NK Cell Lectin-Like Receptor Subfamily A; D010446:Peptide Fragments; D011971:Receptors, Immunologic; D055630:Receptors, NK Cell Lectin-Like