Recognition of class I MHC by NK receptor Ly-49C: identification of critical residues.
The Ly-49 family of inhibitory receptors plays a major role in regulating mouse NK cell cytotoxicity. Two of its members, Ly-49C and I, are recognized by the mAb 5E6, which also defines a subset of NK cells involved in the hybrid resistance phenomenon. Previous studies have shown that Ly-49C binds to a broad spectrum of class I MHC molecules, while Ly-49I apparently does not bind to any class I MHC molecules tested. In the present investigation we have defined the amino acid residues of Ly-49C that are critical for determining its ligand specificities. First, using quantitative COS cell adhesion assays, we demonstrated that Ly-49CB6 bound to Dd, Db, Kb, or Kk as well as to murine leukemic cell lines GM979 (H-2s) and IC-21 (H-2b). In contrast, COS cells expressing Ly-49IB6 did not significantly bind to any of the class I MHC tested. To determine which amino acid residues of Ly-49C are critical for their specific binding to class I MHC, a series of chimeric and mutant Ly-49C and I were generated and tested. Exchanging the critical residues between Ly-49C and I significantly affected their binding specificities. Finally, we identified the epitopes on Ly-49C recognized by mAbs 5E6 and 4LO3311 that functionally inhibit Ly-49C recognition of its ligands. These results further define the class I specificities of Ly-49C and provide insight into the structural basis for how class I MHC is recognized by the Ly-49 family of NK receptors.
Lian
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RH
Terry Fox Laboratory, British Columbia Cancer Agency, Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Li
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Y
Kubota
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Mager
D L
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Takei
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F
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000950:Antigens, Ly / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D001666:Binding Sites, Antibody / Q000235:genetics; D019556:COS Cells; D006183:H-2 Antigens / Q000235:genetics / Q000378:metabolism*; D006825:Hybridomas; D007694:Killer Cells, Natural / Q000276:immunology / Q000378:metabolism*; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D017354:Point Mutation; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D051381:Rats; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D055630:Receptors, NK Cell Lectin-Like; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D000950:Antigens, Ly; D006183:H-2 Antigens; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins; D011971:Receptors, Immunologic; D055630:Receptors, NK Cell Lectin-Like; D011993:Recombinant Fusion Proteins