Receptor glycosylation regulates Ly-49 binding to MHC class I.
Murine NK cells express the Ly-49 family of class I MHC-binding receptors that control their ability to lyse tumor or virally infected host target cells. X-ray crystallography studies have identified two predominant contact sites (sites 1 and 2) that are involved in the binding of the inhibitory receptor, Ly-49A, to H-2D(d). Ly-49G2 (inhibitory) and Ly-49D (activating) are highly homologous to Ly-49A and also recognize H-2D(d). However, the binding of Ly-49D and G(2) to H-2D(d) is of lower affinity than Ly-49A. All Ly-49s contain N-glycosylation motifs; however, the importance of receptor glycosylation in Ly-49-class I interactions has not been determined. Ly-49D and G(2) contain a glycosylation motif (NTT (221-223)), absent in Ly-49A, adjacent to one of the proposed binding sites for H-2D(d) (site 2). The presence of a complex carbohydrate group at this critical site could interfere with class I binding. In this study, we are able to demonstrate for the first time that Ly-49D binds H-2D(d) in the presence of mouse beta(2)-microglobulin. We also demonstrate that glycosylation of the NTT (221-23) motif of Ly-49D inteferes with recognition of H-2D(d). Alteration of the Ly-49D-NTT (221-23) motif to abolish glycosylation at this site resulted in enhanced H-2D(d) binding and receptor activation. Furthermore, glycosylation of Ly-49G2 at NTT (221-23) also reduces receptor binding to H-2D(d) tetramers. Therefore, the addition of complex carbohydrates to the Ly-49 family of receptors may represent a mechanism by which NK cells regulate affinity for host class I ligands.
Mason
Llewellyn H
LH
Laboratory of Experimental Immunology, Division of Basic Sciences, National Cancer Institute-Clinical Cancer Research, National Institutes of Health, Frederick, MD 21702-1201, USA. MasonL@mail.ncifcrf.gov
Willette-Brown
Jami
J
Anderson
Stephen K
SK
Alvord
W Gregory
WG
Klabansky
Richard L
RL
Young
Howard A
HA
Ortaldo
John R
JR
D020816:Amino Acid Motifs / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics / Q000276:immunology; D000818:Animals; D000950:Antigens, Ly / Q000235:genetics / Q000378:metabolism*; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000378:metabolism; D018390:Gene Targeting; D006031:Glycosylation; D006183:H-2 Antigens / Q000378:metabolism*; D064532:Histocompatibility Antigen H-2D; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D037181:Lectins, C-Type; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D011971:Receptors, Immunologic / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D055630:Receptors, NK Cell Lectin-Like; D012260:Ribonucleases / Q000235:genetics; D014162:Transfection; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology
D000950:Antigens, Ly; D003432:Cross-Linking Reagents; D006183:H-2 Antigens; D064532:Histocompatibility Antigen H-2D; D015395:Histocompatibility Antigens Class I; D007376:Interleukin-2; D037181:Lectins, C-Type; D011971:Receptors, Immunologic; D055630:Receptors, NK Cell Lectin-Like; D001120:Arginine; D012260:Ribonucleases