Receptor glycosylation regulates Ly-49 binding to MHC class I.

Abstract

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.

• Authors: Llewellyn H Mason, Jami Willette-Brown, Stephen K Anderson, W Gregory Alvord, Richard L Klabansky, Howard A Young, John R Ortaldo
• Journal: Journal of immunology (Baltimore, Md. : 1950) (J Immunol) Vol. 171 Issue 8 Pg. 4235-42 (Oct 15 2003) ISSN: 0022-1767 [Print] United States
• PMID: 14530347 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antigens, Ly
• Cross-Linking Reagents
• H-2 Antigens
• Histocompatibility Antigen H-2D
• Histocompatibility Antigens Class I
• Interleukin-2
• Lectins, C-Type
• Receptors, Immunologic
• Receptors, NK Cell Lectin-Like
• Arginine
• Ribonucleases

Topics

• Amino Acid Motifs (genetics, immunology)
• Amino Acid Sequence
• Amino Acid Substitution (genetics, immunology)
• Animals
• Antigens, Ly (genetics, metabolism)
• Arginine (genetics, metabolism)
• Cross-Linking Reagents (metabolism)
• Gene Targeting
• Glycosylation
• H-2 Antigens (metabolism)
• Histocompatibility Antigen H-2D
• Histocompatibility Antigens Class I (metabolism)
• Humans
• Interleukin-2 (metabolism)
• Jurkat Cells
• Lectins, C-Type
• Mice
• Molecular Sequence Data
• Mutagenesis, Site-Directed
• Protein Binding (genetics, immunology)
• Receptors, Immunologic (genetics, immunology, metabolism)
• Receptors, NK Cell Lectin-Like
• Ribonucleases (genetics)
• Transfection
• Up-Regulation (genetics, immunology)