The complementarity-determining region-like loops of CD8 alpha interact differently with beta 2-microglobulin of the class I molecules H-2Kb and thymic leukemia antigen, while similarly with their alpha 3 domains

J Immunol. 2002 Apr 15;168(8):3881-6. doi: 10.4049/jimmunol.168.8.3881.

Abstract

The murine CD8 glycoprotein interacts with both classical MHC class I molecules and some nonclassical molecules, including the thymic leukemia Ag (TL). TL binds preferentially to CD8alphaalpha homodimers with a 10-fold higher affinity than H-2K(b) class I molecules. To understand the molecular basis for this difference, we created a panel of CD8alpha mutants and tested the ability of the CD8alphaalpha homodimers to bind to H-2K(b) tetramers and TL tetramers. Mutations in three CD8 residues located on the complementarity-determining region-like loops contacting the negatively charged loop in the alpha3 domain of MHC class I greatly reduced binding to both tetramers. Because TL and H-2K(b) class I sequences are highly conserved in the alpha3 domain of MHC class I, this suggests that CD8 contacts the alpha3 domain of TL and H-2K(b) in a similar manner. In contrast, mutations in residues on the A and B beta strands of CD8 that are involved in contact with beta(2)-microglobulin affected interaction with the H-2K(b) tetramer, but not the TL tetramer. Therefore, the orientation of interaction of TL with CD8 appears to be different from that of H-2K(b). The unique high affinity binding of TL with CD8alphaalpha is most likely a result of amino acid differences in the alpha3 domain between TL and H-2K(b), particularly at positions 198 (K to D) and 228 (M to T), which are contact residues in the CD8alphaalpha-H-2K(b) cocrystal.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution / genetics
  • Amino Acid Substitution / immunology
  • Animals
  • Antigens, Neoplasm / metabolism*
  • CD8 Antigens / genetics
  • CD8 Antigens / immunology
  • CD8 Antigens / metabolism*
  • COS Cells
  • Complementarity Determining Regions / metabolism
  • Dimerization
  • H-2 Antigens / metabolism*
  • Immune Sera / metabolism
  • Membrane Glycoproteins / metabolism*
  • Mice
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Peptide Fragments / immunology
  • Peptide Fragments / metabolism
  • Protein Binding / genetics
  • Protein Binding / immunology
  • Protein Structure, Secondary / genetics
  • Protein Structure, Tertiary / genetics
  • Thymus Gland / immunology
  • Thymus Gland / metabolism
  • Transfection
  • beta 2-Microglobulin / metabolism*

Substances

  • Antigens, Neoplasm
  • CD8 Antigens
  • CD8 antigen, alpha chain
  • CD8alphabeta antigen
  • Complementarity Determining Regions
  • H-2 Antigens
  • H-2Kb protein, mouse
  • Immune Sera
  • Membrane Glycoproteins
  • Peptide Fragments
  • beta 2-Microglobulin
  • thymus-leukemia antigens