A minimal binding footprint on CD1d-glycolipid is a basis for selection of the unique human NKT TCR.
Although it has been established how CD1 binds a variety of lipid antigens (Ag), data are only now emerging that show how alphabeta T cell receptors (TCRs) interact with CD1-Ag. Using the structure of the human semiinvariant NKT TCR-CD1d-alpha-galactosylceramide (alpha-GalCer) complex as a guide, we undertook an alanine scanning mutagenesis approach to define the energetic basis of this interaction between the NKT TCR and CD1d. Moreover, we explored how analogues of alpha-GalCer affected this interaction. The data revealed that an identical energetic footprint underpinned the human and mouse NKT TCR-CD1d-alpha-GalCer cross-reactivity. Some, but not all, of the contact residues within the Jalpha18-encoded invariant CDR3alpha loop and Vbeta11-encoded CDR2beta loop were critical for recognizing CD1d. The residues within the Valpha24-encoded CDR1alpha and CDR3alpha loops that contacted the glycolipid Ag played a smaller energetic role compared with the NKT TCR residues that contacted CD1d. Collectively, our data reveal that the region distant to the protruding Ag and directly above the F' pocket of CD1d was the principal factor in the interaction with the NKT TCR. Accordingly, although the structural footprint at the NKT TCR-CD1d-alpha-GalCer is small, the energetic footprint is smaller still, and reveals the minimal requirements for CD1d restriction.
Wun
Kwok S
KS
Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria, Australia.
Borg
Natalie A
NA
Kjer-Nielsen
Lars
L
Beddoe
Travis
T
Koh
Ruide
R
Richardson
Stewart K
SK
Thakur
Meena
M
Howell
Amy R
AR
Scott-Browne
James P
JP
Gapin
Laurent
L
Godfrey
Dale I
DI
McCluskey
James
J
Rossjohn
Jamie
J
D000409:Alanine; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D018949:Antigens, CD1 / Q000737:chemistry* / Q000276:immunology*; D055610:Antigens, CD1d; D005699:Galactosylceramides; D006017:Glycolipids / Q000737:chemistry*; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry* / Q000276:immunology*; D016415:Sequence Alignment; D013045:Species Specificity; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
D018949:Antigens, CD1; D055610:Antigens, CD1d; C526877:CD1D protein, human; C419393:CD1a antigen; D005699:Galactosylceramides; D006017:Glycolipids; D016693:Receptors, Antigen, T-Cell, alpha-beta; C493154:alpha-galactosylceramide; D000409:Alanine