Differential Recognition of CD1d-α-Galactosyl Ceramide by the Vβ8.2 and Vβ7 Semi-invariant NKT T Cell Receptors

Abstract

CD1d presents lipid-based antigens (Ag) that are recognised by the semi-invariant T cell receptor (TCR) expressed on Natural Killer T (NKT) cells. While the TCR α-chain is typically invariant, the TCR β-chain expression is more diverse, particularly in mice where at least three different Vβ chains are commonly expressed. We report the structures of Vα14-Vβ8.2 and Vα14-Vβ7 NKT TCRs in complex with CD1d-α-galactosylceramide (α-GalCer), as well as a 2.5 Å structure of the human NKT TCR-CD1d-α-GalCer complex. Both Vβ8.2 and Vβ7 NKT TCRs, as well as the human NKT TCR, ligated CD1d-α-GalCer in a broadly similar manner, thereby highlighting the evolutionarily-conserved nature of this interaction. However, differences within the Vβ domains of the Vβ8.2 and Vβ7 NKT TCR-CD1d complexes not only resulted in altered TCR-β-CD1d-mediated contacts, but also surprisingly modulated recognition mediated by the invariant α-chain. Mutagenesis studies revealed the differing contributions of Vβ8.2 and Vβ7 residues within the CDR2β loop in mediating contacts with CD1d. Collectively we provide a structural basis for the differential NKT TCR Vβ usage in NKT cells.

Oligoclonality and innate-like features in the TCR repertoire of type II NKT cells reactive to a β-linked self-glycolipid

“…3B). Consistent with the idea that other CDR2β region residues in the Vβ2 and Vβ7 type I NKT TCRs (11,13) can also bind to CD1d, these tyrosine residues are not present in the Vβ3.1 TCRs of the type II NKT cells. It is noteworthy that all Vβ8.1 and Vβ3.1 TCRs of type II NKT cells carry a negatively charged residue at position 53 in the CDR2β region, whereas a neutral glycine residue is present in most TCRs of type I NKT cells (Fig.…”

“…Recent structural studies have suggested the involvement of crucial residues within the CDR2β, CDR1α, and CDR3α loops of the semi-invariant TCR in recognition of the αGalCer/CD1d complex (9)(10)(11)(12). It is notable that two conserved residues (48Y and 50Y) in the CDR2β loop of the type I NKT TCR that contact the CD1d molecule (9)(10)(11)(12) are also present in the Vβ8.1 TCRs of type II NKT cells (Fig.…”

“…It is notable that two conserved residues (48Y and 50Y) in the CDR2β loop of the type I NKT TCR that contact the CD1d molecule (9)(10)(11)(12) are also present in the Vβ8.1 TCRs of type II NKT cells (Fig. 3B).…”

“…However, CDR1α regions among TCRs of the type II NKT cells are very similar and comprise abundant hydroxyl groups. Because this region of the invariant TCR contacts solely the galactose moiety (9)(10)(11), it is possible that these hydroxyl groups bind to the hydrophilic sulfated galactose. A conserved CDR3β region among TCRs of type II NKT cells is likely to be involved in the recognition of the sulfatide/CD1d complex, consistent with the recent studies of invariant TCRs (11,13).…”

“…Recently, crystallographic and alanine mutagenesis analyses have examined type I NKT TCR interactions with the αGalCer/CD1d complex (9)(10)(11)(12)(13). Unlike the TCR interaction with peptide/MHC complexes, crucial residues for this interaction are mainly located in the CDR2β loop contacting the CD1d molecule, in the CDR3α loop contacting both glycolipid antigen and the CD1d molecule, and in the CDR1α loop contacting solely the α-linked galactose moiety of the antigen (1,(9)(10)(11)(12)(13).…”