Vβ2 natural killer T cell antigen receptor-mediated recognition of CD1d-glycolipid antigen

Abstract

Natural killer T cell antigen receptors (NKT TCRs) recognize lipidbased antigens (Ags) presented by CD1d. Although the TCR α-chain is invariant, NKT TCR Vβ exhibits greater diversity, with one (Vβ11) and three (Vβ8, Vβ7, and Vβ2) Vβ chains in humans and mice, respectively. With the exception of the Vβ2 NKT TCR, NKT TCRs possess canonical tyrosine residues within complementarity determining region (CDR) 2β that are critical for CD1d binding. Thus, how Vβ2 NKT TCR docks with CD1d-Ag was unclear. Despite the absence of the CDR2β-encoded tyrosine residues, we show that the Vβ2 NKT TCR engaged CD1d-Ag in a similar manner and with a comparable affinity and energetic footprint to the manner observed for the Vβ8.2 and Vβ7 NKT TCRs. Accordingly, the germline-encoded regions of the TCR β-chain do not exclusively dictate the innate NKT TCR-CD1d-Ag docking mode. Nevertheless, clear fine specificity differences for the CD1d-Ag existed between the Vβ2 NKT TCR and the Vβ8.2 and Vβ7 NKT TCRs, with the Vβ2 NKT TCR exhibiting greater sensitivity to modifications to the glycolipid Ag. Furthermore, within the Vβ2 NKT TCR-CD1d-αGalCer complex, the CDR2β loop mediated fewer contacts with CD1d, whereas the CDR1β and CDR3β loops contacted CD1d to a much greater extent compared with most Vβ11, Vβ8.2, and Vβ7 NKT TCRs. Accordingly, there is a greater interplay between the germline-and nongermline-encoded loops within the TCR β-chain of the Vβ2 NKT TCR that enables CD1d-Ag ligation.

Structure-Activity Relationship Studies of Novel Glycosphingolipids That Stimulate Natural Killer T-Cells

“…As mentioned in the introduction, the 6 0 -hydroxy group of galactoses is not involved in the hydrogen-bonding network. [22][23][24] Therefore, the former three hydroxy groups seem to play important roles in making a stable CD1d-antigen-TCR complex and hence show the potent immunostimulatory activities. Indeed, many analogs have been developed by modification of the three former hydroxy groups to other functional groups, for example, H (deoxy), F, N 3 , NH 2 , NHAc, OMe, and O(CH 2 ) 2 OH, 46,[104][105][106][107][108][109] but none of these analogs showed potent bioactivities, except for the 3-O-sulfo--galactosyl analog of 1 (37, Fig.…”

“…[22][23][24] According to the crystal information, the 2 0 -, 3 0 -, and 4 0 -hydroxy groups of the galactose head part of 1 interact with Gly96, Ser30, and Phe29 of human TCR respetively (in mouse TCR, Gly96 and Asn30 are common to V7, V8.2, and V2) through hydrogen bonds (Fig. 1).…”

“…Due to the existence of an extra methylene unit, this elongated analog 16 also showed no bioactivity, similarly to homo--C-GalCer (15). Based on X-ray information on mouse and human CD1d/1/TCR complexes, [22][23][24] the spatial relationship between the galactose and the ceramide parts appears to be very important in making a rigid complex with CD1d that shows potent bioactivities. 69) Chen et al reported the synthesis of -galactosylated oxime analog 17, which is also an elongated analog having an extra N-atom, without biological information, in 2010.…”

“…18,19) In 2009, Godfrey, Rossjohn and co-workers reported the X-ray structure of the ternary mouse CD1d/1/TCR complexes. 23,24) They found that the manner of interaction of mouse NKT TCR in recognizing the CD1d/ ligand is influenced by V domains (in mice, >80% of NKT TCRs have the V8.2, V7, or V2 domain, but only V11 in humans) of TCR.…”

Human and Mouse Type I Natural Killer T Cell Antigen Receptors Exhibit Different Fine Specificities for CD1d-Antigen Complex

“…Nevertheless, variations on a theme were apparent in that there were differing roles of the complementarity-determining regions (CDR) of the NKT TCRs for some CD1d-Ag complexes (13,14,25). For example, NKT TCR-CD1d autoreactivity seems attributable to a greater role of the CDR3␤ loop, and altered juxtapositioning of the V␤8/7/2 chains results in differing V␤-mediated footprints that can impact on V␣-J␣ interactions with the CD1d-Ag (6,16,21). Moreover, alterations in the V␣ and/or V␤ usage within the NKT TCR can impact on the specificity toward CD1d-restricted Ags.…”