Interaction Pattern of Arg 62 in the A-Pocket of Differentially Disease-Associated HLA-B27 Subtypes Suggests Distinct TCR Binding Modes

Abstract

The single amino acid replacement Asp116His distinguishes the two subtypes HLA-B*2705 and HLA-B*2709 which are, respectively, associated and non-associated with Ankylosing Spondylitis, an autoimmune chronic inflammatory disease. The reason for this differential association is so far poorly understood and might be related to subtype-specific HLA:peptide conformations as well as to subtype/peptide-dependent dynamical properties on the nanoscale. Here, we combine functional experiments with extensive molecular dynamics simulations to investigate the molecular dynamics and function of the conserved Arg62 of the α1-helix for both B27 subtypes in complex with the self-peptides pVIPR (RRKWRRWHL) and TIS (RRLPIFSRL), and the viral peptides pLMP2 (RRRWRRLTV) and NPflu (SRYWAIRTR). Simulations of HLA:peptide systems suggest that peptide-stabilizing interactions of the Arg62 residue observed in crystal structures are metastable for both B27 subtypes under physiological conditions, rendering this arginine solvent-exposed and, probably, a key residue for TCR interaction more than peptide-binding. This view is supported by functional experiments with conservative (R62K) and non-conservative (R62A) B*2705 and B*2709 mutants that showed an overall reduction in their capability to present peptides to CD8+ T cells. Moreover, major subtype-dependent differences in the peptide recognition suggest distinct TCR binding modes for the B*2705 versus the B*2709 subtype.

The Ankylosing Spondylitis-Associated HLA-B*2705 Presents a B*0702-Restricted EBV Epitope and Sustains the Clonal Amplification of Cytotoxic T Cells in Patients

“…For the binding assay, a self-peptide restricted by HLA-B*27 (TIS, RRLPIFSRL) (29) and an immunodominant CMV-epitope HLA-A*02-restricted (pp65, NLVPMVATV) were included. A modified version of pEBNA3A (APPIFIRRL) has been also analyzed.…”

Differential Impact of HLA-B*44 Allelic Mismaches at Position 156 on Peptide Binding Specificities and T-Cell Diversity

“…Additionally it has been demonstrated in B*27:05 and B*27:09 alleles that the binding of peptides containing a Lys PΩ anchor appears to be weaker and thermodynamically less stable [21]. Such allosteric mechanisms might influence not only the association and dissociation of the trimeric complexes, but also the mode of recognition by the T-cell receptors [22]. Analysis of the peptide binding affinities showed that there were no peptides of low affinity that could be recovered from the B*44:03 molecules, indicating a role for Leu at 156 in increasing the stability of the peptide-HLA complex.…”

Salt bridge-forming residues positioned over viral peptides presented by MHC class I impacts T-cell recognition in a binding-dependent manner

“…Nonpermissive ligands disrupted salt bridge interaction of CD1a, disrupt the properties of A' roof and could hinder engagement of hydrophobic CDR3β loop of the BK6 TCR with CD1a (Birkinshaw et al, 2015). Nurzia et al indicate that the positive charging of Arg62 is preferred for the TCR recognition of Ankylosing Spondylitis-associated B*2705 complexes, as revealed by the R62 K and R62A mutants with an overall reduced capability to present peptides to CD8 + T-cells (Nurzia et al, 2012). Our data also demonstrate that Tcell recognition was significantly alleviated when we broke the MHC I salt bridge with R66A and E163A mutations.…”