Interaction pattern of Arg 62 in the A-pocket of differentially disease-associated HLA-B27 subtypes suggests distinct TCR binding modes.

Elisa Nurzia (1) , Daniele Narzi (2) , Alberto Cauli (3) , Alessandro Mathieu (3) , Valentina Tedeschi (1) , Silvana Caristi (1) , Rosa Sorrentino (1) , Rainer A Böckmann (2) , Maria Teresa Fiorillo (1)

1 Department of Biology and Biotechnology "Charles Darwin"
2 Computational Biology, Department of Biology
3 2nd Chair of Rheumatolog, Department of Medical Sciences

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.

Domains: Life Sciences [q-bio]; Immunology

Elisa Nurzia, Daniele Narzi, Alberto Cauli, Alessandro Mathieu, Valentina Tedeschi, et al.. Interaction pattern of Arg 62 in the A-pocket of differentially disease-associated HLA-B27 subtypes suggests distinct TCR binding modes.. PLoS ONE, 2012, 7 (3), pp.e32865. ⟨10.1371/journal.pone.0032865⟩. ⟨pasteur-00966917⟩