The Peptidome of Behçet's Disease–Associated HLA–B*51:01 Includes Two Subpeptidomes Differentially Shaped by Endoplasmic Reticulum Aminopeptidase 1

Abstract

Objective. To characterize the peptidome of the Behçet's disease-associated HLA-B*51:01 allotype as well as the differential features of major peptide subsets and their distinct endoplasmic reticulum aminopeptidase 1 (ERAP-1)-mediated processing.Methods. The endogenous B*51:01-bound peptidome was characterized from 721.221 transfectant cells, after affinity chromatography and acid extraction, by tandem mass spectrometry. Recombinant ERAP-1 variants were used to digest synthetic B*51:01 ligands. HLA and transporter associated with antigen processing (TAP) binding affinities of peptide ligands were calculated with well-established algorithms. ERAP-1 and ERAP-2 from 721.221 cells were characterized by genomic sequencing and Western blotting.Results. The B*51:01 peptidome consisted of 29.5% octamers, 61.7% nonamers, 4.8% decamers, and 4.0% longer peptides. The major peptide motif consisted of Pro and Ala at position 2, aliphatic/aromatic position 3 residues, and Val and Ile at the C-terminal position. The

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

“…Accordingly, a comparable configuration was previously described by X-ray crystallography of an octameric peptide accommodating itself into the HLA-A2 groove leaving the A-pocket empty and prone to stabilization by water molecules (42). Very recently, the characterization of Behçet's disease-associated B*5101 peptidome revealed that major peptide motifs are pPro2 or pAla2 (43). Interestingly, beside the canonical nonamers and, more rarely, decamers with pPro2 or pAla2, the peptide elution analysis showed the presence of N-terminal truncated versions with pPro1 or pAla1.…”

Functional Interaction of the Ankylosing Spondylitis–Associated Endoplasmic Reticulum Aminopeptidase 2 With the HLA–B*27 Peptidome in Human Cells

“…This was done as previously described (25). Briefly, the samples were analyzed in a Q-Exactive-Plus mass spectrometer fitted with Ultimate 3000 RSLC nanocapillary UHPLC (Thermo Fisher Waltham, MA, USA).…”

Is Behçet's disease a ‘class 1-opathy’? The role of HLA-B*51 in the pathogenesis of Behçet's disease

“…This haplotype carried five non-ancestral alleles, including p.Asp575Asn and p.Arg725Gln, and it was found previously to have lower peptide-trimming activity [29,34]. HLA-B*51 carriers homozygous for the haplotype had an 11-fold increased disease odds compared with individuals who had none of the genetic risk factors.…”

“…The risk ERAP-1 allotype with p.Asp575Asn and p.Arg725Gln SNPs confers lower enzymatic activity and alters the balance between these two peptide subsets, with lower-affinity Ala2 peptides being presented more on HLA-B*51 [29]. In addition to these findings, AS and psoriasis are also associated with ERAP-1 in epistasis with their susceptibility MHC class I alleles and may share similar pathogenesis mechanisms [31,32].…”

“…Further light was shed on this possible pathogenic mechanism when the peptidome of HLA-B*51:01 (a subtype of HLA-B*51) was characterized extensively (> 1600 peptides). Two major peptide subsets were identified, with either Pro or Ala at position 2 (total frequency 89Á3%, Pro : Ala ratio 1Á9) and, importantly, both subsets differed drastically in the susceptibility of their position 1 residues to ERAP-1 [29]. These susceptibilities were based on results of experiments by Hearn et al [30] looking at ERAP1 degradation of peptides with different N-terminal amino acids.…”