The critical amino acids of a nephritogenic epitope on human Goodpasture autoantigen for binding to HLA-DRB1*1501. (August 2017)

• Record Type: Journal Article
• Authors: Gu, Qiu-hua; Jia, Xiao-yu; Li, Jian-nan; Chen, Fang-jin; Cui, Zhao; Zhao, Ming-hui
• Is Part Of: Molecular immunology. Volume 88(2017:Aug.)
• Page Start: 1
• Page End: 9
• Publication Date: 2017-08
• Subjects: Anti-GBM disease -- HLA-DRB1*1501 -- Peptide -- Binding capacity; Immunochemistry -- Periodicals; Molecular biology -- Periodicals; Immunochemistry -- Periodicals; Allergy and Immunology -- Periodicals; Molecular Biology -- Periodicals; Immunochimie -- Périodiques; Biologie moléculaire -- Périodiques; Immunochemistry; Molecular biology; Periodicals; Electronic journals; 571.96
• DOI: 10.1016/j.molimm.2017.05.011
• Languages: English
• ISSNs: 0161-5890

Abstract

Highlights: We investigated the binding capacity of P14 (α3127-148 ), a mutual B cell and T cell epitope in anti-GBM patients, to HLA-DRB1*1501 on B cell surface. We found that the core binding motif of P14 was focused on the N-terminus. We firstly identified the critical amino acids on P14-2 associated with the binding capacity to HLA-DRB1*1501 as C132, W136, K141, and G142 . The modeling showed that (C)132 had a strong interaction with pocket 4 on the β chain of HLA-DR2b and might play a critical role in promoting P14 binding to HLA-DRB1*1501 molecules. Abstract: Background: Anti-GBM disease is caused by autoimmunity to Goodpasture antigen on α3(IV)NC1 and had strong associations with HLA-DRB1*1501. Previous studies identified α3127-148 (P14: TDIPPCPHGWISLWKGFSFIMF) as a T cell epitope. The present study was aimed to investigate the binding capacity of P14 to HLA-DRB1*1501 and the critical amino acids for this binding. Methods: A line of EBV-transformed human B cells homozygous for HLA-DRB1*1501 was used to detect the binding capacity of peptides to HLA-DRB1*1501 using flow cytometry analysis. P14 was sequentially truncated into 8 peptides with 15 amino acids to identify the core binding motif. A set of alanine substituted peptides of P14-2 was then synthesized to identify its critical residues for binding to HLA-DRB1*1501. The structure of HLA-DR2b-Peptide-TCR complex was constructed by modeling to analyze the interaction of each amino acids of P14-2 with the HLA-DR2b molecule. Results: P14 could bind to HLA-DRB1*1501 expressed on B cell surface. The N-terminus of P14 was the core binding motif and the truncated peptide P14-2 (DIPPCPHGWISLWKG)128-142 had the strongest binding capacity. After sequential amino acid substitution, we found the binding capacity of P14-2 was completely lost by the substitution of cysteine (C)132 and significantly decreased by the substitution of tryptophan (W)136, lysine (K)141, or glycine (G)142, but still at a high level. The modeling showed that (C)132 had a strong interaction with pocket 4 on the β chain of DR2b. Thus, C132, W136, K141, and G142 were defined as the critical amino acid residues for the binding capacity of P14 to HLA-DRB1*1501. Conclusion: We identified α3128-142 (DIPPCPHGWISLWKG) as the core binding motif of P14 to HLA-DRB1*1501 molecule. And the critical amino acid residues for this binding were further defined as C132, W136, K141, and G142 .