HLA–DR1001 presents “altered-self” peptides derived from joint-associated proteins by accepting citrulline in three of its binding pockets
Version of Record online: 7 JUN 2010
Copyright © 2010 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 62, Issue 10, pages 2909–2918, October 2010
How to Cite
James, E. A., Moustakas, A. K., Bui, J., Papadopoulos, G. K., Bondinas, G., Buckner, J. H. and Kwok, W. W. (2010), HLA–DR1001 presents “altered-self” peptides derived from joint-associated proteins by accepting citrulline in three of its binding pockets. Arthritis & Rheumatism, 62: 2909–2918. doi: 10.1002/art.27594
- Issue online: 7 JUN 2010
- Version of Record online: 7 JUN 2010
- Accepted manuscript online: 7 JUN 2010 12:00AM EST
- Manuscript Accepted: 27 MAY 2010
- Manuscript Received: 7 JAN 2010
- NIH (Autoimmune Prevention Centers). Grant Numbers: 5U19-AI-050864-07, HHSN-266200400028C
- The Silicon Graphics Fuel work station and the accompanying molecular simulation software were obtained through an equipment grant to Epirus Institute of Technology from the Epirus Regional Development Project of the Third Community Support Framework (80% European Union funds, 20% Hellenic State funds)
HLA–DRB1*1001 (DR1001) is a shared epitope allele associated with rheumatoid arthritis (RA). The present study was undertaken to assess the capacity of DR1001 to accommodate citrulline in its binding pockets and to identify citrullinated T cell epitopes derived from joint-associated proteins.
The binding of peptide derivatives containing citrulline, arginine, and other amino acid substitutions was measured. A prediction algorithm was developed to identify arginine-containing sequences from joint-associated proteins that preferentially bind to DR1001 upon citrullination. Unmodified and citrullinated versions of these sequences were synthesized and were utilized to stimulate CD4+ T cells from healthy subjects and RA patients. Responses were measured by class II major histocompatibility complex tetramer staining and confirmed by isolating CD4+ T cell clones.
DR1001 accepted citrulline, but not arginine, in 3 of its anchoring pockets. The prediction algorithm identified sequences that preferentially bound to DR1001 with arginine replaced by citrulline. Three of these sequences elicited CD4+ T cell responses. T cell clones specific for these sequences proliferated only in response to citrullinated peptides.
Conversion of arginine to citrulline generates “altered-self” peptides that can be bound and presented by DR1001. Responses to these peptides implicate the corresponding proteins (fibrinogen α, fibrinogen β, and cartilage intermediate-layer protein) as relevant antigens. The finding of preferential responses to citrullinated sequences suggests that altered peptide binding affinity due to this posttranslational modification may be an important factor in the initiation or progression of RA. As such, measuring responsiveness to these peptides may be useful for immunologic monitoring.