The rheumatoid arthritis synovial fluid citrullinome reveals novel citrullinated epitopes in apolipoprotein E, myeloid nuclear differentiation antigen, and β-actin
Article first published online: 27 DEC 2012
Copyright © 2013 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 65, Issue 1, pages 69–80, January 2013
How to Cite
van Beers, J. J. B. C., Schwarte, C. M., Stammen-Vogelzangs, J., Oosterink, E., Božič, B. and Pruijn, G. J. M. (2013), The rheumatoid arthritis synovial fluid citrullinome reveals novel citrullinated epitopes in apolipoprotein E, myeloid nuclear differentiation antigen, and β-actin. Arthritis & Rheumatism, 65: 69–80. doi: 10.1002/art.37720
- Issue published online: 27 DEC 2012
- Article first published online: 27 DEC 2012
- Accepted manuscript online: 8 OCT 2012 12:15PM EST
- Manuscript Accepted: 20 SEP 2012
- Manuscript Received: 5 MAR 2012
- Dutch Arthritis Association
- European Union Sixth Framework Programme (project AutoCure). Grant Number: LSH-018661
- Netherlands Proteomics Centre, a program embedded in the Netherlands Genomics Initiative
To generate a catalog of citrullinated proteins that are present in the synovia of patients with rheumatoid arthritis (RA) and to elucidate their relevance for the anti–citrullinated protein antibody response in RA.
Polypeptides isolated from the synovial fluid of patients with RA were identified by mass spectrometry. Three proteins (apolipoprotein E [Apo E], myeloid nuclear differentiation antigen [MNDA], and β-actin) were studied in more detail, using immunoprecipitation and Western blotting. The presence of autoantibodies to synthetic peptides derived from these proteins in sera from patients with RA, sera from patients with other diseases, and sera from healthy control subjects was studied by enzyme-linked immunosorbent assay (ELISA).
RA synovial fluid samples displayed several distinct patterns of citrullinated proteins. Using mass spectrometry, (fragments of) 192 proteins were identified, including 53 citrullinated proteins, some of which contained multiple citrullinated residues. In addition to previously reported citrullinated proteins in RA synovia (e.g., vimentin and fibrinogen), a series of novel citrullinated proteins, including Apo E, MNDA, β-actin, and cyclophilin A, was identified. Immunoprecipitation experiments confirmed the citrullination of Apo E and MNDA. ELISAs demonstrated the presence of autoreactive citrullinated epitopes in Apo E, MNDA, and β-actin.
Synovial fluid samples from the inflamed joints of patients with RA contain many citrullinated proteins. Citrullinated Apo E, MNDA, and β-actin are novel antigens identified in RA synovial fluid, and only a limited number of their citrullinated epitopes are targeted by the immune system in RA.