info:eu-repo/semantics/article
Potential protein targets of the peptidylarginine deiminase 2 and peptidylarginine deiminase 4 enzymes in rheumatoid synovial tissue and its possible meaning
Date
2016Registration in:
2147-9720
2148-4279
Author
Badillo Soto, Martha Adriana
Rodríguez Rodríguez, Mayra
Pérez Pérez, María Elena
Daza Benitez, Leonel
Bollain y Goytia, Juan José
Carrillo Jimenez, Miguel Angel
Avalos Díaz, Esperanza del Refugio
Herrera Esparza, Rafael
Institutions
Abstract
Objective: The molecular mechanism of citrullination involves the calcium-dependent peptidylarginine deiminase (PAD) family of
enzymes. These enzymes induce a stereochemical modification of normal proteins and transform them into autoantigens, which in
rheumatoid arthritis trigger a complex cascade of joint inflammatory events followed by chronic synovitis, pannus formation, and
finally, cartilage destruction. By hypothesizing that PAD2 and PAD4 enzymes produce autoantigens, we investigated five possible
synovial protein targets of PAD enzymes.
Material and Methods: We measured PAD2, PAD4, and citrullinated proteins in 10 rheumatoid and 10 osteoarthritis synovial biopsies and then assessed the post-translational modifications of fibrinogen, cytokeratin, tubulin, IgG, and vimentin proteins using
a double-fluorescence assay with specific antibodies and an affinity-purified anti-citrullinated peptide (CCP) antibody. The degree
of co-localization was analyzed, and statistical significance was determined by ANOVA, Fisher’s exact test, and regression analysis.
Results: The principal results of this study demonstrated that citrullinated proteins, such as fibrinogen, IgG, and other probed proteins, were targets of PAD2 and PAD4 activity in rheumatoid synovial biopsies, whereas osteoarthritis biopsies were negative for this
enzyme (p<0.0001). An analysis of citrullination sites using the UniProtKB/Swiss-Prot data bank predicts that the secondary structure
of the analyzed proteins displays most of the sites for citrullination; a discussion regarding its possible meaning in terms of pathogenesis is made.
Conclusion: Our results support the conclusion that the synovial citrullination of proteins is PAD2 and PAD4 dependent. Furthermore, there is a collection of candidate proteins that can be citrullinated.