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Reed E, Jiang X, Kharlamova N, Ytterberg AJ, Catrina AI, Israelsson L, Mathsson-Alm L, Hansson M, Alfredsson L, Rönnelid J, Lundberg K. Antibodies to carbamylated α-enolase epitopes in rheumatoid arthritis also bind citrullinated epitopes and are largely indistinct from anti-citrullinated protein antibodies. Arthritis Res Ther 2016; 18:96. [PMID: 27145822 PMCID: PMC4855497 DOI: 10.1186/s13075-016-1001-6] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 04/22/2016] [Indexed: 01/06/2023] Open
Abstract
Background In addition to anti-citrullinated protein antibodies (ACPAs), antibodies targeting carbamylated (i.e., homocitrullinated) proteins (anti-CarP antibodies) have been described in rheumatoid arthritis (RA). However, the extent to which anti-CarP antibodies are truly distinct from ACPA remains unclear, and few studies have focused on specific autoantigens. Here, we examine cross-reactivity between ACPA and anti-CarP antibodies, in the context of the candidate autoantigen α-enolase. Methods Cross-reactivity was examined by immunoblotting of citrullinated and carbamylated proteins using purified ACPA; and by peptide absorption experiments, using the citrullinated α-enolase peptide CEP-1 and a homocitrulline-containing version (carb-CEP-1) in ELISA. The population-based case-control cohort EIRA (n = 2836 RA; 373 controls) was screened for reactivity with CEP-1 and carb-CEP-1, using the ISAC multiplex array. Associations between anti-CarP antibodies, smoking and genetic risk factors were analysed using unconditional logistic regression models. Differences in antibody levels were investigated using the Mann-Whitney U test. Results Affinity-purified ACPA was found to bind carbamylated proteins and homocitrulline-containing peptides, demonstrating definitive cross-reactivity between ACPA and anti-CarP antibodies. Anti-carb-CEP-1 reactivity in EIRA was almost exclusively confined to the CEP-1-positive subset, and this group of RA patients (21 %) displayed a particularly strong ACPA response with marked epitope spreading. The small RA subset (3 %) with homocitrulline reactivity in the absence of citrulline reactivity did not associate with smoking or risk genes, and importantly had significantly lower anti-carb-CEP-1 antibody levels. Conclusion Our data presented herein cast doubt on the specificity of anti-CarP antibodies in RA, which we posit may be a subset of cross-reactive ACPA. Electronic supplementary material The online version of this article (doi:10.1186/s13075-016-1001-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Evan Reed
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
| | - Xia Jiang
- Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Nastya Kharlamova
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - A Jimmy Ytterberg
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.,Division of Physiological Chemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Anca I Catrina
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Lena Israelsson
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Linda Mathsson-Alm
- ThermoFisher Scientific, Uppsala, Sweden.,Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Monika Hansson
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Lars Alfredsson
- Cardiovascular Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.,Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden
| | - Johan Rönnelid
- Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Karin Lundberg
- Rheumatology Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
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Ajeganova S, van Steenbergen HW, Verheul MK, Forslind K, Hafström I, Toes REM, Huizinga TWJ, Svensson B, Trouw LA, van der Helm-van Mil AHM. The association between anti-carbamylated protein (anti-CarP) antibodies and radiographic progression in early rheumatoid arthritis: a study exploring replication and the added value to ACPA and rheumatoid factor. Ann Rheum Dis 2016; 76:112-118. [DOI: 10.1136/annrheumdis-2015-208870] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 03/31/2016] [Accepted: 04/09/2016] [Indexed: 11/04/2022]
Abstract
ObjectiveAnti-carbamylated protein (anti-CarP) antibodies are reported to associate with more radiographic progression within the total rheumatoid arthritis (RA) population and anti-citrullinated peptide antibody (ACPA)-negative subgroup. We explored the association of anti-CarP with radiographic progression in RA and aimed to replicate the association and evaluate the added value of anti-CarP antibodies in relation to ACPA and rheumatoid factor (RF).Methods576 Swedish and 628 Dutch patients with RA (2394 and 3247 sets of radiographs, respectively) were longitudinally studied. Replication was restricted to the Swedish patients. In both cohorts, the association of anti-CarP with radiographic progression was determined in strata of patients with similar ACPA and RF status; results of both cohorts were combined in fixed-effect meta-analyses. The net percentage of patients for whom the radiographic progression in 5 years was additionally correctly classified when adding anti-CarP to a model including ACPA and RF was evaluated.ResultsAnti-CarP associated with radiographic progression in the total Swedish RA population (beta=1.11 per year, p=8.75×10−13) and in the ACPA-negative subgroup (beta=1.14 per year, p=0.034). Anti-CarP associated with more radiographic progression in the strata of ACPA-positive/RF-negative, ACPA-negative/RF-positive and ACPA-positive/RF-positive patients with RA (respective p values 0.014, 0.019 and 0.0056). A model including ACPA and RF correctly classified 54% and 57% of the patients; adding anti-CarP to this model did not increase these percentages (54% and 56% were correctly classified).ConclusionsAnti-CarP antibodies associated with more severe radiographic progression in the total and ACPA-negative RA population. Anti-CarP-positivity had a statistically significant additive value to ACPA and RF, but did not improve correct classification of patients.
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Barnoud T, Wilkey DW, Merchant ML, Clark JA, Donninger H. Proteomics Analysis Reveals Novel RASSF2 Interaction Partners. Cancers (Basel) 2016; 8:cancers8030037. [PMID: 26999212 PMCID: PMC4810121 DOI: 10.3390/cancers8030037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 02/18/2016] [Accepted: 03/09/2016] [Indexed: 12/30/2022] Open
Abstract
RASSF2 is a tumor suppressor that shares homology with other Ras-association domain (RASSF) family members. It is a powerful pro-apoptotic K-Ras effector that is frequently inactivated in many human tumors. The exact mechanism by which RASSF2 functions is not clearly defined, but it likely acts as a scaffolding protein, modulating the activity of other pro-apoptotic effectors, thereby regulating and integrating tumor suppressor pathways. However, only a limited number of RASSF2 interacting partners have been identified to date. We used a proteomics based approach to identify additional RASSF2 interactions, and thereby gain a better insight into the mechanism of action of RASSF2. We identified several proteins, including C1QBP, Vimentin, Protein phosphatase 1G and Ribonuclease inhibitor that function in diverse biological processes, including protein post-translational modifications, epithelial-mesenchymal transition, cell migration and redox homeostasis, which have not previously been reported to interact with RASSF2. We independently validated two of these novel interactions, C1QBP and Vimentin and found that the interaction with C1QBP was enhanced by K-Ras whereas, interestingly, the Vimentin interaction was reduced by K-Ras. Additionally, RASSF2/K-Ras regulated the acetylation of Vimentin. Our data thus reveal novel mechanisms by which RASSF2 may exert its functions, several of which may be Ras-regulated.
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Affiliation(s)
- Thibaut Barnoud
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY 40202, USA.
| | - Daniel W Wilkey
- Department of Medicine, James Graham Brown Cancer Center, Molecular Targets Program, University of Louisville, Louisville, KY 40202, USA.
| | - Michael L Merchant
- Department of Medicine, James Graham Brown Cancer Center, Molecular Targets Program, University of Louisville, Louisville, KY 40202, USA.
| | - Jennifer A Clark
- Department of Medicine, James Graham Brown Cancer Center, Molecular Targets Program, University of Louisville, Louisville, KY 40202, USA.
| | - Howard Donninger
- Department of Medicine, James Graham Brown Cancer Center, Molecular Targets Program, University of Louisville, Louisville, KY 40202, USA.
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