SAT0012 ANTIBODY REACTIVITY AGAINST NATIVE PROTEINS IN RHEUMATOID ARTHRITIS

Background:The majority of patients with rheumatoid arthritis (RA) produce autoantibodies against proteins that have undergone post-translational modfication, e.g. citrullination or carbamylation. There is growing evidence of their relevance and their potential utility to improve diagnosis, patient stratification, and prognosis for precision medicine. Investigating new autoantibody patterns may allow further stratification of patients and identifying subsets of patients that benefit from different treatment modalities. Following the discovery of high autoantibody reactivity against multiple modified proteins the interest in native targets decreased. Even though antibodies reacting with native proteins may also have a role in RA pathogenesis, their reactivity patterns are much less studied.Objectives:To identify novel native autoantigens in RA patients and elucidate patterns within autoantibody reactivity against native autoantigens.Methods:We investigated the reactivity of autoantibodies in plasma pools from 15 anti-CCP positive and 10 anti-CCP negative RA patients and 10 healthy donors against more than 1600 human proteins in native configuration using the Immunome high-density protein microarray.Results:We identified 86 native proteins that were recognized by IgG antibodies from anti-CCP positive RA patients and 76 native proteins recognized by IgG antibodies from anti-CCP negative RA patients, but not by antibodies from healthy donors. Examples of proteins recognized by both patient subgroups are calcium/calmodulin-dependent protein kinase type II subunits, histone deacetylases, keratin, and vimentin. Reactivity against the ribonucleic protein SSB was observed in anti-CCP negative RA patients only.Conclusion:Several human proteins in their native conformation are recognized by autoantibodies from anti-CCP positive as well as anti-CCP negative RA patients. In general, anti-CCP positive patients had higher autoantibody activity than anti-CCP negative patients and healthy donors.References:[1] Konig, M.F., Giles, J.T., Nigrovic, P.A., Andrade, F., 2016. Antibodies to native and citrullinated RA33 (hnRNP A2/B1) challenge citrullination as the inciting principle underlying loss of tolerance in rheumatoid arthritis. Ann. Rheum. Dis. 75, 2022–2028.[2] Zheng, Z., Mergaert, A.M., Fahmy, L.M., Bawadekar, M., Holmes, C.L., Ong, I.M., Bridges, A.J., Newton, M.A., Shelef, M.A., 2019. Disordered Antigens and Epitope Overlap Between Anti-Citrullinated Protein Antibodies and Rheumatoid Factor in Rheumatoid Arthritis. Arthritis Rheumatol. art.41074.[3] Sirotti, S., Generali, E., Ceribelli, A., Isailovic, N., De Santis, M., Selmi, C., 2017. Personalized medicine in rheumatology: the paradigm of serum autoantibodies. Autoimmun. Highlights 8.Acknowledgments :The Department of Clinical Immunology at Rigshospitalet Copenhagen is acknowledged for providing the healthy donor blood. The study is part of the PROCIT study financed by the Danish Council for Independent Research (grant no. DFF - 7016-00233). Moreover, the Obelske Family Foundation, the Svend Andersen Foundation, the Spar Nord Foundation and the Danish National Mass Spectrometry Platform for Functional Proteomics (PRO-MS; grant no. 5072-00007B) are acknowledged for grants to the analytical platform are acknowledged for the funding to enabling parts of this study.Disclosure of Interests:Thomas B.G. Poulsen: None declared, Dres Damgaard: None declared, Malene Møller Jørgensen: None declared, Ladislav Senolt: None declared, Jonathan Blackburn Shareholder of: Sengenics Corporation, Consultant of: Director of Sengenics Corporation, Employee of: Director of Sengenics Corporation, Claus Henrik Nielsen: None declared, Allan Stensballe: None declared

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Identification of potential autoantigens in anti-CCP-positive and anti-CCP-negative rheumatoid arthritis using citrulline-specific protein arrays

Scientific Reports ◽

10.1038/s41598-021-96675-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Thomas B. G. Poulsen ◽

Dres Damgaard ◽

Malene M. Jørgensen ◽

Ladislav Senolt ◽

Jonathan M. Blackburn ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Protein Microarray ◽

Specific Protein ◽

Immune Reactivity ◽

Igg Antibodies ◽

Native Proteins ◽

Array Technology ◽

Citrullinated Proteins ◽

Folded Proteins

AbstractThe presence or absence of autoantibodies against citrullinated proteins (ACPAs) distinguishes two main groups of rheumatoid arthritis (RA) patients with different etiologies, prognoses, disease severities, and, presumably, disease pathogenesis. The heterogeneous responses of RA patients to various biologics, even among ACPA-positive patients, emphasize the need for further stratification of the patients. We used high-density protein array technology for fingerprinting of ACPA reactivity. Identification of the proteome recognized by ACPAs may be a step to stratify RA patients according to immune reactivity. Pooled plasma samples from 10 anti-CCP-negative and 15 anti-CCP-positive RA patients were assessed for ACPA content using a modified protein microarray containing 1631 different natively folded proteins citrullinated in situ by protein arginine deiminases (PADs) 2 and PAD4. IgG antibodies from anti-CCP-positive RA plasma showed high-intensity binding to 87 proteins citrullinated by PAD2 and 99 proteins citrullinated by PAD4 without binding significantly to the corresponding native proteins. Curiously, the binding of IgG antibodies in anti-CCP-negative plasma was also enhanced by PAD2- and PAD4-mediated citrullination of 29 and 26 proteins, respectively. For only four proteins, significantly more ACPA binding occurred after citrullination with PAD2 compared to citrullination with PAD4, while the opposite was true for one protein. We demonstrate that PAD2 and PAD4 are equally efficient in generating citrullinated autoantigens recognized by ACPAs. Patterns of proteins recognized by ACPAs may serve as a future diagnostic tool for further subtyping of RA patients.

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Identification of Novel Native Autoantigens in Rheumatoid Arthritis

Biomedicines ◽

10.3390/biomedicines8060141 ◽

2020 ◽

Vol 8 (6) ◽

pp. 141 ◽

Cited By ~ 1

Author(s):

Thomas B. G. Poulsen ◽

Dres Damgaard ◽

Malene Møller Jørgensen ◽

Ladislav Senolt ◽

Jonathan M. Blackburn ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

High Density ◽

Protein Array ◽

Post Translational Modification ◽

Native Proteins ◽

Healthy Donors ◽

Array Technology ◽

Human Proteins ◽

Patient Subgroups ◽

Citrullinated Peptide

The majority of patients diagnosed with rheumatoid arthritis (RA) have developed autoantibodies against neoepitopes in proteins that have undergone post-translational modification, e.g., citrullination or carbamylation. There is growing evidence of their molecular relevance and their potential utility to improve diagnosis, patient stratification, and prognosis for precision medicine. Autoantibodies reacting to native proteins may also have a role in RA pathogenesis, however, their reactivity patterns remain much less studied. We hypothesized that a high-density protein array technology could shed light onto the normal and disease-related autoantibodies produced in healthy and RA patient subgroups. In an exploratory study, we investigated the global reactivity of autoantibodies in plasma pools from 15 anti-cyclic citrullinated peptide (CCP)-positive and 10 anti-CCP-negative RA patients and 10 healthy donors against more than 1600 native and unmodified human proteins using a high-density protein array. A total of 102 proteins recognized by IgG autoantibodies were identified, hereof 86 were recognized by antibodies from CCP-positive RA patients and 76 from anti-CCP-negative RA patients, but not by antibodies from healthy donors. Twenty-four of the identified autoantigens have previously been identified in synovial fluid. Multiple human proteins in their native conformation are recognized by autoantibodies from anti-CCP-positive as well as anti-CCP-negative RA patients.

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Distinct Mechanisms Involving Diverse Histone Deacetylases Repress Expression of the Two Gonadotropin β-Subunit Genes in Immature Gonadotropes, and Their Actions Are Overcome by Gonadotropin-Releasing Hormone

Molecular and Cellular Biology ◽

10.1128/mcb.00248-07 ◽

2007 ◽

Vol 27 (11) ◽

pp. 4105-4120 ◽

Cited By ~ 54

Author(s):

Stefan Lim ◽

Min Luo ◽

Mingshi Koh ◽

Meng Yang ◽

Mohammed Nizam bin Abdul Kadir ◽

...

Keyword(s):

Histone Deacetylases ◽

Reproductive Function ◽

Gonadotropin Releasing Hormone ◽

Β Subunit ◽

Releasing Hormone ◽

Calcium Calmodulin Dependent ◽

Gnrh Release ◽

Dependent Protein ◽

Reproductive Cycles ◽

Class Iia Hdacs

ABSTRACT The gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are produced in the embryonic pituitary in response to delivery of the hypothalamic gonadotropin releasing hormone (GnRH). GnRH has a pivotal role in reestablishing gonadotropin levels at puberty in primates, and for many species with extended reproductive cycles, these are reinitiated in response to central nervous system-induced GnRH release. Thus, a clear role is evident for GnRH in overcoming repression of these genes. Although the mechanisms through which GnRH actively stimulates LH and FSH β-subunit (FSHβ) gene transcription have been described in some detail, there is currently no information on how GnRH overcomes repression in order to terminate reproductively inactive stages. We show here that GnRH overcomes histone deacetylase (HDAC)-mediated repression of the gonadotropin β-subunit genes in immature gonadotropes. The repressive factors associated with each of these genes comprise distinct sets of HDACs and corepressors which allow for differentially regulated derepression of these two genes, produced in the same cell by the same regulatory hormone. We find that GnRH activation of calcium/calmodulin-dependent protein kinase I (CaMKI) plays a crucial role in the derepression of the FSHβ gene involving phosphorylation of several class IIa HDACs associated with both the FSHβ and Nur77 genes, and we propose a model for the mechanisms involved. In contrast, derepression of the LH β-subunit gene is not CaMK dependent. This demonstration of HDAC-mediated repression of these genes could explain the temporal shut-down of reproductive function at certain periods of the life cycle, which can easily be reversed by the actions of the hypothalamic regulatory hormone.

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Novel autoantibodies identified in ACPA-negative rheumatoid arthritis

Annals of the Rheumatic Diseases ◽

10.1136/annrheumdis-2020-218460 ◽

2021 ◽

pp. annrheumdis-2020-218460

Author(s):

Ketian Li ◽

Wenxiu Mo ◽

Lijun Wu ◽

Xunyao Wu ◽

Cainan Luo ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Early Diagnosis ◽

Protein Microarray ◽

Healthy Controls ◽

Microarray Technology ◽

Validation And Verification ◽

Human Proteins ◽

Diagnostic Values ◽

Acpa Status ◽

Citrullinated Protein

ObjectivesLack of effective biomarkers in anti-citrullinated protein antibody (ACPA)-negative rheumatoid arthritis (RA) impedes early diagnosis and treatment. This study aimed to identify novel autoantibodies in RA and verify their diagnostic values in ACPA-negative RA based on protein microarray technology.MethodsA total of 1011 sera from 559 RA (276 ACPA-positive and 283 ACPA-negative), 239 disease controls (DCs) and 213 healthy controls (HCs) were collected and sampled on two sequential microarrays and ELISA and western blot (WB) detection, for novel autoantibodies discovery, validation and verification, respectively. The high-density protein microarray printed with a broad spectrum of recombinant human proteins was first employed to screen candidate autoantibodies, then focused microarrays composed of candidate autoantigens were used for validation, followed by ELISA and WB to verify the presence of the most promising candidates in ACPA-negative RA.ResultsNine novel autoantibodies were identified by two sequential microarrays with positivity 17.93%–27.59% and specificities >90% in ACPA-negative RA. Among these, anti-PTX3 and anti-DUSP11 autoantibodies presented with the highest sensitivity and were consistently verified by ELISA and WB. Pooling samples of all cohorts, the positivities of anti-PTX3 and anti-DUSP11 in ACPA-negative RA were 27.56% and 31.80%, respectively, similar to those in ACPA-positive RA, and significantly higher than in HCs (4.69% and 2.35%) and DCs (10.04% and 8.49%) (p<0.0001). Combination of anti-PTX3 with anti-DUSP11 significantly increased the diagnostic sensitivity (38.00%) with specificity of 88.72%, regardless of ACPA status.ConclusionAnti-PTX3 and anti-DUSP11 autoantibodies are newly identified biomarkers for diagnosis of ACPA-negative RA.

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p38 Mitogen-activated Protein Kinase-, Calcium-Calmodulin–dependent Protein Kinase-, and Calcineurin-mediated Signaling Pathways Transcriptionally Regulate Myogenin Expression

Molecular Biology of the Cell ◽

10.1091/mbc.02-02-0016 ◽

2002 ◽

Vol 13 (6) ◽

pp. 1940-1952 ◽

Cited By ~ 54

Author(s):

Qing Xu ◽

Lu Yu ◽

Lanying Liu ◽

Ching Fung Cheung ◽

Xue Li ◽

...

Keyword(s):

Protein Kinase ◽

Signaling Pathways ◽

Histone Deacetylases ◽

Mitogen Activated Protein Kinase ◽

Cis Elements ◽

Dependent Protein Kinase ◽

Calcium Calmodulin Dependent ◽

Mitogen Activated Protein ◽

Rd Cells ◽

Dependent Protein

In this report, we identify myogenin as an important transcriptional target under the control of three intracellular signaling pathways, namely, the p38 mitogen-activated protein kinase- (MAPK), calcium-calmodulin–dependent protein kinase- (CaMK), and calcineurin-mediated pathways, during skeletal muscle differentiation. Three cis-elements (i.e., the E box, myocyte enhancer factor [MEF] 2, and MEF3 sites) in the proximal myogenin promoter in response to these three pathways are defined. MyoD, MEF2s, and Six proteins, the trans-activators bound to these cis-elements, are shown to be activated by these signaling pathways. Our data support a model in which all three signaling pathways act in parallel but nonredundantly to control myogenin expression. Inhibition of any one pathway will result in abolished or reduced myogenin expression and subsequent phenotypic differentiation. In addition, we demonstrate that CaMK and calcineurin fail to activate MEF2s in Rhabdomyosarcoma-derived RD cells. For CaMK, we show its activation in response to differentiation signals and its effect on the cytoplasmic translocation of histone deacetylases 5 are not compromised in RD cells, suggesting histone deacetylases 5 cytoplasmic translocation is necessary but not sufficient, and additional signal is required in conjunction with CaMK to activate MEF2 proteins.

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