The Sjögren’s Syndrome-Associated Autoantigen Ro52 Is an E3 Ligase That Regulates Proliferation and Cell Death

Espinosa, Alexander; Zhou, Wei; Ek, Monica; Hedlund, Marie; Brauner, Susanna; Popovic, Karin; Horvath, Linn; Wallerskog, Therese; Oukka, Mohamed; Nyberg, Filippa; Kuchroo, Vijay K.; Wahren‐Herlenius, Marie

doi:10.4049/jimmunol.176.10.6277

Cited by 153 publications

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“…In this study, we addressed the question whether patient-derived autoantibodies can inhibit the function of their corresponding antigen, as well as the mechanism for such inhibition. For this investigation, we studied the effect of autoantibodies on the autoantigen and immunomodulatory protein, Ro52, which we recently identified as an E3 ubiquitin ligase (7).…”

Section: Discussionmentioning

confidence: 99%

“…Ubiquitination Assays-The ubiquitination assays were performed as described previously (7). In short, 0.50 M MaBPRo52 or MaBP-Ro52 mutant proteins were used in each reaction.…”

Section: Methodsmentioning

confidence: 99%

“…A B30.2 domain is located in the C-terminal region (6). Several TRIM family members, including Ro52, have been identified as E3 ubiquitin ligases involved in the ubiquitination process (7)(8)(9)(10). Ubiquitination is a covalent post-translational modification of proteins by the 76-amino acid residue polypeptide ubiquitin, leading either to proteolysis in the proteasome, internalization from membranes, or functional alteration (11,12).…”

Section: Ro52 (Trim21)mentioning

confidence: 99%

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Anti-Ro52 Autoantibodies from Patients with Sjögren's Syndrome Inhibit the Ro52 E3 Ligase Activity by Blocking the E3/E2 Interface

Espinosa

Hennig

Ambrosi

et al. 2011

Journal of Biological Chemistry

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Ro52 (TRIM21)is an E3 ligase of the tripartite motif family that negatively regulates proinflammatory cytokine production by ubiquitinating transcription factors of the interferon regulatory factor family. Autoantibodies to Ro52 are present in patients with lupus and Sjögren's syndrome, but it is not known if these autoantibodies affect the function of Ro52. To address this question, the requirements for Ro52 E3 ligase activity were first analyzed in detail. Scanning a panel of E2 ubiquitin-conjugating enzymes, we found that UBE2D1-4 and UBE2E1-2 supported the E3 ligase activity of Ro52 and that the E3 ligase activity of Ro52 was dependent on its RING domain. We also found that the N-terminal extensions in the class III E2 enzymes affected their interaction with Ro52. Although the N-terminal extension in UBE2E3 made this E2 enzyme unable to function together with Ro52, the N-terminal extensions in UBE2E1 and UBE2E2 allowed for a functional interaction with Ro52. AntiRo52-positive patient sera and affinity-purified anti-RING domain autoantibodies inhibited the E3 activity of Ro52 in ubiquitination assays. Using NMR, limited proteolysis, ELISA, and Ro52 mutants, we mapped the interactions between Ro52, UBE2E1, and anti-Ro52 autoantibodies. We found that antiRo52 autoantibodies inhibited the E3 ligase activity of Ro52 by sterically blocking the E2/E3 interaction between Ro52 and UBE2E1. Our data suggest that anti-Ro52 autoantibodies binding the RING domain of Ro52 may be actively involved in the pathogenesis of rheumatic autoimmune disease by inhibiting Ro52-mediated ubiquitination.Ro52 (TRIM21) is an interferon-inducible protein frequently targeted by autoantibodies in patients with primary Sjögren's syndrome (SS) 4 and systemic lupus erythematosus (SLE) (1, 2). As a member of the tripartite motif (TRIM) protein family (3), Ro52 is characterized by a RING domain (4), a B-box type 2 motif (5), and a coiled-coil region. A B30.2 domain is located in the C-terminal region (6). Several TRIM family members, including Ro52, have been identified as E3 ubiquitin ligases involved in the ubiquitination process (7-10). Ubiquitination is a covalent post-translational modification of proteins by the 76-amino acid residue polypeptide ubiquitin, leading either to proteolysis in the proteasome, internalization from membranes, or functional alteration (11,12). After activation by a ubiquitin-activating enzyme (E1), ubiquitin is transferred to a ubiquitin-conjugating enzyme (E2) followed by a ubiquitin ligase (E3)-mediated transfer of ubiquitin from the E2 to a target protein (13). Ro52 mediates ubiquitination of several members of the interferon regulatory factor (IRF) transcription factor family, thereby regulating cytokine production (14 -17). Gene disruption of Ro52 leads to increased production of proinflammatory cytokines by embryonic fibroblasts and immune cells after Toll-like receptor activation, suggesting that Ro52 negatively regulates IRF activity (16,17).Autoantibodies to Ro52 can appear years before tissue damage is ...

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Section: Discussionmentioning

confidence: 99%

“…Ubiquitination Assays-The ubiquitination assays were performed as described previously (7). In short, 0.50 M MaBPRo52 or MaBP-Ro52 mutant proteins were used in each reaction.…”

Section: Methodsmentioning

confidence: 99%

Section: Ro52 (Trim21)mentioning

confidence: 99%

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Anti-Ro52 Autoantibodies from Patients with Sjögren's Syndrome Inhibit the Ro52 E3 Ligase Activity by Blocking the E3/E2 Interface

Espinosa

Hennig

Ambrosi

et al. 2011

Journal of Biological Chemistry

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“…A large number of TRIM genes are induced by type I or type II IFNs (e.g., during viral or bacterial infections) (20,21). Interestingly, some TRIM genes are also overexpressed in systemic autoimmune diseases such as systemic lupus erythematosus and Sjögren's syndrome, suggesting that TRIM proteins participate in the pathogenesis of these diseases (22)(23)(24). Trim21 is induced by both type I and type II IFNs and is overexpressed in patients with systemic lupus erythematosus and Sjögren's syndrome compared with healthy controls (23,24).…”

Section: /2mentioning

confidence: 99%

Expression of the Immune Regulator Tripartite-Motif 21 Is Controlled by IFN Regulatory Factors

Sjöstrand

Ambrosi

Brauner

et al. 2013

The Journal of Immunology

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Tripartite-motif 21 (TRIM21) is an E3 ubiquitin ligase that regulates innate immune responses by ubiquitinating IFN regulatory factors (IRFs). TRIM21 is mainly found in hematopoietic cells in which its expression is induced by IFNs during viral. infections and in systemic autoimmune diseases such as systemic lupus erythematosus and Sjögren’s syndrome. However, the exact molecular mechanism by which the expression of the Trim21 gene is regulated is unknown. In this study, we demonstrate that IFNs induce Trim21 expression in immune cells via IRFs and that IFN-α and IFN-β are the most potent inducers of Trim21. A functional IFN-stimulated response element but no conserved IFN-γ–activated site was detected in the promoter of Trim21. IRF1 and IRF2 strongly induced Trim21 expression in an IFN-stimulated response element–dependent manner, whereas IRF4 and IRF8 strongly repressed the IRF1-mediated induction of Trim21. Consistent with this observation, baseline expression of Trim21 was elevated in Irf4−/− cells. TRIM21, IRF1, and IRF2 expression was increased in PBMCs from patients with Sjögren’s syndrome compared with healthy controls. In contrast, IRF4 and IRF8 expression was not increased in PBMCs from patients. The IFN-γ–mediated induction of Trim21 was completely abolished by inhibiting protein synthesis with cycloheximide, and Trim21 expression could not be induced by IFN-γ in Irf1−/− cells, demonstrating that IFN-γ induces Trim21 indirectly via IRF1 and not directly via STAT1 activation. Our data demonstrate that multiple IRFs tightly regulate expression of Trim21 in immune cells, suggesting that a well-controlled expression of the E3 ligase TRIM21 is important for regulation of immune responses.

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“…The asbestos induced SLE-like disease is characterized by the production of AAs that recognize the SSA/Ro52 autoantigen. SSA/Ro52 is a newly characterized RING-finger-type E3 ubiquitin ligase (Espinosa et al 2006;Wada and Kamitani 2006), which in unstimulated cells localizes to the cytoplasm (Ohlsson et al 2002). Autoantibodies against SSA/Ro52 are commonly found in patients with SLE (Hassan et al 2002;Hoffman et al 2004;Popovic et al 2007;Routsias et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Autoantibodies from mice exposed to Libby amphibole asbestos bind SSA/Ro52-enriched apoptotic blebs of murine macrophages

2008

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Asbestos exposure is associated with increased autoimmune responses in humans. For example, in Libby, MT where significant asbestos exposure has occurred due to an asbestos contaminated vermiculite mine near the community, residents have developed increased autoimmune responses compared to an unexposed population. However, the exact mechanism by which Libby amphibole asbestos generates autoimmune responses is unclear. A murine model of amphibole asbestos-induced autoimmunity was recently established, and one of the targets of the autoantibodies was the SSA/ Ro52 autoantigen. The purpose of this study was to determine whether the SSA/Ro52 autoantigen is exposed at the surface of cells as a result of asbestos exposure as a possible mechanism leading to antigenicity. Our results indicate that Libby asbestos induces apoptosis in murine macrophages as determined by phosphatidylserine exposure, cleavage of poly (ADP-ribose) polymerase and morphological changes such as nuclear condensation. Moreover, asbestos induced apoptosis results in the formation of apoptotic cell surface blebs enriched in SSA/Ro52 as determined by confocal microscopy. Most importantly, apoptotic cell surface blebs are recognized by autoantibodies from mice exposed to amphibole asbestos suggesting that these cell surface structures may be antigenic when presented in a pro-inflammatory context. This study supports the hypothesis that the induction of apoptosis plays a key role in environmentally-induced autoimmunity through cell surface exposure of a known autoantigen.

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The Sjögren’s Syndrome-Associated Autoantigen Ro52 Is an E3 Ligase That Regulates Proliferation and Cell Death

Cited by 153 publications

References 44 publications

Anti-Ro52 Autoantibodies from Patients with Sjögren's Syndrome Inhibit the Ro52 E3 Ligase Activity by Blocking the E3/E2 Interface

Anti-Ro52 Autoantibodies from Patients with Sjögren's Syndrome Inhibit the Ro52 E3 Ligase Activity by Blocking the E3/E2 Interface

Expression of the Immune Regulator Tripartite-Motif 21 Is Controlled by IFN Regulatory Factors

Autoantibodies from mice exposed to Libby amphibole asbestos bind SSA/Ro52-enriched apoptotic blebs of murine macrophages

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