Dramatic improvement with colchicine in antihistamine- and omalizumab-resistant chronic spontaneous urticaria.

Chronic spontaneous urticaria (CSU) is defined as the presence of recurrent urticaria, angioedema or both without any specific triggers, which persists for ≥ 6 weeks. Refractory cases to standard therapeutic regimens including antihistamines, immunosuppressants and biologics have been reported. Therefore, it is crucial to evolve novel therapeutic strategies through accumulating refractory CSU cases, which are successfully treated. We here report a refractory case of CSU to antihistamines and omalizumab, which was dramatically improved with colchicine.

Crystalglobulinemia manifesting as chronic arthralgia and acute limb ischemia: A clinical case report.

RATIONALE: Crystalglobulinemia is a rare disease caused by monoclonal immunoglobulins, characterized by irreversible crystallization on refrigeration. It causes systemic symptoms including purpura, arthralgia, and vessel occlusive conditions to be exacerbated by exposure to cold. We report a patient with crystalglobulinemia associated with monoclonal gammopathy of undetermined significance (MGUS) manifesting as chronic arthralgia and recurrent acute arterial occlusion. PRESENTING CONCERNS: A 61-year-old man, who had been diagnosed with MGUS and who had arthralgia of unknown origin, presented with recurrent acute limb ischemia after surgical thromboembolectomy. Refrigeration of his serum formed precipitates that looked like needle-shaped crystals. These crystals did not dissolve with warming, which is not a characteristic of cryoglobulins. Skin biopsy results showed crystal-liked eosinophilic bodies in small vessels and we diagnosed crystalglobulinemia. INTERVENTION AND OUTCOMES: Although he underwent above-knee amputation, he was treated with a bortezomib and dexamethasone-based chemotherapeutic regimen, following lenalidomide maintenance therapy. Finally, he achieved complete remission and serum crystalglobulins diminished. LESSONS: Monoclonal gammopathy, previously diagnosed as MGUS, can cause systemic symptoms and thrombotic conditions by producing pathologic immunoglobulins, such as crystalglobulins. In such situations, MGUS, even when it has not progressed to multiple myeloma, can be a target of aggressive chemotherapy. Crystalglobulinemia should be considered for patients with monoclonal gammopathy manifesting as systemic and thrombotic symptoms exacerbated by cooling.

RNF168 and USP10 regulate topoisomerase IIα function via opposing effects on its ubiquitylation.

Topoisomerase IIα (TOP2α) is essential for chromosomal condensation and segregation, as well as genomic integrity. Here we report that RNF168, an E3 ligase mutated in the human RIDDLE syndrome, interacts with TOP2α and mediates its ubiquitylation. RNF168 deficiency impairs decatenation activity of TOP2α and promotes mitotic abnormalities and defective chromosomal segregation. Our data also indicate that RNF168 deficiency, including in human breast cancer cell lines, confers resistance to the anti-cancer drug and TOP2 inhibitor etoposide. We also identify USP10 as a deubiquitylase that negatively regulates TOP2α ubiquitylation and restrains its chromatin association. These findings provide a mechanistic link between the RNF168/USP10 axis and TOP2α ubiquitylation and function, and suggest a role for RNF168 in the response to anti-cancer chemotherapeutics that target TOP2.

RNF168 ubiquitylates 53BP1 and controls its response to DNA double-strand breaks.

Defective signaling or repair of DNA double-strand breaks has been associated with developmental defects and human diseases. The E3 ligase RING finger 168 (RNF168), mutated in the human radiosensitivity, immunodeficiency, dysmorphic features, and learning difficulties syndrome, was shown to ubiquitylate H2A-type histones, and this ubiquitylation was proposed to facilitate the recruitment of p53-binding protein 1 (53BP1) to the sites of DNA double-strand breaks. In contrast to more upstream proteins signaling DNA double-strand breaks (e.g., RNF8), deficiency of RNF168 fully prevents both the initial recruitment to and retention of 53BP1 at sites of DNA damage; however, the mechanism for this difference has remained unclear. Here, we identify mechanisms that regulate 53BP1 recruitment to the sites of DNA double-strand breaks and provide evidence that RNF168 plays a central role in the regulation of 53BP1 functions. RNF168 mediates K63-linked ubiquitylation of 53BP1 which is required for the initial recruitment of 53BP1 to sites of DNA double-strand breaks and for its function in DNA damage repair, checkpoint activation, and genomic integrity. Our findings highlight the multistep roles of RNF168 in signaling DNA damage.

Ymer acts as a multifunctional regulator in nuclear factor-κB and Fas signaling pathways.

The nuclear factor (NF)-κB family of transcription factors regulates diverse cellular functions, including inflammation, oncogenesis and apoptosis. It was reported that A20 plays a critical role in the termination of NF-κB signaling after activation. Previously, we showed that Ymer interacts and collaborates with A20, followed by degradation of receptor-interacting protein (RIP) and attenuation of NF-κB signaling. Here we show the function of Ymer in regulation of several signaling pathways including NF-κB on the basis of results obtained by using Ymer transgenic (Ymer Tg) mice. Ymer Tg mice exhibited impaired immune responses, including NF-κB and mitogen-activated protein kinase (MAPK) activation, cell proliferation and cytokine production, to tumor necrosis factor (TNF)-α, polyI:C or lipopolysaccharide (LPS) stimulation. Ymer Tg mice were more resistant to LPS-induced septic shock than wild-type mice. Transgene of Ymer inhibited the onset of glomerulonephritis in lpr/lpr mice as an autoimmune disease model. In contrast to the inflammatory immune response to LPS, Fas-mediated cell death was strongly induced in liver cells of Ymer Tg mice in which Ymer is abundantly expressed. These findings suggest that Ymer acts as a regulator downstream of several receptors and that Ymer functions as a positive or negative regulator in a signaling pathway-dependent manner.

Role of Pirh2 in mediating the regulation of p53 and c-Myc.

Ubiquitylation is fundamental for the regulation of the stability and function of p53 and c-Myc. The E3 ligase Pirh2 has been reported to polyubiquitylate p53 and to mediate its proteasomal degradation. Here, using Pirh2 deficient mice, we report that Pirh2 is important for the in vivo regulation of p53 stability in response to DNA damage. We also demonstrate that c-Myc is a novel interacting protein for Pirh2 and that Pirh2 mediates its polyubiquitylation and proteolysis. Pirh2 mutant mice display elevated levels of c-Myc and are predisposed for plasma cell hyperplasia and tumorigenesis. Consistent with the role p53 plays in suppressing c-Myc-induced oncogenesis, its deficiency exacerbates tumorigenesis of Pirh2(-/-) mice. We also report that low expression of human PIRH2 in lung, ovarian, and breast cancers correlates with decreased patients' survival. Collectively, our data reveal the in vivo roles of Pirh2 in the regulation of p53 and c-Myc stability and support its role as a tumor suppressor.

Caspase-8 inactivation in T cells increases necroptosis and suppresses autoimmunity in Bim-/- mice.

Dysregulation of either the extrinsic or intrinsic apoptotic pathway can lead to various diseases including immune disorders and cancer. In addition to its role in the extrinsic apoptotic pathway, caspase-8 plays nonapoptotic functions and is essential for T cell homeostasis. The pro-apoptotic BH3-only Bcl-2 family member Bim is important for the intrinsic apoptotic pathway and its inactivation leads to autoimmunity that is further exacerbated by loss of function of the death receptor Fas. We report that inactivation of caspase-8 in T cells of Bim(-/-) mice restrained their autoimmunity and extended their life span. We show that, similar to caspase-8(-/-) T cells, Bim(-/-) T cells that also lack caspase-8 displayed elevated levels of necroptosis and that inhibition of this cell death process fully rescued the survival and proliferation of these cells. Collectively, our data demonstrate that inactivation of caspase-8 suppresses the survival and proliferative capacity of Bim(-/-) T cells and restrains autoimmunity in Bim(-/-) mice.

Inactivation of chk2 and mus81 leads to impaired lymphocytes development, reduced genomic instability, and suppression of cancer.

Chk2 is an effector kinase important for the activation of cell cycle checkpoints, p53, and apoptosis in response to DNA damage. Mus81 is required for the restart of stalled replication forks and for genomic integrity. Mus81(Δex3-4/Δex3-4) mice have increased cancer susceptibility that is exacerbated by p53 inactivation. In this study, we demonstrate that Chk2 inactivation impairs the development of Mus81(Δex3-4/Δex3-4) lymphoid cells in a cell-autonomous manner. Importantly, in contrast to its predicted tumor suppressor function, loss of Chk2 promotes mitotic catastrophe and cell death, and it results in suppressed oncogenic transformation and tumor development in Mus81(Δex3-4/Δex3-4) background. Thus, our data indicate that an important role for Chk2 is maintaining lymphocyte development and that dual inactivation of Chk2 and Mus81 remarkably inhibits cancer.

Genomic instability, defective spermatogenesis, immunodeficiency, and cancer in a mouse model of the RIDDLE syndrome.

Eukaryotic cells have evolved to use complex pathways for DNA damage signaling and repair to maintain genomic integrity. RNF168 is a novel E3 ligase that functions downstream of ATM,γ-H2A.X, MDC1, and RNF8. It has been shown to ubiquitylate histone H2A and to facilitate the recruitment of other DNA damage response proteins, including 53BP1, to sites of DNA break. In addition, RNF168 mutations have been causally linked to the human RIDDLE syndrome. In this study, we report that Rnf168(-/-) mice are immunodeficient and exhibit increased radiosensitivity. Rnf168(-/-) males suffer from impaired spermatogenesis in an age-dependent manner. Interestingly, in contrast to H2a.x(-/-), Mdc1(-/-), and Rnf8(-/-) cells, transient recruitment of 53bp1 to DNA double-strand breaks was abolished in Rnf168(-/-) cells. Remarkably, similar to 53bp1 inactivation, but different from H2a.x deficiency, inactivation of Rnf168 impairs long-range V(D)J recombination in thymocytes and results in long insertions at the class-switch junctions of B-cells. Loss of Rnf168 increases genomic instability and synergizes with p53 inactivation in promoting tumorigenesis. Our data reveal the important physiological functions of Rnf168 and support its role in both γ-H2a.x-Mdc1-Rnf8-dependent and -independent signaling pathways of DNA double-strand breaks. These results highlight a central role for RNF168 in the hierarchical network of DNA break signaling that maintains genomic integrity and suppresses cancer development in mammals.

Plasma gelsolin facilitates interaction between ß2 glycoprotein I and α5ß1 integrin.

Antiphospholipid syndrome (APS) is characterized by thrombosis and the presence of antiphospholipid antibodies (aPL) that directly recognizes plasma ß(2)-glycoprotein I (ß(2) GPI). Tissue factor (TF), the major initiator of the extrinsic coagulation system, is induced on monocytes by aPL in vitro, explaining in part the pathophysiology in APS. We previously reported that the mitogen-activated protein kinase (MAPK) pathway plays an important role in aPL-induced TF expression on monocytes. In this study, we identified plasma gelsolin as a protein associated with ß(2) GPI by using immunoaffinity chromatography and mass spectrometric analysis. An in vivo binding assay showed that endogenous ß(2) GPI interacts with plasma gelsolin, which binds to integrin a(5) ß(1) through fibronectin. The tethering of ß(2) GPI to monoclonal anti-ß(2) GPI autoantibody on the cell surface was enhanced in the presence of plasma gelsolin. Immunoblot analysis demonstrated that p38 MAPK protein was phosphorylated by monoclonal anti-ß(2) GPI antibody treatment, and its phosphorylation was attenuated in the presence of anti-integrin a(5) ß(1) antibody. Furthermore, focal adhesion kinase, a downstream molecule of the fibronectin-integrin signalling pathway, was phosphorylated by anti-ß(2) GPI antibody treatment. These results indicate that molecules including gelsolin and integrin are involved in the anti-ß(2) GPI antibody-induced MAPK pathway on monocytes and that integrin is a possible therapeutic target to modify a prothrombotic state in patients with APS.

DNA double-strand break signaling and human disorders.

DNA double-strand breaks are among the most serious types of DNA damage and their signaling and repair is critical for all cells and organisms. The repair of both induced and programmed DNA breaks is fundamental as demonstrated by the many human syndromes, neurodegenerative diseases, immunodeficiency and cancer associated with defective repair of these DNA lesions. Homologous recombination and non-homologous end-joining pathways are the two major DNA repair pathways responsible for mediating the repair of DNA double-strand breaks. The signaling of DNA double-strand breaks is critical for cells to orchestrate the repair pathways and maintain genomic integrity. This signaling network is highly regulated and involves a growing number of proteins and elaborated posttranslational modifications including phosphorylation and ubiquitylation. Here, we highlight the recent progress in the signaling of DNA double-strand breaks, the major proteins and posttranslational modifications involved and the diseases and syndromes associated with impaired signaling of these breaks.

The effects of phosphatidylserine-dependent antiprothrombin antibody on thrombin generation.

OBJECTIVE: Antibodies to prothrombin (APTs) and to beta2-glycoprotein I are the major autoantibodies responsible for lupus anticoagulant (LAC) activity. APTs comprise antibodies against prothrombin alone as well as antibodies against phosphatidylserine/prothrombin complex (anti-PS/PT), the latter being highly associated with the antiphospholipid syndrome (APS). The effect of anti-PS/PT on thrombin generation has not been elucidated, and the paradoxical effect of LAC (an anticoagulant in vitro, but a procoagulant in vivo) remains an enigma. The purpose of this study was to investigate the effects of anti-PS/PT on thrombin generation and to examine the LAC paradox. METHODS: We evaluated 36 anti-PS/PT-positive APS patients and 127 healthy subjects. Markers of in vivo thrombin/fibrin generation, including prothrombin fragment F1+2, thrombin-antithrombin III complex, soluble fibrin monomer, D-dimer, and fibrin degradation products, were measured. Mouse monoclonal anti-PS/PT antibody 231D was established, and its effects on in vitro thrombin generation were investigated by chromogenic assay. RESULTS: Significantly elevated levels of markers of thrombin/fibrin generation were observed in anti-PS/PT-positive patients, regardless of the presence or absence of anticardiolipin antibodies, as compared with healthy subjects. In the presence of low concentrations of human activated factor V (FVa), monoclonal antibody 231D increased thrombin generation in a dose-dependent manner. In contrast, when high concentrations of FVa were added, monoclonal antibody 231D decreased thrombin generation. Under a constant concentration of FVa, a high concentration of human FXa enhanced the effect of 231D. CONCLUSION: The presence of anti-PS/PT greatly correlated with increased thrombin generation in APS patients. The in vitro effects of monoclonal antibody 231D on thrombin generation are "biaxial" according to the FVa/FXa balance. These data may serve as a clue to understanding the LAC paradox and the thrombogenic properties of anti-PS/PT.

Immunological reconstitution after autologous hematopoietic stem cell transplantation in patients with systemic sclerosis: relationship between clinical benefits and intensity of immunosuppression.

OBJECTIVE: To analyze the relationship between clinical benefits and immunological changes in patients with systemic sclerosis (SSc) treated with autologous hematopoietic stem cell transplantation (HSCT). METHODS: Ten patients with SSc were treated with high-dose cyclophosphamide followed by highly purified CD34+ cells (n=5) or unpurified grafts (n=5). Two groups of patients were retrospectively constituted based on their clinical response (good responders, n=7; and poor responders, n=3). As well as clinical findings, immunological reconstitution through autologous HSCT was assessed by fluorescence-activated cell sorter analysis, quantification of signal joint T cell receptor rearrangement excision circles (sjTREC), reflecting the thymic function, and foxp3, a key gene of regulatory T cells, mRNA levels. RESULTS: Patients' clinical and immunological findings were similar between good and poor responders, or CD34-purified and unpurified groups at inclusion. The sjTREC values were significantly suppressed at 3 months after autologous HSCT in good responders compared with poor responders (p=0.0152). Reconstitution of CD4+CD45RO- naive T cells was delayed in good responders compared with poor responders. The phenotype of other lymphocytes, cytokine production in T cells, and foxp3 gene expression levels after autologous HSCT did not correlate with clinical response in good or poor responders. Clinical and immunological findings after autologous HSCT were similar between CD34-purified and unpurified groups. CONCLUSION: Our results suggest that immunosuppression intensity, sufficient to induce transient suppression of thymic function, is attributable to the feasible clinical response in patients with SSc treated with autologous HSCT. Appropriate monitoring of sjTREC values may predict clinical benefits in transplanted SSc patients after autologous HSCT.

Inhibition of NF-kappaB signaling via tyrosine phosphorylation of Ymer.

Cytoplasmic zinc finger protein A20 functionally dampens inflammatory signals and apoptosis via inhibition of NF-kappaB activation. We have reported that Ymer interacts with A20 and lysine (K)-63-linked polyubiquitin chain and that Ymer inhibits NF-kappaB signaling in collaboration with A20. It has also been reported that Ymer is phosphorylated by EGF stimulation. We found that Ymer was considerably phosphorylated on tyrosine residues also via Src family kinases such as Lck. A luciferase reporter assay showed that mutation of tyrosines on Ymer (YmerY217/279/304F) results in loss of the inhibitory activity for NF-kappaB signaling. Furthermore, a soft agar colony formation assay showed that the combination of SrcY527F and YmerY217/279/304F has no ability for anchorage-independent growth, suggesting that tyrosine phosphorylation of Ymer is important for inhibition of the NF-kappaB-mediated apoptotic pathway. These findings demonstrate that Ymer is likely to be a negative regulator for the NF-kappaB signaling pathway.

The E3 ligase TTC3 facilitates ubiquitination and degradation of phosphorylated Akt.

The serine threonine kinase Akt is a core survival factor that underlies a variety of human diseases. Although regulatory phosphorylation and dephosphorylation have been well documented, the other posttranslational mechanisms that modulate Akt activity remain unclear. We show here that tetratricopeptide repeat domain 3 (TTC3) is an E3 ligase that interacts with Akt. TTC3 contains a canonical RING finger motif, a pair of tetratricopeptide motifs, a putative Akt phosphorylation site, and nuclear localization signals, and is encoded by a gene within the Down syndrome (DS) critical region on chromosome 21. TTC3 is an Akt-specific E3 ligase that binds to phosphorylated Akt and facilitates its ubiquitination and degradation within the nucleus. Moreover, DS cells exhibit elevated TTC3 expression, reduced phosphorylated Akt, and accumulation in the G(2)M phase, which can be reversed by TTC3 siRNA or Myr-Akt. Thus, interaction between TTC3 and Akt may contribute to the clinical symptoms of DS.