Complement Regulatory Protein CD59 Research Articles

Complement regulatory protein CD46 promotes bladder cancer metastasis through activation of MMP9.

CD46, a transmembrane protein known for protecting cells from complement‑mediated damage, is frequently dysregulated in various types of cancer. Its overexpression in bladder cancers safeguards the cancer cells against both complement and antibody‑mediated cytotoxicity. The present study explored a new role of CD46 in facilitating cancer cell invasion and metastasis, examining its regulatory effect on matrix metalloproteases (MMPs) and their effect on the metastatic capability of bladder cancer cells. Specifically, CD46 alteration positively influenced MMP9 expression, but not MMP2, in several bladder cancer cell lines. Furthermore, CD46 overexpression triggered phosphorylation of p38 MAPK and protein kinase B (AKT), leading to enhanced activator protein 1 (AP‑1) activity via c‑Jun upregulation. The inhibition of p38 or AKT pathways attenuated the CD46‑induced MMP9 and AP‑1 upregulation, indicating that the promotion of MMP9 by CD46 involved activating both p38 MAPK and AKT. Functionally, the upregulation of MMP9 by CD46 translated to increased migratory and invasive capabilities of bladder cancer cells, as well as enhanced in vivo metastasis. Overall, the present study revealed a novel role for CD46 as a metastasis promoter through MMP9 activation in bladder cancers and highlighted the regulatory mechanism of CD46‑mediated MMP9 promotion via p38 MAPK and AKT activation.

The complement regulatory protein CD46 serves as a novel biomarker for cervical cancer diagnosis and prognosis evaluation.

CD46 has been revealed to be a key factor in malignant transformation and cancer treatment. However, the clinical significance of CD46 in cervical cancer remains unclear, and this study aimed to evaluate its role in cervical cancer diagnosis and prognosis evaluation. A total of 180 patients with an initial diagnosis of cervical cancer were enrolled at Taizhou Hospital of Zhejiang Province, China. The plasma levels of soluble CD46 (sCD46) and the expression of membrane-bound CD46 (mCD46) were detected by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC), respectively. CD46 was found to be significantly upregulated in cervical cancer tissues vs. normal tissues, while no CD46 staining was detected in paired adjacent noncancerous tissues. CD46 staining was more pronounced in cancer cells than in stromal cells in situ (in tissues). Moreover, the plasma levels of sCD46 were able to some extent discriminate between cancer patients and healthy women (AUC=0.6847, 95% CI:0.6152-0.7541). Analysis of Kaplan-Meier survival curves revealed that patients with low CD46 expression had slightly longer overall survival (OS) than patients with high CD46 expression in the tumor microenvironment, but no significant difference. Univariate Cox regression analysis revealed that CD46 (P=0.034) is an independent risk factor for OS in cervical cancer patients. The present study demonstrated that cervical cancer patients exhibit aberrant expression of CD46, which is closely associated with a poor prognosis, suggesting that CD46 plays a key role in promoting cervical carcinogenesis and that CD46 could serve as a promising potential target for precision therapy for cervical cancer.

ARTICULAR CHONDROCYTES FROM DIABETIC AND NON-DIABETIC RATS EXPOSED TO NORMO- OR HYPERGLYCAEMIA RESPOND DIFFERENTIALLY TO THE COMPLEMENT SPLIT FRAGMENT ANAPHYLATOXIN C5A AND TNFA

Osteoarthritis (OA) and diabetis mellitus type 2 (DMT2) are pathogenetically linked. Complement dysregulation contributes to OA and could be involved in DMT2. The inflammatory anaphylatoxin C5a is released during complement activation. This study aims to understand the specific responses of chondrocytes isolated from diabetic and non-diabetic rats exposed to C5a and/or the proinflammatory cytokine TNFα in vitro dependent on the glucose supply. Articular chondrocytes of adult Zucker Diabetic Fatty (ZDF) rats (homozygous: fa/fa, diabetic, heterozygous: fa/+, lean controls) were exposed to 10 ng/mL TNFα and 25 ng/mL C5a alone or in combination, both, under normo- (NG, 1 g/L glucose) and hyperglycemic (HG, 4.5 g/L glucose) conditions (4 or 24 h). Chondrocyte survival, metabolic activity and gene expression of collagen type 2, suppressors of cytokine signaling (SOCS)1, −3 and anti-oxidative hemoxygenase-1 (HMOX1) were assessed. The complement regulatory protein CD46 and cell nuclei sizes were analyzed. Chondrocyte vitality remained unaffected by the treatment. Metabolic activity was impaired in chondrocytes of non-diabetic rats under HG conditions. Collagen type 2 transcription was suppressed by TNFα under HG condition in chondrocytes from nondiabetic donors and under both conditions in those of DMT2 rats (24 h)Except for DMT2 chondrocytes under HG (4 h), HMOX1 was generally induced by TNFα +/- C5a (NG, HG). C5a elevated HMOX1 only in chondrocytes of controls. The SOCS1/3 genes were increased by TNFα (NG, diabetic, non diabetic, 4 and 24 h). This could also be observed in chondrocytes of diabetic, but not of lean rats (24 h, HG). At 4 h, C5a induced SOCS1 only in non diabetic chondrocytes (NG, HG). Cytoprotective CD46 protein was suppressed by TNFα under NG condition. Nuclear volumes of chondrocyte were lower in chondrocytes from DMT2 rats compared to those from controls. The differential response suggests that chondrocytes are irreversibly compromised by DMT2.Achnowledgement: The authors are grateful for the support by the “Stiftung Edoprothetik (S 04/21)”

Complement Regulatory Protein CD46 Manifests a Unique Role in Promoting the Migration of Bladder Cancer Cells.

CD46 is a membrane-bound complement regulatory protein (mCRP) possessing a regulatory role with the complement system. CD46 protects the host cells from damage by complement. Expression of CD46 is also highly maintained in many cancers, including bladder cancers, and thus functions as a receptor for many cancer therapeutic viruses. In this study we report a unique role of CD46 as a progression factor of cancer cells in bladder cancers. Resulting data from a DNA microarray using CD46-altered HT1376 bladder cancers demonstrated a pool of target genes, including complement C3 α chain (C3α), matrix Gla protein (MGP), AFAP-AS1, follicular dendritic cell secreted protein (FDCSP), MAM domain containing 2 (MAMDC2), gamma-aminobutyric acid A receptor pi (GABRP), transforming growth factor, beta-induced (TGFBI), a family of cytochrome P450 (CYP24A1), sialic acid binding Ig-like lectin 6 (SIGLEC6), metallothionein 1E (MT1E), and several members of cytokeratins. Subsequent studies using quantitative RT-PCR and Western blot analyses confirmed CD46-mediated regulation of C3α, MGP, and keratin 13 (KRT13). MGP and KRT13 are known to be involved in cell migration and cancer cell metastasis. A cell migration assay demonstrated that CD46 enhanced migratory potential of bladder cancer cells. Taken all together, this report demonstrated that CD46 is generally overexpressed in bladder cancers and plays a unique role in the promotion of cancer cell migration. Further detailed studies are needed to be performed to clarify the action mechanism of CD46 and its application to cancer therapeutics.

CD59-Regulated Ras Compartmentalization Orchestrates Antitumor T-cell Immunity.

T cell-mediated immunotherapy represents a promising strategy for cancer treatment; however, it has achieved satisfactory clinical responses in only a limited population. Thus, a broader view of the T-cell immune response is required. The Ras/MAPK pathway operates in many important signaling cascades and regulates multiple cellular activities, including T-cell development, proliferation, and function. Herein, we found that the typical membrane-bound complement regulatory protein CD59 is located intracellularly in T cells and that the intracellular form is increased in the T cells of patients with cancer. When intracellular CD59 is abundant, it facilitates Ras transport to the inner plasma membrane via direct interaction; in contrast, when CD59 is insufficient or deficient, Ras is arrested in the Golgi, thus enhancing Ras/MAPK signaling and T-cell activation, proliferation, and function. mCd59ab deficiency almost completely abolished tumor growth and metastasis in tumor-bearing mice, in which CD4+ and CD8+ T cells were significantly increased compared with their proportions in wild-type littermates, and their proportions were inversely correlated with tumor growth. Using bone marrow transplantation and CD4+ and CD8+ T-cell depletion assays, we further demonstrated the critical roles of these cells in the potent antitumor activity induced by mCd59ab deficiency. Reducing CD59 expression also enhanced MAPK signaling and T-cell activation in human T cells. Therefore, the subcellular compartmentalization of Ras regulated by intracellular CD59 provides spatial selectivity for T-cell activation and a potential T cell-mediated immunotherapeutic strategy.

Identification and functional characterization of complement regulatory protein CD59 in golden pompano (Trachinotus ovatus)

CD59, one of the essential inhibitors of the complement membrane attack complex (MAC), plays a crucial role in regulation of complement activation. In this study, we cloned and identified the CD59 gene (named ToCD59) of golden pompano (Trachinotus ovatus). The ORF sequence of ToCD59 is 357 bp long encoding 118 amino acids with a molecular weight of 13.09 kDa. Prediction of protein domains showed that ToCD59 contained an Lu domain and a C-terminal glycosylphosphatidylinositol (GPI) partial anchor. Homology comparisons indicated that ToCD59 shared the high sequence similarity with other fish CD59. RT-qPCR analysis showed that ToCD59 was expressed in all tested healthy tissues of golden pompano, with the highest level of expression in the brain. After stimulation with bacteria, ToCD59 expression levels were significantly up-regulated in head kidney, liver, gill and brain, but down-regulated in spleen. Subcellular localization results showed that ToCD59 localized to the cytoplasm of A549 cells. The hemolytic activity analysis showed that rToCD59 might have complement inhibitory activity through the alternative complement pathway. In addition, antibacterial test showed that rToCD59 had antibacterial ability against S. agalactiae and V. alginolyticus in vitro. These results suggest that ToCD59 might play an important role in the immune response against pathogens, which would provide basic information for elucidating the functional evolutionary history of complement system in teleost.

Exploring complement-dependent cytotoxicity by rituximab isotypes in 2D and 3D-cultured B-cell lymphoma

BackgroundThe therapeutic IgG1 anti-CD20 antibody, rituximab (RTX), has greatly improved prognosis of many B-cell malignancies. Despite its success, resistance has been reported and detailed knowledge of RTX mechanisms are lacking. Complement-dependent cytotoxicity (CDC) is one important mode of action of RTX. The aim of this study was to systematically evaluate factors influencing complement-mediated tumor cell killing by RTX.MethodsDifferent RTX isotypes, IgG1, IgG3, IgA1 and IgA2 were evaluated and administered on four human CD20+ B-cell lymphoma cell lines, displaying diverse expression of CD20 and complement-regulatory protein CD59. Complement activation was assessed on lymphoma cells grown in 2 and 3-dimensional (3D) culture systems by trypan blue exclusion. CDC in 3D spheroids was additionally analyzed by Annexin V and propidium iodide staining by flow cytometry, and confocal imaging. Anti-CD59 antibody was used to evaluate influence of CD59 in RTX-mediated CDC responses. Statistical differences were determined by one-way ANOVA and Tukey post hoc test.ResultsWe found that 3 out of 4 lymphomas were sensitive to RTX-mediated CDC when cultured in 2D, while 2 out of 4 when grown in 3D. RTX-IgG3 had the greatest CDC potential, followed by clinical standard RTX-IgG1 and RTX-IgA2, whereas RTX-IgA1 displayed no complement activation. Although the pattern of different RTX isotypes to induce CDC were similar in the sensitive lymphomas, the degree of cell killing differed. A greater CDC activity was seen in lymphoma cells with a higher CD20/CD59 expression ratio. These lymphomas were also sensitive to RTX when grown in 3D spheroids, although the CDC activity was substantially reduced compared to 2D cultures. Analysis of RTX-treated spheroids demonstrated apoptosis and necrosis essentially in the outer cell-layers. Neutralization of CD59 overcame resistance to RTX-mediated CDC in 2D-cultured lymphoma cells, but not in spheroids.ConclusionsThe results demonstrate that CDC outcome in CD20+ B-cell lymphoma is synergistically influenced by choice of RTX isotype, antigen density, tumor structure, and degree of CD59 expression. Assessment of tumor signatures, such as CD20/CD59 ratio, can be advantageous to predict CDC efficiency of RTX in vivo and may help to develop rational mAbs to raise response rates in patients.

NANOG confers resistance to complement-dependent cytotoxicity in immune-edited tumor cells through up-regulating CD59

Cancer immunoediting drives the adaptation of tumor cells to host immune surveillance. Previously, we have demonstrated that immunoediting driven by cytotoxic T lymphocytes (CTLs) enriches NANOG+ tumor cells with immune-refractory properties. Here, we found that CTL-mediated immune pressure triggered cross-resistance of tumor cells to the complement system, a part of the innate immune system. In this process, NANOG upregulated the membrane-bound complement regulatory protein (mCRP) CD59 through promoter occupancy, thereby contributing to the resistance of tumor cells against complement-dependent cytotoxicity (CDC). Notably, targeting of NANOG sensitized the immune-refractory tumor cells to trastuzumab-mediated CDC. Collectively, our results revealed a possible mechanism through which selection imposed by T-cell based immunotherapy triggered complement-resistant phenotypes in the tumor microenvironment (TME), by establishing a firm molecular link between NANOG and CD59 in immune-edited tumor cells. We believe these results hold important implications for the clinical application of CDC-mediated therapeutic antibody.

Complement Proteins C5/C5a, Cathepsin D and Prolactin in Chondrocytes: A Possible Crosstalk in the Pathogenesis of Osteoarthritis.

Introduction: Both increased activity of the complement system (CS) and the role of the pituitary hormone prolactin (PRL) are implicated in osteoarthritis (OA) pathogenesis. Besides, Cathepsin D (CatD) activity is increased in the context of OA and can exert not only proteolytic but also non-proteolytic effects on cells. For the first time, possible crosstalk between two separate humoral systems: the CS and the PRL hormone systems in chondrocytes are examined together. Methods: Primary human articular chondrocytes (hAC) were stimulated with complement protein C5 (10 µg /mL), PRL (25 ng/mL), CatD (100 ng/mL), or anaphylatoxin C5a (25 ng/mL) for 24 h or 72 h, while unstimulated cells served as controls. In addition, co-stimulations of C5 or PRL with CatD were carried out under the same conditions. The influence of the stimulants on cell viability, cell proliferation, and metabolic activity of hAC, the chondrosarcoma cell line OUMS-27, and endothelial cells of the human umbilical cord vein (HUVEC) was investigated. Gene expression analysis of C5a receptor (C5aR1), C5, complement regulatory protein CD59, PRL, PRL receptor (PRLR), CatD, and matrix metal-loproteinases (MMP)-13 were performed using real-time PCR. Also, collagen type (Col) I, Col II, C5aR1, CD59, and PRL were detected on protein level using immunofluorescence labeling. Results: The stimulation of the hAC showed no significant impairment of the cell viability. C5, C5a, and PRL induced cell growth in OUMS-27 and HUVEC, but not in chondrocytes. CatD, as well as C5, significantly reduced the gene expression of CatD, C5aR1, C5, and CD59. PRLR gene expression was likewise impaired by C5, C5a, and PRL+CatD stimulation. On the protein level, CatD, as well as C5a, decreased Col II as well as C5aR1 synthesis. Conclusions: The significant suppression of the C5 gene expression under the influence of PRL+CatD and that of CD59 via PRL+/−CatD and conversely a suppression of the PRLR gene expression via C5 alone or C5a stimulation indicates an interrelation between the two mentioned systems. In addition, CatD and C5, in contrast to PRL, directly mediate possible negative feedback of their own gene expression.

Membrane complement regulatory protein CD59 in systemic lupus erythematosus and rheumatoid arthritis

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Xenotransplantation Is the Future of Pediatric Cardiac Surgery

Norman Shumway coined the aphorism that “xenotransplantation is the future of transplantation, and always will be.” In this issue of The Annals of Thoracic Surgery, Cleveland and colleagues1 from the University of Alabama give us a glimpse of this future. Nonhuman primates survived for up to 241 days after orthotopic cardiac xenotransplantation from alpha 1-3 galactosyltransferase gene knockout swine expressing human complement regulatory protein CD46 and human thrombomodulin using a clinically feasible immunosuppression regime.

Soluble CD59 in peritoneal dialysis: a potential biomarker for peritoneal membrane function

IntroductionVarious studies have reported the importance of complement regulators in preventing mesothelial damage during peritoneal dialysis (PD). Its assessment, however, is limited in clinical practice due to the lack of easy access to the peritoneal membrane. Recently, a soluble form of the complement regulatory protein CD59 (sCD59) has been described. We therefore aimed to investigate the role of sCD59 in PD.MethodsPlasma sCD59 was measured in 48 PD patients, 41 hemodialysis patients, 15 non-dialysis patients with chronic kidney disease and 14 healthy controls by ELISA (Hycult; HK374-02). Additionally, sCD59 and sC5b-9 were assessed in the peritoneal dialysate.ResultssCD59 and sC5b-9 were detectable in the peritoneal dialysate of all patients, and marginally correlated (r = 0.27, P = 0.06). Plasma sCD59 levels were significantly higher in PD patients than in patients with chronic kidney disease and healthy controls, but did not differ from hemodialysis patients. During follow-up, 19% of PD patients developed peritoneal membrane failure and 27% of PD patients developed loss of residual renal function. In adjusted models, increased sCD59 levels in the dialysate (HR 3.44, 95% CI 1.04–11.40, P = 0.04) and in plasma (HR 1.08, 95% CI 1.01–1.17, P = 0.04) were independently associated with the occurrence of peritoneal membrane failure. Higher plasma levels of sCD59 were also associated with loss of residual renal function (HR 1.10, 95% CI 1.04–1.17, P < 0.001).ConclusionsOur study suggests that sCD59 has potential as a biomarker to predict peritoneal membrane function and loss of residual renal function in PD, thereby offering a tool to improve patient management.Graphic abstract

Complements and allergic asthma

Regulatory T (Treg) cells play a central role in protecting against the development of allergic asthma and interleukin-10 (IL-10) producing T regulatory type 1 (Tr1) cells contribute to the regulation of asthma. Complement regulatory protein CD46 was shown to stimulate the development of IL-10 producing Tr1 cells. Crosslinking of CD46 during CD4+ T cell priming induces production of large amount of IL-10 and granzyme B. These CD46-induced regulatory T cells (Tr1) does not require pre-existing basal expression of FoxP3. Through local IL-10 and granzyme B secretion, such Tr1 cell could control T-cell-mediated inflammation. In asthmatic patients, we found that diminished IL-10, granzyme B, and CCR 4 expression from CD3/CD46-activated Tr1 cells. CD3/CD46-activated Tr1 cells from asthma patients co-cultured with BEAS-2B cells suppressed dermatophagoides pteronyssinus 2 (Der p 2)-induced nuclear factor-κB/p65 by cell contact inhibition. Decreased interaction of CD3/CD46-activated Tr1 and BEAS-2B cells from asthmatics was associated with downregulation of phosphorylation of protein kinase B expression. Decreased interaction between CD46-mediated Tr1 and lung epithelial cells with less IL-10 and granzyme B production may contribute to airway inflammation in allergic asthma. Der p specific immunotherapy enhances the suppressive function of IL-10 in CD46-mediated Tr1 cell from asthmatic patients and suppresses airway inflammation in these patients. Based on these results, it might be possible to design therapeutic strategies to manipulate complement activated Tr1 cells to achieve allergen tolerance and suppress airway inflammation in patients with allergic asthma.

High Glucose Reduces the Shear Stress-Induced CD59 Expression on EPCs through F-Actin Alteration

Endothelial progenitor cells (EPCs) play a vital role in postnatal vascular injury and repair, especially vasculogenesis and angiogenesis. The purpose of this study was to investigate the effect of laminar shear stress in attenuating the decreased-expression of complement regulatory protein CD59 and the mechanism of cytoskeleton F-actin. Methods: EPCs were isolated from human umbilical vein blood and planted on glass slides, which applied to the laminar shear stress force (12 dyne/cm2) in a high glucose (20 mM) culture environment. The gene and protein expression of CD59 were detected by SYBGreen quantitative PCR and fluorescence activated cell sorter (FACS) respectively. The rearrangement of cytoskeleton F-actin was detected by FITC-phalloidin staining. Results: The elevated effect of shear stress on the expression of CD59 was significantly reduced in high glucose condition. Moreover, we found that F-actin was disorganized by high glucose, while rearrangement of cytoskeleton would be reversed by a moderate concentration of jasplakinolide (JAS) intervention. Conclusion: Our study indicated that high glucose inhibiting the rearrangement of EPCs cytoskeleton resulted the sensitivity of EPCs to laminar shear stress which should elevate the expression of complement regulatory protein CD59. As a result, EPCs was sensitive to membrane attack complex (MAC) -mediated cell autolysis.

Complement regulatory protein CD46 induces autophagy against oxidative stress-mediated apoptosis in normal and asthmatic airway epithelium

Autophagy plays a major role in defending against oxidative stress in respiratory epithelial cells. The complement regulatory protein CD46 can enhance autophagy and decrease local complement activation at sites of inflammation. This study investigated the mechanism by which CD46 protects against oxidative stress-mediated apoptosis in respiratory epithelium in asthmatic patients. Nasal mucosa samples were obtained from 60 adults with mild asthma who received turbinectomy and 30 controls. A decreased expression of CD46 and increased apoptosis were noted in the damaged nasal epithelium from the asthmatic patients. Primary epithelial cells cultured with Dermatophagoides pteronyssinus 2 showed decreased CD46 and increased cleaved CASPASE-3A expressions. Crosslinking CD46 mAb could induce the formation of autophagosomes and LC3-II expression in primary epithelial cells. CD46 engagement could induce autophagy against hydrogen peroxide-induced epithelial cell death, whereas the autophagy inhibitor 3-methyladenine decreased this effect. In addition, CD46 engagement decreased the expressions of PRO-IL-1β and NLRP3, enhanced the expression of scaffold protein GOPC, and diminished hydrogen peroxide-induced 8-OHdG, IL-1β and IL-6 production. Silencing ATG5 in human lung epithelial A549 cells decreased CD46-activated autophagy with LC3-II. CD46 induced autophagy and decreased the oxidative stress-mediated apoptosis of respiratory epithelium, and this may offer a new therapeutic strategy to treat asthma.

Reduced Expression of Membrane Complement Regulatory Protein CD59 on Leukocytes following Lung Transplantation.

Cellular protection against undesired effects of complement activation is provided by expression of membrane-bound complement regulatory proteins including CD59. This protein prevents membrane attack complex formation and is considered to be involved in graft accommodation. Also, CD59 downregulates CD4+ and CD8+ T-cell activation and proliferation. It is unknown whether CD59 expression is affected by transplantation. The aim of this study was to evaluate the quantitative CD59 antigen expression on distinct leukocyte subsets following lung transplantation (n = 26) and to investigate whether this differs from pretransplantation (n = 9). The results show that CD59 expression on leukocytes is significantly lower posttransplantation compared with healthy controls (p = 0.002) and pretransplantation (p < 0.0001). Moreover, the CD59 expression diminishes posttransplantation on all distinct lymphocyte subsets (p < 0.02). This effect appeared to be specific for CD59 since the expression of other surface markers remained stable or inclined following transplantation. The highest antigen expression posttransplantation was observed on CD4+ T cells and monocytes (p ≤ 0.002). These findings show that CD59 expression on leukocytes diminishes posttransplantation, which could result in decreased resistance against complement and enhanced T-cell activation. If such reduction in CD59 expression also occurs on endothelial cells from the transplanted organ, this could lead to a change into a prothrombotic and proinflammatory phenotype.

TCR-stimulated changes in cell surface CD46 expression generate type 1 regulatory T cells.

A lack of regulatory T cell function is a critical factor in the pathogenesis of autoimmune diseases, such as multiple sclerosis (MS). Ligation of the complement regulatory protein CD46 facilitates the differentiation of T helper 1 (TH1) effector cells into interleukin-10 (IL-10)-secreting type 1 regulatory T cells (Tr1 cells), and this pathway is defective in MS patients. Cleavage of the ectodomain of CD46, which contains three N-glycosylation sites and multiple O-glycosylation sites, enables CD46 to activate T cells. We found that stimulation of the T cell receptor (TCR)-CD3 complex was associated with a reduction in the apparent molecular mass of CD46 in a manner that depended on O-glycosylation. CD3-stimulated changes in CD46 O-glycosylation status reduced CD46 processing and subsequent T cell signaling. During T cell activation, CD46 was recruited to the immune synapse in a manner that required its serine-, threonine-, and proline-rich (STP) region, which is rich in O-glycosylation sites. Recruitment of CD46 to the immune synapse switched T cells from producing the inflammatory cytokine interferon-γ (IFN-γ) to producing IL-10. Furthermore, CD4+ T cells isolated from MS patients did not exhibit a CD3-stimulated reduction in the mass of CD46 and thus showed increased amounts of cell surface CD46. Together, these data suggest a possible mechanism underlying the regulatory function of CD46 on T cells. Our findings may explain why this pathway is defective in patients with MS and provide insights into MS pathogenesis that could help to design future immunotherapies.

Shear stress-mediated changes in the expression of complement regulatory protein CD59 on human endothelial progenitor cells by ECM-integrinαVβ3-F-actin pathway in vitro

Membrane regulatory proteins, such as CD46, CD55, and CD59, prevent excess complement activation and to protect cells from damage. Previous investigations confirmed that shear stress in the physiological range was more favorable for endothelial progenitor cells (EPCs) to repair injured vascular endothelial cells and operates mainly in atheroprotective actions. However, detailed events that contribute to shear stress-induced protection in EPCs, particularly the mechanisms of signal transduction, remain poorly understood. In this study, we observed shear stress-mediated changes in the expression of complement regulatory proteins CD46, CD55, and CD59 on human EPCs and focused on the mechanical transmission mechanism in transformed cells in response to the ECM-F-actin pathway in vitro. Shear stress was observed to promote the expression of complement regulatory protein CD59, but not CD46 or CD55, on EPCs. In addition, the shear stress-induced CD59 expression was confirmed to be associated with the ECM components and was alleviated in EPCs pretreated with GRGDSP, which inhibits ECM components-integrin interaction. Furthermore, shear stress also promotes the rearrangement and polymerization of F-actin. However, shear stress-induced CD59 expression was reduced when the F-actin stress fiber formation process was delayed by Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) or destroyed by cytochalasin D (Cyto D), while Jasplakinolide (JAS) reversed the expression of CD59 through promotion of F-actin polymerization and its stabilizing capacities. Our results indicates that shear stress is an important mediator in EPC expression of CD59 regulated by the ECM-F-actin pathway, which is a key factor in preventing membrane attack complex (MAC) -mediated cell autolysis.

C-reactive protein upregulates the whole blood expression of CD59 - an integrative analysis.

Elevated C-reactive protein (CRP) concentrations in the blood are associated with acute and chronic infections and inflammation. Nevertheless, the functional role of increased CRP in multiple bacterial and viral infections as well as in chronic inflammatory diseases remains unclear. Here, we studied the relationship between CRP and gene expression levels in the blood in 491 individuals from the Estonian Biobank cohort, to elucidate the role of CRP in these inflammatory mechanisms. As a result, we identified a set of 1,614 genes associated with changes in CRP levels with a high proportion of interferon-stimulated genes. Further, we performed likelihood-based causality model selection and Mendelian randomization analysis to discover causal links between CRP and the expression of CRP-associated genes. Strikingly, our computational analysis and cell culture stimulation assays revealed increased CRP levels to drive the expression of complement regulatory protein CD59, suggesting CRP to have a critical role in protecting blood cells from the adverse effects of the immune defence system. Our results show the benefit of integrative analysis approaches in hypothesis-free uncovering of causal relationships between traits.

Enhanced CDC of B cell chronic lymphocytic leukemia cells mediated by rituximab combined with a novel anti-complement factor H antibody.

Rituximab therapy for B cell chronic lymphocytic leukemia (B-CLL) has met with mixed success. Among several factors to which resistance can be attributed is failure to activate complement dependent cytotoxicity (CDC) due to protective complement regulatory proteins, including the soluble regulator complement factor H (CFH). We hypothesized that rituximab killing of non-responsive B-CLL cells could be augmented by a novel human monoclonal antibody against CFH. The B cells from 11 patients with B-CLL were tested ex vivo in CDC assays with combinations of CFH monoclonal antibody, rituximab, and a negative control antibody. CDC of rituximab non-responsive malignant B cells from CLL patients could in some cases be augmented by the CFH monoclonal antibody. Antibody-mediated cytotoxicity of cells was dependent upon functional complement. In one case where B-CLL cells were refractory to CDC by the combination of rituximab plus CFH monoclonal antibody, additionally neutralizing the membrane complement regulatory protein CD59 allowed CDC to occur. Inhibiting CDC regulatory proteins such as CFH holds promise for overcoming resistance to rituximab therapy in B-CLL.