BACKGROUND: CD27 is recently known as a memory B cell marker and is mainly expressed in activated T cells, some B cell population and NK cells. CD27 is a member of tumor necrosis factor receptor family. Like CD40 molecule, CD27 has (P/S/T/A) X(Q/E)E motif for interacting with TNF receptor-associated factors (TRAFs), and TRAF2 and TRAF5 bindings to CD27 in 293T cells were reported. METHODS: To investigate the CD27 signaling effect in B cells, human CD40 extracellular domain containing mouse CD27 cytoplamic domain construct (hCD40-mCD27) was transfected into mouse B cell line CH12.LX and M12.4.1. RESULTS: Through the stimulation of hCD40-mCD27 molecule via anti-human CD40 antibody or CD154 ligation, expression of CD11a, CD23, CD54, CD70 and CD80 were increased and secretion of IgM was induced, which were comparable to the effect of CD40 stimulation. TRAF2 and TRAF3 were recruited into lipid-enriched membrane raft and were bound to CD27 in M12.4.1 cells. CD27 stimulation, however, did not increase TRAF2 or TRAF3 degradation. CONCLUSION: In contrast to CD40 signaling pathway, TRAF2 and TRAF3 degradation was not observed after CD27 stimulation and it might contribute to prolonged B cell activation through CD27 signaling.
Animals ; B-Lymphocytes* ; Cell Line ; Humans ; Immunoglobulin M ; Killer Cells, Natural ; Ligation ; Membranes ; Memory ; Mice* ; Necrosis* ; Receptors, Tumor Necrosis Factor ; T-Lymphocytes ; TNF Receptor-Associated Factor 2 ; TNF Receptor-Associated Factor 3 ; TNF Receptor-Associated Factor 5 ; Tumor Necrosis Factor Receptor-Associated Peptides and Proteins

Osteoclasts are multinucleated cells formed mainly on bone surfaces in response to cytokines by fusion of bone marrow-derived myeloid lineage precursors that circulate in the blood. Major advances in understanding of the molecular mechanisms regulating osteoclast formation and functions have been made in the past 20 years since the discovery that their formation requires nuclear factor-kappa B (NF-kappaB) signaling and that this is activated in response to the essential osteoclastogenic cytokine, receptor activator of NF-kappaB ligand (RANKL), which also controls osteoclast activation to resorb (degrade) bone. These studies have revealed that RANKL and some pro-inflammatory cytokines, including tumor necrosis factor, activate NF-kappaB and downstream signaling, including c-Fos and nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), and inhibition of repressors of NFATc1 signaling, to positively regulate osteoclast formation and functions. However, these cytokines also activate NF-kappaB signaling that can limit osteoclast formation through the NF-kappaB signaling proteins, TRAF3 and p100, and the suppressors of c-Fos/NFATc1 signaling, IRF8, and RBP-J. This paper reviews current understanding of how NF-kappaB signaling is involved in the positive and negative regulation of cytokine-mediated osteoclast formation and activation.
Cytokines ; NF-kappa B ; NFATC Transcription Factors ; Osteoclasts ; RANK Ligand ; Receptor Activator of Nuclear Factor-kappa B ; TNF Receptor-Associated Factor 3 ; Tumor Necrosis Factor-alpha

OBJECTIVETo investigate the function of unclassical NF-kappaB signaling pathway and TNF associated-factor (TRAF)-3 in Hodgkin's lymphoma (HL) cells, and explore a reasonable explanation for alternative NF-kappaB signaling pathway activation in HL cells.

METHODSThe intranuclear NF-kappaB activity in L428 and KM-H2 cells was examined by electrophoretic mobility shift assay (EMSA). The NF-kappaB DNA complex in L428 cell nuclear extracts was further quantified by an ELISA-based NF-kappaB family transcription factor activity assay. The expression of other NF-kappaB family members in the cytoplasm, and the TRAF3 expression were detected by Western blot analysis. The effects of TRAF3 on the unclassical NF-kappaB signaling pathway in L428 cells were studied by transient expression of TRAF3.

RESULTSThe NF-kappaB signaling pathway activity persistently remained in L428 and KM-H2 cells. Both classical and unclassical NF-kappaB activity in L428 cells was highly expressed. There were enhanced p52 protein accumulation and RelB expression and a very weak expression of TRAF3 in both L428 and KM-H2 cells. Transient transfection of TRAF3-expression vector increased the TRAF3 expression and blocked the p100 processing and p52 protein accumulation in both cells.

CONCLUSIONThe classical as well as the unclassical NF-kappaB activities characterized by p100 processing and p52-RelB nuclear localization are persistently present in HL cells. Lack of the TRAF3 expression might be one of the reasons for the aberrant expression of the unclassical NF-kappaB activity.

Hodgkin Disease ; metabolism ; pathology ; Humans ; NF-kappa B ; genetics ; metabolism ; Signal Transduction ; TNF Receptor-Associated Factor 3 ; genetics ; metabolism ; Tumor Cells, Cultured

Cell death and survival are tightly controlled through the highly coordinated activation/inhibition of diverse signal transduction pathways to insure normal development and physiology. Imbalance between cell death and survival often leads to autoimmune diseases and cancer. Death receptors sense extracellular signals to induce caspase-mediated apoptosis. Acting upstream of CED-3 family proteases, such as caspase-3, Bcl-2 prevents apoptosis. Using short hairpin RNAs (shRNAs), we suppressed Bcl-2 expression in Jurkat T cells, and this increased TCR-triggered AICD and enhanced TNFR gene expression. Also, knockdown of Bcl-2 in Jurkat T cells suppressed the gene expression of FLIP, TNF receptor-associated factors 3 (TRAF3) and TRAF4. Furthermore, suppressed Bcl-2 expression increased caspase-3 and diminished nuclear factor kappa B (NF-kappaB) translocation.
Apoptosis ; Autoimmune Diseases ; Caspase 3 ; Cell Death* ; Gene Expression ; Humans ; NF-kappa B ; Peptide Hydrolases ; Physiology ; Receptors, Death Domain ; RNA, Small Interfering ; Signal Transduction ; T-Lymphocytes* ; TNF Receptor-Associated Factor 4 ; Tumor Necrosis Factor Receptor-Associated Peptides and Proteins

OBJECTIVE: To investigate the role of tumor necrosis factor receptor-associated factor 6 (TRAF6) in regulating Bacillus Calmette-Guérin (BCG)-induced macrophage apoptosis. METHODS: The expression of TRAF6 in peripheral blood samples of 50 patients with active tuberculosis (TB) and 50 healthy individuals were detected using quantitative real-time PCR (qPCR). RAW264.7 macrophages were infected with BCG at different MOI and for different lengths of time, and the changes in expressions of Caspase 3 and TRAF6 were detected with Western blotting and qPCR. In a RAW264.7 cell model of BCG infection with TRAF6 knockdown established using RNA interference technique, the bacterial load was measured and cell apoptotic rate and mitochondrial membrane potential (MMP) were determined with flow cytometry. The expression levels of TRAF6, Caspase 3, PARP, BAX and Bcl-2 in the cells were detected using Western blotting, and the expressions of TRAF6 and Caspase 3 were also examined with immunofluorescence assay. RESULTS: The expression of TRAF6 was significantly upregulated in the peripheral blood of patients with active TB as compared with healthy subjects (P < 0.001). In RAW264.7 cells, BCG infection significantly increased the expressions of Caspase 3 and TRAF6, which were the highest in cells infected for 18 h and at the MOI of 15. TRAF6 knockdown caused a significant increase of bacterial load in BCG-infected macrophages (P=0.05), lowered the cell apoptotic rate (P < 0.001) and reduced the expressions of Caspase 3 (P=0.002) and PARP (P < 0.001). BCG-infected RAW264.7 cells showed a significantly increased MMP (P < 0.001), which was lowered by TRAF6 knockdown (P < 0.001); the cells with both TRAF6 knockdown and BCG infection showed a lowered BAX expression (P=0.005) and an increased expression of Bcl-2 (P=0.04). CONCLUSION TRAF6 promotes BCG-induced macrophage apoptosis by regulating the intrinsic apoptosis pathway.
Apoptosis ; BCG Vaccine ; Caspase 3/metabolism* ; Humans ; Intracellular Signaling Peptides and Proteins ; Macrophages ; Mycobacterium bovis/metabolism* ; Poly(ADP-ribose) Polymerase Inhibitors ; TNF Receptor-Associated Factor 6/metabolism* ; bcl-2-Associated X Protein/metabolism*

The study investigated the inhibitory effect and mechanism of tectorigenin derivative(SGY) against herpes simplex virus type Ⅰ(HSV-1) by in vitro experiments. The cytotoxicity of SGY and positive drug acyclovir(ACV) on African green monkey kidney(Vero) cells and mouse microglia(BV-2) cells was detected by cell counting kit-8(CCK-8) method, and the maximum non-toxic concentration and median toxic concentration(TC_(50)) of the drugs were calculated. After Vero cells were infected with HSV-1, the virulence was determined by cytopathologic effects(CPE) to calculate viral titers. The inhibitory effect of the tested drugs on HSV-1-induced cytopathy in Vero cells was measured, and their modes of action were initially explored by virus adsorption, replication and inactivation. The effects of the drugs on viral load of BV-2 cells 24 h after HSV-1 infection and the Toll-like receptor(TLR) mRNA expression were detected by real-time fluorescence quantitative PCR(RT-qPCR). The maximum non-toxic concentrations of SGY against Vero and BV-2 cells were 382.804 μg·mL~(-1) and 251.78 μg·mL~(-1), respectively, and TC_(50) was 1 749.98 μg·mL~(-1) and 2 977.50 μg·mL~(-1), respectively. In Vero cell model, the half maximal inhibitory concentration(IC_(50)) of SGY against HSV-1 was 54.49 μg·mL~(-1), and the selection index(SI) was 32.12, with the mode of action of significantly inhibiting replication and directly inactivating HSV-1. RT-qPCR results showed that SGY markedly reduced the viral load in cells. The virus model group had significantly increased relative expression of TLR2, TLR3 and tumor necrosis factor receptor-associated factor 3(TRAF3) and reduced relative expression of TLR9 as compared with normal group, and after SGY intervention, the expression of TLR2, TLR3 and TRAF3 was decreased to different degrees and that of TLR9 was enhanced. The expression of inflammatory factors inducible nitric oxide synthase(iNOS), tumor necrosis factor-α(TNF-α), and interleukin-1β(IL-1β) was remarkably increased in virus model group as compared with that in normal group, and the levels of these inflammatory factors dropped after SGY intervention. In conclusion, SGY significantly inhibited and directly inactivated HSV-1 in vitro. In addition, it modulated the expression of TLR2, TLR3 and TLR9 related pathways, and suppressed the increase of inflammatory factor levels.
Animals ; Antiviral Agents/therapeutic use* ; Chlorocebus aethiops ; Herpes Simplex/pathology* ; Herpesvirus 1, Human/metabolism* ; Isoflavones ; Mice ; TNF Receptor-Associated Factor 3/pharmacology* ; Toll-Like Receptor 2/metabolism* ; Toll-Like Receptor 3/metabolism* ; Toll-Like Receptor 9/metabolism* ; Toll-Like Receptors/metabolism* ; Tumor Necrosis Factor-alpha/metabolism* ; Vero Cells ; Virus Replication

SARS coronavirus (SARS-CoV) develops an antagonistic mechanism by which to evade the antiviral activities of interferon (IFN). Previous studies suggested that SARS-CoV papain-like protease (PLpro) inhibits activation of the IRF3 pathway, which would normally elicit a robust IFN response, but the mechanism(s) used by SARS PLpro to inhibit activation of the IRF3 pathway is not fully known. In this study, we uncovered a novel mechanism that may explain how SARS PLpro efficiently inhibits activation of the IRF3 pathway. We found that expression of the membrane-anchored PLpro domain (PLpro-TM) from SARS-CoV inhibits STING/TBK1/IKKε-mediated activation of type I IFNs and disrupts the phosphorylation and dimerization of IRF3, which are activated by STING and TBK1. Meanwhile, we showed that PLpro-TM physically interacts with TRAF3, TBK1, IKKε, STING, and IRF3, the key components that assemble the STING-TRAF3-TBK1 complex for activation of IFN expression. However, the interaction between the components in STING-TRAF3-TBK1 complex is disrupted by PLpro-TM. Furthermore, SARS PLpro-TM reduces the levels of ubiquitinated forms of RIG-I, STING, TRAF3, TBK1, and IRF3 in the STING-TRAF3-TBK1 complex. These results collectively point to a new mechanism used by SARS-CoV through which PLpro negatively regulates IRF3 activation by interaction with STING-TRAF3-TBK1 complex, yielding a SARS-CoV countermeasure against host innate immunity.
Dimerization ; HEK293 Cells ; Humans ; I-kappa B Kinase ; metabolism ; Interferon Regulatory Factor-3 ; metabolism ; Interferon Type I ; antagonists & inhibitors ; metabolism ; Membrane Proteins ; chemistry ; genetics ; metabolism ; Papain ; metabolism ; Peptide Hydrolases ; chemistry ; metabolism ; Phosphorylation ; Protein Binding ; Protein Structure, Tertiary ; Protein-Serine-Threonine Kinases ; metabolism ; SARS Virus ; enzymology ; Signal Transduction ; TNF Receptor-Associated Factor 3 ; metabolism ; Ubiquitination

Tripartite motif (TRIM) family proteins are important effectors of innate immunity against viral infections. Here we identified TRIM35 as a regulator of TRAF3 activation. Deficiency in or inhibition of TRIM35 suppressed the production of type I interferon (IFN) in response to viral infection. Trim35-deficient mice were more susceptible to influenza A virus (IAV) infection than were wild-type mice. TRIM35 promoted the RIG-I-mediated signaling by catalyzing Lys63-linked polyubiquitination of TRAF3 and the subsequent formation of a signaling complex with VISA and TBK1. IAV PB2 polymerase countered the innate antiviral immune response by impeding the Lys63-linked polyubiquitination and activation of TRAF3. TRIM35 mediated Lys48-linked polyubiquitination and proteasomal degradation of IAV PB2, thereby antagonizing its suppression of TRAF3 activation. Our in vitro and in vivo findings thus reveal novel roles of TRIM35, through catalyzing Lys63- or Lys48-linked polyubiquitination, in RIG-I antiviral immunity and mechanism of defense against IAV infection.
A549 Cells ; Animals ; Apoptosis Regulatory Proteins/immunology* ; DEAD Box Protein 58/immunology* ; Dogs ; HEK293 Cells ; Humans ; Influenza A Virus, H1N1 Subtype/immunology* ; Madin Darby Canine Kidney Cells ; Mice ; Mice, Knockout ; Orthomyxoviridae Infections/pathology* ; Proteolysis ; RAW 264.7 Cells ; Signal Transduction/immunology* ; THP-1 Cells ; TNF Receptor-Associated Factor 3/immunology* ; Ubiquitination/immunology* ; Viral Proteins/immunology*

Hepatitis B virus (HBV) is regarded as a stealth virus, invading and replicating efficiently in human liver undetected by host innate antiviral immunity. Here, we show that type I interferon (IFN) induction but not its downstream signaling is blocked by HBV replication in HepG2.2.15 cells. This effect may be partially due to HBV X protein (HBx), which impairs IFNβ promoter activation by both Sendai virus (SeV) and components implicated in signaling by viral sensors. As a deubiquitinating enzyme (DUB), HBx cleaves Lys63-linked polyubiquitin chains from many proteins except TANK-binding kinase 1 (TBK1). It binds and deconjugates retinoic acid-inducible gene I (RIG I) and TNF receptor-associated factor 3 (TRAF3), causing their dissociation from the downstream adaptor CARDIF or TBK1 kinase. In addition to RIG I and TRAF3, HBx also interacts with CARDIF, TRIF, NEMO, TBK1, inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase epsilon (IKKi) and interferon regulatory factor 3 (IRF3). Our data indicate that multiple points of signaling pathways can be targeted by HBx to negatively regulate production of type I IFN.
Animals ; B-Lymphocytes ; immunology ; metabolism ; Cell Line ; DEAD Box Protein 58 ; DEAD-box RNA Helicases ; antagonists & inhibitors ; immunology ; metabolism ; Hep G2 Cells ; Hepatitis B virus ; immunology ; metabolism ; Humans ; I-kappa B Kinase ; antagonists & inhibitors ; immunology ; metabolism ; Immune Evasion ; Immunity, Innate ; Interferon Regulatory Factor-3 ; antagonists & inhibitors ; immunology ; metabolism ; Interferon Type I ; antagonists & inhibitors ; immunology ; metabolism ; Mice ; Molecular Targeted Therapy ; Polyubiquitin ; antagonists & inhibitors ; metabolism ; Protein Binding ; immunology ; Sendai virus ; immunology ; metabolism ; Signal Transduction ; immunology ; TNF Receptor-Associated Factor 3 ; antagonists & inhibitors ; immunology ; metabolism ; Trans-Activators ; immunology ; metabolism