TRAF-mediated regulation of immune and inflammatory responses

Uncovering the Interaction between TRAF1 and MAVS in the RIG-I Pathway to Enhance the Upregulation of IRF1/ISG15 during Classical Swine Fever Virus Infection

Classical swine fever (CSF) is caused by the classical swine fever virus (CSFV), which poses a threat to swine production. The activation of host innate immunity through linker proteins such as tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) is crucial for the induction of the NF-κB pathway. Recent research has revealed the involvement of mitochondrial antiviral-signaling protein (MAVS) in the interaction with TRAF2, 3, 5, and 6 to activate both the NF-κB and IRF3 pathways. This study revealed that CSFV infection led to the upregulation of TRAF1 mRNA and protein levels; moreover, TRAF1 overexpression inhibited CSFV replication, while TRAF1 knockdown promoted replication, highlighting its importance in the host response to CSFV infection. Additionally, the expression of RIG-I, MAVS, TRAF1, IRF1, and ISG15 were detected in PK-15 cells infected with CSFV, revealing that TRAF1 plays a role in regulating IRF1 and ISG15 within the RIG-I pathway. Furthermore, Co-IP, GST pull-down, and IFA analyses demonstrated that TRAF1 interacted with MAVS and co-localized in the cytoplasm during CSFV infection. Ultimately, TRAF1 acted as a novel member of the TRAF family, bound to MAVS as a linker molecule, and functioned as a mediator downstream of MAVS in the RIG-I/MAVS pathway against CSFV replication.

miR-144 affects the immune response and activation of inflammatory responses in Cynoglossus semilaevis by regulating the expression of CsMAPK6

MicroRNAs are increasingly recognized for their pivotal role in the immune system, yet the specific regulatory functions of fish-derived microRNAs remain largely unexplored. In this research, we discovered a novel miRNA, Cse-miR-144, in the Chinese tongue sole (Cynoglossus semilaevis), characterized by a 73-base pair precursor and a 21-nucleotide mature sequence. Our findings revealed that the expression of Cse-miR-144 was notably inhibited by various Vibrio species. Utilizing bioinformatics and dual-luciferase assay techniques, we established that the pro-inflammatory cytokine gene CsMAPK6 is a direct target of Cse-miR-144. Subsequent in vitro and in vivo western blotting analyses confirmed that Cse-miR-144 can effectively reduce the protein levels of CsMAPK6 post-transcriptionally. Moreover, CsMAPK6 is known to be involved in the activation of the Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-kB). Additional investigations using qPCR and ELISA demonstrated that suppression of Cse-miR-144 leads to an upsurge in the liver mRNA levels of various immune genes (including MYD88, TRAF6, NF-κB, TRAF2, TRAF3, and TNF), alongside a marked increase in the production and secretion of pro-inflammatory cytokines (IL-1β, IL-6, and IL-8) in the bloodstream of C. semilaevis. These findings collectively underscore the potential of Cse-miR-144 as a key inhibitor of CsMAPK and its crucial role in modulating the immune and inflammatory responses in teleost fish. Compared to the siRNA, miRNA is a better tool in controlling the expression of target gene with a lower cost.

Decoding the contextual duality of CD40 functions

Previously, we established that as a function of its mode of interaction with its ligand or cellular conditions such as membrane lipids, preexisting signaling intermediates activation status, a transmembrane receptor, as represented here with CD40, can induce counteractive cellular responses. Using CD40-binding peptides, recombinant mutated CD40-ligands, and an agonistic antibody, we have established the functional duality of CD40. CD40 builds up two constitutionally different signalosomes on lipid raft and non-raft membrane domains initiating two different signaling pathways. Although this initial signaling may be modified by the pre-existing signaling conditions downstream and may be subjected to feed-forward or negative signaling effects, the initial CD40-CD40L interaction plays a crucial role in the functional outcome of CD40. Herein, we have reviewed the influence of interaction between the CD40-CD40L evoking the functional duality of CD40 contingent upon different physiological states of the cells.

NS5 hijacks TRAF3 to inhibit type I interferon signaling during duck Tembusu virus infection

The tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) is a key signaling molecule in the retinoic acid-inducible gene I (RIG-I) signaling pathway and plays an important role in host innate immune regulation. The function of TRAF3 has been extensively studied in mammals, however, the role of TRAF3 in ducks remains unclear. In order to reveal the function of duck TRAF3 (duTRAF3) in the innate immune response induced by virus infection, the TRAF3 homologue of mallard (Anas platyrhynchos) has been cloned and the function of duTRAF3 is investigated in this study. We sequenced duTRAF3 and found that the open reading frame (ORF) region of duTRAF3 is 1704 bp long and encodes 567 amino acids (aa), which has a similar functional domain to the mammalian gene. Analysis of tissue distribution of duTRAF3 in 7-day-old ducks showed that the expression of duTRAF3 was highest in harderian gland, followed by heart and lung. Subsequently, duck Tembusu virus (DTMUV) has been shown to enhance duTRAF3 expression, and overexpression of duTRAF3 inhibits DTMUV replication in a dose-dependent manner. In addition, duTRAF3 activates the transcriptional activity of IFN-α and its downstream interferon-stimulating genes (ISGs) induced after DTMUV infection. In this process, DTMUV non-structural (NS) protein 5 resists this innate immune process by interacting with TRAF3 and inhibiting TRAF3 expression. These data support the conclusion that duTRAF3 is an antiviral protein that plays a key role in the defense against DTMUV invasion. These results lay a theoretical foundation for developing new anti-DTMUV strategies.

TRAF6 as a potential target in advanced breast cancer: a systematic review, meta-analysis, and bioinformatics validation

TRAF6 has emerged as a key regulator of breast cancer (BCa). However, the TRAF family constitutes of seven members that exhibit distinct and overlapping functions. To explore which TRAF represents a potential druggable target for BCa treatment, we searched Medline, Web of Science and Scopus for relevant studies from inception to June 27, 2021. We identified 14 in vitro, 11 in vivo and 4 human articles. A meta-analysis of pharmacological studies showed that in vitro inhibition of TRAF2/4 (mean difference (MD): - 57.49, 95% CI: - 66.95, - 48.02, P < 0.00001) or TRAF6 (standard(Std.)MD: - 4.01, 95% CI: - 5.75, - 2.27, P < 0.00001) is associated with reduction in BCa cell migration. Consistently, inhibition of TRAF2/4 (MD: - 51.08, 95% CI: - 64.23, - 37.94, P < 0.00001) and TRAF6 (Std.MD: - 2.80, 95% CI: - 4.26, - 1.34, P = 0.0002) is associated with reduced BCa cell invasion, whereas TRAF2/4 inhibition (MD: - 40.54, 95% CI: - 52.83, - 28.26, P < 0.00001) is associated with reduced BCa cell adhesion. Interestingly, only inhibition of TRAF6 (MD: - 21.46, 95% CI: - 30.40, - 12.51, P < 0.00001) is associated with reduced cell growth. In animal models of BCa, administration of pharmacological inhibitors of TRAF2/4 (Std.MD: - 3.36, 95% CI: - 4.53, - 2.18, P < 0.00001) or TRAF6 (Std.MD: - 4.15, 95% CI: - 6.06, - 2.24, P < 0.0001) in mice is associated with reduction in tumour burden. In contrast, TRAF6 inhibitors (MD: - 2.42, 95% CI: - 3.70, - 1.14, P = 0.0002) reduced BCa metastasis. In BCa patients, high expression of TRAF6 (Hazard Ratio: 1.01, CI: 1.01, 1.01, P < 0.00001) is associated with poor survival rate. Bioinformatics validation of clinical and pathway and process enrichment analysis in BCa patients confirmed that gain/amplification of TRAF6 is associated with secondary BCa in bone (P = 0.0079), and poor survival rate (P < 0.05). Overall, TRAF6 inhibitors show promise in the treatment of metastatic BCa. However, low study number and scarcity of evidence from animal and human studies may limit the translation of present findings into clinical practice.

A novel miRNA, Cse-miR-33, functions as an immune regulator by targeting CsTRAF6 in Chinese tongue sole (Cynoglossus semilaevis)

The tumor necrosis factor receptor-associated factor 6 (TRAF6) can act as a fundamental adaptor protein in a chain reaction of signal transduction and cascade events to finish off immune defenses. However, immunomodulatory research on TRAF6 gene is still limited in fish. In this study, a novel miRNA, Cse-miR-33 was identified from the whole genome of Chinese tongue sole (Cynoglossus semilaevis). After separate infections with three different Vibrio strains (V. harveyi, V. anguillarum, V. parahemolyticus) and one virus (nervous necrosis virus, NNV), the expressions of CsTRAF6 and Cse-miR-33 displayed significant time-dependent changes in immune related tissues and the trends were opposite in general. Through target gene prediction and dual luciferase reporter assay, Cse-miR-33 was proven to regulate CsTRAF6 by combining with 3'-UTR sequence of the gene. The results of qRT-PCR and western blotting (WB) analyses showed that Cse-miR-33 blocked the translation of CsTRAF6 protein at post-transcriptional level, rather than degrading the target mRNA. Further experiment indicated that Cse-miR-33 inhibitor largely reduced the death rate of Chinese tongue sole caused by V. harveyi and NNV. The expressions of CsTRAF6-associated immune genes (such as CsIL-1R, CsMYD88, CsIRAK1, CsTNFα, CsIL6 and CsIL8) were also significantly changed in response to Cse-miR-33 agomir and inhibitor. The study suggested that Cse-miR-33 affected the immune response via targeting CsTRAF6 in C. semilaevis, which would provide us deep insights into miRNA-mediated regulatory network and help improve the immunity in fish.

miR-548d-3p Alters Parasite Growth and Inflammation in Leishmania (Viannia) braziliensis Infection

American Tegumentary Leishmaniasis (ATL) is an endemic disease in Latin America, mainly caused in Brazil by Leishmania (Viannia) braziliensis. Clinical manifestations vary from mild, localized cutaneous leishmaniasis (CL) to aggressive mucosal disease. The host immune response strongly determines the outcome of infection and pattern of disease. However, the pathogenesis of ATL is not well understood, and host microRNAs (miRNAs) may have a role in this context. In the present study, miRNAs were quantified using qPCR arrays in human monocytic THP-1 cells infected in vitro with L. (V.) braziliensis promastigotes and in plasma from patients with ATL, focusing on inflammatory response-specific miRNAs. Patients with active or self-healed cutaneous leishmaniasis patients, with confirmed parasitological or immunological diagnosis, were compared with healthy controls. Computational target prediction of significantly-altered miRNAs from in vitro L. (V.) braziliensis-infected THP-1 cells revealed predicted targets involved in diverse pathways, including chemokine signaling, inflammatory, cellular proliferation, and tissue repair processes. In plasma, we observed distinct miRNA expression in patients with self-healed and active lesions compared with healthy controls. Some miRNAs dysregulated during THP-1 in vitro infection were also found in plasma from self-healed patients, including miR-548d-3p, which was upregulated in infected THP-1 cells and in plasma from self-healed patients. As miR-548d-3p was predicted to target the chemokine pathway and inflammation is a central to the pathogenesis of ATL, we evaluated the effect of transient transfection of a miR-548d-3p inhibitor on L. (V.) braziliensis infected-THP-1 cells. Inhibition of miR-548d-3p reduced parasite growth early after infection and increased production of MCP1/CCL2, RANTES/CCL5, and IP10/CXCL10. In plasma of self-healed patients, MCP1/CCL2, RANTES/CCL5, and IL-8/CXCL8 concentrations were significantly decreased and MIG/CXCL9 and IP-10/CXCL10 increased compared to patients with active disease. These data suggest that by modulating miRNAs, L. (V.) braziliensis may interfere with chemokine production and hence the inflammatory processes underpinning lesion resolution. Our data suggest miR-548d-3p could be further evaluated as a prognostic marker for ATL and/or as a host-directed therapeutic target.

TRAF3 mediates neuronal apoptosis in early brain injury following subarachnoid hemorrhage via targeting TAK1-dependent MAPKs and NF-κB pathways

Neuronal apoptosis has an important role in early brain injury (EBI) following subarachnoid hemorrhage (SAH). TRAF3 was reported as a promising therapeutic target for stroke management, which covered several neuronal apoptosis signaling cascades. Hence, the present study is aimed to determine whether downregulation of TRAF3 could be neuroprotective in SAH-induced EBI. An in vivo SAH model in mice was established by endovascular perforation. Meanwhile, primary cultured cortical neurons of mice treated with oxygen hemoglobin were applied to mimic SAH in vitro. Our results demonstrated that TRAF3 protein expression increased and expressed in neurons both in vivo and in vitro SAH models. TRAF3 siRNA reversed neuronal loss and improved neurological deficits in SAH mice, and reduced cell death in SAH primary neurons. Mechanistically, we found that TRAF3 directly binds to TAK1 and potentiates phosphorylation and activation of TAK1, which further enhances the activation of NF-κB and MAPKs pathways to induce neuronal apoptosis. Importantly, TRAF3 expression was elevated following SAH in human brain tissue and was mainly expressed in neurons. Taken together, our study demonstrates that TRAF3 is an upstream regulator of MAPKs and NF-κB pathways in SAH-induced EBI via its interaction with and activation of TAK1. Furthermore, the TRAF3 may serve as a novel therapeutic target in SAH-induced EBI.

Human DUBs' gene expression and regulation in antiviral signaling in response to poly (I:C) treatment

Type I interferons (IFNs) play a central role in host defense against viral infection. Multiple posttranslational modifications including ubiquitination and deubiquitination regulate the function of diverse molecules in type I IFN signaling. Many ubiquitin ligase enzymes, such as those of the TRAF and TRIM families, have been shown to participate in the production of type I IFNs and inflammatory cytokines. However, the function of deubiquitinating enzymes (DUBs), a protein family that counteracts the action of protein ubiquitination, on the regulation of antiviral immune responses is not well understood. In this study, we used the broad-spectrum DUB inhibitor G5 to reveal their function in antiviral signaling, and then systematically analyzed mRNA expression of the DUB genes upon poly (I:C) treatment in THP-1 cells. Based on this analysis, we cloned some DUB genes whose expression changed and determined their function in antiviral signaling. Taken together, we present a comprehensive DUB gene expression analysis in THP-1 cells, and suggest the involvement of this family of proteins in the regulation of host antiviral activities.

Porcine parvovirus nonstructural protein NS1 activates NF-κB and it involves TLR2 signaling pathway

BACKGROUND

Porcine parvovirus (PPV) is a single-stranded DNA virus that causes porcine reproductive failure. It is of critical importance to study PPV pathogenesis for the prevention and control of the disease. NS1, a PPV non-structural protein, is participated in viral DNA replication, transcriptional regulation, and cytotoxicity. Our previous research showed that PPV can activate nuclear factor kappa B (NF-κB) signaling pathway and then up-regulate the expression of interleukin (IL)-6.

OBJECTIVES

Herein, the purpose of this study is to determine whether the non-structural protein NS1 of PPV also has the same function.

METHODS

Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), enzyme-linked immunosorbent assay, western blot, immunofluorescence assay and small interfering RNA (siRNA) were used.

RESULTS

Our findings demonstrated that PPV NS1 protein can up-regulate the expression levels of IL-6 and tumor necrosis factor-alpha in a dose-dependent manner. Moreover, PPV NS1 protein was found to induce the phosphorylation of IκBα, then leading to the phosphorylation and nuclear translocation of NF-κB. In addition, the NS1 protein activated the upstream pathways of NF-κB. Meanwhile, TLR2-siRNA assay showed TLR2 plays an important role in the activation of NF-κB signaling pathway induced by PPV-NS1.

CONCLUSIONS

These findings indicated that PPV NS1 protein induced the up-regulated of IL-6 expression through activating the TLR2 and NF-κB signaling pathways. In conclusion, these findings provide a new avenue to study the innate immune mechanism of PPV infection.

Identification of putative phenotype-modifying genetic factors associated with phenotypic diversity in Brooke-Spiegler syndrome

Brooke-Spiegler syndrome (BSS, OMIM 605041) is a rare monogenic skin disease characterized by the development of skin appendage tumors caused by mutations in the cylindromatosis gene. We recently investigated a Hungarian and an Anglo-Saxon pedigrees affected by Brooke-Spiegler syndrome. Despite carrying the same disease-causing mutation (c.2806C>T, p.Arg936X) of the cylindromatosis (CYLD) gene, the affected family members of the two pedigrees exhibit striking differences in their phenotypes. To identify phenotype-modifying genetic factors, whole exome sequencing was performed and the data from the Hungarian and Anglo-Saxon BSS patients were compared. Three putative phenotype-modifying genetic variants were identified: the rs1053023 SNP of the signal transducer and activator of transcription 3 (STAT3) gene, the rs1131877 SNP of the tumor necrosis factor receptor-associated factor 3 (TRAF3) gene and the rs202122812 SNP of the neighbour of BRCA1 gene 1 (NBR1) gene. Our study contributes to the accumulating evidence for the clinical importance of phenotype-modifying genetic factors, which are potentially important for the elucidation of disease prognosis.

Identification and characterisation of tumour necrosis factor receptor (TNFR) associated factor 3 from Nile tilapia, Oreochromis niloticus

In this study, we cloned the complementary (c)DNA sequences of tumour necrosis factor receptor (TNFR)-associated factor 3 (traf3) in Nile tilapia, Oreochromis niloticus. The expression patterns of the traf3 gene were investigated and preliminary functional analyses were performed. In healthy fish, traf3 transcript was broadly expressed in all examined tissues, with the highest expression level in the blood and the lowest in the liver. The traf3 gene reached its highest expression at 8 days post-fertilisation (dpf) during embryonic development. Moreover, we found that expression of traf3 was clearly altered following stimulation with Streptococcus agalactiae in vivo and that traf3 could be induced by lipopolysaccharides (LPS), Poly I: C and S. agalactiae WC1535 in Nile tilapia macrophages. Overexpression in 293T cells showed that Traf3 protein was mainly distributed in the cytoplasm and could significantly increase nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. Taken together, these results implied that traf3 could play important roles in the immune response to pathogen invasion.

Suppression of NF-κB Activity: A Viral Immune Evasion Mechanism

Nuclear factor-κB (NF-κB) is an important transcription factor that induces the expression of antiviral genes and viral genes. NF-κB activation needs the activation of NF-κB upstream molecules, which include receptors, adaptor proteins, NF-κB (IκB) kinases (IKKs), IκBα, and NF-κB dimer p50/p65. To survive, viruses have evolved the capacity to utilize various strategies that inhibit NF-κB activity, including targeting receptors, adaptor proteins, IKKs, IκBα, and p50/p65. To inhibit NF-κB activation, viruses encode several specific NF-κB inhibitors, including NS3/4, 3C and 3C-like proteases, viral deubiquitinating enzymes (DUBs), phosphodegron-like (PDL) motifs, viral protein phosphatase (PPase)-binding proteins, and small hydrophobic (SH) proteins. Finally, we briefly describe the immune evasion mechanism of human immunodeficiency virus 1 (HIV-1) by inhibiting NF-κB activity in productive and latent infections. This paper reviews a viral mechanism of immune evasion that involves the suppression of NF-κB activation to provide new insights into and references for the control and prevention of viral diseases.

Functional characterization of tumor necrosis factor receptor-associated factor 3 of sea perch (Lateolabrax japonicas) in innate immune

Tumor necrosis factor receptor-associated factor 3 (TRAF3) is a multifunctional regulator implicated in both bacterial defense and antiviral immunity. Here, a TRAF3 gene from the seawater fish sea perch, designated as LjTRAF3, was characterized. The full-length cDNA of LjTRAF3 was 2972 bp including a 5' untranslated region (UTR) of 243 bp, a 3'UTR of 941 bp and a putative open reading frame of 1608 bp encoding a putative protein of 536 amino acid. The deduced LjTRAF3 protein contained a RING finger, two zinc fingers, a coiled-coil, and a meprin and TRAF-C homology domain. Phylogenetic analysis showed that LjTRAF3 shared the closest genetic relationship with Larimichthys crocea TRAF3. Gene expression analyses suggested that LjTRAF3 mRNA was ubiquitously expressed in all the tissues tested, and was up-regulated post red spotted grouper nervous necrosis virus (RGNNV) infection in vivo and in vitro. Reporter gene assay showed that LjTRAF3 significantly activated zebrafish type I interferon (IFN) promoter in vitro. During RGNNV infection, ectopic expression of LjTRAF3 significantly reduced the RNA dependent RNA polymerase transcription of RGNNV, and enhanced the expression of RIG-I-like receptors (RLR), janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling pathway related genes and IFN stimulated genes (ISGs), including ISG15, PKR, VIG and TRIM39. Taken together, our results suggested that LjTRAF3 might trigger the expression of various ISGs to counter RGNNV infection by regulating the RLR-induced IFN and JAK-STAT signaling pathways.

Role of TRAF3 in neurological and cardiovascular diseases: an overview of recent studies

Tumour necrosis factor receptor-associated factor 3 (TRAF3) is a member of the TRAF adaptor protein family, which exerts different effects on the cell depending on the receptor to which it binds and the cell type in which it is expressed. TRAF3 is a major regulator of the innate immune response. To perform its functions properly, TRAF3 is transcriptionally and epigenetically regulated. At the transcriptional level, TRAF3 expression has been associated with neurological and cardiovascular diseases including stroke, among other pathologies. Epigenetic modifications of TRAF3 have been observed at the histone and DNA levels. It has been observed that acetylation of TRAF3, as well as other NF-κβ target genes, is associated with cardiac hypertrophy. Furthermore, TRAF3 methylation has been associated with vascular recurrence after ischemic stroke in patients treated with clopidogrel. In this overview, we summarise the most interesting studies related to transcriptional and epigenetic regulation of TRAF3 focusing on those studies performed in neurological and cardiovascular diseases.

TRAF2 in osteotropic breast cancer cells enhances skeletal tumour growth and promotes osteolysis

NFκB plays an important role in inflammation and bone remodelling. Tumour necrosis factor receptor associated factor 2 (TRAF2), a key component of NFκB signalling, has been identified as an oncogene, but its role in the regulation of breast cancer osteolytic metastasis remains unknown. Here, we report that stable overexpression of TRAF2 in parental and osteotropic sub-clones of human MDA-MB-231 (MDA-231) breast cancer cells increased cell growth and motility in vitro, whereas TRAF2 knockdown was inhibitory. In vivo, TRAF2 overexpression in the parental MDA-231-P cells enhanced tumour growth after orthotopic injection into the mammary fat pad of mice but failed to promote the metastasis of these cells to bone. In contrast, overexpression of TRAF2 in osteotropic MDA-231-BT cells increased skeletal tumour growth, enhanced osteoclast formation and worsened osteolytic bone loss after intra-tibial injection in mice. Mechanistic and functional studies in osteotropic MDA-231-BT and osteoclasts revealed that upregulation of TRAF2 increased the ability of osteotropic MDA-231-BT cells to migrate and to enhance osteoclastogenesis by a mechanism dependent, at least in part, on NFκB activation. Thus, the TRAF2/NFκB axis is implicated in the regulation of skeletal tumour burden and osteolysis associated with advanced breast cancer.

Fbxo3-Dependent Fbxl2 Ubiquitination Mediates Neuropathic Allodynia through the TRAF2/TNIK/GluR1 Cascade

Emerging evidence has indicated that the pathogenesis of neuropathic pain is mediated by spinal neural plasticity in the dorsal horn, which provides insight for analgesic therapy. Here, we report that the abundance of tumor necrosis factor receptor-associated factor 2 and NcK-interacting kinase (TNIK), a kinase that is presumed to regulate neural plasticity, was specifically enhanced in ipsilateral dorsal horn neurons after spinal nerve ligation (SNL; left L5 and L6). Spinal TNIK-associated allodynia is mediated by downstream TNIK-GluR1 coupling and the subsequent phosphorylation-dependent trafficking of GluR1 toward the plasma membrane in dorsal horn neurons. Tumor necrosis factor receptor-associated factor 2 (TRAF2), which is regulated by spinal F-box protein 3 (Fbxo3)-dependent F-box and leucine-rich repeat protein 2 (Fbxl2) ubiquitination, contributes to SNL-induced allodynia by modifying TNIK/GluR1 phosphorylation-associated GluR1 trafficking. Although exhibiting no effect on Fbxo3/Fbxl2/TRAF2 signaling, focal knockdown of spinal TNIK expression prevented SNL-induced allodynia by attenuating TNIK/GluR1 phosphorylation-dependent subcellular GluR1 redistribution. In contrast, intrathecal administration of BC-1215 (N1,N2-Bis[[4-(2-pyridinyl)phenyl]methyl]-1,2-ethanediamine) (a novel Fbxo3 inhibitor) prevented SNL-induced Fbxl2 ubiquitination and subsequent TFAF2 de-ubiquitination to ameliorate behavioral allodynia via antagonizing TRAF2/TNIK/GluR1 signaling. By targeting spinal Fbxo3-dependent Fbxl2 ubiquitination and the subsequent TRAF2/TNIK/GluR1 cascade, spinal application of a TNF-α-neutralizing antibody ameliorated SNL-induced allodynia, and, conversely, intrathecal TNF-α injection into naive rats induced allodynia via a spinal Fbxo3/Fbxl2-dependent modification of the TRAF2/TNIK/GluR1 cascade. Together, our results suggest that spinal TNF-α contributes to the development of neuropathic pain by upregulating TRAF2/TNIK/GluR1 signaling via Fbxo3-dependent Fbxl2 ubiquitination and degradation. Thus, we propose a potential medical treatment strategy for neuropathic pain by targeting the F-box protein or TNIK.

SIGNIFICANCE STATEMENT

TNF-α participates in neuropathic pain development by facilitating the spinal TRAF2-dependent TNIK-GluR1 association, which drives GluR1-containing AMPA receptor trafficking toward the plasma membrane. In addition, F-box protein 3 modifies this pathway by inhibiting F-box and leucine-rich repeat protein 2-mediated TRAF2 ubiquitination, suggesting that protein ubiquitination contributes crucially to the development of neuropathic pain. These results provide a novel therapeutic strategy for pain relief.

Genome-wide identification and characterization of TRAF genes in the Yesso scallop (Patinopecten yessoensis) and their distinct expression patterns in response to bacterial challenge

The tumor necrosis factor (TNF) receptor associated factors (TRAFs) are the major signal transducers for the TNF receptor superfamily and the interleukin-1 receptor/Toll-like receptor (IL-1R/TLR) superfamily, which regulate a variety of cellular activities and innate immune responses. TRAF genes have been extensively studied in various species, including vertebrates and invertebrates. However, as one of the key component of NF-κB pathway, TRAF genes have not been systematically characterized in marine invertebrates. In this study, we identified and characterized five TRAF genes, PyTRAF2, PyTRAF3, PyTRAF4, PyTRAF6 and PyTRAF7, in the Yesso scallop (Patinopecten yessoensis). Phylogenetic and protein structural analyses were conducted to determine their identities and evolutionary relationships. In comparison with the TRAF genes from vertebrate species, the structural features were all relatively conserved in the PyTRAF genes. To gain insights into the roles of TRAF genes during scallop innate immune responses, quantitative real-time PCR was used to investigate the expression profiles in the different stages of scallop development, in the healthy adult tissues, and in the hemocytes after bacterial infection with Micrococcus luteus and Vibrio anguillarum. Based on the qRT-PCR analysis, the expression of most of the PyTRAFs was significantly induced in the acute phases (3-6 h) after infection with Gram-positive (M. luteus) and Gram-negative (V. anguillarum) bacteria, and many more dramatic changes in PyTRAFs expression were observed after V. anguillarum challenge. Notably, the strong response in the up-regulation of PyTRAF6 post-bacterial challenge was distinct from that previously reported in scallops and crabs but was similar to that of other shellfish, Echinodermata and even teleost fish. The high level expressions of PyTRAFs in the hemocytes and the gill, and their specific expression patterns after challenges provide insights into the versatile roles and responses of TRAFs in the innate immune system against Gram-negative bacterial pathogens in bivalves.

Structural Insights into mitochondrial antiviral signaling protein (MAVS)-tumor necrosis factor receptor-associated factor 6 (TRAF6) signaling

In response to viral infection, cytosolic retinoic acid-inducible gene I-like receptors sense viral RNA and promote oligomerization of mitochondrial antiviral signaling protein (MAVS), which then recruits tumor necrosis factor receptor-associated factor (TRAF) family proteins, including TRAF6, to activate an antiviral response. Currently, the interaction between MAVS and TRAF6 is only partially understood, and atomic details are lacking. Here, we demonstrated that MAVS directly interacts with TRAF6 through its potential TRAF6-binding motif 2 (T6BM2; amino acids 455-460). Further, we solved the crystal structure of MAVS T6BM2 in complex with the TRAF6 TRAF_C domain at 2.95 Å resolution. T6BM2 of MAVS binds to the canonical adaptor-binding groove of the TRAF_C domain. Structure-directed mutational analyses in vitro and in cells revealed that MAVS binding to TRAF6 via T6BM2 instead of T6BM1 is essential but not sufficient for an optimal antiviral response. Particularly, a MAVS mutant Y460E retained its TRAF6-binding ability as predicted but showed significantly impaired signaling activity, highlighting the functional importance of this tyrosine. Moreover, these observations were further confirmed in MAVS(-/-) mouse embryonic fibroblast cells. Collectively, our work provides a structural basis for understanding the MAVS-TRAF6 antiviral response.

Expression, correlation, and prognostic value of TRAF2 and TRAF4 expression in malignant plural effusion cells in human breast cancer

BACKGROUND

TRAF2 and TRAF4, members of the tumor necrosis factor receptor- associated factor family of intracellular signal transduction proteins, are associated with breast cancer progression and metastasis.

METHODS

We collected malignant serous effusion cells from the patients with breast cancer (n = 46). Cell blocks prepared from plural effusions (n = 46) and primary breast cancer (n = 50), lymph node metastases (n = 50), and normal breast tissue specimens (n = 30). The immunohistochemistry was performed for the detection of TRAF2 and TRAF4 expression with the correlation of their expression with clinicopathological parameters and survival rate analyzed.

RESULTS

Compared with normal breast tissues, TRAF2 expression was upregulated, and nuclear TRAF4 expression was downregulated in malignant pleural effusion cells, primary tumors, and lymph node metastases (P < 0.05). Multivariate analysis revealed TRAF2 expression in pleural effusions was associated with the molecular/pathological type, venous invasion, and lymph node metastasis, while nuclear TRAF4 expression was associated with age, tumor size, venous invasion, and lymph node metastasis, clinical staging, molecular/pathological subtype and p53 status (P < 0.05). There was a significant positive correlation between TRAF2 and TRAF4 expression levels in malignant pleural effusion cells (r = 0.937; P < 0.01). Kaplan-Meire analysis demonstrated a close correlation of TRAF2 and TRAF4 expression in malignant pleural effusion cells with cumulative overall survival (P < 0.05).

CONCLUSION

TRAF2 and nuclear TRAF4 expression in malignant pleural effusion cells may represent potential prognostic factors and biomarkers of invasion and metastasis in breast cancer.

IL-17 regulates the expressions of RANKL and OPG in human periodontal ligament cells via TRAF6/TBK1-JNK/NF-κB pathways

Interleukin-17 (IL-17 or IL-17A), a pleiotropic cytokine produced by T helper (Th) 17 cells, is involved in the pathogenesis of various autoimmune and inflammatory disorders, including periodontitis. Although the ability of pro-inflammation in periodontitis have been widely investigated, the other biological functions of IL-17, including its role in bone remodeling and the underlying molecular mechanism, have not been well clarified. In the present study, IL-17 could significantly enhance the expression of receptor activator for nuclear factor-κB ligand (RANKL) and inhibit the expression of osteoprotegerin (OPG) in human periodontal ligament cells (hPDLCs), the two critical indicators for osteoclastogenesis, suggesting IL-17 may play a destructive role in the pathogenesis of periodontal bone remodeling. Pharmaceutical signal inhibitors targeted at MAPKs, Akt or NF-κB signals, inhibited IL-17-induced RANKL and OPG regulation. Notably, the enhancement of RANKL was significantly blocked by the inhibitors of JNK and NF-κB signals. The upstream signals were further investigated with the small interfering RNA (siRNA). Both TRAF6 and TBK1 were found to be the critically signal molecules for IL-17-dependent RANKL regulation in hPDLCs. These findings may provide comprehensive understanding of the role of IL-17 in the pathogenesis of periodontitis and might also provide a reasonable way for periodontitis therapy. This article is protected by copyright. All rights reserved.

TRIM13 regulates ubiquitination and turnover of NEMO to suppress TNF induced NF-κB activation

The NF-κB family of transcription factors is activated in response to various intracellular or extracellular stimuli and its dysregulation leads to pathological conditions like infection, cancer, neurodegenerative disorders. The post-translational modification by ubiquitination regulates various steps of NF-κB pathway. In the current study, we have described the role of TRIM13, an endoplasmic reticulum (ER) membrane anchored E3 ligase in regulation of NF-κB. The expression of TRIM13 represses TNF induced NF-κB while the knockdown has the opposite effect. The E3 ligase activity and ER localization is essential for NF-κB suppression whereas TRIM13 regulated autophagy is not essential. TRIM13 interacts with NEMO and modulates its ubiquitination and turnover, hence may regulate IKK complex activity. TRIM13 mediated NF-κB repression is essential for negative regulation of clonogenic ability of the cells. This study for the first time demonstrated the role of TRIM13, ER resident RING E3 ligase as a novel regulator of NEMO ubiquitination, negative regulator of NF-κB signaling and its role as a tumor suppressor.

Effects of magnesium deficiency--more than skin deep

Dead Sea and magnesium salt therapy are two of the oldest forms of treatment for skin disease and several other disorders, supported by a body of largely anecdotal evidence. In this paper we review possible pathways for penetration of magnesium ions through the epidermis to reach the circulation, in turn replenishing cellular magnesium levels. We also discuss mechanisms for intercellular movement of magnesium ions and possible mechanisms for the interaction between magnesium ions and inflammatory mediators. Upon addition of magnesium ions in vitro, the expression of inflammatory mediators such as tumour necrosis factor α (TNFα) and nuclear factor κβ (NFκβ) is down regulated. Dysregulation of these and other inflammatory mediators has been linked to several inflammatory disorders, including asthma, arthritis, atherosclerosis and neuroinflammation.

TRAF4 is a novel phosphoinositide-binding protein modulating tight junctions and favoring cell migration

The cancer-associated TRAF4 protein has a TRAF domain that is a bona fide phosphoinositide-binding domain and involved in the modulation of tight junctions and cell migration.

Tumor necrosis factor (TNF) receptor-associated factor 4 (TRAF4) is frequently overexpressed in carcinomas, suggesting a specific role in cancer. Although TRAF4 protein is predominantly found at tight junctions (TJs) in normal mammary epithelial cells (MECs), it accumulates in the cytoplasm of malignant MECs. How TRAF4 is recruited and functions at TJs is unclear. Here we show that TRAF4 possesses a novel phosphoinositide (PIP)-binding domain crucial for its recruitment to TJs. Of interest, this property is shared by the other members of the TRAF protein family. Indeed, the TRAF domain of all TRAF proteins (TRAF1 to TRAF6) is a bona fide PIP-binding domain. Molecular and structural analyses revealed that the TRAF domain of TRAF4 exists as a trimer that binds up to three lipids using basic residues exposed at its surface. Cellular studies indicated that TRAF4 acts as a negative regulator of TJ and increases cell migration. These functions are dependent from its ability to interact with PIPs. Our results suggest that TRAF4 overexpression might contribute to breast cancer progression by destabilizing TJs and favoring cell migration.

Tumor necrosis factor (TNF) receptor-associated factor 4, also known as TRAF4, is an unusual member of the TRAF protein family. While TRAFs are primarily known as regulators of inflammation, antiviral responses, and apoptosis, research on TRAF4 has identified its involvement in development and cancer. Importantly TRAF4 overexpression has been associated with a poor prognosis in breast cancers. TRAF4 has multiple subcellular localizations: to the plasma membrane in tight junctions (TJs), cytoplasmic and nuclear. The recruitment mechanisms and the functional impact of these distinct localizations are not completely understood. Here we investigate how TRAF4 is recruited to TJs and its involvement in cell–cell contacts in mammary epithelial cells (MECs). We show that the TRAF domain of all TRAFs contains a lipid binding module, and that TRAF4 uses this domain to form a trimeric complex that associates with phosphoinositides at the plasma membrane. Moreover this interaction is necessary for its recruitment to TJs. Additionally, we show that through its interaction with lipids TRAF4 delays TJ assembly and increases cell migration. We propose that TRAF4 has an important function in cancer progression by destabilizing TJs and favoring cell migration.

Medullary thymic epithelial cells, the indispensable player in central tolerance

Crosstalk between thymocytes and thymic epithelial cells is critical for T cell development and the establishment of central tolerance. Medullary thymic epithelial cells (mTECs) play important roles in the late stage of T cell development, especially negative selection and Treg generation. The function of mTECs is highly dependent on their characteristic features such as ectopic expression of peripheral tissue restricted antigens (TRAs) and their master regulator-autoimmune regulator (Aire), expression of various chemokines and cytokines. In this review, we summarize the current understanding of cellular and molecular mechanisms of mTEC development and its functions in T cell development and the establishment of central tolerance. The open questions in this field are also discussed. Understanding the function and underlying mechanisms of mTECs will contribute to the better control of autoimmune diseases and the improvement of immune reconstitution during aging or after infection, chemotherapy or radiotherapy.

Comparative genomic study of gastric epithelial cells co-cultured with Helicobacter pylori

AIM: To identify genes potentially involved in Helicobacter pylori (H. pylori)-induced gastric carcinogenesis.

METHODS: GES-1 cells were co-cultured with H. pylori strains isolated from patients with gastric carcinoma (GC, n = 10) or chronic gastritis (CG, n = 10) for in vitro proliferation and apoptosis assays to identify the most and least virulent strains. These two strains were cagA-genotyped and used for further in vivo carcinogenic virulence assays by infecting Mongolian gerbils for 52 wk, respectively; a broth free of H. pylori was lavaged as control. Genomic profiles of GES-1 cells co-cultured with the most and least virulent strains were determined by microarray analysis. The most differentially expressed genes were further verified using quantitative real-time polymerase chain reaction in GES-1 cells infected with the most and least virulent strains, and by immunohistochemistry in H. pylori positive CG, precancerous diseases, and GC biopsy specimens in an independent experiment.

RESULTS: GC-derived H. pylori strains induced a potent proliferative effect in GES-1 cells in co-culture, whereas CG-derived strains did not. The most (from a GC patient) and least (from a CG patient) virulent strains were cagA-positive and negative, respectively. At week 52, CG, atrophy, metaplasia, dysplasia, and GC were observed in 90.0%, 80.0%, 80.0%, 90%, and 60.0%, respectively, of the animals lavaged with the most virulent strain. However, only mild CG was observed in 90% of the animals lavaged with the least virulent strain. On microarray analysis, 800 differentially expressed genes (49 up- and 751 down-regulated), involving those associated with cell cycle regulation, cell apoptosis, cytoskeleton, immune response, and substance and energy metabolisms, were identified in cells co-cultured with the most virulent strain as compared with those co-cultured with the least virulent strain. The six most differentially expressed genes (with a betweenness centrality of 0.1-0.2) were identified among the significant differential gene profile network, including JUN, KRAS, BRCA1, SMAD2, TRAF1, and HDAC6. Quantitative real-time polymerase chain reaction analyses verified that HDAC6 and TRFA1 mRNA expressions were significantly more up-regulated in GES-1 cells co-cultured with the most virulent strain than in those co-cultured with the least virulent strain. Immunohistochemistry of gastric mucosal specimens from H. pylori-positive patients with CG, intestinal metaplasia (IM), dysplasia, and GC showed that moderately positive and strongly positive HDAC6 expression was detected in 21.7% of CG patients, 30.0% of IM patients, 54.5% of dysplasia patients, and 77.8% of GC patients (P < 0.001). The up-regulation of TRAF1 expressions was detected in 34.8%, 53.3%, 72.7%, and 88.9% specimens of CG, IM, dysplasia, and GC, respectively (P < 0.001).

CONCLUSION: The overexpression of HDAC6 and TRAF1 in GES-1 cells co-cultured with the GC-derived strain and in H. pylori-positive dysplasia and GC suggests that HDAC6 and TRAF1 may be involved in H. pylori-induced gastric carcinogenesis.

Single amino acid substitutions confer the antiviral activity of the TRAF3 adaptor protein onto TRAF5

The TRAF [tumor necrosis factor receptor-associated factor] family of cytoplasmic adaptor proteins link cell-surface receptors to intracellular signaling pathways that regulate innate and adaptive immune responses. In response to activation of RIG-I (retinoic acid-inducible gene I), a component of a pattern recognition receptor that detects viruses, TRAF3 binds to the adaptor protein Cardif [caspase activation and recruitment domain (CARD) adaptor-inducing interferon-β (IFN-β)], leading to induction of type I IFNs. We report the crystal structures of the TRAF domain of TRAF5 and that of TRAF3 bound to a peptide from the TRAF-interacting motif of Cardif. By comparing these structures, we identified two residues located near the Cardif binding pocket in TRAF3 (Tyr(440) and Phe(473)) that potentially contributed to Cardif recognition. In vitro and cellular experiments showed that forms of TRAF5 with mutation of the corresponding residues to those of TRAF3 had TRAF3-like antiviral activity. Our results provide a structural basis for the critical role of TRAF3 in activating RIG-I-mediated IFN production.

The role of costimulatory receptors of the tumour necrosis factor receptor family in atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is mediated by both the innate and adaptive immune responses. T lymphocytes, that together with B cells are the cellular effectors of the adaptive immune system, are currently endowed with crucial roles in the development and progression of atherosclerosis. Costimulatory receptors are a class of molecules expressed by T lymphocytes that regulate the activation of T cells and the generation of effector T-cell responses. In this review we present the roles of costimulatory receptors of the tumour necrosis factor receptor (TNFR) superfamily in atherosclerosis and discuss the implications for future therapies that could be used to specifically modulate the immune response of pathogenic T cells in this disease.

Some latest achievements in immunology research

Immunology has become as an attractive discipline of biomedical science in the 21st century, integrated with the rapid development of molecular biology, cell biology, structural biology, genetics and other branches in life sciences. A special issue of Sci China Life Sci was published in February 2010 to highlight recent progresses in immunology. Six review articles focusing on various specific topics were contributed by leading scientists who work in respective fields of immunology. Some progresses of immunology research in China are also described.

Pleiotropic functions of EAPII/TTRAP/TDP2: cancer development, chemoresistance and beyond

EAPII (also called TTRAP, TDP2), a protein identified a decade ago, has recently been shown to function as an oncogenic factor. This protein was also proven to be the first 5'- tyrosyl-DNA phosphodiesterase. EAPII has been demonstrated to have promiscuous protein associations, broad responsiveness to various extracellular signals, and pleiotropic functions in the development of human diseases including cancer and neurodegenerative disease. Emerging data suggest that EAPII is a multi-functional protein: EAPII repairs enzyme (topoisomerase)-mediated DNA damage by removing phosphotyrosine from DNA adducts; EAPII is involved in multiple signal transduction pathways such as TNF-TNFR, TGFβ and MAPK, and EAPII is responsive to immune defense, inflammatory response, virus infection and DNA toxins (chemo or radiation therapy). This review focuses on the current understanding of EAPII biology and its potential relations to many aspects of cancer development, including chromosome instability, tumorigenesis, tumor metastasis and chemoresistance, suggesting it as a potential target for intervention in cancer and other human diseases.

Expression of TRAF6 and pro-inflammatory cytokines through activation of TLR2, TLR4, NOD1, and NOD2 in human periodontal ligament fibroblasts

OBJECTIVE

Human periodontal ligament fibroblasts (HPDLFs) play a crucial role in protecting against oral bacteria in periapical tissue. Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD) are two major forms of innate immune sensors that recognize microbial pathogens and initiate pro-inflammatory signalling. Tumour necrosis factor receptor-associated factor 6 (TRAF6) is an adapter protein for TLR-mediated nuclear factor-κB (NF-κB) signalling pathway activation that induces the production of pro-inflammatory cytokines. The aim of this study was to investigate the expression of TLR2, TLR4, NOD1, and NOD2 in HPDLFs. We also investigated the expression of TRAF6 and pro-inflammatory cytokines induced by the activation of TLRs and NODs.

METHODS

The expression of TLR2, TLR4, NOD1, and NOD2 was measured by reverse transcription-polymerase chain reaction (RT-PCR), flow cytometry, and immunostaining. HPDLFs were stimulated with TLR and NOD agonists. Then, the expression of TRAF6 was measured by real-time PCR and western blot. Concentrations of IL-1β, IL-6, and IL-8 in the culture supernatants were determined by enzyme-linked immunosorbent assay (ELISA). Finally, by using small interfering RNA (siRNA) for TRAF6, we analysed the production of IL-1β, IL-6, and IL-8 in HPDLFs upon stimulation with TLRs and NODs agonists.

RESULTS

We found clear mRNA and protein expression of TLR2, TLR4, NOD1, and NOD2 in HPDLFs. The expression levels of TRAF6 and pro-inflammatory cytokines (IL-1β, IL-6, and IL-8) were markedly up-regulated upon the activation of TLRs and NODs. Furthermore, the co-activation of TLRs and NODs had synergistic effect on the production of TRAF6 and pro-inflammatory cytokines. We also found TRAF6 suppression resulted in reduced IL-1β, IL-6, and IL-8 expression upon TLR and NOD agonists challenge.

CONCLUSION

These findings indicated that TLR2, TLR4, NOD1, and NOD2 are functional receptors in HPDLFs during innate immune responses to invading bacteria, and a combination of signalling through TLRs and NODs leads to the synergistic enhancement of inflammatory reactions in HPDLFs. In addition, TLR and NOD signalling involving TRAF6 contribute to inflammatory responses in HPDLFs.