Lower levels of TRAF1 in Brodmann's area 24, but not 46, in bipolar disorders are not detectable in major depressive disorders

INTRODUCTION

Multiple lines of research implicate inflammation-related pathways in the molecular pathology of mood disorders, with our data suggesting a critical role for aberrant cortical tumour necrosis factor α (TNF)-signaling in the molecular pathology of bipolar disorders (BPD) and major depressive disorders (MDD).

METHODS

To extend our understanding of changes in TNF-signaling pathways in mood disorders we used Western blotting to measure levels of tumour necrosis factor receptor associated factor 1 (TRAF1) and transmembrane TNF receptor superfamily member 1B (tmTNFRSF1B) in Brodmann's areas (BA) 24 and 46 from people with BPD and MDD. These proteins are key rate-limiting components within TNF-signaling pathways.

RESULTS

Compared to controls, there were higher levels of TRAF1 of large effect size (η = 0.19, Cohen's d = 0.97) in BA 24, but not BA 46, from people with BPD. Levels of TRAF1 were not altered in MDD and levels of tmTNFRSF1B were not altered in either disorder.

LIMITATIONS

The cases studied had been treated with psychotropic drugs prior to death which is an unresolvable study confound. Cohort sizes are relatively small but not untypical of postmortem CNS studies.

CONCLUSIONS

To facilitate post-synaptic signaling, TRAF1 is known to associate with tmTNFRSF1B after that receptor takes its activated conformation which occurs predominantly after it binds to transmembrane TNF (tmTNF). Simultaneously, when tmTNFRSF1B binds to tmTNF reverse signaling through tmTNF is activated. Hence our findings in BA 24 argues that bidirectional TNF-signaling may be an important component of the molecular pathology of BPD.

Association between TRAF1/C5 Gene Polymorphisms and IgA Vasculitis in Chinese Children

OBJECTIVE

To investigate the association between loci rs3761847 and rs10818488 of tumor necrosis factor receptor-associated factor 1/complement C5 (TRAF1/C5) gene and the susceptibility to IgAV.

METHODS

100 blood samples of children with IgAV and 100 blood samples of healthy children were collected from the Third Xiangya Hospital of Central South University from June 2017 to June 2019. The target gene fragment was amplified by polymerase chain reaction (PCR), and the single nucleic acid gene polymorphism of the gene loci was detected by PCR sequencing based typing technique. The association between gene polymorphism of each locus and susceptibility to IgAV was analyzed.

RESULTS

There were significant differences in both genotype (P < .05) and allele frequencies （P < .05) of rs3761847 of TRAF1/C5 gene between the IgAV group and the control group.Besides, the risks of developing IgAV in children with the TT genotype was 0.495 times and in children with the C allele was 1.627 times of that in children with other genotypes and alleles, respectively (P < .05). For IgAV patients, renal involvement risk in children with CC genotype was 5.859 times of that in children with other genotypes (P < .05). There were no significant differences in genotype (P > .05) and allele frequencies (P > .05) of rs10818488 of TRAF1/C5 gene between the IgAV group and the control group. IgAV patients with TT genotype had a 3.2 times higher risk of renal involvement than those with other genotypes (P < .05).

CONCLUSIONS

There is an association between locus rs3761847 of TRAF1/C5 gene single nucleotide polymorphisms and susceptibility to IgAV. The T allele at locus rs3761847 of TRAF1/C5 gene may be a protective factor for IgAV. The C allele at locus rs3761847 and the T allele at locus rs10818488 of TRAF1/C5 gene may be associated with kidney injury in IgAV.

CIRCESPL1 SILENCING PROTECTS AGAINST LPS-INDUCED LUNG FIBROBLAST DYSFUNCTION PARTLY BY TARGETING THE MIR-146B-3P/TRAF1 AXIS IN PNEUMONIA

ABSTRACT

Background: Neonatal pneumonia is a common disease in the neonatal period with high mortality. The present work concentrated on the role and mechanism of circular RNA extra spindle pole bodies like 1, separase (circESPL1) in LPS-induced dysfunction of lung fibroblasts. Methods: Reverse transcription-quantitative polymerase chain reaction and Western blot assay were conducted to analyze RNA and protein expression, respectively. Cell viability, proliferation, apoptosis, and inflammation were assessed by Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine assay, flow cytometry, and enzyme-linked immunosorbent assay, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation assay were conducted to verify the intermolecular interactions among circESPL1, miR-146b-3p, and TRAF1. Results: CircESPL1 expression was upregulated in the serum samples of pneumonia patients and LPS-induced lung fibroblasts. CircESPL1 silencing protected lung fibroblasts against LPS-induced dysfunction. CircESPL1 bound to microRNA-146b-3p (miR-146b-3p) in lung fibroblasts. CircESPL1 knockdown-mediated protective effects on LPS-induced lung fibroblasts were largely reversed by the silence of miR-146b-3p. miR-146b-3p directly interacted with the 3' untranslated region of TNF receptor associated factor 1 (TRAF1), and TRAF1 expression was regulated by the circESPL1/miR-146b-3p axis in lung fibroblasts. TRAF1 overexpression largely reversed miR-146b-3p accumulation-mediated protective effects on LPS-induced lung fibroblasts. Conclusion: CircESPL1 knockdown protected lung fibroblasts from LPS-induced injury partly by targeting the miR-146b-3p/TRAF1 axis.

CD40/TRAF1 decreases synovial cell apoptosis in patients with rheumatoid arthritis through JNK/NF-κB pathway

INTRODUCTION

A genome-wide association analysis revealed a rheumatoid arthritis (RA)-risk-associated genetic locus on chromosome 9, which contained the tumor necrosis factor receptor-associated factor 1 (TRAF1). However, the detail mechanism by TRAF1 signaled to fibroblast-like synoviocytes (FLSs) apoptosis remains to be fully understood.

MATERIALS AND METHODS

Synovial tissue of 10 RA patients and osteoarthritis patients were obtained during joint replacement surgery. We investigated TRAF1 level and FLSs apoptosis percentage in vivo and elucidated the mechanism involved in the regulation of apoptotic process in vitro.

RESULTS

We proved the significant increase of TRAF1 level in FLSs of RA patients and demonstrated that TRAF1 level correlated positively with DAS28 score and negatively with FLSs apoptosis. Treatment with siTRAF1 was able to decrease MMPs levels and the phosphorylated forms of JNK/NF-κB in vitro. Moreover, JNK inhibitor could attenuate expression of MMPs and increase percentage of apoptosis in RA-FLSs, while siTRAF1 could not promote apoptosis when RA-FLSs were pretreated with JNK activator.

CONCLUSIONS

High levels of TRAF1 in RA synovium play an important role in the synovial hyperplasia of RA by suppressing apoptosis through activating JNK/NF-kB-dependent signaling pathways in response to the engagement of CD40.

Metabolic profiling of maternal serum of women at high-risk of spontaneous preterm birth using NMR and MGWAS approach

Preterm birth (PTB) is a leading global cause of infant mortality. Risk factors include genetics, lifestyle choices and infection. Understanding the mechanism of PTB could aid the development of novel approaches to prevent PTB. This study aimed to investigate the metabolic biomarkers of PTB in early pregnancy and the association of significant metabolites with participant genotypes. Maternal sera collected at 16 and 20 weeks of gestation, from women who previously experienced PTB (high-risk) and women who did not (low-risk controls), were analysed using 1H nuclear magnetic resonance (NMR) metabolomics and genome-wide screening microarray. ANOVA and probabilistic neural network (PNN) modelling were performed on the spectral bins. Metabolomics genome-wide association (MGWAS) of the spectral bins and genotype data from the same participants was applied to determine potential metabolite-gene pathways. Phenylalanine, acetate and lactate metabolite differences between PTB cases and controls were obtained by ANOVA and PNN showed strong prediction at week 20 (AUC = 0.89). MGWAS identified several metabolite bins with strong genetic associations. Cis-eQTL analysis highlighted TRAF1 (involved in the inflammatory pathway) local to a non-coding SNP associated with lactate at week 20 of gestation. MGWAS of a well-defined cohort of participants highlighted a lactate-TRAF1 relationship that could potentially contribute to PTB.

CagA promotes proliferation and inhibits apoptosis of GES-1 cells by upregulating TRAF1/4-1BB

Cytotoxin-associated gene A (CagA) is one of the most important virulence factors of Helicobacter pylori, and serves a role in H. pylori‑mediated tumorigenesis in gastric cancer. However, the underlying molecular mechanism remains to be elucidated. The present study aimed to investigate the effects of CagA on the proliferation and apoptosis of GES‑1 cells, and the underlying mechanism. A CagA eukaryotic expression plasmid was constructed and transfected into GES‑1 cells. The mRNA and protein levels of CagA, tumor necrosis factor receptor‑associated factor 1 (TRAF1) and tumor necrosis factor receptor superfamily member 9 (4‑1BB) were determined using the reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. Western blot and ELISA analysis was used to detect the release of interleukin (IL)‑8. An MTT assay and flow cytometric analysis was used to assess cell viability and apoptosis, respectively. Ectopic expression of CagA markedly increased TRAF1 and 4‑1BB mRNA and protein levels in GES‑1 cells. CagA increased the expression and release of IL‑8 in GES‑1 cells. The expression of CagA significantly promoted the proliferation (P<0.05) and inhibited the apoptosis (P<0.05) of GES‑1 cells. In conclusion, CagA upregulated TRAF1/4‑1BB, thereby promoting the proliferation and inhibiting the apoptosis of GES-1 cells.

TRAF Family Proteins Regulate Autophagy Dynamics by Modulating AUTOPHAGY PROTEIN6 Stability in Arabidopsis

Eukaryotic cells use autophagy to recycle cellular components. During autophagy, autophagosomes deliver cytoplasmic contents to the vacuole or lysosome for breakdown. Mammalian cells regulate the dynamics of autophagy via ubiquitin-mediated proteolysis of autophagy proteins. Here, we show that the Arabidopsis thaliana Tumor necrosis factor Receptor-Associated Factor (TRAF) family proteins TRAF1a and TRAF1b (previously named MUSE14 and MUSE13, respectively) help regulate autophagy via ubiquitination. Upon starvation, cytoplasmic TRAF1a and TRAF1b translocated to autophagosomes. Knockout traf1a/b lines showed reduced tolerance to nutrient deficiency, increased salicylic acid and reactive oxygen species levels, and constitutive cell death in rosettes, resembling the phenotypes of autophagy-defective mutants. Starvation-activated autophagosome accumulation decreased in traf1a/b root cells, indicating that TRAF1a and TRAF1b function redundantly in regulating autophagosome formation. TRAF1a and TRAF1b interacted in planta with ATG6 and the RING finger E3 ligases SINAT1, SINAT2, and SINAT6 (with a truncated RING-finger domain). SINAT1 and SINAT2 require the presence of TRAF1a and TRAF1b to ubiquitinate and destabilize AUTOPHAGY PROTEIN6 (ATG6) in vivo. Conversely, starvation-induced SINAT6 reduced SINAT1- and SINAT2-mediated ubiquitination and degradation of ATG6. Consistently, SINAT1/SINAT2 and SINAT6 knockout mutants exhibited increased tolerance and sensitivity, respectively, to nutrient starvation. Therefore, TRAF1a and TRAF1b function as molecular adaptors that help regulate autophagy by modulating ATG6 stability in Arabidopsis.

Linkage and Association Analysis Identifies TRAF1 Influencing Common Carotid Intima-Media Thickness

BACKGROUND AND PURPOSE

Carotid intima-media thickness is a marker for subclinical atherosclerosis that predicts subsequent clinical cardiovascular events. The aim of this study was to identify chromosomal loci with linkage or association to common carotid intima-media thickness.

METHODS

Nuclear families were recruited using the single parental proband sib-pair design. Genotype data were available for 546 individuals from 132 nuclear families of the Bonn IMT Family Study using the Affymetrix GeneChip Human Mapping 250K Sty chip. Multipoint logarithm of the odds (LOD) scores were determined with the quantitative trait locus statistic implemented in multipoint engine for rapid likelihood. Linkage analysis and family-based association tests were conducted. Data from 2471 German participants from the HNR (Heinz Nixdorf Recall) Study were used for subsequent replication.

RESULTS

Two new genomic regions with suggestive linkage (LOD>2) were identified on chromosome 4 (LOD=2.26) and on chromosome 17 (LOD=2.01). Previously reported linkage findings were replicated on chromosomes 13 and 14. Fifteen single nucleotide polymorhisms, located on chromosomes 4, 6, and 9, revealed P<10^-4 in the family-based association analyses. One of these signals was replicated in HNR (rs2416804, 1-sided P=1.60×10^-3, located in the gene TRAF1).

CONCLUSIONS

This study presents the first genome-wide linkage and association study of common carotid intima-media thickness in the German population. Alleles of rs2416804 in TRAF1 were identified as being linked and associated with carotid intima-media thickness. Further studies are needed to evaluate the contribution of this locus to the development of atherosclerosis.

TRAF1 Coordinates Polyubiquitin Signaling to Enhance Epstein-Barr Virus LMP1-Mediated Growth and Survival Pathway Activation

The Epstein-Barr virus (EBV) encoded oncoprotein Latent Membrane Protein 1 (LMP1) signals through two C-terminal tail domains to drive cell growth, survival and transformation. The LMP1 membrane-proximal TES1/CTAR1 domain recruits TRAFs to activate MAP kinase, non-canonical and canonical NF-kB pathways, and is critical for EBV-mediated B-cell transformation. TRAF1 is amongst the most highly TES1-induced target genes and is abundantly expressed in EBV-associated lymphoproliferative disorders. We found that TRAF1 expression enhanced LMP1 TES1 domain-mediated activation of the p38, JNK, ERK and canonical NF-kB pathways, but not non-canonical NF-kB pathway activity. To gain insights into how TRAF1 amplifies LMP1 TES1 MAP kinase and canonical NF-kB pathways, we performed proteomic analysis of TRAF1 complexes immuno-purified from cells uninduced or induced for LMP1 TES1 signaling. Unexpectedly, we found that LMP1 TES1 domain signaling induced an association between TRAF1 and the linear ubiquitin chain assembly complex (LUBAC), and stimulated linear (M1)-linked polyubiquitin chain attachment to TRAF1 complexes. LMP1 or TRAF1 complexes isolated from EBV-transformed lymphoblastoid B cell lines (LCLs) were highly modified by M1-linked polyubiqutin chains. The M1-ubiquitin binding proteins IKK-gamma/NEMO, A20 and ABIN1 each associate with TRAF1 in cells that express LMP1. TRAF2, but not the cIAP1 or cIAP2 ubiquitin ligases, plays a key role in LUBAC recruitment and M1-chain attachment to TRAF1 complexes, implicating the TRAF1:TRAF2 heterotrimer in LMP1 TES1-dependent LUBAC activation. Depletion of either TRAF1, or the LUBAC ubiquitin E3 ligase subunit HOIP, markedly impaired LCL growth. Likewise, LMP1 or TRAF1 complexes purified from LCLs were decorated by lysine 63 (K63)-linked polyubiqutin chains. LMP1 TES1 signaling induced K63-polyubiquitin chain attachment to TRAF1 complexes, and TRAF2 was identified as K63-Ub chain target. Co-localization of M1- and K63-linked polyubiquitin chains on LMP1 complexes may facilitate downstream canonical NF-kB pathway activation. Our results highlight LUBAC as a novel potential therapeutic target in EBV-associated lymphoproliferative disorders.

The linear ubiquitin assembly complex (LUBAC) plays crucial roles in immune receptor-mediated NF-kB and MAP kinase pathway activation. Comparatively little is known about the extent to which microbial pathogens use LUBAC to activate downstream pathways. We demonstrate that TRAF1 enhances EBV oncoprotein LMP1 TES1/CTAR1 domain mediated MAP kinase and canonical NF-kB activation. LMP1 TES1 signaling induces association between TRAF1 and LUBAC, and triggers M1-polyubiquitin chain attachment to TRAF1 complexes. TRAF1 and LMP1 complexes are decorated by M1-polyubiquitin chains in LCL extracts. TRAF2 plays a key role in LMP1-induced LUBAC recruitment and M1-chain attachment to TRAF1 complexes. TRAF1 and LMP1 complexes are modified by lysine 63-linked polyubiquitin chains in LCL extracts, and TRAF2 is a target of LMP1-induced K63-ubiquitin chain attachment. Thus, the TRAF1:TRAF2 heterotrimer may coordinate ubiquitin signaling downstream of TES1. Depletion of TRAF1 or the LUBAC subunit HOIP impairs LCL growth and survival. Thus, although TRAF1 is the only TRAF without a RING finger ubiquitin ligase domain, TRAF1 nonetheless has important roles in ubiqutin-mediated signal transduction downstream of LMP1. Our work suggests that LUBAC is important for EBV-driven B-cell proliferation, and suggests that LUBAC may be a novel therapeutic target in EBV-associated lymphoproliferative disorders.

Proteomic identification and characterization of Ctenopharyngodon idella tumor necrosis factor receptor-associated protein 1 (CiTrap1): an anti-apoptosis factor upregulated by grass carp reovirus infection

Human tumor necrosis factor receptor-associated protein 1 (Trap1) is a mitochondrial protein identical to heat shock protein 75 (HSP75) that plays an important role in protecting cells from oxidative stress and apoptosis. In this study, grass carp (Ctenopharyngodon idella) tumor necrosis factor receptor-associated protein 1 (designated as CiTrap1) was identified through two-dimensional electrophoresis (2-DE) analysis and its pattern of expression was investigated in grass carp kidney (CIK) cells infected with grass carp reovirus (GCRV). The full length cDNA of CiTrap1 contained an opening reading frame of 2157 bp that encoded a peptide of 718 amino acids. Phylogenetic analyses indicated that the CiTrap1 shared 87% identity with its homologue from zebrafish (Danio rerio). The transcriptional level of CiTrap1 in CIK cells was upregulated post virus infection as well as poly (I: C) stimulation. Following virus infection, grass carp PTEN-induced putative kinase 1 (PINK1) and Sorcin, whose coding proteins interact with Trap1 in human, were simultaneously upregulated with CiTrap1. Typical characteristics of apoptosis were observed in CIK cells infected with GCRV by DAPI staining, DNA ladder electrophoresis, TUNEL assay and Annexin Ⅴ labeling. RNAi-mediated silencing of CiTrap1 in CIK cells resulted in the increased rate of virus-induced apoptotic cells. The results of this study suggest that CiTrap1 is involved in the host's innate immune response to viral infection possibly through protecting infected cells from apoptosis.

DNMT3L interacts with transcription factors to target DNMT3L/DNMT3B to specific DNA sequences: role of the DNMT3L/DNMT3B/p65-NFκB complex in the (de-)methylation of TRAF1

DNMT3L i.e. DNA (cytosine-5)-methyltransferase 3-like protein, is devoid of cytosine methyltransferase activity, despite clear homology to DNMT3A and DNMT3B, due to the mutation of key catalytic residues. However, DNMT3L participates in de novo methylation reactions through its direct interaction with DNMT3A and DNMT3B. In the present study, we investigated if DNMT3L interacts also directly with transcription factors (TFs). Using TF arrays, we identified 73 TFs that interacted with DNMT3L, 13 of which (ASH2L, ATF1, ATF3, BLZF1, CDX2, CERM, E2F3, E2F4, GCNF, GTF2I, GTF3C5, NFkB-p65 and RXRα) interacted only with DNMT3L, but not with DNMT3A/B. By focusing on the interaction with NFkB-p65, we demonstrate that DNMT3L forms a complex with DNMT3B and NFkB-p65 and that this complex is required for the control of DNA methylation at the TRAF1 promoter in the T98G glioma cell line. In addition, our experiments describe the DNA methylation at TRAF1 as being dynamic with a demethylation phase involving TET3. Thus, our data suggests that DNMT3L can address DNMT3A/B to specific sites by directly interacting with TFs that do not directly interact with DNMT3A/B. In summary, our data provide a new avenue for the direction of site-specific de novo DNA methylation catalyzed by DNMT3A/B.

A single nucleotide polymorphism of TRAF1 predicts the clinical response to anti-TNF treatment in Japanese patients with rheumatoid arthritis

OBJECTIVES

Recent genome-wide association studies disclosed that several single nucleotide polymorphisms (SNPs), including tumour necrosis factor (TNF) receptor-associated factor 1 (TRAF1) (+16860A/G), are associated with the pathophysiology of rheumatoid arthritis (RA). We assessed the usefulness of TRAF1 genotyping as a genetic predictor of the response to anti-TNF treatment in Japanese RA patients.

METHODS

TRAF1 (+16860A/G) was genotyped using the TaqMan SNP genotyping assay in 101 Japanese RA patients treated with anti-TNF drugs for >24 weeks. We retrospectively analysed the association between SNP and the clinical response to treatment. TRAF1 mRNA and protein expression was also evaluated in CD4+, CD8+, CD14+, or CD19+ cells from 25 healthy subjects using quantitative polymerase chain reaction and intracellular staining flow cytometry, respectively.

RESULTS

No statistical difference in DAS28-ESR at baseline was observed between the patient groups with the AA, AG, or GG genotype. The GG genotype was more frequent in non-responders than in good or moderate responders [odds ratio (OR) 7.4, 95% confidence interval (CI) 1.5-37.5]. The non-responders possessed the G allele more frequently than the good or moderate responders (OR 3.5, 95% CI 1.4-9.0). TRAF1 protein expression increased significantly in CD14+ monocytes from healthy subjects with the GG genotype compared with that in subjects with the AA or AG genotype.

CONCLUSIONS

TRAF1 (+16860A/G) may be useful for predicting the clinical response to anti-TNF treatment and may contribute to resistance to treatment in RA patients with the GG genotype by increasing the TRAF1 expression in circulating inflammatory cells.

Lack of association between single nucleotide polymorphism rs10818488 in TRAF1/C5 region and rheumatoid arthritis in iranian population

The association of rs10818488 SNP located in TRAF1/C5 region with Rheumatoid Arthritis (RA), has been picked up by genome-wide association studies. Independent studies in different populations revealed inconsistent results. The aim of this study was to investigate the possible association of this SNP with RA in Iranian population. A total of 362 cases and 422 healthy controls were recruited in this study. Genomic DNA was extracted from whole blood and the genotyping was performed by PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism). A set of genotypes was confirmed by sequencing. Genotype and allele frequencies were compared between the case and control groups. Analysis indicated a higher frequency of A allele in cases, although the difference was not statistically significant (Chi-square=2.8, p=0.09). Comparison of genotype frequencies, revealed higher frequencies of AA and AG genotypes in case group but statistically the difference was not significant (Chi-square=2.72, p=0.25). These findings suggest that the rs0818488 in TRAF1/C5 region is not associated with rheumatoid arthritis in Iranian population.

Opposing roles for TRAF1 in the alternative versus classical NF-κB pathway in T cells

T cells lacking TRAF1 hyperproliferate in response to T cell receptor signaling but have impaired signaling downstream of specific TNFR family members such as 4-1BB. Here we resolve this paradox by showing that while TRAF1 is required for maximal activation of the classical NF-κB pathway downstream of 4-1BB in primary T cells, TRAF1 also restricts the constitutive activation of NIK in anti-CD3-activated T cells. Activation of the alternative NF-κB pathway is restricted in unstimulated cells by a cIAP1/2:TRAF2:TRAF3:NIK complex. Using knockdown of NIK by siRNA we show that in activated CD8 T cells TRAF1 is also involved in this process and that constitutive activation of the alternative NF-κB pathway is responsible for costimulation independent hyperproliferation and excess cytokine production in TRAF1-deficient CD8 T cells compared with WT CD8 T cells. The T cell costimulatory molecule 4-1BB critically regulates the survival of activated and memory CD8 T cells. We demonstrate that stimulation through 4-1BB induces cIAP1-dependent TRAF3 degradation and activation of the alternative NF-κB pathway. We also show that while both TRAF1 and cIAP1 have non-redundant roles in suppressing the alternative NF-κB pathway in T cells activated in the absence of costimulation, activation of the classical NF-κB pathway downstream of 4-1BB requires TRAF1, whereas cIAP1 plays a redundant role with cIAP2. Collectively these results demonstrate that TRAF1 plays a critical role in regulating T cell activation both through restricting the costimulation independent activation of NIK in activated T cells and by promoting the 4-1BB-induced classical NF-κB pathway.

TRAF1/C5, eNOS, C1q, but not STAT4 and PTPN22 gene polymorphisms are associated with genetic susceptibility to systemic lupus erythematosus in Turkey

A significant source of variability in the literature on systemic lupus erythematosus (SLE) susceptibility genes has been the inability to replicate genetic findings across different racial or ethnic groups. We investigated whether a single nucleotide polymorphism (SNP) of the STAT4 (rs7574865), PTPN22 (rs2476601), TRAF1/C5 (rs10818488), and C1q (rs292001) genes as well as the 27-bp VNTR polymorphism on intron 4 of eNOS, previously associated with SLE in other populations, are also associated with SLE risk in Turkey. A group of 158 SLE patients and 155 healthy controls were included in this study. A genetic association of the TRAF1/C5, C1q, and eNOS gene polymorphism, but not of STAT4 and PTPN22, was found to confer a degree of risk for SLE. These data highlight the importance of comparative studies in different populations to confirm the previously detected genetic associations.

Single nucleotide polymorphisms at the TRAF1/C5 locus are associated with rheumatoid arthritis in a Han Chinese population

BACKGROUND

Genetic variants in TRAF1C5 and PTPN22 genes have been shown to be significantly associated with arthritis rheumatoid in Caucasian populations. This study investigated the association between single nucleotide polymorphisms (SNPs) in TRAF1/C5 and PTPN22 genes and rheumatoid arthritis (RA) in a Han Chinese population. We genotyped SNPs rs3761847 and rs7021206 at the TRAF1/C5 locus and rs2476601 SNP in the PTPN22 gene in a Han Chinese cohort composed of 576 patients with RA and 689 controls. The concentrations of anti-cyclic citrullinated peptide antibodies (CCP) and rheumatoid factor (RF) were determined for all affected patients. The difference between the cases and the controls was compared using χ2 analysis.

RESULTS

Significant differences in SNPs rs3761847 and rs7021206 at TRAF1/C5 were observed between the case and control groups in this cohort; the allelic p-value was 0.0018 with an odds ratio of 1.28 for rs3761847 and 0.005 with an odds ratio of 1.27 for rs7021206. This significant association between rs3761847 and RA was independent of the concentrations of anti-CCP and RF. No polymorphism of rs2476601 was observed in this cohort.

CONCLUSIONS

We first demonstrated that genetic variants at the TRAF1/C5 locus are significantly associated with RA in Han Chinese, suggesting that TRAF1/C5 may play a role in the development of RA in this population, which expands the pathogenesis role of TRAF1/C5 in a different ethnicity.

Interaction of the TNFR-receptor associated factor TRAF1 with I-kappa B kinase-2 and TRAF2 indicates a regulatory function for NF-kappa B signaling

BACKGROUND

I-kappa B kinase 2 (IKK2 or IKK-beta) is one of the most crucial signaling kinases for activation of NF-kappa B, a transcription factor that is important for inflammation, cell survival and differentiation. Since many NF-kappa B activating pathways converge at the level of IKK2, molecular interactions of this kinase are pivotal for regulation of NF-kappa B signaling.

METHODOLOGY/PRINCIPAL FINDINGS

We searched for proteins interacting with IKK2 using the C-terminal part (amino acids 466-756) as bait in a yeast two-hybrid system and identified the N-terminal part (amino acids 1-228) of the TNF-receptor associated factor TRAF1 as putative interaction partner. The interaction was confirmed in human cells by mammalian two-hybrid and coimmunoprecipitation experiments. The IKK2/TRAF1 interaction seemed weaker than the interaction between TRAF1 and TRAF2, an important activating adapter molecule of NF-kappa B signaling. Reporter gene and kinase assays using ectopic expression of TRAF1 indicated that it can both activate and inhibit IKK2 and NF-kappa B. Co-expression of fluorescently tagged TRAF1 and TRAF2 at different ratios implied that TRAF1 can affect clustering and presumably the activating function of TRAF2 in a dose dependent manner.

CONCLUSIONS/SIGNIFICANCE

The observation that TRAF1 can either activate or inhibit the NF-kappa B pathway and the fact that it influences the oligomerization of TRAF2 indicates that relative levels of IKK2, TRAF1 and TRAF2 may be important for regulation of NF-kappa B activity. Since TRAF1 is an NF-kappa B induced gene, it might act as a feedback effector molecule.

Lack of association of PTPN22, STAT4 and TRAF1/C5 gene polymorphisms with cardiovascular risk in rheumatoid arthritis

OBJECTIVES

To determine whether the PTPN22, STAT4 and TRAF1/C5 gene polymorphisms may be implicated in the development of cardiovascular (CV) events and subclinical atherosclerosis manifested by the presence of endothelial dysfunction or increased carotid intima-media thickness (IMT) in a series of Spanish patients with rheumatoid arthritis (RA).

METHODS

Six hundred and twelve patients fulfilling the 1987 American College of Rheumatology classification criteria for RA, seen at the rheumatology outpatient clinics of Hospital Xeral-Calde, Lugo, and Hospital San Carlos, Madrid, were studied. Patients were genotyped using predesigned TaqMan single nucleotide polymorphism genotyping assays. Moreover, between March and December 2007, a subgroup of unselected RA patients with no history of CV events was studied for the presence of subclinical atherosclerosis by the assessment of the endothelial function (n=126) and the carotid artery IMT (n=110) by ultrasonography studies.

RESULTS

No significant differences in the allele or genotype frequencies for the PTPN22, STAT4 and TRAF1/C5 gene polymorphisms between RA patients with or without CV events were found. It was also the case when we analysed the potential influence of the genotypes in the presence of endothelial dysfunction or increased carotid artery IMT of patients with RA.

CONCLUSIONS

Our results do not show that the PTPN22, STAT4 and TRAF1/C5 gene polymorphisms may confer a direct risk of CV disease in patients with RA.

Genetic risk factors in lupus nephritis and IgA nephropathy--no support of an overlap

Background

IgA nephropathy (IgAN) and nephritis in Systemic Lupus Erythematosus (SLE) are two common forms of glomerulonephritis in which genetic findings are of importance for disease development. We have recently reported an association of IgAN with variants of TGFB1. In several autoimmune diseases, particularly in SLE, IRF5, STAT4 genes and TRAF1-C5 locus have been shown to be important candidate genes. The aim of this study was to compare genetic variants from the TGFB1, IRF5, STAT4 genes and TRAF1-C5 locus with susceptibility to IgAN and lupus nephritis in two Swedish cohorts.

Patients and Methods

We genotyped 13 single nucleotide polymorphisms (SNPs) in four genetic loci in 1252 DNA samples from patients with biopsy proven IgAN or with SLE (with and without nephritis) and healthy age- and sex-matched controls from the same population in Sweden.

Results

Genotype and allelic frequencies for SNPs from selected genes did not differ significantly between lupus nephritis patients and SLE patients without nephritis. In addition, haplotype analysis for seven selected SNPs did not reveal a difference for the SLE patient groups with and without nephritis. Moreover, none of these SPNs showed a significant difference between IgAN patients and healthy controls. IRF5 and STAT4 variants remained significantly different between SLE cases and healthy controls. In addition, the data did not show an association of TRAF1-C5 polymorphism with susceptibility to SLE in this Swedish population.

Conclusion

Our data do not support an overlap in genetic susceptibility between patients with IgAN or SLE and reveal no specific importance of SLE associated SNPs for the presence of lupus nephritis.

TNF receptor-associated factor 1 is a positive regulator of the NF-kappaB alternative pathway

Tumor necrosis factor receptor-associated factor 1 (TRAF1) is unique among the members of the TRAF family, as it lacks the N-terminal RING/zinc-finger domain. Also the function of TRAF1 is not clearly established, with many papers reporting contradictory results. Here we show that TRAF1 interacts with BAFF receptor, a member of the TNF receptor family, and positively regulates activation of the alternative NF-kappaB pathway. Ectopic expression of TRAF1 causes degradation of TRAF3, stabilization of NIK, and processing of p100 to produce the mature form p52. In addition, we show that knocking-down expression of TRAF1 in the Hodgkin's disease derived cell line L1236, interfere with p100 processing and with p52 mediate gene transcription. Collectively these results support a role for TRAF1 as a positive regulator of the NF-kappaB alternative pathway.

[Influence of genetic factors on development and severity of rheumatoid arthritis--part II]

In our previous paper we have presented recent advances in the knowledge of the genetic risk factors predisposing to rheumatoid arthritis development. In contrast to the progress that has been made in identification of genes responsible for susceptibility to RA, there is still little known about genetic risk factors of the more aggressive and (or) refractory RA. In this part of our review we present a detailed knowledge of the role of genetic factors in severity of RA. Gene polymorphisms of the TNF-alpha gene (-238G/A, -308G/A, +489G/ A), IL-1beta gene (-11C/T, +3953C/T), IL-4 gene (-590C/T), MMP genes (-1607 ins1G/del2G, -1612 ins/del A) and TRAF1/C5 genes region (rs 10818488) are among the most intensively investigated HLA independent genetic risk factors of the severe course of RA.

[Influence of genetic factors on development and severity of rheumatoid arthritis--part I]

Both genetic and environmental factors affect susceptibility, severity and probably drugs' efficacy in patients with rheumatoid arthritis (RA). After initial completion of the Human Genome Project on the 16th February 2001, significant progress has been made in identifying other than HLA genome regions linked to the increased RA susceptibility. As an effect several new genes have been recognized as an HLA-independent genetic risk factors of RA. PTPN22 gene polymorphism, C5/TRAF1 genes region polymorphism and TNFAIP3-OLIG3 genes region polymorphism(s) are among newly identified and already confirmed genetic risk factors, whereas STAT 4, CTLA4, PADI4 and IRF5 genes polymorphisms are listed among probable RA development genetic risk factors.

Cytokine-mediated induction of anti-apoptotic genes that are linked to nuclear factor kappa-B (NF-kappaB) signalling in human islets and in a mouse beta cell line

AIMS/HYPOTHESIS

The destruction of pancreatic beta cells leading to type 1 diabetes in humans is thought to occur mainly through apoptosis and necrosis induced by activated macrophages and T cells, and in which secreted cytokines play a significant role. The transcription factor nuclear factor kappa-B (NF-kappaB) plays an important role in mediating the apoptotic action of cytokines in beta cells. We therefore sought to determine the changes in expression of genes modulated by NF-kappaB in human islets exposed to a combination of IL1beta, TNF-alpha and IFN-gamma.

METHODS

Microarray and gene set enrichment analysis were performed to investigate the global response of gene expression and pathways modulated in cultured human islets exposed to cytokines. Validation of a panel of NF-kappaB-regulated genes was performed by quantitative RT-PCR. The mechanism of induction of BIRC3 by cytokines was examined by transient transfection of BIRC3 promoter constructs linked to a luciferase gene in MIN6 cells, a mouse beta cell line.

RESULTS

Enrichment of several metabolic and signalling pathways was observed in cytokine-treated human islets. In addition to the upregulation of known pro-apoptotic genes, a number of anti-apoptotic genes including BIRC3, BCL2A1, TNFAIP3, CFLAR and TRAF1 were induced by cytokines through NF-kappaB. Significant synergy between the cytokines was observed in NF-kappaB-mediated induction of the promoter of BIRC3 in MIN6 cells.

CONCLUSIONS/INTERPRETATION

These findings suggest that, via NF-kappaB activation, cytokines induce a concurrent anti-apoptotic pathway that may be critical for preserving islet integrity and viability during the progression of insulitis in type 1 diabetes.

A large-scale rheumatoid arthritis genetic study identifies association at chromosome 9q33.2

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease affecting both joints and extra-articular tissues. Although some genetic risk factors for RA are well-established, most notably HLA-DRB1 and PTPN22, these markers do not fully account for the observed heritability. To identify additional susceptibility loci, we carried out a multi-tiered, case-control association study, genotyping 25,966 putative functional SNPs in 475 white North American RA patients and 475 matched controls. Significant markers were genotyped in two additional, independent, white case-control sample sets (661 cases/1322 controls from North America and 596 cases/705 controls from The Netherlands) identifying a SNP, rs1953126, on chromosome 9q33.2 that was significantly associated with RA (OR(common) = 1.28, trend P(comb) = 1.45E-06). Through a comprehensive fine-scale-mapping SNP-selection procedure, 137 additional SNPs in a 668 kb region from MEGF9 to STOM on 9q33.2 were chosen for follow-up genotyping in a staged-approach. Significant single marker results (P(comb)<0.01) spanned a large 525 kb region from FBXW2 to GSN. However, a variety of analyses identified SNPs in a 70 kb region extending from the third intron of PHF19 across TRAF1 into the TRAF1-C5 intergenic region, but excluding the C5 coding region, as the most interesting (trend P(comb): 1.45E-06 --> 5.41E-09). The observed association patterns for these SNPs had heightened statistical significance and a higher degree of consistency across sample sets. In addition, the allele frequencies for these SNPs displayed reduced variability between control groups when compared to other SNPs. Lastly, in combination with the other two known genetic risk factors, HLA-DRB1 and PTPN22, the variants reported here generate more than a 45-fold RA-risk differential.

Blockade of tumor necrosis factor (TNF) receptor type 1-mediated TNF-alpha signaling protected Wistar rats from diet-induced obesity and insulin resistance

TNF-alpha plays an important role in the pathogenesis of obesity and insulin resistance in which the effect of TNF-alpha signaling via TNF receptor type 1 (TNFR1) largely remains controversial. To delineate the role of TNFR1-mediated TNF-alpha signaling in the pathogenesis of this disorder, a TNFR1 blocking peptide-Fc fusion protein (TNFR1BP-Fc) was used for the present study. Wistar rats were fed a high-fat/high-sucrose (HFS) diet for 16 wk until obesity and insulin resistance developed. In comparison with increased body weight and fat weight, enlarged adipocytes, and hypertriglyceridemia in the obese state, the subsequent 4-wk treatment with TNFR1BP-Fc resulted in significant weight loss characterized by decreased fat pad weight and adipocyte size and reduced plasma triglycerides. Furthermore, obesity-induced insulin resistance, including hyperinsulinemia, elevated C-peptide, higher degree of hyperglycemia after glucose challenge, and less hypoglycemic response to insulin, was markedly improved, and the compensatory hyperplasia and hypertrophy of pancreatic islets were reduced. Interestingly, treatment with TNFR1BP-Fc markedly suppressed systemic TNF-alpha release and its local expression in pancreatic islets and muscle and adipose tissues. In addition, blockage of TNFR1-mediated TNF-alpha signaling in obese rats significantly enhanced tyrosine phosphorylation of insulin receptor substrate 1 (IRS-1) in the muscle and fat tissues. Our results strongly suggest a pivotal role for TNFR1-mediated TNF-alpha signaling in the pathogenesis of obesity and insulin resistance. Thus, TNFR1BP-Fc may be a good candidate for the treatment of this disease.

[Genomic approaches to bone and joint diseases. Current status of human disease genomics in rheumatoid arthritis]

Rheumatoid arthritis (RA) is an autoimmune/inflammatory disorder which causes progression of polyarticular destruction. RA is a multifactorial disorder, in which genetic and environmental factors contribute to the onset of diseases. Linkage analyses and case-control association studies in RA have identified several susceptible genes including genetic variation in human leukocyte antigen region. Here, we review major genes susceptible to RA, and discuss effects of these genes on production of anti-cyclic citrullinated peptides antibody.

Characterization and expression analysis of TNFR-associated factor 1 (TRAF1) in grass carp Ctenopharyngodon idella

TNF receptor associated factor 1 (TRAF1) plays an important role in regulating the TNF signaling and protecting cells from apoptosis. In the present study, a TRAF1 gene has been cloned from grass carp (Ctenopharyngodon idella) by reverse transcription (RT)-PCR and rapid amplification of cDNA ends (RACE). The full-length cDNA is 2235bp, including a 250bp 5' UTR (untranslated region), a 1659bp open reading frame, and a 326bp 3' UTR. The polyadenylation signal (AATAAA, AATAA) and one mRNA instability motif (AUUUA) were found followed by a poly (A) tail in the 3' UTR. No signal peptide or transmembrane region has been found in the putative amino acids of grass carp TRAF1 (gcTRAF1). The putative amino acids of gcTRAF1 share 72% identity with the homologue in zebrafish. It is characterized by a zinc finger at the N-terminus and a TRAF domain (contains one TRAF-C and one TRAF-N) at the C-terminus. The identity of the TRAF domain among all the TRAF1 homologues in vertebrates varies from 52% to 58%, while the identities of TRAF-C were almost the same as 70%. The recombinant gcTRAF1 has been constructed successfully and expressed in Escherichia coli by using pET-32a expression vector. The polyclonal antibody for rabbit has been successfully obtained. The expression of gcTRAF1 in different organs was examined by real-time quantitative PCR and Western blotting, respectively. It was widely distributed in heart, head kidney, thymus, brain, gill, liver, spleen, and trunk kidney. This is the first report of TRAF1 homologue molecule found in fish.

TRAF1 and its biological functions

Tumor necrosis factor (TNF) receptor-associated factor (TRAF)1 was originally identified based on its ability to interact with the cytosolic domain ofTNF receptor type 2 (TNFR2). TRAF1 is unique among TRAF proteins in that it lacks RING domain found in the N-terminal regions of other TRAFs. TRAF1 can associate with multiple TNFR family members and can also bind several protein kinases and adaptor proteins suggesting that this protein likely possesses multiple functions in cytokine signaling networks. Although our understanding ofTRAF 1 functions and the underlying mechanisms at molecular and cellular levels has been advanced in recent years, much still needs to be learned before we have a full grasp of TRAF1 biology.

TRAF1-C5 as a risk locus for rheumatoid arthritis--a genomewide study

BACKGROUND

Rheumatoid arthritis has a complex mode of inheritance. Although HLA-DRB1 and PTPN22 are well-established susceptibility loci, other genes that confer a modest level of risk have been identified recently. We carried out a genomewide association analysis to identify additional genetic loci associated with an increased risk of rheumatoid arthritis.

METHODS

We genotyped 317,503 single-nucleotide polymorphisms (SNPs) in a combined case-control study of 1522 case subjects with rheumatoid arthritis and 1850 matched control subjects. The patients were seropositive for autoantibodies against cyclic citrullinated peptide (CCP). We obtained samples from two data sets, the North American Rheumatoid Arthritis Consortium (NARAC) and the Swedish Epidemiological Investigation of Rheumatoid Arthritis (EIRA). Results from NARAC and EIRA for 297,086 SNPs that passed quality-control filters were combined with the use of Cochran-Mantel-Haenszel stratified analysis. SNPs showing a significant association with disease (P<1x10(-8)) were genotyped in an independent set of case subjects with anti-CCP-positive rheumatoid arthritis (485 from NARAC and 512 from EIRA) and in control subjects (1282 from NARAC and 495 from EIRA).

RESULTS

We observed associations between disease and variants in the major-histocompatibility-complex locus, in PTPN22, and in a SNP (rs3761847) on chromosome 9 for all samples tested, the latter with an odds ratio of 1.32 (95% confidence interval, 1.23 to 1.42; P=4x10(-14)). The SNP is in linkage disequilibrium with two genes relevant to chronic inflammation: TRAF1 (encoding tumor necrosis factor receptor-associated factor 1) and C5 (encoding complement component 5).

CONCLUSIONS

A common genetic variant at the TRAF1-C5 locus on chromosome 9 is associated with an increased risk of anti-CCP-positive rheumatoid arthritis.

A candidate gene approach identifies the TRAF1/C5 region as a risk factor for rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disorder affecting approximately 1% of the population. The disease results from the interplay between an individual's genetic background and unknown environmental triggers. Although human leukocyte antigens (HLAs) account for approximately 30% of the heritable risk, the identities of non-HLA genes explaining the remainder of the genetic component are largely unknown. Based on functional data in mice, we hypothesized that the immune-related genes complement component 5 (C5) and/or TNF receptor-associated factor 1 (TRAF1), located on Chromosome 9q33-34, would represent relevant candidate genes for RA. We therefore aimed to investigate whether this locus would play a role in RA.

METHODS AND FINDINGS

We performed a multitiered case-control study using 40 single-nucleotide polymorphisms (SNPs) from the TRAF1 and C5 (TRAF1/C5) region in a set of 290 RA patients and 254 unaffected participants (controls) of Dutch origin. Stepwise replication of significant SNPs was performed in three independent sample sets from the Netherlands (ncases/controls = 454/270), Sweden (ncases/controls = 1,500/1,000) and US (ncases/controls = 475/475). We observed a significant association (p < 0.05) of SNPs located in a haplotype block that encompasses a 65 kb region including the 3' end of C5 as well as TRAF1. A sliding window analysis revealed an association peak at an intergenic region located approximately 10 kb from both C5 and TRAF1. This peak, defined by SNP14/rs10818488, was confirmed in a total of 2,719 RA patients and 1,999 controls (odds ratiocommon = 1.28, 95% confidence interval 1.17-1.39, pcombined = 1.40 x 10(-8)) with a population-attributable risk of 6.1%. The A (minor susceptibility) allele of this SNP also significantly correlates with increased disease progression as determined by radiographic damage over time in RA patients (p = 0.008).

CONCLUSIONS

Using a candidate-gene approach we have identified a novel genetic risk factor for RA. Our findings indicate that a polymorphism in the TRAF1/C5 region increases the susceptibility to and severity of RA, possibly by influencing the structure, function, and/or expression levels of TRAF1 and/or C5.

Mechanisms involved in Korean mistletoe lectin-induced apoptosis of cancer cells

AIM: To investigate the anti-cancer mechanisms of Korean mistletoe lectin (Viscum album coloratum agglutinin, VCA) using a human colon cancer cell line (COLO).

METHODS: Cytotoxic effects of VCA on COLO cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in vitro and tumor-killing effects in vivo. To study the mechanisms involved, the expression of various pro-caspases, anti-apoptotic proteins, and death receptors was determined by western blot. To determine which death receptor is involved in VCA-induced apoptosis of COLO cells, cytotoxicity was examined by MTT assay after treatment with agonists or antagonists of death receptors.

RESULTS: VCA killed COLO cells in a time- and dose-dependent manner and induced complete regression of tumors in nude mice transplanted with COLO cells. Treatment of COLO cells with VCA activated caspase-2, -3, -8, and -9 and decreased expression of anti-apoptotic molecules including receptor interacting protein, nuclear factor-κB, X-linked inhibitor of apoptosis protein, and Akt/protein kinase B. We then examined the involvement of death receptors in VCA-induced apoptosis. Only tumor necrosis factor receptor 1, among the death receptors examined, was involved in apoptosis of COLO cells, evidenced by inhibition of VCA-induced apoptosis and decreased activation of caspases, particularly caspase-8, by tumor necrosis factor receptor 1 antagonizing antibody.

CONCLUSION: VCA-induced apoptotic COLO cell death is due to the activation of caspases and inhibition of anti-apoptotic proteins, in part through the tumor necrosis factor receptor 1 signaling pathway.

TRAF-1, -2, -3, -5, and -6 are induced in atherosclerotic plaques and differentially mediate proinflammatory functions of CD40L in endothelial cells

OBJECTIVE

Several lines of evidence implicate CD40 ligand (CD40L, CD154) as a mediator and marker of atherosclerosis. This study investigated the involvement of tumor necrosis factor receptor-associated factors (TRAFs) in CD40 signaling in endothelial cells (ECs) and their expression in atheromata and cells involved in atherogenesis.

METHODS AND RESULTS

CD40L enhanced the basal expression of TRAF-1, -2, -3, and 6, but not TRAF-5 in ECs. TRAFs associated with CD40 on ligation by CD40L. Study of ECs from TRAF-1, -2, and -5-deficient mice demonstrated functional involvement of TRAFs in proinflammatory CD40 signaling. Whereas TRAF-1 deficiency enhanced CD40L-induced IL-6 and MCP-1 expression, TRAF-2 and TRAF-5 deficiency inhibited CD40L-inducible IL-6 but not MCP-1 expression. Gene silencing in human ECs further delineated functions of TRAFs in CD40 signaling. TRAF-3 silencing in ECs showed increased CD40L-induced IL-6, MCP-1, and IL-8 expression, whereas TRAF-6 silencing increased selectively CD40L-induced MCP-1 expression. Enhanced TRAF levels in atherosclerotic lesions further supports involvement of members of this family of signaling molecules in arterial disease.

CONCLUSIONS

These results implicate endothelial TRAF-1, -2, -3, -5, and -6 in CD40 signaling in atherogenesis, identifying these molecules as potential targets for selective therapeutic intervention.

Investigation of association between the TRAF family genes and RA susceptibility

OBJECTIVE

The tumour necrosis factor (TNF) receptor-associated factor (TRAF) family is important in activating multiple inflammatory and immune related processes induced by cytokines such as TNFalpha and interleukin-1. These genes therefore represent strong candidate susceptibility factors for rheumatoid arthritis (RA). A study was undertaken to investigate the association between single nucleotide polymorphisms (SNPs) spanning six TRAF genes and RA in a British population.

METHODS

Twenty-three haplotype tagging (ht) SNPs and 26 random SNPs spanning the six TRAF genes were initially tested for association in a cohort of 351 unrelated patients with RA and 368 controls. Any SNPs demonstrating an association were genotyped in further samples. Sequenom MassARRAY technology was preferentially used for genotyping. Both single point and haplotypic analyses were performed.

RESULTS

Forty-four SNPs were successfully genotyped and conformed to Hardy-Weinberg expectation. A single SNP, rs7514863, mapping upstream of the TRAF5 gene and affecting a putative transcription factor binding site, demonstrated a significant association across the entire cohort of 1273 cases with RA compared with 2463 healthy controls (OR for minor T allele 1.2 (95% CI 1.06 to 1.36), p = 0.005). The association was stronger in the subgroup carrying at least one copy of the shared epitope alleles (OR 1.43 (95% CI 1.18 to 1.73), p = 0.0003).

CONCLUSION

These findings provide evidence for the association of an SNP upstream of a strong candidate RA susceptibility gene, TRAF5, in a large cohort of patients and controls. Further association and functional studies are required to investigate the role of this variant, or one in linkage disequilibrium with it, in RA disease causation.

Relationship between Mycobacterium avium subspecies paratuberculosis, IL-1alpha, and TRAF1 in primary bovine monocyte-derived macrophages

Mycobacterium avium subspecies paratuberculosis (MAP) is a facultative intracellular pathogen that resides in host macrophage cells. Presently, little is known about how MAP is able to subvert the normal bacteriocidal functions of infected macrophages. Previously, we reported that ileal tissues from MAP infected cattle contained high levels of interleukin-1 alpha (IL-1alpha) and tumor necrosis factor receptor-associated factor 1 (TRAF1), relative to ileal tissues from uninfected cattle. High-level expression of these two proteins could have profound effects on macrophage function, intracellular signaling, and apoptosis. We now demonstrate that high levels of TRAF1 protein are located primarily within macrophages infiltrating areas of MAP infection. We have also utilized cultured bovine monocyte-derived macrophage cells (MDM) either infected with live MAP or stimulated with recombinant IL-1alpha (rIL-1alpha) to determine if there is a relationship between IL-1alpha and TRAF1 expression. These studies have identified a dose dependent increase in TRAF1 protein levels in bovine MDM in response to infection with live MAP or following treatment with rIL-1alpha. Sustained TRAF1 protein expression was dependent upon interaction of rIL-1alpha with it's receptor and rIL-1beta was also able to enhance TRAF1 gene expression. Our results suggest that MAP may use the IL-1-TRAF1 system to enhance TRAF1 protein expression in infected bovine MDM. These novel results provide evidence for a new avenue of research on the effect of MAP and other intracellular pathogens on macrophage signaling and apoptosis.

A critical role for TNF receptor-associated factor 1 and Bim down-regulation in CD8 memory T cell survival

The mechanisms that allow the maintenance of immunological memory remain incompletely defined. Here we report that tumor necrosis factor receptor (TNFR)-associated factor (TRAF) 1, a protein recruited in response to several costimulatory TNFR family members, is required for maximal CD8 T cell responses to influenza virus in mice. Decreased recovery of CD8 T cells in vivo occurred under conditions where cell division was unimpaired. In vitro, TRAF1-deficient, antigen-activated T cells accumulated higher levels of the proapoptotic BH3-only family member Bim, particularly the most toxic isoform, Bim(S). In the presence of excess IL-15, memory phenotype T cells with similar surface phenotype and comparable levels of Bcl-2 family members could be generated from WT or TRAF1-deficient T cell receptor transgenic OT-I T cells. However, when the memory CD8 T cells were allowed to compete for survival signals in the absence of antigen in vivo, the TRAF1-deficient T cells showed decreased recovery compared with TRAF1-sufficient T cells. This defect in T cell recovery in vivo was alleviated by introduction of siRNA to down-modulate Bim in TRAF1-deficient memory T cells. These studies identify the TRAF1 signaling axis and Bim down-regulation as critical for CD8 memory T cell survival in vivo.

The Proinflammatory Cytokine Interleukin-18 Alters Multiple Signaling Pathways to Inhibit Natural Killer Cell Death

The proinflammatory cytokine, interleukin-18 (IL-18), is a natural killer (NK) cell activator that induces NK cell cytotoxicity and interferon-gamma (IFN-gamma) expression. In this report, we define a novel role for IL-18 as an NK cell protective agent. Specifically, IL-18 prevents NK cell death initiated by different and distinct stress mechanisms. IL-18 reduces NK cell self-destruction during NK-targeted cell killing, and in the presence of staurosporin, a potent apoptotic inducer, IL-18 reduces caspase-3 activity. The critical regulatory step in this process is downstream of the mitochondrion and involves reduced cleavage and activation of caspase-9 and caspase-3. The ability of IL-18 to regulate cell survival is not limited to a caspase death pathway in that IL-18 augments tumor necrosis factor (TNF) signaling, resulting in increased and prolonged mRNA expression of c-apoptosis inhibitor 2 (cIAP2), a prosurvival factor and caspase-3 inhibitor, and TNF receptor-associated factor 1 (TRAF1), a prosurvival protein. The cumulative effects of IL-18 define a novel role for this cytokine as a molecular survival switch that functions to both decrease cell death through inhibition of the mitochondrial apoptotic pathway and enhance TNF induction of prosurvival factors.

Testis-specific expression and genomic multiplicity of the rat Rtdpoz genes that encode bipartite TRAF- and POZ/BTB-domain proteins

Based on bioinformatics analysis, we previously hypothesized the existence of a bipartite TDPOZ protein family members of which carry the TRAF domain (TD) and POZ/BTB [Huang, C.-J., Chen, C.-Y., Chen, H.-H., Tsai, S.-F., Choo, K.-B., 2004. TDPOZ, a family of bipartite animal and plant proteins that contain the TRAF (TD) and POZ/BTB domains. Gene 324, 117-127.]. Conservation in animals and plants suggests important biological functions for the putative TDPOZ proteins. In this work, we report testis-specific expression of two new Tdpoz members, Rtdpoz-T1 and -T2, of the rat genome; the result clearly indicates that members of the hypothetical gene family are, indeed, expressed. T1 and T2 cDNA sequences were derived by rapid amplification of cDNA ends (RACE). The exons of the genes were determined by queries of the rat genome sequence draft and selectively confirmed in splicing assays. The results indicate that T1 and T2 share a common leader exon indicative of alternative splicing, and that the genes are uninterrupted by introns in their respective coding sequences. Database interrogations also reveal a combined 297 hits of Rtdpoz-like sequences on 7 chromosomes; however, the bulk of the hits (264) and 26 putative TDPOZ-encoding genes, including T1 and T2, are found in a approximately 2.5 Mb cluster in the Rn2_2148 supercontig on chromosome 2. Our data signify retrotransposition in the generation and expansion of the Rtdpoz repertoire in the rat genome. We also anticipate spatio-temporal-specific expression of many more TDPOZ members in the rat or other animals and plants.

Cooperation between TNF Receptor-Associated Factors 1 and 2 in CD40 Signaling

TNFR-associated factor 1 (TRAF1) is unique among the TRAF family, lacking most zinc-binding features, and showing marked up-regulation following activation signals. However, the biological roles that TRAF1 plays in immune cell signaling have been elusive, with many reports assigning contradictory roles to TRAF1. The overlapping binding site for TRAFs 1, 2, and 3 on many TNFR superfamily molecules, together with the early lethality of mice deficient in TRAFs 2 and 3, has complicated the quest for a clear understanding of the functions of TRAF1. Using a new method for gene targeting by homologous recombination in somatic cells, we produced and studied signaling by CD40 and its viral oncogenic mimic, latent membrane protein 1 (LMP1) in mouse B cell lines lacking TRAF1, TRAF2, or both TRAFs. Results indicate that TRAFs 1 and 2 cooperate in CD40-mediated activation of the B cell lines, with a dual deficiency leading to a markedly greater loss of function than that of either TRAF alone. In the absence of TRAF1, an increased amount of TRAF2 was recruited to lipid rafts, and subsequently, more robust degradation of TRAF2 and TRAF3 was induced in response to CD40 signaling. In contrast, LMP1 did not require either TRAFs 1 or 2 to induce activation. Taken together, our findings indicate that TRAF1 and TRAF2 cooperate in CD40 but not LMP1 signaling and suggest that cellular levels of TRAF1 may play an important role in modulating the degradation of TRAF2 and TRAF3 in response to signals from the TNFR superfamily.

Expression of the tumor necrosis factor receptor-associated factors 1 and 2 and regulation of the nuclear factor-kappaB antiapoptotic activity in human gliomas

OBJECT

Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) are a recently established group of proteins involved in the intracellular signaling of the TNFR superfamily members. The TRAFs have been implicated in promoting cell survival through the activation of transcription factor nuclear factor (NF)-kappaB. The authors investigated the expression of NF-kappaB, caspase 3, TRAF1, TRAF2, and TRAF-associated NF-kappaB activator/TRAF-interacting protein (TANK/I-TRAF), a regulator of TRAF activity, in human gliomas.

METHODS

Tumor samples were obtained in 27 adult patients harboring seven low-grade gliomas, nine anaplastic astrocytomas, and 11 glioblastomas multiforme. The NF-kappaB activation was analyzed using the electrophoresis mobility shift assay; TRAF1, TRAF2, TANK/I-TRAF, and caspase 3 expression were studied using Western blot analysis. Upregulated NF-kappaB DNA-binding activity, compared with that in normal brain tissue, was detected in all tumor samples (p = 0.002). The level of NF-kappaB activity showed some correlation with World Health Organization tumor grades (p = 0.01), even though variable activity levels were demonstrated in relation to tissue heterogeneity, which resulted in a substantial number of outliers in the quantitative analysis. Increased levels of TRAF1, TRAF2, and TANK/ I-TRAF were expressed in astrocytomas compared with levels in normal brain tissue (p = 0.02, 0.006, and 0.01, respectively).

CONCLUSIONS

Data in this study confirm the upregulation of NF-kappaB in gliomas and reveal a correlation between levels of this transcription factor and tumor grade. A constitutive expression of TRAF1, TRAF2, and TANK/I-TRAF in human gliomas was documented. These proteins are involved in the intracellular signal transduction of the TNFR superfamily and in the control of NF-kappaB expression and its antiapoptotic activity.

Experimental Intestinal Endometriosis Is Characterized by Increased Levels of Soluble TNFRSF1B and Downregulation of Tnfrsf1a and Tnfrsf1b Gene Expression1

Endometriosis is commonly associated with symptoms similar to those of gastrointestinal diseases, such as inflammatory bowel disease (IBD), leading to erroneous diagnosis and inappropriate management. The role of tumor necrosis factor alpha (TNF) in IBD is well established, but its role in endometriosis--also characterized by the activation of inflammatory mechanisms--is still under study. Furthermore, little is known about the involvement of TNF receptors. Intestinal endometriosis was surgically induced in female Sprague-Dawley rats (n = 10). Control rats (n = 10) received sutures with no implants. Samples of tissue and fluids were collected 60 days after surgery. Endometriotic implants were classified in grades, and the gastrointestinal tract was examined for damage. A significant increase was observed in protein levels of TNF and soluble TNFRSF1B in the peritoneal fluid of experimental rats compared to controls. Expression of Tnf mRNA was significantly increased both in peritoneal leukocytes and in intestinal segments associated with implants in experimental animals. Bioactivity of TNF in tissues was confirmed by overexpression of Icam1, Sele, Vegfa, Flt1 and Kdr. Gene expression of Tnfrsf1a and Tnfrsf1b was downregulated in colon and small intestine of experimental animals, possibly as a mechanism of protection against TNF cytotoxicity. Significant overexpression of genes encoding TNF receptor-associated factors that have been linked to activation of antiapoptotic pathways also was observed. Overexpression of TNF and target genes, underexpression of TNF-receptor genes, and increased shedding of TNFRSF1B in this animal model provide further evidence for involvement of the TNF system in the pathogenesis of endometriosis.

The Nef-mediated AIDS-like disease of CD4C/human immunodeficiency virus transgenic mice is associated with increased Fas/FasL expression on T cells and T-cell death but is not prevented in Fas-, FasL-, tumor necrosis factor receptor 1-, or interleukin-1beta-converting enzyme-deficient or Bcl2-expressing transgenic mice

CD4(+)- and CD8(+)-T-cell death is a frequent immunological dysfunction associated with the development of human AIDS. We studied a murine model of AIDS, the CD4C/HIV transgenic (Tg) mouse model, to assess the importance of the apoptotic pathway in human immunodeficiency virus type 1 (HIV-1) pathogenesis. In these Tg mice, Nef is the major determinant of the disease and is expressed in immature and mature CD4(+) T cells and in cells of the macrophage/myeloid lineage. We report here a novel AIDS-like phenotype: enhanced death, most likely by apoptosis (as assessed by 7-aminoactinomycin D and annexin V/propidium iodide staining), of Tg thymic and peripheral CD4(+) and CD8(+) T cells. The Tg CD4(+) and CD8(+) T cells were also more susceptible to cell death after activation in vitro in mixed lymph node (LN) cultures. However, activation-induced cell death was not higher in Tg than in non-Tg-purified CD4(+) T cells. In addition, expression of Fas and FasL, assessed by flow cytometry, was increased in CD4(+) and CD8(+) T cells from Tg mice compared to that of non-Tg littermates. Despite the enhanced expression of Fas and FasL on Tg CD4(+) and CD8(+) T cells, Fas (lpr/lpr) and FasL (gld/gld) mutant CD4C/HIV Tg mice developed an AIDS-like disease indistinguishable from lpr/+ and gld/+ CD4C/HIV Tg mice, including loss of CD4(+) T cells. Similarly, CD4C/HIV Tg mice homozygous for mutations of two other genes implicated in cell death (interleukin-1beta-converting enzyme [ICE], tumor necrosis factor receptor 1 [TNFR-1]) developed similar AIDS-like disease as their respective heterozygous controls. Moreover, the double-Tg mice from a cross between the Bcl2/Wehi25 and CD4C/HIV Tg mice showed no major protection against disease. These results represent genetic evidence for the dispensable role of Fas, FasL, ICE, and TNFR-1 on the development of both T-cell loss and organ disease of these Tg mice. They also provide compelling evidence on the lack of protection by Bcl2 against Tg CD4(+)-T-cell death. In view of the high resemblance between numerous phenotypes observed in the CD4C/HIV Tg mice and in human AIDS, our findings are likely to be relevant for the human disease.

Human RPE Expression of Cell Survival Factors

PURPOSE

To determine basal and tumor necrosis factor (TNF)-alpha-regulated expression of retinal pigment epithelial (RPE) cell survival factors and whether regulation is dependent on nuclear transcription factor (NF)-kappaB.

METHODS

Cultured human RPE cells were infected with adenovirus encoding either mutant inhibitory (I)-kappaB or beta-galactosidase and treated with TNF-alpha for various times. Freshly prepared RPE/choroid and RPE samples were isolated from human donor eyes. Real-time reverse transcription-polymerase chain reaction, Western blot, and immunocytochemistry were used to determine survival factor gene expression, cellular protein levels, and localization, respectively.

RESULTS

Multiple survival factor genes, including cellular inhibitor of apoptosis protein (c-IAP1), c-IAP2, TNF receptor-associated factor-1 (TRAF-1), TRAF-2, B-cell leukemia/lymphoma-2 (Bcl-2), Bcl-x, A1, and cellular Fas-associated death domain (FADD)-like interleukin-1beta-converting enzyme-like inhibitory protein (c-FLIP), were expressed in basal conditions in both cultured RPE cells and RPE cells in situ, whereas survivin was expressed only by cultured cells. TNF-alpha upregulated expression of TRAF-1, TRAF-2, c-IAP1, c-IAP2, c-FLIP, and A1. TRAF-1, c-FLIP, and to a lesser extent c-IAP2 protein levels were increased by TNF-alpha in a time-dependent manner, whereas c-IAP1, survivin, Bcl-x(L), and TRAF-2 protein levels were not influenced by TNF-alpha treatment at any time point tested. In contrast, Bcl-2 and A1 proteins were not detected under basal conditions or after TNF-alpha treatment. Overexpression of mutant IkappaB blocked TNF-alpha-induced TRAF-1, TRAF-2, c-IAP1, c-IAP2, c-FLIP, and A1 gene expression and downregulated TRAF-1 protein levels. TRAF-1 and Bcl-x(L) proteins were localized diffusely in RPE cytoplasm.

CONCLUSIONS

Multiple RPE cell survival factors are expressed by human RPE cells. TNF-alpha regulates expression of some of these factors in an NF-kappaB-dependent manner, whereas others are not influenced by NF-kappaB. RPE cell survival factors may protect RPE cells from apoptosis normally and in diseases such as age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR).

Mass spectrometric analysis of tumor necrosis factor receptor-associated factor 1 ubiquitination mediated by cellular inhibitor of apoptosis 2

Signaling complexes formed on tumor necrosis factor receptor 2 (TNF-R2) contain adaptor proteins TNF-R-associated factors (TRAFs) 1 and 2, and cellular inhibitors of apoptosis (cIAPs) 1 and 2 which function as regulators of programmed cell death. TRAF2, cIAP1 and cIAP2 all have RING finger domains known to possess E3 ubiquitin ligase activity, implying that ubiquitination may play an important role in the TNF signaling pathway. In this report, we have shown that cIAP2 specifically mediated ubiquitination and proteasome-dependent degradation of TRAF1. To identify the sites for cIAP2-mediated ubiquitination of TRAF1, we used high pressure liquid chromatography coupled with tandem mass spectrometry. Lys185 and Lys193 of TRAF1 were found to be modified with ubiquitin chains. Mutation of Lys185 and Lys193 to Arg almost completely blocked cIAP2-mediated ubiquitination of TRAF1, indicating that they are the major, if not the only, sites of TRAF1 ubiquitination. Our data suggest that cIAP2 may regulate the turnover of TRAF1 by adding polyubiquitin chains on Lys185 or Lys193 following its recruitment to TNF-R signaling complexes.

Tumor necrosis factor receptor I from patients with tumor necrosis factor receptor-associated periodic syndrome interacts with wild-type tumor necrosis factor receptor I and induces ligand-independent NF-κB activation

OBJECTIVE

To investigate the molecular consequences of expressing mutated forms of tumor necrosis factor receptor I (TNFRI) as found in patients with TNFR-associated periodic syndrome (TRAPS).

METHODS

We cloned and expressed full-length wild-type (WT) and T50K and P46L variants of TNFRI using a new tightly regulated doxycycline-dependent expression system. This system enabled the study of molecular interactions between these receptors at both physiologic and pathophysiologic levels of expression.

RESULTS

We used chemical crosslinking on the cell surface to show that WT and mutant forms of TNFRI, derived from TRAPS patients, interact in the absence of TNF ligand. Doxycycline-controlled up-regulation of one TNFRI allele, either WT or mutant, caused down-regulation of the other allele, indicating dynamic control of cell surface assembly. We also demonstrated that increased expression of mutant TNFRI (T50K) was associated with a parallel increase in NF-kappaB p65 (RelA) subunit activation, which did not occur with increased expression of WT TNFRI.

CONCLUSION

The T50K TRAPS-related variant is capable of sustaining inappropriate NF-kappaB activation, resulting in persistent auto-inflammation in target organs such as skin, synovial membrane, and the central nervous system. We conclude that some of the inflammatory processes seen in TRAPS do not involve direct interaction of TNF with its receptors, but that other proinflammatory mechanisms capable of up-regulating TNFRI expression may cause cellular activation through the NF-kappaB signaling pathway.

Major histocompatibility complex (MHC2+) perivascular macrophages in the axotomized facial motor nucleus are regulated by receptors for interferon-gamma (IFNgamma) and tumor necrosis factor (TNF)

The major histocompatibility complex (MHC) glycoproteins, MHC1 and MHC2, play a key role in the presentation of antigen and the development of the immune response. In the current study we examined the regulation of the MHC2 in the mouse brain after facial axotomy. The normal facial motor nucleus showed very few slender and elongated MHC2+ cells. Transection of the facial nerve led to a gradual but strong upregulation in the number of MHC2+ cells, beginning at day 2 and reaching a maximum 14 days after axotomy, correlated with the induction of mRNA for tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta and interferon-gamma (IFNgamma) and a peak in neuronal cell death. In almost all cases, MHC2 immunoreactivity was restricted to perivascular macrophages that colocalized with vascular basement membrane laminin and macrophage IBA1-immunoreactivity, with no immunoreactivity on phagocytic microglia, astrocytes or invading T-cells. Heterologous transplantation and systemic injection of endotoxin or IFNgamma did not affect this perivascular MHC2 immunoreactivity, and transgenic deletion of the IL1 receptor type I, or TNF receptor type 1, also had no effect. However, the deletion of IFNgamma receptor subunit 1 caused a significant increase, and that of TNF receptor type 2 a strong reduction in the number of MHC2+ macrophages, pointing to a counter-regulatory role of IFNgamma and TNFalpha in the immune surveillance of the injured nervous system.