Mutant forms of tumour necrosis factor receptor I that occur in TNF-receptor-associated periodic syndrome retain signalling functions but show abnormal behaviour

TNFR1 signaling converging on FGF14 controls neuronal hyperactivity and sickness behavior in experimental cerebral malaria

BACKGROUND

Excess tumor necrosis factor (TNF) is implicated in the pathogenesis of hyperinflammatory experimental cerebral malaria (eCM), including gliosis, increased levels of fibrin(ogen) in the brain, behavioral changes, and mortality. However, the role of TNF in eCM within the brain parenchyma, particularly directly on neurons, remains underdefined. Here, we investigate electrophysiological consequences of eCM on neuronal excitability and cell signaling mechanisms that contribute to observed phenotypes.

METHODS

The split-luciferase complementation assay (LCA) was used to investigate cell signaling mechanisms downstream of tumor necrosis factor receptor 1 (TNFR1) that could contribute to changes in neuronal excitability in eCM. Whole-cell patch-clamp electrophysiology was performed in brain slices from eCM mice to elucidate consequences of infection on CA1 pyramidal neuron excitability and cell signaling mechanisms that contribute to observed phenotypes. Involvement of identified signaling molecules in mediating behavioral changes and sickness behavior observed in eCM were investigated in vivo using genetic silencing.

RESULTS

Exploring signaling mechanisms that underlie TNF-induced effects on neuronal excitability, we found that the complex assembly of fibroblast growth factor 14 (FGF14) and the voltage-gated Na+ (Nav) channel 1.6 (Nav1.6) is increased upon tumor necrosis factor receptor 1 (TNFR1) stimulation via Janus Kinase 2 (JAK2). On account of the dependency of hyperinflammatory experimental cerebral malaria (eCM) on TNF, we performed patch-clamp studies in slices from eCM mice and showed that Plasmodium chabaudi infection augments Nav1.6 channel conductance of CA1 pyramidal neurons through the TNFR1-JAK2-FGF14-Nav1.6 signaling network, which leads to hyperexcitability. Hyperexcitability of CA1 pyramidal neurons caused by infection was mitigated via an anti-TNF antibody and genetic silencing of FGF14 in CA1. Furthermore, knockdown of FGF14 in CA1 reduced sickness behavior caused by infection.

CONCLUSIONS

FGF14 may represent a therapeutic target for mitigating consequences of TNF-mediated neuroinflammation.

The dichotomous outcomes of TNFα signaling in CD4+ T cells

TNFa blocking agents were the first-in-class biologic drugs used for the treatment of autoimmune disease. Paradoxically, however, exacerbation of autoimmunity was observed in some patients. TNFa is a pleiotropic cytokine that has both proinflammatory and regulatory effects on CD4+ T cells and can influence the adaptive immune response against autoantigens. Here, we critically appraise the literature and discuss the intricacies of TNFa signaling that may explain the controversial findings of previous studies. The pleiotropism of TNFa is based in part on the existence of two biologically active forms of TNFa, soluble and membrane-bound, with different affinities for two distinct TNF receptors, TNFR1 and TNFR2, leading to activation of diverse downstream molecular pathways involved in cell fate decisions and immune function. Distinct membrane expression patterns of TNF receptors by CD4+ T cell subsets and their preferential binding of distinct forms of TNFα produced by a diverse pool of cellular sources during different stages of an immune response are important determinants of the differential outcomes of TNFa-TNF receptor signaling. Targeted manipulation of TNFa-TNF receptor signaling on select CD4+ T cell subsets may offer specific therapeutic interventions to dampen inflammation while fortifying immune regulation for the treatment of autoimmune diseases.

Inflammasome activation: from molecular mechanisms to autoinflammation

Inflammasomes are assembled by innate immune sensors that cells employ to detect a range of danger signals and respond with pro-inflammatory signalling. Inflammasomes activate inflammatory caspases, which trigger a cascade of molecular events with the potential to compromise cellular integrity and release the IL-1β and IL-18 pro-inflammatory cytokines. Several molecular mechanisms, working in concert, ensure that inflammasome activation is tightly regulated; these include NLRP3 post-translational modifications, ubiquitination and phosphorylation, as well as single-domain proteins that competitively bind to key inflammasome components, such as the CARD-only proteins (COPs) and PYD-only proteins (POPs). These diverse regulatory systems ensure that a suitable level of inflammation is initiated to counteract any cellular insult, while simultaneously preserving tissue architecture. When inflammasomes are aberrantly activated can drive excessive production of pro-inflammatory cytokines and cell death, leading to tissue damage. In several autoinflammatory conditions, inflammasomes are aberrantly activated with subsequent development of clinical features that reflect the degree of underlying tissue and organ damage. Several of the resulting disease complications may be successfully controlled by anti-inflammatory drugs and/or specific cytokine inhibitors, in addition to more recently developed small-molecule inhibitors. In this review, we will explore the molecular processes underlying the activation of several inflammasomes and highlight their role during health and disease. We also describe the detrimental effects of these inflammasome complexes, in some pathological conditions, and review current therapeutic approaches as well as future prospective treatments.

A Cysteine Variant at an Allosteric Site Alters MIF Dynamics and Biological Function in Homo- and Heterotrimeric Assemblies

Macrophage migration inhibitory factor (MIF) is an inflammatory protein with various non-overlapping functions. It is not only conserved in mammals, but it is found in parasites, fish, and plants. Human MIF is a homotrimer with an enzymatic cavity between two subunits with Pro1 as a catalytic base, activates the receptors CD74, CXCR2, and CXCR4, has functional interactions in the cytosol, and is reported to be a nuclease. There is a solvent channel down its 3-fold axis with a recently identified gating residue as an allosteric site important for regulating, to different extents, the enzymatic activity and CD74 binding and signaling. In this study we explore the consequence of converting the allosteric residue Tyr99 to cysteine (Y99C) and characterize its crystallographic structure, NMR dynamics, stability, CD74 function, and enzymatic activity. In addition to the homotrimeric variant, we develop strategies for expressing and purifying a heterotrimeric variant consisting of mixed wild type and Y99C for characterization of the allosteric site to provide more insight.

CRISPR/Cas9 Guided Mutagenesis of Grain Size 3 Confers Increased Rice (Oryza sativa L.) Grain Length by Regulating Cysteine Proteinase Inhibitor and Ubiquitin-Related Proteins

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein (Cas9)-mediated genome editing has become an important way for molecular breeding in crop plants. To promote rice breeding, we edited the Grain Size 3 (GS3) gene for obtaining valuable and stable long-grain rice mutants. Furthermore, isobaric tags for the relative and absolute quantitation (iTRAQ)-based proteomic method were applied to determine the proteome-wide changes in the GS3 mutants compared with wild type (WT). Two target sites were designed to construct the vector, and the Agrobacterium-mediated method was used for rice transformation. Specific mutations were successfully introduced, and the grain length (GL) and 1000-grain weight (GWT) of the mutants were increased by 31.39% and 27.15%, respectively, compared with WT. The iTRAQ-based proteomic analysis revealed that a total of 31 proteins were differentially expressed in the GS3 mutants, including 20 up-regulated and 11 down-regulated proteins. Results showed that differentially expressed proteins (DEPs) were mainly related to cysteine synthase, cysteine proteinase inhibitor, vacuolar protein sorting-associated, ubiquitin, and DNA ligase. Furthermore, functional analysis revealed that DEPs were mostly enriched in cellular process, metabolic process, binding, transmembrane, structural, and catalytic activities. Pathway enrichment analysis revealed that DEPs were mainly involved in lipid metabolism and oxylipin biosynthesis. The protein-to-protein interaction (PPI) network found that proteins related to DNA damage-binding, ubiquitin-40S ribosomal, and cysteine proteinase inhibitor showed a higher degree of interaction. The homozygous mutant lines featured by stable inheritance and long-grain phenotype were obtained using the CRISPR/Cas9 system. This study provides a convenient and effective way of improving grain yield, which could significantly accelerate the breeding process of long-grain japonica parents and promote the development of high-yielding rice.

Molecular and clinical spectrum of four pedigrees of TRAPS in Greece: results from a national referral center

OBJECTIVE

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is a rare autosomal dominantly inherited autoinflammatory disease caused by mutations of the TNFRSF1A gene. To address the association between TNFRSF1A mutations and clinical phenotype, we analyzed four pedigrees of TRAPS patients.

METHODS

Four Greek patients with TRAPS-like clinical features were screened for TNFRSF1A mutations by sequencing exons 2, 3 and 4. Following positive testing, twenty-two members of their families were also genetically and clinically screened.

RESULTS

Twenty-six members of four unrelated Greek families were investigated. The C73Y (c.305G>A) mutation of the TNFRSF1A gene was identified in five patients, with two of the five carrying a concomitant R92Q variation. We also identified seven C73W (c.306C>G), two T50M (c.236C>T) and seven R92Q (c.362G>A) carriers. Symptoms varied and the C73Y, C73W and T50M mutations were associated with the most severe clinical manifestations. The R92Q phenotype ranged from asymptomatic to mild disease. Molecular modelling linked pathogenicity with aberrant TNFRSF1A disulphide bond formation.

CONCLUSION

In this first pedigree analysis of TRAPS in Greece, we identified the rare C73Y TNFRSF1A mutation. A wide clinical spectrum was observed with the C73Y, C73W and T50M mutations that affect TNFRSF1A disulphide bonds and are associated with worse symptoms.

Distinct modes of TNF signaling through its two receptors in health and disease

TNF is a key proinflammatory and immunoregulatory cytokine whose deregulation is associated with the development of autoimmune diseases and other pathologies. Recent studies suggest that distinct functions of TNF may be associated with differential engagement of its two receptors: TNFR1 or TNFR2. In this review, we discuss the relative contributions of these receptors to pathogenesis of several diseases, with the focus on autoimmunity and neuroinflammation. In particular, we discuss the role of TNFRs in the development of regulatory T cells during neuroinflammation and recent findings concerning targeting TNFR2 with agonistic and antagonistic reagents in various murine models of autoimmune and neuroinflammatory disorders and cancer.

Functional analysis of a novel G87V TNFRSF1A mutation in patients with TNF receptor-associated periodic syndrome

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autoinflammatory disease that is caused by heterozygous mutations in the TNFRSF1A gene. Although more than 150 TNFRSF1A mutations have been reported to be associated with TRAPS phenotypes only a few, such as p.Thr79Met (T79M) and cysteine mutations, have been functionally analyzed. We identified two TRAPS patients in one family harboring a novel p.Gly87Val (G87V) mutation in addition to a p.Thr90Ile (T90I) mutation in TNFRSF1A. In this study, we examined the functional features of this novel G87V mutation. In-vitro analyses using mutant TNF receptor 1 (TNF-R1)-over-expressing cells demonstrated that this mutation alters the expression and function of TNF-R1 similar to that with the previously identified pathogenic T79M mutation. Specifically, cell surface expression of the mutant TNF-R1 in transfected cells was inhibited with both G87V and T79M mutations, whereas the T90I mutation did not affect this. Moreover, peripheral blood mononuclear cells (PBMCs) from TRAPS patients harboring the G87V and T90I mutations showed increased mitochondrial reactive oxygen species (ROS). Furthermore, the effect of various Toll-like receptor (TLR) ligands on inflammatory responses was explored, revealing that PBMCs from TRAPS patients are hyper-responsive to TLR-2 and TLR-4 ligands and that interleukin (IL)-8 and granulocyte-macrophage colony-stimulating factor (GM-CSF) are likely to be involved in the pathogenesis of TRAPS. These findings suggest that the newly identified G87V mutation is one of the causative mutations of TRAPS. Our findings based on unique TRAPS-associated mutations provide novel insight for clearer understanding of inflammatory responses, which would be basic findings of developing a new therapeutic and prophylactic approach to TRAPS.

Patients with tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) are hypersensitive to Toll-like receptor 9 stimulation

Tumour necrosis factor receptor-associated periodic syndrome (TRAPS) is a hereditary autoinflammatory disorder characterized by recurrent episodes of fever and inflammation. It is associated with autosomal dominant mutations in TNFRSF1A, which encodes tumour necrosis factor receptor 1 (TNF-R1). Our aim was to understand the influence of TRAPS mutations on the response to stimulation of the pattern recognition Toll-like receptor (TLR)-9. Peripheral blood mononuclear cells (PBMCs) and serum were isolated from TRAPS patients and healthy controls: serum levels of 15 proinflammatory cytokines were measured to assess the initial inflammatory status. Interleukin (IL)-1β, IL-6, IL-8, IL-17, IL-22, tumour necrosis factor (TNF)-α, vascular endothelial growth factor (VEGF), interferon (IFN)-γ, monocyte chemoattractant protein 1 (MCP-1) and transforming growth factor (TGF)-β were significantly elevated in TRAPS patients' sera, consistent with constitutive inflammation. Stimulation of PBMCs with TLR-9 ligand (ODN2006) triggered significantly greater up-regulation of proinflammatory signalling intermediates [TNF receptor-associated factor (TRAF 3), IL-1 receptor-associated kinase-like 2 (IRAK2), Toll interacting protein (TOLLIP), TRAF6, phosphorylated transforming growth factor-β-activated kinase 1 (pTAK), transforming growth factor-β-activated kinase-binding protein 2 (TAB2), phosphorylated TAK 2 (pTAB2), IFN-regulatory factor 7 (IRF7), receptor interacting protein (RIP), nuclear factor kappa B (NF-κB) p65, phosphorylated NF-κB p65 (pNF-κB p65) and mitogen-activated protein kinase kinase (MEK1/2)] in TRAPS patients' PBMCs. This up-regulation of proinflammatory signalling intermediates and raised serum cytokines occurred despite concurrent anakinra treatment and no overt clinical symptoms at time of sampling. These novel findings further demonstrate the wide-ranging nature of the dysregulation of innate immune responses underlying the pathology of TRAPS and highlights the need for novel pathway-specific therapeutic treatments for this disease.

Treating TNF Receptor Associated Periodic Fever Syndrome in End-Stage Renal Failure

Tumor necrosis factor receptor associated periodic syndrome (TRAPS) is a rare monogenic autoinflammatory disease. Its most severe manifestation is secondary amyloidosis. A 44-year-old male presented with nephrotic syndrome. Kidney biopsy was conclusive for secondary amyloidosis. The patient and his children had a history of recurrent febrile periods since infancy. All subjects were positive for a heterozygous variant of the TNFRSF1A gene, confirming TRAPS diagnosis. The patient progressed to end-stage renal failure and developed recurrent pericarditis episodes. He was started on anakinra while on hemodialysis with marked reduction of his serum amyloid A protein (SAA) levels. Meanwhile he received a cadaveric renal transplant and maintains anakinra treatment. Despite renal failure being the most feared complication of AA amyloidosis caused by TRAPS, little data is available about safety of anti-IL-1 treatment in patients with severe kidney failure. The authors report this case of a patient on dialysis treated with anakinra in which no complications were registered. Though amyloidosis is established, the authors believe containing its progression and reducing inflammatory activity can improve patient prognosis and reduce recurrence of amyloidosis in kidney transplant, as has been demonstrated in transplanted patients due to familial Mediterranean fever amyloidosis.

The classification, genetic diagnosis and modelling of monogenic autoinflammatory disorders

Monogenic autoinflammatory disorders are an increasingly heterogeneous group of conditions characterised by innate immune dysregulation. Improved genetic sequencing in recent years has led not only to the discovery of a plethora of conditions considered to be 'autoinflammatory', but also the broadening of the clinical and immunological phenotypic spectra seen in these disorders. This review outlines the classification strategies that have been employed for monogenic autoinflammatory disorders to date, including the primary innate immune pathway or the dominant cytokine implicated in disease pathogenesis, and highlights some of the advantages of these models. Furthermore, the use of the term 'autoinflammatory' is discussed in relation to disorders that cross the innate and adaptive immune divide. The utilisation of next-generation sequencing (NGS) in this population is examined, as are potential in vivo and in vitro methods of modelling to determine pathogenicity of novel genetic findings. Finally, areas where our understanding can be improved are highlighted, such as phenotypic variability and genotype-phenotype correlations, with the aim of identifying areas of future research.

A signalome screening approach in the autoinflammatory disease TNF receptor associated periodic syndrome (TRAPS) highlights the anti-inflammatory properties of drugs for repurposing

TNF receptor associated periodic syndrome (TRAPS) is an autoinflammatory disease caused by mutations in TNF Receptor 1 (TNFR1). Current therapies for TRAPS are limited and do not target the pro-inflammatory signalling pathways that are central to the disease mechanism. Our aim was to identify drugs for repurposing as anti-inflammatories based on their ability to down-regulate molecules associated with inflammatory signalling pathways that are activated in TRAPS. This was achieved using rigorously optimized, high through-put cell culture and reverse phase protein microarray systems to screen compounds for their effects on the TRAPS-associated inflammatory signalome. 1360 approved, publically available, pharmacologically active substances were investigated for their effects on 40 signalling molecules associated with pro-inflammatory signalling pathways that are constitutively upregulated in TRAPS. The drugs were screened at four 10-fold concentrations on cell lines expressing both wild-type (WT) TNFR1 and TRAPS-associated C33Y mutant TNFR1, or WT TNFR1 alone; signalling molecule levels were then determined in cell lysates by the reverse-phase protein microarray. A novel mathematical methodology was developed to rank the compounds for their ability to reduce the expression of signalling molecules in the C33Y-TNFR1 transfectants towards the level seen in the WT-TNFR1 transfectants. Seven high-ranking drugs were selected and tested by RPPA for effects on the same 40 signalling molecules in lysates of peripheral blood mononuclear cells (PBMCs) from C33Y-TRAPS patients compared to PBMCs from normal controls. The fluoroquinolone antibiotic lomefloxacin, as well as others from this class of compounds, showed the most significant effects on multiple pro-inflammatory signalling pathways that are constitutively activated in TRAPS; lomefloxacin dose-dependently significantly reduced expression of 7/40 signalling molecules across the Jak/Stat, MAPK, NF-κB and PI3K/AKT pathways. This study demonstrates the power of signalome screening for identifying candidates for drug repurposing.

Tumour necrosis factor receptor I blockade shows that TNF-dependent and TNF-independent mechanisms synergise in TNF receptor associated periodic syndrome

TNF receptor associated periodic syndrome (TRAPS) is an autoinflammatory disease involving recurrent episodes of fever and inflammation. It is associated with autosomal dominant mutations in TNF receptor superfamily 1A gene localised to exons encoding the ectodomain of the p55 TNF receptor, TNF receptor-1 (TNFR1). The aim of this study was to investigate the role of cell surface TNFR1 in TRAPS, and the contribution of TNF-dependent and TNF-independent mechanisms to the production of cytokines. HEK-293 and SK-HEP-1 cell lines were stably transfected with WT or TRAPS-associated variants of human TNF receptor superfamily 1A gene. An anti-TNFR1 single domain antibody (dAb), and an anti-TNFR1 mAb, bound to cell surface WT and variant TNFR1s. In HEK-293 cells transfected with death domain-inactivated (R347A) TNFR1, and in SK-HEP-1 cells transfected with normal (full-length) TNFR1, cytokine production stimulated in the absence of exogenous TNF by the presence of certain TNFR1 variants was not inhibited by the anti-TNFR1 dAb. In SK-Hep-1 cells, specific TRAPS mutations increased the level of cytokine response to TNF, compared to WT, and this augmented cytokine production was suppressed by the anti-TNFR1 dAb. Thus, TRAPS-associated variants of TNFR1 enhance cytokine production by a TNF-independent mechanism and by sensitising cells to a TNF-dependent stimulation. The TNF-dependent mechanism requires cell surface expression of TNFR1, as this is blocked by TNFR1-specific dAb.

The novel S59P mutation in the TNFRSF1A gene identified in an adult onset TNF receptor associated periodic syndrome (TRAPS) constitutively activates NF-κB pathway

Introduction

Mutations in the TNFRSF1A gene, encoding tumor necrosis factor receptor 1 (TNF-R1), are associated with the autosomal dominant autoinflammatory disorder, called TNF receptor associated periodic syndrome (TRAPS). TRAPS is clinically characterized by recurrent episodes of long-lasting fever and systemic inflammation. A novel mutation (c.262 T > C; S59P) in the TNFRSF1A gene at residue 88 of the mature protein was recently identified in our laboratory in an adult TRAPS patient. The aim of this study was to functionally characterize this novel TNFRSF1A mutation evaluating its effects on the TNF-R1-associated signaling pathways, firstly NF-κB, under particular conditions and comparing the results with suitable control mutations.

Methods

HEK-293 cell line was transfected with pCMV6-AC construct expressing wild-type (WT) or c.262 T > C (S59P), c.362G > A (R92Q), c.236C > T (T50M) TNFRSF1A mutants. Peripheral blood mononuclear cells (PBMCs) were instead isolated from two TRAPS patients carrying S59P and R92Q mutations and from five healthy subjects. Both transfected HEK-293 and PBMCs were stimulated with tumor necrosis factor (TNF) or interleukin 1β (IL-1β) to evaluate the expression of TNF-R1, the activation of TNF-R1-associated downstream pathways and the pro-inflammatory cytokines by means of immunofluorescent assay, array-based technique, immunoblotting and immunometric assay, respectively.

Results

TNF induced cytoplasmic accumulation of TNF-R1 in all mutant cells. Furthermore, all mutants presented a particular set of active TNF-R1 downstream pathways. S59P constitutively activated IL-1β, MAPK and SRC/JAK/STAT3 pathways and inhibited apoptosis. Also, NF-κB pathway involvement was demonstrated in vitro by the enhancement of p-IκB-α and p65 nuclear subunit of NF-κB expression in all mutants in the presence of TNF or IL-1β stimulation. These in vitro results correlated with patients’ data from PBMCs. Concerning the pro-inflammatory cytokines secretion, mainly IL-1β induced a significant and persistent enhancement of IL-6 and IL-8 in PBMCs carrying the S59P mutation.

Conclusions

The novel S59P mutation leads to defective cellular trafficking and to constitutive activation of TNF-R1. This mutation also determines constitutive activation of the IL-1R pathway, inhibition of apoptosis and enhanced and persistent NF-κB activation and cytokine secretion in response to IL-1β stimulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0604-7) contains supplementary material, which is available to authorized users.

TNF and TNF-receptors: From mediators of cell death and inflammation to therapeutic giants - past, present and future

Tumor Necrosis Factor (TNF), initially known for its tumor cytotoxicity, is a potent mediator of inflammation, as well as many normal physiological functions in homeostasis and health, and anti-microbial immunity. It also appears to have a central role in neurobiology, although this area of TNF biology is only recently emerging. Here, we review the basic biology of TNF and its normal effector functions, and discuss the advantages and disadvantages of therapeutic neutralization of TNF - now a commonplace practice in the treatment of a wide range of human inflammatory diseases. With over ten years of experience, and an emerging range of anti-TNF biologics now available, we also review their modes of action, which appear to be far more complex than had originally been anticipated. Finally, we highlight the current challenges for therapeutic intervention of TNF: (i) to discover and produce orally delivered small molecule TNF-inhibitors, (ii) to specifically target selected TNF producing cells or individual (diseased) tissue targets, and (iii) to pre-identify anti-TNF treatment responders. Although the future looks bright, the therapeutic modulation of TNF now moves into the era of personalized medicine with society's challenging expectations of durable treatment success and of achieving long-term disease remission.

A pro-inflammatory signalome is constitutively activated by C33Y mutant TNF receptor 1 in TNF receptor-associated periodic syndrome (TRAPS)

Mutations in TNFRSF1A encoding TNF receptor 1 (TNFR1) cause the autosomal dominant TNF receptor-associated periodic syndrome (TRAPS): a systemic autoinflammatory disorder. Misfolding, intracellular aggregation, and ligand-independent signaling by mutant TNFR1 are central to disease pathophysiology. Our aim was to understand the extent of signaling pathway perturbation in TRAPS. A prototypic mutant TNFR1 (C33Y), and wild-type TNFR1 (WT), were expressed at near physiological levels in an SK-Hep-1 cell model. TNFR1-associated signaling pathway intermediates were examined in this model, and in PBMCs from C33Y TRAPS patients and healthy controls. In C33Y-TNFR1-expressing SK-Hep-1 cells and TRAPS patients’ PBMCs, a subtle, constitutive upregulation of a wide spectrum of signaling intermediates and their phosphorylated forms was observed; these were associated with a proinflammatory/antiapoptotic phenotype. In TRAPS patients’ PBMCs, this upregulation of proinflammatory signaling pathways was observed irrespective of concurrent treatment with glucocorticoids, anakinra or etanercept, and the absence of overt clinical symptoms at the time that the blood samples were taken. This study reveals the pleiotropic effect of a TRAPS-associated mutant form of TNFR1 on inflammatory signaling pathways (a proinflammatory signalome), which is consistent with the variable and limited efficacy of cytokine-blocking therapies in TRAPS. It highlights new potential target pathways for therapeutic intervention.

Clinical relevance and functional consequences of the TNFRSF1A multiple sclerosis locus

OBJECTIVE

We set out to characterize the clinical impact and functional consequences of rs1800693(G), the multiple sclerosis (MS) susceptibility allele found in the TNFRSF1A locus.

METHODS

We analyzed prospectively collected data on patients with MS to assess the role of the TNFRSF1A locus on disease course and treatment response. Using archival serum samples and freshly isolated monocytes from patients with MS and healthy subjects, we evaluated the effects of rs1800693(G) and a second risk allele, R92Q, on immune function.

RESULTS

In 772 patients with MS, we see no evidence that rs1800693(G) strongly influences clinical or radiographic indices of disease course and treatment response; thus, rs1800693(G) appears to be primarily involved in the onset of MS. At the molecular level, this validated susceptibility allele generates an RNA isoform, TNFRSF1A Δ6, that lacks the transmembrane and cytoplasmic domains. While there was no measurable effect on serum levels of soluble TNFRSF1A, rs1800693(G) appears to alter the state of monocytes, which demonstrate a more robust transcriptional response of CXCL10 and other genes in response to tumor necrosis factor (TNF)-α. We also report that activation of the TNF-α pathway results in altered expression of 6 other MS susceptibility genes, including T-cell activation rho GTPase activating protein (TAGAP) and regulator of G-protein signaling 1 (RGS1), which are not previously known to be responsive to TNF-α.

CONCLUSIONS

The MS rs1800693(G) susceptibility allele affects the magnitude of monocyte responses to TNF-α stimulation, and the TNF pathway may be one network in which the effect of multiple MS genes becomes integrated.

Involvement of the same TNFR1 residue in mendelian and multifactorial inflammatory disorders

Objectives

TNFRSF1A is involved in an autosomal dominant autoinflammatory disorder called TNFR-associated periodic syndrome (TRAPS). Most TNFRSF1A mutations are missense changes and, apart from those affecting conserved cysteines, their deleterious effect remains often questionable. This is especially true for the frequent R92Q mutation, which might not be responsible for TRAPS per se but represents a susceptibility factor to multifactorial inflammatory disorders. This study investigates TRAPS pathophysiology in a family exceptional by its size (13 members) and compares the consequences of several mutations affecting arginine 92.

Methods

TNFRSF1A screening was performed by PCR-sequencing. Comparison of the 3-dimensional structure and electrostatic properties of wild-type and mutated TNFR1 proteins was performed by in silico homology modeling. TNFR1 expression was assessed by FACS analysis, western blotting and ELISA in lysates and supernatants of HEK293T cells transiently expressing wild-type and mutated TNFR1.

Results

A TNFRSF1A heterozygous missense mutation, R92W (c.361C>T), was shown to perfectly segregate with typical TRAPS manifestations within the family investigated (p<5.10⁻⁴). It was associated with very high disease penetrance (0.9). Prediction of its impact on the protein structure revealed local conformational changes and alterations of the receptor electrostatic properties. R92W also impairs the TNFR1 expression at the cell surface and the levels of soluble receptor. Similar results were obtained with R92P, another mutation previously identified in a very small familial form with incomplete penetrance and variable expressivity. In contrast, TNFR1-R92Q behaves like the wild-type receptor.

Conclusions

These data demonstrate the pathogenicity of a mutation affecting arginine 92, a residue whose involvement in inflammatory disorders is deeply debated. Combined with previous reports on arginine 92 mutations, this study discloses an unusual situation in which different amino acid substitutions at the same position in the protein are associated with a clinical spectrum bridging Mendelian to multifactorial conditions.

The association of TNFRSF1A gene and MEFV gene mutations with adult onset Still's disease

Adult onset Still's disease (ASD) is a systemic inflammatory disorder of unknown etiology. ASD is characterized by fever with unknown etiology, rash, arthritis, and involvement of several organ systems. FMF and TRAPS are two important autoinflammatory diseases which characterized with recurrent inflammatory attacks. We aimed in this study to investigate the MEFV gene and TNFRSF1A gene variations in ASD. Twenty consecutive Turkish ASD patients (14 female and 6 male; mean age 38.45 ± 14; mean disease duration 3.3 ± 2.3; mean age of the disease onset 35.1 ± 14.4) and 103 healthy controls of Turkish origin were analyzed. All ASD patients were genotyped for the 4 MEFV mutations (M694V, E148Q, V726A, M680I) and TNFRSF1A gene exon 2-3 and exon 4-5 by using sequence analysis. The healthy controls are genotyped using PCR-RFLP method for intron 4 variation. The results of MEFV gene mutations screening show an increase in the MEFV mutation rate in ASD group, but it was not significantly different (p = 0.442, OR 1.64, 95 % CI 0.409-6.589). T-C polymorphism (rs1800692) was the only variation in the intron 4 of TNFRSF1A gene that we observed at the ASD patients. The frequency of TT genotype was 15 %, TC: 45 %, and CC: 40 % in ASD patients and the frequencies were 22, 41, and 37 % in healthy controls, respectively. When we analyzed the allele difference between both groups, there was no difference (p = 0.54, OR 1.24, 0.619-2.496-2.654). The variations in MEFV may have role in ASD pathogenesis. Our findings suggest that there is no significant association between ASD and TNFRSF1A variations.

The rice HGW gene encodes a ubiquitin-associated (UBA) domain protein that regulates heading date and grain weight

Heading date and grain weight are two determining agronomic traits of crop yield. To date, molecular factors controlling both heading date and grain weight have not been identified. Here we report the isolation of a hemizygous mutation, heading and grain weight (hgw), which delays heading and reduces grain weight in rice. Analysis of hgw mutant phenotypes indicate that the hemizygous hgw mutation decreases latitudinal cell number in the lemma and palea, both composing the spikelet hull that is known to determine the size and shape of brown grain. Molecular cloning and characterization of the HGW gene showed that it encodes a novel plant-specific ubiquitin-associated (UBA) domain protein localized in the cytoplasm and nucleus, and functions as a key upstream regulator to promote expressions of heading date- and grain weight-related genes. Moreover, co-expression analysis in rice and Arabidopsis indicated that HGW and its Arabidopsis homolog are co-expressed with genes encoding various components of ubiquitination machinery, implying a fundamental role for the ubiquitination pathway in heading date and grain weight control.

Setting up TRAPS

Tumour necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is a dominantly inherited autoinflammatory disease caused by heterozygous mutations in the TNFRSF1A gene encoding for the TNF receptor 1 (TNFR1). TRAPS is a multi-faceted and heterogeneous disease which commonly manifests as recurrent episodes of high fever accompanied by abdominal pain, pleurisy, migratory rash, and myalgia. Disease attacks occur spontaneously or may be elicited by minor triggers. Because of a vigorous and sustained acute-phase response it may be complicated by systemic AA amyloidosis. Therapeutically interleukin-1 blockade seems even more promising than TNF blockade. Studies on the pathogenesis of TRAPS have shown TNFα-dependent cellular signalling to be defective, an enigmatic finding considering the hyperinflammatory phenotype of the disease. Several studies indicate that most mutated receptors never reach the cell surface but are misfolded and trapped in the endoplasmic reticulum, where they may elicit an intracellular inflammatory response, and thus lead to constitutional expression of proinflammatory cytokines. The aim of this review is to describe the current understanding of the pathogenesis of TRAPS by integrating recent clinical and laboratory data.

Skin manifestations in tumor necrosis factor receptor-associated periodic syndrome (TRAPS)

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is a rare autosomal dominant inherited disease that belongs to the group of hereditary fever syndromes, that are also named hereditary auto-inflammatory syndromes. TRAPS is characterized by a variety of naturally occurring mutations in a TNF receptor (TNFR), that affect the soluble TNFRSF1A gene in the 12p13 region. In some patients, the pathogenesis of TRAPS involves defective TNFRSF1A shedding from cell membranes in response to varying stimuli. TRAPS is characterized by the periodic occurrence of a broad variety of different clinical symptoms that represent an acute-phase response, including fever and pain in the joints, abdomen, muscles, skin or eyes, with broad variations across patients. In many cases, skin involvement is present that may include migratory patches, skin rashes, erysepela-like erythema, edematous plaques, urticaria, periorbital edema and/or conjunctivitis. The histology of skin lesions in TRAPS is nonspecific, in general a perivascular dermal infiltrate of lymphocytes and monocytes can be found. Cutaneous findings are of particular importance in TRAPS: they have been shown to give direction to the diagnosis of TRAPS and in most cases their treatment is challenging. As the incidence of TRAPS is very low, no prospective randomized controlled trials and only a few studies with case numbers up to twenty-five patients have been published. No guidelines for TRAPS treatment have been established so far. This review summarizes our present knowledge about pathogenesis, clinical outcome and treatment options of skin manifestations in TRAPS.

Silencer of death domains (SODD) inhibits skeletal muscle and kidney enriched inositol 5-phosphatase (SKIP) and regulates phosphoinositide 3-kinase (PI3K)/Akt signaling to the actin cytoskeleton

Phosphoinositide 3-kinase (PI3K) regulates cell polarity and migration by generating phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3)) at the leading edge of migrating cells. The serine-threonine protein kinase Akt binds to PI(3,4,5)P(3), resulting in its activation. Active Akt promotes spatially regulated actin cytoskeletal remodeling and thereby directed cell migration. The inositol polyphosphate 5-phosphatases (5-ptases) degrade PI(3,4,5)P(3) to form PI(3,4)P(2), which leads to diminished Akt activation. Several 5-ptases, including SKIP and SHIP2, inhibit actin cytoskeletal reorganization by opposing PI3K/Akt signaling. In this current study, we identify a molecular co-chaperone termed silencer of death domains (SODD/BAG4) that forms a complex with several 5-ptase family members, including SKIP, SHIP1, and SHIP2. The interaction between SODD and SKIP exerts an inhibitory effect on SKIP PI(3,4,5)P(3) 5-ptase catalytic activity and consequently enhances the recruitment of PI(3,4,5)P(3)-effectors to the plasma membrane. In contrast, SODD(-/-) mouse embryonic fibroblasts exhibit reduced Akt-Ser(473) and -Thr(308) phosphorylation following EGF stimulation, associated with increased SKIP PI(3,4,5)P(3)-5-ptase activity. SODD(-/-) mouse embryonic fibroblasts exhibit decreased EGF-stimulated F-actin stress fibers, lamellipodia, and focal adhesion complexity, a phenotype that is rescued by the expression of constitutively active Akt1. Furthermore, reduced cell migration was observed in SODD(-/-) macrophages, which express the three 5-ptases shown to interact with SODD (SKIP, SHIP1, and SHIP2). Therefore, this study identifies SODD as a novel regulator of PI3K/Akt signaling to the actin cytoskeleton.

Mitochondrial reactive oxygen species promote production of proinflammatory cytokines and are elevated in TNFR1-associated periodic syndrome (TRAPS)

ROS generated by mitochondrial respiration are needed for optimal proinflammatory cytokine production in healthy cells, and are elevated in cells from patients with an autoinflammatory disorder.

Reactive oxygen species (ROS) have an established role in inflammation and host defense, as they kill intracellular bacteria and have been shown to activate the NLRP3 inflammasome. Here, we find that ROS generated by mitochondrial respiration are important for normal lipopolysaccharide (LPS)-driven production of several proinflammatory cytokines and for the enhanced responsiveness to LPS seen in cells from patients with tumor necrosis factor receptor-associated periodic syndrome (TRAPS), an autoinflammatory disorder caused by missense mutations in the type 1 TNF receptor (TNFR1). We find elevated baseline ROS in both mouse embryonic fibroblasts and human immune cells harboring TRAPS-associated TNFR1 mutations. A variety of antioxidants dampen LPS-induced MAPK phosphorylation and inflammatory cytokine production. However, gp91^phox and p22^phox reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits are dispensable for inflammatory cytokine production, indicating that NADPH oxidases are not the source of proinflammatory ROS. TNFR1 mutant cells exhibit altered mitochondrial function with enhanced oxidative capacity and mitochondrial ROS generation, and pharmacological blockade of mitochondrial ROS efficiently reduces inflammatory cytokine production after LPS stimulation in cells from TRAPS patients and healthy controls. These findings suggest that mitochondrial ROS may be a novel therapeutic target for TRAPS and other inflammatory diseases.

A novel TNFRSF1 gene mutation in a Turkish family: a report of three cases

Tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS) is an autosomal dominantly inherited rare autoinflammatory disease. It is caused by mutations in exons 2-3 and 4-5 of the tumor necrosing factor receptor superfamily 1A (TNFRSF1A) gene on chromosome 12p13.2. TNFRSF1A gene encodes the 55-kDa receptor for tumor necrosis factor. Attacks are associated with abdominal pain, myalgia, erythematous skin rash, conjunctivitis, and periorbital edema. Until now, more than 80 mutations have been identified. We herein report three patients with TRAPS of Turkish origin. The patients were followed up in our outpatient clinic in Kocaeli University Division of Rheumatology. Because of their TRAPS associated clinical features, we isolated genomic DNA from whole blood and sequenced the exon 2-3 and 4-5 third exon of TNFRSF1A gene after amplification with appropriate primers. One of the patients with TRAPS was 47-year-old female, who described recurrent attacks of fever, urticarial rash, conjunctivitis, arthralgia, myalgia, abdominal pain, thoracic pain, headache, fatigue, and elevated acute phase response since her childhood. With the sequencing of the TNFRSF1A gene, we identified heterozygous C29R mutation, which has not been reported before in any TRAPS patient. The other patients are her sons with similar findings and age 29 and 26. They were heterozygous for C29R mutation in TNFRSF1A gene too. We report novel C29R mutation in three TRAPS patients of Turkish origin, in which the main clinical features are recurrent fever attacks, erythematous skin rash, conjunctivitis, myalgia, and arthralgia. Treatment with steroids resolved the symptoms and lesions.

Concerted action of wild-type and mutant TNF receptors enhances inflammation in TNF receptor 1-associated periodic fever syndrome

TNF, acting through p55 tumor necrosis factor receptor 1 (TNFR1), contributes to the pathogenesis of many inflammatory diseases. TNFR-associated periodic syndrome (TRAPS, OMIM 142680) is an autosomal dominant autoinflammatory disorder characterized by prolonged attacks of fevers, peritonitis, and soft tissue inflammation. TRAPS is caused by missense mutations in the extracellular domain of TNFR1 that affect receptor folding and trafficking. These mutations lead to loss of normal function rather than gain of function, and thus the pathogenesis of TRAPS is an enigma. Here we show that mutant TNFR1 accumulates intracellularly in peripheral blood mononuclear cells of TRAPS patients and in multiple cell types from two independent lines of knockin mice harboring TRAPS-associated TNFR1 mutations. Mutant TNFR1 did not function as a surface receptor for TNF but rather enhanced activation of MAPKs and secretion of proinflammatory cytokines upon stimulation with LPS. Enhanced inflammation depended on autocrine TNF secretion and WT TNFR1 in mouse and human myeloid cells but not in fibroblasts. Heterozygous TNFR1-mutant mice were hypersensitive to LPS-induced septic shock, whereas homozygous TNFR1-mutant mice resembled TNFR1-deficient mice and were resistant to septic shock. Thus WT and mutant TNFR1 act in concert from distinct cellular locations to potentiate inflammation in TRAPS. These findings establish a mechanism of pathogenesis in autosomal dominant diseases where full expression of the disease phenotype depends on functional cooperation between WT and mutant proteins and also may explain partial responses of TRAPS patients to TNF blockade.

Horror autoinflammaticus: the molecular pathophysiology of autoinflammatory disease (*)

The autoinflammatory diseases are characterized by seemingly unprovoked episodes of inflammation, without high-titer autoantibodies or antigen-specific T cells. The concept was proposed ten years ago with the identification of the genes underlying hereditary periodic fever syndromes. This nosology has taken root because of the dramatic advances in our knowledge of the genetic basis of both mendelian and complex autoinflammatory diseases, and with the recognition that these illnesses derive from genetic variants of the innate immune system. Herein we propose an updated classification scheme based on the molecular insights garnered over the past decade, supplanting a clinical classification that has served well but is opaque to the genetic, immunologic, and therapeutic interrelationships now before us. We define six categories of autoinflammatory disease: IL-1beta activation disorders (inflammasomopathies), NF-kappaB activation syndromes, protein misfolding disorders, complement regulatory diseases, disturbances in cytokine signaling, and macrophage activation syndromes. A system based on molecular pathophysiology will bring greater clarity to our discourse while catalyzing new hypotheses both at the bench and at the bedside.

Novel markers of inflammation identified in tumor necrosis factor receptor-associated periodic syndrome (TRAPS) by transcriptomic analysis of effects of TRAPS-associated tumor necrosis factor receptor type I mutations in an endothelial cell line

OBJECTIVE

To analyze the effects of tumor necrosis factor receptor-associated periodic syndrome (TRAPS)-associated mutant tumor necrosis factor receptor type I (TNFRI) expression in a cell type directly relevant to the inflammation in TRAPS, and to identify novel markers associated with mutant TNFRI expression.

METHODS

Transcriptome analysis on 30,000 human genes was performed on SK-Hep-1 human endothelial cells transfected with either wild-type (WT) or TRAPS-associated mutant TNFRI. Quantitative reverse transcriptase-polymerase chain reaction and protein expression levels measured by enzyme-linked immunosorbent assay verified transcriptional changes for selected genes both in supernatants from cells expressing mutant TNFRI and in patient plasma.

RESULTS

Cells expressing mutant TNFRI showed up-regulation of multiple proinflammatory genes relative to WT transfectants, including genes for pentraxin 3, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, CCL2, and CCL5, which were also expressed as proteins. In addition, the expression of most of these markers was increased in the plasma and peripheral blood mononuclear cells from TRAPS patients relative to those from healthy controls. The cysteine mutations (C33Y and C52F), which are associated with a more severe clinical phenotype, induced more genes than the low-penetrance mutation R92Q, which is associated with a milder phenotype. The expression of most genes was induced by a death domain (DD)-dependent mechanism, since they were not induced by expression of TNFRI mutants with an inactivated DD.

CONCLUSION

TRAPS-associated TNFRI mutants induce the expression of multiple genes encoding inflammatory molecules, cellular receptors, transcription factors, and regulators of apoptosis in endothelial cells that require the cytoplasmic signaling properties of the receptor. Different mutants have specific expression profiles, indicating mutation-specific effects. The expression of some of these markers was also elevated in samples from TRAPS patients.

Alix and ALG-2 are involved in tumor necrosis factor receptor 1-induced cell death

Alix/AIP1 regulates cell death in a way involving interactions with the calcium-binding protein ALG-2 and with proteins of ESCRT (endosomal sorting complex required for transport). Using mass spectrometry we identified caspase-8 among proteins co-immunoprecipitating with Alix in dying neurons. We next demonstrated that Alix and ALG-2 interact with pro-caspase-8 and that Alix forms a complex with the TNFalpha receptor-1 (TNF-R1), depending on its capacity to bind ESCRT proteins. Thus, Alix and ALG-2 may allow the recruitment of pro-caspase-8 onto endosomes containing TNF-R1, a step thought to be necessary for activation of the apical caspase. In line with this, expression of Alix deleted of its ALG-2-binding site (AlixDeltaALG-2) significantly reduced TNF-R1-induced cell death, without affecting endocytosis of the receptor. In a more physiological setting, we found that programmed cell death of motoneurons, which can be inhibited by AlixDeltaALG-2, is regulated by TNF-R1. Taken together, these results highlight Alix and ALG-2 as new actors of the TNF-R1 pathway.

Dysregulation of innate immunity: hereditary periodic fever syndromes

The hereditary periodic fever syndromes encompass a rare group of diseases that have lifelong recurrent episodes of inflammatory symptoms and an acute phase response in common. Clinical presentation can mimic that of lymphoproliferative disorders and patients often go undiagnosed for many years. These syndromes follow an autosomal inheritance pattern, and the major syndromes are linked to specific genes, most of which are involved in regulation of the innate immune response through pathways of apoptosis, nuclear factor kappaBeta activation and cytokine production. In others, the link between the protein involved and inflammation is less clear. The recurrent inflammation can lead to complications, such as renal impairment due to amyloidosis and vasculitis, visual impairment, hearing loss, and joint destruction, depending on the specific syndrome. In recent years, treatment options for these diseases have improved significantly. Early establishment of an accurate diagnosis and start of appropriate therapy improves prognosis in these patients.

Activated human neutrophils rapidly release the chemotactically active D2D3 form of the urokinase-type plasminogen activator receptor (uPAR/CD87)

The urokinase-type plasminogen activator receptor (uPAR/CD87) exists both in cell-bound and soluble forms. Neutrophils contain extensive intracellular pools of uPAR that are translocated to the plasma membrane upon activation. In the present study, we investigated the ability of human neutrophils to shed uPAR from cell surface following activation and addressed the possible involvement of the released receptor in the inflammatory response. We first observed that the spontaneous release of suPAR by resting neutrophils was strongly and rapidly (within minutes) enhanced by calcium ionophore ionomycin and to a lesser extent when cells were primed with TNF-alpha and then stimulated with fMLP or IL-8. We demonstrated that suPAR is produced by resting and activated neutrophils predominantly as a truncated form devoid of N-terminal D1 domain (D2D3 form) that lacks GPI anchor. Migration of formyl peptide receptor-like 1 (FPRL1)-transfected human embryonic kidney (HEK) 293 cells toward the supernatants harvested from activated neutrophils was significantly diminished when D2D3 form of suPAR was immunodepleted from the supernatants. We conclude that activated neutrophils release the chemotactically active D2D3 form of suPAR that acts as a ligand of FPRL1. Interestingly, we present evidence that GPI-specific phospholipase D (GPI-PLD) that has previously been shown to shed uPAR in cancer cells is not involved in suPAR release from human neutrophils. We suggest that production of the chemotactically active D2D3 form of suPAR by activated human neutrophils in vivo could contribute to the recruitment of monocytes and other formyl peptide receptors-expressing cells to the sites of acute inflammation where neutrophil accumulation and activation occur.

Persistent efficacy of anakinra in patients with tumor necrosis factor receptor-associated periodic syndrome

OBJECTIVE

To evaluate the efficacy and safety of treatment with the interleukin-1 receptor antagonist anakinra in patients with tumor necrosis factor receptor-associated periodic syndrome (TRAPS) requiring high cumulative doses of steroids.

METHODS

Four children (mean age 9.1 years [range 4-13 years]) and 1 adult (age 33 years) with TRAPS were enrolled in the study. The 3 children with cysteine mutations (C52Y, C55Y, C43R) had prolonged and frequent attacks of fever. One child with the R92Q mutation and the adult patient with the C43R mutation displayed a more chronic disease course, with fluctuating, nearly continuous symptoms and persistent elevation of acute-phase reactant levels (including serum amyloid A [SAA]). All patients were treated with anakinra (1.5 mg/kg/day).

RESULTS

All of the patients had a prompt response to anakinra, with disappearance of symptoms and normalization of acute-phase reactant levels, including SAA. In all pediatric patients, anakinra was withdrawn after 15 days of treatment. After a few days (mean 5.6 days [range 3-8]) a disease relapse occurred, which dramatically responded to reintroduction of anakinra. During the following period of observation (mean 11.4 months [range 4-20 months]), the patients did not experience episodes of fever or other disease-related clinical manifestations. Levels of acute-phase reactants remained in the normal range. No major adverse reactions or severe infections were observed.

CONCLUSION

Continuous treatment with anakinra effectively controlled both the clinical and laboratory manifestations in patients with TRAPS and prevented disease relapses.

Falling into TRAPS--receptor misfolding in the TNF receptor 1-associated periodic fever syndrome

TNF receptor-associated periodic syndrome (TRAPS) is a dominantly inherited disease caused by missense mutations in the TNF receptor 1 (TNFR1) gene. Patients suffer from periodic bouts of severe abdominal pain, localised inflammation, migratory rashes, and fever. More than 40 individual mutations have been identified, all of which occur in the extracellular domain of TNFR1. In the present review we discuss new findings describing aberrant trafficking and function of TNFR1 harbouring TRAPS mutations, challenging the hypothesis that TRAPS pathology is driven by defective receptor shedding, and we suggest that TNFR1 might acquire novel functions in the endoplasmic reticulum, distinct from its role as a cell surface receptor. We also describe the clinical manifestations of TRAPS, current treatment regimens, and the widening array of patient mutations.

Elevated CD16 expression by monocytes from patients with tumor necrosis factor receptor-associated periodic syndrome

OBJECTIVE

Tumor necrosis factor receptor-associated periodic syndrome (TRAPS) is an inherited autosomal-dominant autoinflammatory condition caused by mutations in the ectodomain of the 55-kd tumor necrosis factor (TNF) receptor superfamily 1A. Proinflammatory blood monocytes with the phenotype CD14+,CD16+,HLA-DR++ are a major source of TNF, and the number of such monocytes is increased during infection and inflammation. The aim of this study was to investigate whether the expression of circulating CD16+ monocytes is affected in patients with TRAPS.

METHODS

Peripheral blood obtained from patients with TRAPS and healthy control subjects was stained with monoclonal antibodies to detect CD14++,CD16- monocytes and CD14+,CD16+ monocytes, using flow cytometry. Lipopolysaccharide-induced TNF production was measured by intracellular cytokine staining. Activation-induced shedding of CD16 was investigated by treating blood samples with phorbol myristate acetate.

RESULTS

The level of CD16 expression by CD14+,CD16+ monocytes, but not their absolute number, was significantly elevated in patients with TRAPS, even though the patients were not experiencing clinically overt episodes of autoinflammation at the time of sampling. These findings are similar to those for the C-reactive protein levels and erythrocyte sedimentation rates in the same patients. The enhanced level of CD16 expression by monocytes from patients with TRAPS was not attributable to a defect in activation-induced shedding of CD16. The CD14+,CD16+ monocytes were the predominant source of TNF in both patients and healthy control subjects.

CONCLUSION

The level of CD16 expression by monocytes was elevated in patients with TRAPS, as a feature of the underlying constitutive inflammation status.

Auto-inflammatory fever syndromes

Human autoinflammatory diseases (except for PFAPA) are a heterogeneous group of genetically determined diseases characterized by seemingly unprovoked inflammation in the absence of autoimmune or infective causes (Table 2). The last decade has witnessed tremendous advances in the understanding of these disorders. These advances have allowed therapeutic interventions resulting in improvement in the short-term and long-term morbidity of all of these diseases. Future research into the molecular mechanisms underlying these inflammatory diseases should lead to a better understanding of inflammatory diseases in general and, it is hoped, to better and more targeted therapies.

Mutant tumor necrosis factor receptor associated with tumor necrosis factor receptor-associated periodic syndrome is altered antigenically and is retained within patients' leukocytes

OBJECTIVE

To investigate the effect of mutations in tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) in TNFR-associated periodic syndrome (TRAPS) on the binding of anti-TNFRSF1A monoclonal antibodies (mAb), and to investigate the subcellular distribution of mutant versus wild-type (WT) TNFRSF1A in patients with TRAPS.

METHODS

HEK 293 cells transfected with WT and/or mutant TNFRSF1A were used to investigate the interaction of anti-TNFRSF1A mAb with the WT and mutant proteins. Monoclonal antibodies that differentially bound to C33Y TNFRSF1A were used to investigate the distribution of WT and mutant TNFRSF1A in TRAPS patients with the C33Y mutation.

RESULTS

We identified a mAb whose binding to TNFRSF1A was completely abolished by the C33Y or C52F TRAPS-associated mutations, whereas other mutations (T50M, C88Y, R92Q) had lesser effects on the binding of this mAb. A different mAb was found to bind efficiently to all of the mutant forms of TNFRSF1A examined as well as to the WT receptor. Exploitation of the differential binding properties of these mAb indicated that mutant (as distinct from WT) TNFRSF1A showed abnormal intracellular retention in the neutrophils of TRAPS patients with the C33Y mutation, with little if any expression of mutant TNFRSF1A on the cell surface or as soluble receptor in plasma.

CONCLUSION

TRAPS-associated mutant TNFRSF1A has an antigenically altered structure and shows abnormal retention in the leukocytes of patients with TRAPS, which is consistent with previous findings from in vitro and transgenic model systems. This is consistent with a misfolded protein response contributing to the pathophysiology of TRAPS.

[TNF receptor-associated periodic syndrome (TRAPS) in Japan: clinical characterization, pathogenesis, diagnostic criteria, and treatment]

TNF receptor-associated periodic syndrome (TRAPS) is an autosomal dominant inherited disease characterized by prolonged episodes of periodic fever and localized inflammation. The hypothetical pathogenesis of TRAPS is defective TNF receptor 1 (TNFRSF1A) shedding from cell membranes in response to a stimulus including TNFalpha. This mechanism has recently been shown to account for a minor population of TRAPS patients and other mechanisms are reported to explain the disease, such as resistance to apoptosis, TNFRSF1A internalization, or TNFRSF1A misfolding and aggregation, leading to NF-kappaB activation and apoptosis. Until now 15 TRAPS patients from 5 pedigree including 5 different mutations (C30R, C30Y, T61I, C70S, C70G) had been reported in Japan. There were many sporadic cases of TRAPS without TNFRSF1A mutation in our epidemiological study. In this issue, we described the clinical characterization, pathogenesis, diagnostic criteria, and treatment of TRAPS according to our case and literature.