Biochemical and structural characterization of the human TL1A ectodomain

Targeting TL1A and DR3: the new frontier of anti-cytokine therapy in IBD

TNF-like cytokine 1A (TL1A) and its functional receptor, death-domain receptor 3 (DR3), are members of the TNF and TNFR superfamilies, respectively, with recognised roles in regulating innate and adaptive immune responses; additional existence of a decoy receptor, DcR3, indicates a tightly regulated cytokine system. The significance of TL1A:DR3 signalling in the pathogenesis of inflammatory bowel disease (IBD) is supported by several converging lines of evidence. Herein, we aim to provide a comprehensive understanding of what is currently known regarding the TL1A/DR3 system in the context of IBD. TL1A and DR3 are expressed by cellular subsets with important roles for the initiation and maintenance of intestinal inflammation, serving as potent universal costimulators of effector immune responses, indicating their participation in the pathogenesis of IBD. Recent evidence also supports a homoeostatic role for TL1A:DR3 via regulation of Tregs and innate lymphoid cells. TL1A and DR3 are also expressed by stromal cells and may contribute to inflammation-induced or inflammation-independent intestinal fibrogenesis. Finally, discovery of genetic polymorphisms with functional consequences may allow for patient stratification, including differential responses to TL1A-targeted therapeutics. In conclusion, TL1A:DR3 signalling plays a central and multifaceted role in the immunological pathways that underlie intestinal inflammation, such as that observed in IBD. Such evidence provides the foundation for developing pharmaceutical approaches targeting this ligand-receptor pair in IBD.

The ever-expanding role of cytokine receptor DR3 in T cells

Death Receptor 3 (DR3) is a cytokine receptor of the Tumor Necrosis Factor receptor superfamily that plays a multifaceted role in both innate and adaptive immunity. Based on the death domain motif in its cytosolic tail, DR3 had been proposed and functionally affirmed as a trigger of apoptosis. Further studies, however, also revealed roles of DR3 in other cellular pathways, including inflammation, survival, and proliferation. DR3 is expressed in various cell types, including T cells, B cells, innate lymphocytes, myeloid cells, fibroblasts, and even outside the immune system. Because DR3 is mainly expressed on T cells, DR3-mediated immune perturbations leading to autoimmunity and other diseases were mostly attributed to DR3 activation of T cells. However, which T cell subset and what T effector functions are controlled by DR3 to drive these processes remain incompletely understood. DR3 engagement was previously found to alter CD4 T helper subset differentiation, expand the Foxp3+ Treg cell pool, and maintain intraepithelial γδ T cells in the gut. Recent studies further unveiled a previously unacknowledged aspect of DR3 in regulating innate-like invariant NKT (iNKT) cell activation, expanding the scope of DR3-mediated immunity in T lineage cells. Importantly, in the context of iNKT cells, DR3 ligation exerted costimulatory effects in agonistic TCR signaling, unveiling a new regulatory framework in T cell activation and proliferation. The current review is aimed at summarizing such recent findings on the role of DR3 on conventional T cells and innate-like T cells and discussing them in the context of immunopathogenesis.

TL1A promotes metastasis and EMT process of colorectal cancer

Background

Metastasis is the major problem of colorectal cancer (CRC) and is correlated with the high mortality. Tumor necrosis factor-like cytokine 1A (TL1A) is a novel regulatory factor for inflammatory diseases. This work aimed to investigate the role of TL1A in CRC metastasis.

Method

AOM/DSS-induced mouse model, xenograft tumor model and metastasis murine model were established to mimic the colitis-associated CRC and investigate CRC growth and metastasis in vivo. Colon tissues were assessed by hematoxylin/eosin (HE) staining and immunohistochemistry (IHC). CRC cell metastasis in vivo was observed using in vivo imaging system (IVIS). Cell viability and proliferation were examined using cell counting kit 8 (CCK-8) and EdU experiments. The expression of tumor growth factor β (TGFβ) and metastatic biomarkers were detected using western blotting experiment. The in vitro cell metastasis was measured by Transwell.

Results

Knockdown of TL1A notably suppressed the generation of colonic tumors in azoxymethane/dextran sodium sulfate (AOM/DSS) model, suppressed in vivo CRC cell growth, as well as lung and liver metastasis. The inflammation response and inflammatory cell infiltration in tumor sites were decreased by TL1A depletion. The in vitro CRC cell growth and metastasis was also suppressed by shTL1A, along with altered expression of epithelial mesenchymal transition (EMT) biomarkers. TL1A depletion suppressed the level of the TGF-β1 receptor (TβRI) and phosphorylation of Smad3 in CRC cells. Stimulation with TGF-β recovered the CRC cell migration and invasion that suppressed by shTL1A.

Conclusion

Our work implicated TL1A as a promoter of CRC generation and metastasis and defines TGF-β/Smad3 signaling as mediator of TL1A-regualated CRC cell metastasis.

Roles of tumor necrosis factor-like ligand 1A in γδT-cell activation and psoriasis pathogenesis

Background

Interleukin (IL)-17-producing γδT (γδT17) cells mediate inflammatory responses in barrier tissues. Dysregulated γδT17 cell activation can lead to the overproduction of IL-17 and IL-22 and the development of inflammatory diseases, including psoriasis. IL-23 and IL-1β are known to synergistically activate γδT17 cells, but the regulatory mechanisms of γδT17 cells have not been fully elucidated. This study aimed to reveal the contribution of the inflammatory cytokine tumor necrosis factor-like ligand 1A (TL1A) to γδT17 cell activation and psoriasis development.

Methods

Anti-TL1A antibody was injected into an imiquimod (IMQ)-induced murine psoriasis model. TL1A receptor expression was analyzed in splenic and dermal γδT cells. γδT cells were tested for cytokine production in vitro and in vivo under stimulation with IL-23, IL-1β, and TL1A. TL1A was applied to a psoriasis model induced by intradermal IL-23 injection. Mice deficient in γδT cells were intradermally injected with IL-23 plus TL1A to verify the contribution of TL1A-dependent γδT-cell activation to psoriasis development.

Results

Neutralization of TL1A attenuated γδT17 cell activation in IMQ-treated skin. TL1A induced cytokine production by splenic γδT17 cells in synergy with IL-23. Dermal γδT17 cells constitutively expressed a TL1A receptor at high levels and vigorously produced IL-22 upon intradermal IL-23 and TL1A injection but not IL-23 alone. TL1A exacerbated the dermal symptoms induced by IL-23 injection in wild-type but not in γδT cell-deficient mice.

Conclusion

These findings suggest a novel regulatory mechanism of γδT cells through TL1A and its involvement in psoriasis pathogenesis as a possible therapeutic target.

A stable, engineered TL1A ligand co-stimulates T cells via specific binding to DR3

TL1A (TNFSF15) is a TNF superfamily ligand which can bind the TNFRSF member death receptor 3 (DR3) on T cells and the soluble decoy receptor DcR3. Engagement of DR3 on CD4+ or CD8+ effector T cells by TL1A induces downstream signaling, leading to proliferation and an increase in secretion of inflammatory cytokines. We designed a stable recombinant TL1A molecule that (1) displays high monodispersity and stability, (2) displays the ability to activate T cells in vitro and in vivo, and (3) lacks binding to DcR3 while retaining functional activity via DR3. Together these results suggest the TL1A ligand can be amenable to therapeutic development on its own or paired with a tumor-targeting moiety.

Role of TL1A in Inflammatory Autoimmune Diseases: A Comprehensive Review

TL1A, also called TNFSF15, is a member of tumor necrosis factor family. It is expressed in different immune cell, such as monocyte, macrophage, dendritic cell, T cell and non-immune cell, for example, synovial fibroblast, endothelial cell. TL1A competitively binds to death receptor 3 or decoy receptor 3, providing stimulatory signal for downstream signaling pathways, and then regulates proliferation, activation, apoptosis of and cytokine, chemokine production in effector cells. Recent findings showed that TL1A was abnormally expressed in autoimmune diseases, including rheumatoid arthritis, inflammatory bowel disease, psoriasis, primary biliary cirrhosis, systemic lupus erythematosus and ankylosing spondylitis. In vivo and in vitro studies further demonstrated that TL1A was involved in development and pathogenesis of these diseases. In this study, we comprehensively discussed the complex immunological function of TL1A and focused on recent findings of the pleiotropic activity conducted by TL1A in inflammatory autoimmune disease. Finish of the study will provide new ideas for developing therapeutic strategies for these diseases by targeting TL1A.

A gold revision of the Golgi Dynamics (GOLD) domain structure and associated cell functionalities

The classical secretory pathway is the key membrane-based delivery system in eukaryotic cells. Several families of proteins involved in the secretory pathway, with functionalities going from cargo sorting receptors to the maintenance and dynamics of secretory organelles, share soluble globular domains predicted to mediate protein-protein interactions. One of them is "Golgi Dynamics" (GOLD) domain, named after its strong association with the Golgi apparatus. There are many GOLD-containing protein families, such as the Transmembrane emp24 domain-containing proteins (TMED/p24 family), animal SEC14-like proteins, Human Golgi resident protein ACBD3, a splice variant of TICAM2 called TRAM with GOLD domain and FYCO1. Here, we critically review the state-of-the-art knowledge of the structures and functions of the main representatives of GOLD-containing proteins in vertebrates. We provide the first unified description of the GOLD domain structure across different families since the first high-resolution structure was determined. With a brand-new update on the definition of the GOLD domain, we also discuss how its tertiary structure fits the β-sandwich-like fold map and give exciting new directions for forthcoming studies.

TL1A: A New Potential Target in the Treatment of Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), are chronic inflammatory diseases of the gastrointestinal tract. In the last few years, the development of biological agents targeting cytokines and receptors involved in IBD pathogenesis has led to better outcomes and has improved the course of the disease. Despite their effectiveness, drugs such as tumor necrosis factor (TNF) inhibitors, anti-Interleukin-12/23 and anti-integrins, do not induce a response in about one-third of patients, and 40% of patients lose response over time. Therefore, more efficient therapies are required. Recent studies showed that TL1A (Tumor necrosis factor-like cytokine 1A) acts as a regulator of mucosal immunity and participates in immunological pathways involved in the IBD pathogenesis. In this review article, we analyze the role of TL1A as a new potential target therapy in IBD patients.

Cloning and characterization of tumor necrosis factor superfamily 15 in rock bream, Oplegnathus fasciatus; phylogenetic, in silico, and expressional analysis

Tumor necrosis factor superfamily (TNFSF)15 is a member of TNFSF which shares a high homology with other TNFSFs, especially lymphotoxin (LT)-α in teleost. In this study, we have cloned a putative TNFSF15 gene in rock bream which was highly homologous with other fish TNFSF15 and performed bioinformatic analysis to confirm the membership. The RB-TNFSF15 cDNA consists of 3192 bp (193 bp of 5'-untranslated region (UTR), 732 bp of ORF, and 2267 bp of 3'-UTR) and encodes a polypeptide of 243 amino acids containing a predicted TNF superfamily signature with 43-61% identities with fish TNFSF15. The predicted 3D structure was similar to human TNFSF15 with β barrel structure containing 10 β strands and 1 α helix while human LT-α and β contain 10 β strands and 2 α helices. Consequently, the synteny and phylogenetic analysis of fish TNFSF15 genes and structural similarity of the predicted protein to mammalian TNFSF15 implicate that they can be identified as TNFSF15. In healthy rock bream, RB-TNFSF15 gene expression level was the highest in fin and the lowest in blood. In vitro, TNFSF15 gene expression was up-regulated by lipopolysaccharide, polyinosinic:polycytidylic acid (poly I:C) and rock bream iridovirus (RBIV) in head kidney, while up-regulated by poly I:C and RBIV at later time in spleen. In vivo, RB-TNFSF15 gene expression was up-regulated in head kidney, liver and blood after vaccination with a formalin inactivated RBIV. After challenging with RBIV, RB-TNFSF15 gene expression was up-regulated in unvaccinated group at day 3 post-infection in head kidney. In gill, it was significantly up-regulated in vaccinated group at day 1 post-challenge and all groups at day 7, indicating that RB-TNFSF may play a key role in mucosal immunity during viral infection. Since the regulation mechanism of TNFSF15 gene expression in fish has not yet been elucidated, the present study will help to understand the roles of TNFSF15 in fish immune system.

High-resolution crystal structure of arthropod Eiger TNF suggests a mode of receptor engagement and altered surface charge within endosomes

The tumour necrosis factor alpha (TNFα) superfamily of proteins are critical in numerous biological processes, such as in development and immunity. Eiger is the sole TNFα member described in arthropods such as in the important model organism Drosophila. To date there are no structural data on any Eiger protein. Here we present the structure of the TNF domain of Eiger from the fall armyworm Spodoptera frugiperda (SfEiger) to 1.7 Å from a serendipitously obtained crystal without prior knowledge of the protein sequence. Our structure confirms that canonical trimerization is conserved from ancestral TNFs and points towards a mode of receptor engagement. Furthermore, we observe numerous surface histidines on SfEiger, potentially acting as pH switches following internalization into endosomes. Our data contributes to the genome annotation of S. frugiperda, a voracious agricultural pest, and can serve as a basis for future structure-function investigations of the TNF system in related arthropods such as Drosophila.

TL1A (TNFSF15) and DR3 (TNFRSF25): A Co-stimulatory System of Cytokines With Diverse Functions in Gut Mucosal Immunity

TL1A and its functional receptor DR3 are members of the TNF/TNFR superfamilies of proteins. Binding of APC-derived TL1A to lymphocytic DR3 provides co-stimulatory signals for activated lymphocytes. DR3 signaling affects the proliferative activity of and cytokine production by effector lymphocytes, but also critically influences the development and suppressive function of regulatory T-cells. DR3 was also found to be highly expressed by innate lymphoid cells (ILCS), which respond to stimulation by TL1A. Several recent studies with transgenic and knockout mice as well as neutralizing or agonistic antibodies for these two proteins, have clearly shown that TL1A/DR3 are important mediators of several chronic immunological disorders, including Inflammatory Bowel Disease (IBD). TL1A and DR3 are abundantly localized at inflamed intestinal areas of patients with IBD and mice with experimental ileitis or colitis and actively participate in the immunological pathways that underlie mucosal homeostasis and intestinal inflammation. DR3 signaling has demonstrated a dichotomous role in mucosal immunity. On the one hand, during acute mucosal injury it exerts protective functions by ameliorating the severity of acute inflammatory responses and facilitating tissue repair. On the other hand, it critically participates in the pro-inflammatory pathways that underlie chronic inflammatory responses, such as those that take place in IBD. These effects are mediated through modulation of the relative mucosal abundance and function of Th1, Th2, Th17, Th9, and Treg lymphocytes, but also of all types of ILCs. Recently, an important role was demonstrated for TL1A/DR3 as potential mediators of intestinal fibrosis that is associated with the presence of gut inflammation. These accumulating data have raised the possibility that TL1A/DR3 pathways may represent a valid therapeutic target for chronic immunological diseases. Nevertheless, applicability of such a therapeutic approach will greatly rely on the net result of TL1A/DR3 manipulation on the various cell populations that will be affected by this approach.

Insights into ligand binding by a viral tumor necrosis factor (TNF) decoy receptor yield a selective soluble human type 2 TNF receptor

Etanercept is a soluble form of the tumor necrosis factor receptor 2 (TNFR2) that inhibits pathological tumor necrosis factor (TNF) responses in rheumatoid arthritis and other inflammatory diseases. However, besides TNF, etanercept also blocks lymphotoxin-α (LTα), which has no clear therapeutic value and might aggravate some of the adverse effects associated with etanercept. Poxviruses encode soluble TNFR2 homologs, termed viral TNF decoy receptors (vTNFRs), that display unique specificity properties. For instance, cytokine response modifier D (CrmD) inhibits mouse and human TNF and mouse LTα, but it is inactive against human LTα. Here, we analyzed the molecular basis of these immunomodulatory activities in the ectromelia virus-encoded CrmD. We found that the overall molecular mechanism to bind TNF and LTα from mouse and human origin is fairly conserved in CrmD and dominated by a groove under its 50s loop. However, other ligand-specific binding determinants optimize CrmD for the inhibition of mouse ligands, especially mouse TNF. Moreover, we show that the inability of CrmD to inhibit human LTα is caused by a Glu-Phe-Glu motif in its 90s loop. Importantly, transfer of this motif to etanercept diminished its anti-LTα activity in >60-fold while weakening its TNF-inhibitory capacity in 3-fold. This new etanercept variant could potentially be used in the clinic as a safer alternative to conventional etanercept. This work is the most detailed study of the vTNFR-ligand interactions to date and illustrates that a better knowledge of vTNFRs can provide valuable information to improve current anti-TNF therapies.

Role of TNFSF15 in the intestinal inflammatory response

Gastrointestinal diseases, specifically Crohn’s disease, ulcerative colitis, diverticular disease, and primary biliary cirrhosis are all characterized by complicated inflammation of the digestive tract. Their pathology is multifactorial, and risk factors encompass both genetic and environmental factors. Recent advances in the genetic component of inflammatory bowel diseases (IBDs) have revealed that the tumor necrosis factor superfamily member 15 (TNFSF15) contains a number of risk alleles associated not only with IBD but also with other diseases such as diverticular disease and primary biliary cirrhosis. These risk alleles in TNFSF15 and the altered expression of its gene product can serve as the common ground between these disorders by explaining at least some of the underlying processes that lead to a dysregulated immune response and subsequent chronic inflammation. Here, we aim to outline how the TNFSF15 gene is involved in the proliferation and cell fate of different populations of T cells and subsequently in the control of both pro- and anti-inflammatory cytokines. Furthermore, we summarize what is currently known of TNFSF15 control region variants, how they are associated with each mentioned disease, and how these variants can explain the autoimmune pathology of said diseases through altered TNFSF15 expression.

Structural principles of tumor necrosis factor superfamily signaling

The tumor necrosis factor (TNF) ligand and receptor superfamilies play an important role in cell proliferation, survival, and death. Stimulating or inhibiting TNF superfamily signaling pathways is expected to have therapeutic benefit for patients with various diseases, including cancer, autoimmunity, and infectious diseases. We review our current understanding of the structure and geometry of TNF superfamily ligands, receptors, and their interactions. A trimeric ligand and three receptors, each binding at the interface of two ligand monomers, form the basic unit of signaling. Clustering of multiple receptor subunits is necessary for efficient signaling. Current reports suggest that the receptors are prearranged on the cell surface in a "nonsignaling," resting state in a large hexagonal structure of antiparallel dimers. Receptor activation requires ligand binding, and cross-linking antibodies can stabilize the receptors, thereby maintaining the active, signaling state. On the other hand, an antagonist antibody that locks receptor arrangement in antiparallel dimers effectively blocks signaling. This model may aid the design of more effective TNF signaling-targeted therapies.

Enhanced Signal and Quantitative Detection of Anti-Interferon-Gamma Antibody by Using a Nanometer Biolinker

For rapid screening and quantification of an antisera antibody, a nanometer bithiophene-based conductive biolinker can enhanced signal performance and can be used to verify the interaction of an anti-IFN-γ antibody with an IFN-γ protein. The experimental measurements take a generic approach which takes advantage of the functionality of thiophene-based linkers for biosensors. Effects associated with using bithiophene as a biolinker for surface plasmon resonance (SPR) spectroscopy are examined in this paper. By using an atomic force microscope (AFM), it was observed that the morphology of the bithiophene modified gold sensor surface became smoother than the original gold surface. We compared the response and concentration of the anti-IFN-γ antibody on a bithiophene-coated and dextran-coated biochip as well as on different thickness-modified surfaces under SPR relevant conditions. The results indicate that a response to IFN-γ molecules immobilized on a sensor using a bithiophene biolinker improved more than 8-fold when compared to that of a sensor using a dextran biolinker. Furthermore, the regeneration ability of the sensor surface shows good repeatability as only less than a 1% decrease was found after repeating the experimental work over 6 cycles. The characteristics provided us with a good platform for rapid screening, real-time monitoring and quantitative concentration of the autoimmune antibody activities.

Comparative genomic analysis of eutherian tumor necrosis factor ligand genes

The present analysis made attempts to resolve discrepancies in descriptions of eutherian tumor necrosis factor ligand genes implicated in cell signalling pathways, as well as in major physiological and pathological processes. Among 455 potential coding sequences, the eutherian comparative genomic analysis protocol annotated 211 complete coding sequences using public genomic sequence assemblies. The most comprehensive third party data gene data set first described 8 superclusters of eutherian tumor necrosis factor ligand genes, including 18 major gene clusters. The integrated gene annotations, phylogenetic analysis, and protein molecular evolution analysis proposed new classification and nomenclature of eutherian tumor necrosis factor ligand genes, as new framework of future experiments.

Tumor Necrosis Factor-like Cytokine TL1A and Its Receptors DR3 and DcR3: Important New Factors in Mucosal Homeostasis and Inflammation

Tumor necrosis factor (TNF)-like cytokine 1A (TL1A) is a member of the TNF superfamily of proteins (TNFSF15), which signals through association with death domain receptor 3 (DR3). Decoy receptor 3 (DcR3) competes with DR3 for TL1A binding and inhibits functional signaling. These proteins are significantly upregulated in inflamed intestinal tissues, and their pathogenetic importance for inflammatory bowel disease (IBD) is suggested by accumulating evidence. TL1A/DR3 induce costimulatory signals to activated lymphocytes, including the gut-specific populations of CD4+CD161+ and CD4+CCR9+ cells, affecting all major effector pathways and inducing the mucosal upregulation of Th1, Th2, and Th17 factors. They may also participate in mucosal homeostasis and defense against pathogens through their effects on the development and function of the recently described innate lymphoid cells. T-regulatory lymphocytes highly express DR3, and they respond to TL1A stimulation also. Mechanistic studies by transgenic expression of TL1A, deletion of TL1A or DR3, and therapeutic blockade by anti-TL1A antibodies all support the critical involvement of the corresponding pathways in the pathogenesis of chronic mucosal inflammation. Wide genome association studies have identified IBD-specific polymorphisms in TNFSF15 gene, which have functional implications and serve as poor prognostic factors. Recently, TL1A blockade in mice was presented as a unique pharmacological treatment for the reversal of established intestinal fibrosis. Finally, TL1A/DR3 signaling seems to critically participate in extraintestinal inflammatory conditions that are frequently associated with IBD as part of the gut-joint-skin-eye axis. These converging lines of evidence make TL1A/DR3 a suitable model for personalized approaches to IBD therapy.

Principles of antibody-mediated TNF receptor activation

From the beginning of research on receptors of the tumor necrosis factor (TNF) receptor superfamily (TNFRSF), agonistic antibodies have been used to stimulate TNFRSF receptors in vitro and in vivo. Indeed, CD95, one of the first cloned TNFRSF receptors, was solely identified as the target of cell death-inducing antibodies. Early on, it became evident from in vitro studies that valency and Fcγ receptor (FcγR) binding of antibodies targeting TNFRSF receptors can be of crucial relevance for agonistic activity. TNFRSF receptor-specific antibodies of the IgM subclass and secondary cross-linked or aggregation prone dimeric antibodies typically display superior agonistic activity compared with dimeric antibodies. Likewise, anchoring of antibodies to cell surface-expressed FcγRs potentiate their ability to trigger TNFRSF receptor signaling. However, only recently has the relevance of oligomerization and FcγR binding for the in vivo activity of antibody-induced TNFRSF receptor activation been straightforwardly demonstrated in vivo. This review discusses the crucial role of oligomerization and/or FcγR binding for antibody-mediated TNFRSF receptor stimulation in light of current models of TNFRSF receptor activation and especially the overwhelming relevance of these issues for the rational development of therapeutic TNFRSF receptor-targeting antibodies.

The TL1A/DR3/DcR3 pathway in autoimmune rheumatic diseases

IMPORTANCE

TNF-like cytokine 1A (TL1A) and its receptors, death receptor 3 (DR3) and decoy receptor 3 (DcR3) are members of the TNF and TNF receptor superfamilies of proteins, respectively. They constitute a cytokine system that actively interferes with the regulation of immune responses and may participate in the pathogenesis of autoimmune diseases.

OBJECTIVES

This review aims to present the current knowledge on the role of the TL1A/DR3/DcR3 system in the pathophysiology of autoimmune rheumatic diseases, with a focus on rheumatoid arthritis (RA).

METHODS

An extensive literature search was performed in the PubMed database using the following keywords: TL1A, death receptor 3, DR3, decoy receptor 3, DcR3, TNFSF15, TNFRSF25, and TNFSF6B. Studies were assessed and selected in view of their relevance to autoimmune rheumatic diseases.

CONCLUSION

The TL1A/DR3/DcR3 axis is a novel immune pathway that participates in the pathogenesis of a variety of autoimmune rheumatic diseases. These molecules may be promising therapeutic targets for inflammatory arthritis.

Mechanistic basis for functional promiscuity in the TNF and TNF receptor superfamilies: structure of the LIGHT:DcR3 assembly

LIGHT initiates intracellular signaling via engagement of the two TNF receptors, HVEM and LTβR. In humans, LIGHT is neutralized by DcR3, a unique soluble member of the TNFR superfamily, which tightly binds LIGHT and inhibits its interactions with HVEM and LTβR. DcR3 also neutralizes two other TNF ligands, FasL and TL1A. Due to its ability to neutralize three distinct different ligands, DcR3 contributes to a wide range of biological and pathological processes, including cancer and autoimmune diseases. However, the mechanisms that support the broad specificity of DcR3 remain to be fully defined. We report the structures of LIGHT and the LIGHT:DcR3 complex, which reveal the structural basis for the DcR3-mediated neutralization of LIGHT and afford insights into DcR3 function and binding promiscuity. Based on these structures, we designed LIGHT mutants with altered affinities for DcR3 and HVEM, which may represent mechanistically informative probe reagents.

The role of TL1A and DR3 in autoimmune and inflammatory diseases

TNF-like ligand 1A (TL1A), which binds its cognate receptor DR3 and the decoy receptor DcR3, is an identified member of the TNF superfamily. TL1A exerts pleiotropic effects on cell proliferation, activation, and differentiation of immune cells, including helper T cells and regulatory T cells. TL1A and its two receptors expression is increased in both serum and inflamed tissues in autoimmune diseases such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and ankylosing spondylitis (AS). Polymorphisms of the TNFSF15 gene that encodes TL1A are associated with the pathogenesis of irritable bowel syndrome, leprosy, and autoimmune diseases, including IBD, AS, and primary biliary cirrhosis (PBC). In mice, blocking of TL1A-DR3 interaction by either antagonistic antibodies or deletion of the DR3 gene attenuates the severity of multiple autoimmune diseases, whereas sustained TL1A expression on T cells or dendritic cells induces IL-13-dependent small intestinal inflammation. This suggests that modulation of TL1A-DR3 interaction may be a potential therapeutic target in several autoimmune diseases, including IBD, RA, AS, and PBC.

MMP-2 and DcR3 expression in esophageal cancer tissue and correlation with patient survival

OBJECTIVE

This study aims to explore the expression of decoy receptor 3 (DcR3) and the matrix metalloproteinase-2 (MMP-2) in esophageal carcinoma and their relationship with patient survival.

METHODS

The EnVision(TM) immunohistochemistry method was used to examine DcR3 and MMP-2 expression in 150 surgical biopsies of esophageal carcinoma. Expression level was compared with clinical indices and with patient survival.

RESULTS

In cancer tissues, the positive expression rate of DcR3 and MMP-2 was 54.00% and 54.67% respectively; this was higher than levels in adjacent normal tissue. DcR3 and MMP-2 were positively correlated with carcinoma size, lymphatic metastasis, invasion degree, clinical stage and 3-year survival. DcR3 and MMP-2 were not correlated with gender, age and tumor degree of differentiation. DcR3 and MMP-2 were positively correlated between in the two groups (r = 0.37, P < 0.01). Kaplan-Meier survival curve showed that higher rates of DcR3 and MMP-2 expression correlated with lower survival.

CONCLUSIONS

Determining DcR3 and MMP-2 expression may be useful for the diagnosis, treatment and prognosis of patients with esophageal carcinoma.

Cloning, expression, and functional characterization of TL1A-Ig

TNF superfamily member 15 (TL1A) is the ligand for TNFR superfamily (TNFRSF)25. We previously reported that TNFRSF25 stimulation with an agonist Ab, 4C12, expands pre-existing CD4(+)Foxp3(+) regulatory T cells (Tregs) in vivo. To determine how the physiological ligand differs from the Ab, we generated a soluble mouse TL1A-Ig fusion protein that forms a dimer of TL1A trimers in solution with an apparent molecular mass of 516 kDa. In vitro, TL1A-Ig mediated rapid proliferation of Foxp3(+) Tregs and a population of CD4(+)Foxp3(-) conventional T cells. TL1A-Ig also blocked de novo biogenesis of inducible Tregs and it attenuated the suppressive function of Tregs. TNFRSF25 stimulation by TL1A-Ig in vivo induced expansion of Tregs such that they increased to 30-35% of all CD4(+) T cells in the peripheral blood within 5 d of treatment. Treg proliferation in vivo was dependent on TCR engagement with MHC class II. Elevated Treg levels can be maintained for at least 20 d with daily injections of TL1A-Ig. TL1A-Ig-expanded Tregs expressed high levels of activation/memory markers KLRG1 and CD103 and were highly suppressive ex vivo. TL1A-Ig-mediated Treg expansion in vivo was protective against allergic lung inflammation, a mouse model for asthma, by reversing the ratio of conventional T cells to Tregs in the lung and blocking eosinophil exudation into the bronchoalveolar fluid. Thus, TL1A-Ig fusion proteins are highly active and tightly controllable agents to stimulate Treg proliferation in vivo, and they are uniquely able to maintain high levels of expanded Tregs by repeated administration.

TNFSF15 Modulates Neovascularization and Inflammation

Tumor necrosis factor superfamily-15 (TNFSF15; also known as VEGI or TL1A) is a unique cytokine that functions in the modulation of vascular homeostasis and inflammation. TNFSF15 is expressed abundantly in established vasculature but is down-regulated at sites of neovascularization such as in cancers and wounds. TNFSF15 inhibits endothelial cell proliferation and endothelial progenitor cell differentiation. Additionally, TNFSF15 stimulates T cell activation, Th1 cytokine production, and dendritic cell maturation. Some of the functions of TNFSF15 are mediated by death receptor-3. We review the experimental evidences on TNFSF15 activities in angiogenesis, vasculogenesis, inflammation, and immune system mobilization.

Decoy strategies: the structure of TL1A:DcR3 complex

Decoy Receptor 3 (DcR3), a secreted member of the Tumor Necrosis Factor (TNF) receptor superfamily, neutralizes three different TNF ligands: FasL, LIGHT, and TL1A. Each of these ligands engages unique signaling receptors which direct distinct and critical immune responses. We report the crystal structures of the unliganded DcR3 ectodomain and its complex with TL1A, as well as complementary mutagenesis and biochemical studies. These analyses demonstrate that DcR3 interacts with invariant backbone and side-chain atoms in the membrane-proximal half of TL1A which supports recognition of its three distinct TNF ligands. Additional features serve as antideterminants that preclude interaction with other members of the TNF superfamily. This mode of interaction is unique among characterized TNF:TNFR family members and provides a mechanistic basis for the broadened specificity required to support the decoy function of DcR3, as well as for the rational manipulation of specificity and affinity of DcR3 and its ligands.

T cell stimulator cells, an efficient and versatile cellular system to assess the role of costimulatory ligands in the activation of human T cells

It is well established that full activation of T cells requires the interaction of the TCR complex with the peptide–MHC complex (Signal 1) and additional signals (Signal 2). These second signals are generated by the interaction of costimulatory ligands expressed on antigen presenting cells with activating receptors on T cells. In addition, T cell responses are negatively regulated by inhibitory costimulatory pathways. Since professional antigen presenting cells (APC) harbour a plethora of stimulating and inhibitory surface molecules, the contribution of individual costimulatory molecules is difficult to assess on these cells. We have developed a system of stimulator cells that can give signal 1 to human T cells via a membrane bound anti-CD3 antibody fragment. By expressing human costimulatory ligands on these cells, their role in T cell activation processes can readily be analyzed. We demonstrate that T cell stimulator cells are excellent tools to study various aspects of human T cell costimulation, including the effects of immunomodulatory drugs or how costimulatory signals contribute to the in vitro expansion of T cells. T cell stimulator cells are especially suited for the functional evaluation of ligands that are implicated in costimulatory processes. In this study we have evaluated the role of the CD2 family member CD150 (SLAM) and the TNF family member TL1A (TNFSF15) in the activation of human T cells. Whereas our results do not point to a significant role of CD150 in T cell activation we found TL1A to potently costimulate human T cells. Taken together our results demonstrate that T cell stimulator cells are excellent tools to study various aspects of costimulatory processes.

Receptors and ligands implicated in human T cell costimulatory processes

It is well established that full activation of T cells that recognize antigens requires additional signals. These second signals are generated by the interaction of costimulatory ligands expressed on antigen presenting cells with their receptors on T cells. In addition, T cell activation processes are negatively regulated by inhibitory costimulatory pathways. Interaction of members of the B7 and the TNF superfamilies with members of the CD28 and TNF-R-superfamilies plays major roles in costimulatory processes. However, a large number of molecules that do not belong to these families have been reported to be involved in the generation of T cell costimulatory signals. In addition to well-defined costimulatory pathways, where both receptors and ligands are known, there are many T cell surface molecules that have been described to generate a second signal under certain experimental conditions, f.i. when ligated with antibodies. Furthermore there are several ligands that have been shown to positively or negatively modulate T cell activation by interacting with as of yet unknown T cell receptors. Here we give a comprehensive overview of molecules that have been implicated in human T cell activation processes and propose criteria that define genuine T cell costimulatory pathways.