IL-1 Receptor Accessory Protein Research Articles

IL-1 Receptor Accessory Protein-Ig/IL-1 Receptor Type II-Ig Heterodimer Inhibits IL-1 Response More Strongly than Other IL-1 Blocking Biopharmaceutical Agents

Interleukin (IL)-1 is a key orchestrator of inflammation and IL-1 inhibitors are expected to be promising pharmaceutical agents for such pathologies. IL-1 is bound to the complex of two receptor components with much higher affinity than with either receptor component alone. We examined the effect of a heterodimer of IL-1 receptor accessory protein (Acp)-immunoglobulin (Ig) and IL-1R type II (IL1R2)-Ig named AcP-Ig/IL1R2-Ig heterodimer, and compared its effects with other IL-1 inhibitors reported previously. Our results demonstrated that the rat AcP-Ig/IL1R2-Ig heterodimer (IC50=1.95 pM) inhibited IL-1 response to a greater extent than IL1RA (IC50=1,935 pM), Acp-IL1R type I (IL1R1)-Ig homodimer (IC50=73.7 pM) and Acp-IL1R2-Ig homodimer (IC50=72.8 pM). Moreover, human AcP-Ig/IL1R2-Ig heterodimer (IC50=0.14 pM) inhibited it to a greater extent than Acp-IL1R1-Ig homodimer (IC50=4.48 pM) and strongly inhibited responses of both IL-1α and IL-1β. The AcP-Ig/IL1R2-Ig heterodimer, which is similar to the original extracellular structure of the Acp/IL1R1 complex, may inhibit the IL-1 response more vigorously than other IL-1 blocking biopharmaceutical agents.

Homing in on CML stem cells

Lund University researchers have shown that IL-1 receptor accessory protein is a cell surface marker that could be used to isolate and kill chronic myelogenous leukemia stem cells. On the basis of these findings, Cantargia AB is developing a mAb to attack this cell population, which is partially resistant to standard treatments.

IL-1 receptor accessory protein (IL-1RAP)

IL-1 receptor accessory protein (IL-1RAP)

Isolation and killing of candidate chronic myeloid leukemia stem cells by antibody targeting of IL-1 receptor accessory protein

Chronic myeloid leukemia (CML) is genetically characterized by the Philadelphia (Ph) chromosome, formed through a reciprocal translocation between chromosomes 9 and 22 and giving rise to the constitutively active tyrosine kinase P210 BCR/ABL1. Therapeutic strategies aiming for a cure of CML will require full eradication of Ph chromosome-positive (Ph(+)) CML stem cells. Here we used gene-expression profiling to identify IL-1 receptor accessory protein (IL1RAP) as up-regulated in CML CD34(+) cells and also in cord blood CD34(+) cells as a consequence of retroviral BCR/ABL1 expression. To test whether IL1RAP expression distinguishes normal (Ph(-)) and leukemic (Ph(+)) cells within the CML CD34(+)CD38(-) cell compartment, we established a unique protocol for conducting FISH on small numbers of sorted cells. By using this method, we sorted cells directly into drops on slides to investigate their Ph-chromosome status. Interestingly, we found that the CML CD34(+)CD38(-)IL1RAP(+) cells were Ph(+), whereas CML CD34(+)CD38(-)IL1RAP(-) cells were almost exclusively Ph(-). By performing long-term culture-initiating cell assays on the two cell populations, we found that Ph(+) and Ph(-) candidate CML stem cells could be prospectively separated. In addition, by generating an anti-IL1RAP antibody, we provide proof of concept that IL1RAP can be used as a target on CML CD34(+)CD38(-) cells to induce antibody-dependent cell-mediated cytotoxicity. This study thus identifies IL1RAP as a unique cell surface biomarker distinguishing Ph(+) from Ph(-) candidate CML stem cells and opens up a previously unexplored avenue for therapy of CML.

Structural insights into the assembly and activation of IL-1β with its receptors

Interleukin 1β (IL-1β) is a key orchestrator of inflammation and host defense that exerts its effects through IL-1 receptor type I (IL-1RI) and IL-1 receptor accessory protein (IL-1RAcP). How IL-1RAcP is recruited by IL-1β-IL-1RI to form the signaling-competent complex remains elusive. Here we present the crystal structure of IL-1β bound to IL-1 receptor type II (IL-1RII) and IL-1RAcP. IL-1β-IL-1RII generated a composite binding surface to recruit IL-1RAcP. Biochemical analysis demonstrated that IL-1β-IL-1RI and IL-1β-IL-1RII interacted similarly with IL-1RAcP. It also showed the importance of two loops of IL-1 receptor antagonist (IL-1Ra) in determining its antagonism. Our results provide a structural basis for assembly and activation of the IL-1 receptor and offer a general cytokine-receptor architecture that governs the IL-1 family of cytokines.

The receptor tyrosine kinase c-Kit controls IL-33 receptor signaling in mast cells

AbstractMembers of the Toll/interleukin-1 receptor (TIR) family are of importance for host defense and inflammation. Here we report that the TIR-family member interleukin-33R (IL-33R) cross-activates the receptor tyrosine kinase c-Kit in human and murine mast cells. The IL-33R–induced activation of signal transducer and activator of transcription 3 (STAT3), extracellular signal-regulated kinase 1/2 (Erk1/2), protein kinase B (PKB), and Jun NH2-terminal kinase 1 (JNK1) depends on c-Kit and is required to elicit optimal effector functions. Costimulation with the c-Kit ligand stem cell factor (SCF) is necessary for IL-33–induced cytokine production in primary mast cells. The structural basis for this cross-activation is the complex formation between c-Kit, IL-33R, and IL-1R accessory protein (IL-1RAcP). We found that c-Kit and IL-1RAcP interact constitutively and that IL-33R joins this complex upon ligand binding. Our findings support a model in which signals from seemingly disparate receptors are integrated for full cellular responses.

TILRR, a Novel IL-1RI Co-receptor, Potentiates MyD88 Recruitment to Control Ras-dependent Amplification of NF-κB

Host defense against infection is induced by Toll-like and interleukin (IL)-1 receptors, and controlled by the transcription factor NF-κB. Our earlier studies have shown that IL-1 activation impacts cytoskeletal structure and that IL-1 receptor (IL-1RI) function is substrate-dependent. Here we identify a novel regulatory component, TILRR, which amplifies activation of IL-1RI and coordinates IL-1-induced control with mechanotransduction. We show that TILRR is a highly conserved and widely expressed enhancer of IL-1-regulated inflammatory responses and, further, that it is a membrane-bound glycosylated protein with sequence homology to members of the FRAS-1 family. We demonstrate that TILRR is recruited to the IL-1 receptor complex and magnifies signal amplification by increasing receptor expression and ligand binding. In addition, we show that the consequent potentiation of NF-κB is controlled through IL-1RI-associated signaling components in coordination with activation of the Ras GTPase. Using mutagenesis, we demonstrate that TILRR function is dependent on association with its signaling partner and, further, that formation of the TILRR-containing IL-1RI complex imparts enhanced association of the MyD88 adapter during ligand-induced activation of NF-κB. We conclude that TILRR is an IL-1RI co-receptor, which associates with the signaling receptor complex to enhance recruitment of MyD88 and control Ras-dependent amplification of NF-κB and inflammatory responses.

Excessive interleukin‐1 signaling determines the development of Th1 and Th17 responses in chronic inflammation

The proinflammatory cytokines tumor necrosis factor (TNF ) and interleukin-1 (IL-1) are considered to be key mediators in chronic autoimmune diseases such as rheumatoid arthritis (RA), Crohn’s disease, and multiple sclerosis (1). IL-1 and TNF have been linked to joint inflammation and cartilage and bone destruction in patients with RA (2,3). This is underscored in animal models in which human TNF has been overexpressed or the IL-1 receptor antagonist (IL-1Ra), the natural inhibitor of IL-1, has been deleted (4,5). Intriguingly, the latter model is strongly T cell–dependent. It has been shown that T cells are important in the IL-1Ra mouse model of spontaneous arthritis, since arthritis did not develop when mice had no functional T cells. Moreover, arthritis could be transferred to naive nude mice by injection of T cells isolated from arthritic IL-1Ra mice (6). Interestingly, IL-1Ra mice displayed increased levels of IL-17 after T cell stimulation, and the role of IL-17 in this arthritis model was further explored by crossing IL-1Ra mice with IL-17 mice (7,8). The lack of IL-17 completely abrogated the onset of disease, indicating a crucial role of IL-17 in the development of arthritis in IL-1Ra mice. Since the discovery of IL-17 in 1995, the role of this cytokine has been examined in several models of inflammation. IL-17 was originally believed to belong to the IL-1 family of proteins because of an overlap, although less potent, of biologic activities with IL-1 (9). Several studies have shown that IL-17 plays a role in the development of collagen-induced arthritis (CIA). Studies exploring the neutralization of IL-17 by antibodies or by the use of IL-17–deficient mice showed that IL-17 is involved in this model of autoimmune arthritis (10). Local overexpression of IL-17 during the onset of CIA demonstrated that IL-17 could aggravate cartilage and bone destruction (11). As indicated above, there are several current reports indicating that IL-17 contributes to autoimmune inflammation, but less potently as compared with IL-1. The dominant role of IL-1 in T cell processes was rediscovered by the demonstration of its role in the generation of Th17 cells. It should be remembered that IL-1 was initially named lymphocyte proliferation factor (1). Studies of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE) demonstrated that IL-1 is crucial in the induction of Th17-producing cells (12). One study elegantly showed that IL-1 drives the development of pathogenic Th17 cells during the onset of arthritis in IL-1Ra mice (7). Of high interest was the finding that IL-1 signaling is crucial for the development and production of IL-17 and TNF by these Th17 cells (13). Very recently, it was demonstrated that predominantly Th17 cells express both of the IL-1 receptor components IL-1 receptor type I (IL-1RI) and IL-1 receptor accessory protein (IL-1RAcP) as compared with Th1 or Th2 cells (14). It is now commonly accepted that Th17 cells play a pathogenic role in several autoimmune diseases, including RA and multiple sclerosis (9). IL-1 has been demonstrated to be critical for the development of autoimmune arthritis. Blockade of endogenous IL-1, in particular IL-1 , was shown to prevent the onset of type II collagen–induced arthritis (CIA) in mice. Even full-blown CIA was impressively reduced after treatment with neutralizing anti–IL-1 antibodies (15,16). The strong IL-1 dependency of murine CIA was further demonstrated by elegant studies using either IL-1–knockout mice, caspase 1 (also known as IL-1 –converting enzyme) inhibitors, and caspase 1 gene–deficient mice (17,18). In models of EAE, it was also demonstrated that IL-1 signaling was decisive for the induction of chronic inflammation. IL-1RI gene– deficient mice were shown to be completely protected against EAE. Nowadays, the important role of IL-1 in Leo A. B. Joosten, PhD: Nijmegen Institute for Infection, Inflammation and Immunity, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. Address correspondence and reprint requests to Leo A. B. Joosten, PhD, Department of Medicine (463), Radboud University Nijmegen Medical Centre, Geert Grooteplein Zuid 8, 6525 GA, Nijmegen, The Netherlands. E-mail: l.joosten@aig.umcn.nl. Submitted for publication September 30, 2009; accepted in revised form October 26, 2009.

Disease-associated functions of IL-33: the new kid in the IL-1 family

Interleukin-33 (IL-33), a newly described member of the IL-1 family, is expressed by many cell types following pro-inflammatory stimulation and is thought to be released on cell lysis. The IL-33 receptor, consisting of ST2 and IL-1 receptor accessory protein, is also widely expressed, particularly by T helper 2 (T(H)2) cells and mast cells. IL-33 is host-protective against helminth infection and reduces atherosclerosis by promoting T(H)2-type immune responses. However, IL-33 can also promote the pathogenesis of asthma by expanding T(H)2 cells and mediate joint inflammation, atopic dermatitis and anaphylaxis by mast cell activation. Thus IL-33 could be a new target for therapeutic intervention across a range of diseases.

IL‐33 broadens its repertoire to affect DC

IL-33 is a novel multi-functional IL-1 family member that, in contrast to other family members, is associated with Th2 responses. IL-33 signals via a heterodimer composed of its receptor, IL-1 receptor-like-1 (IL-1RL1), more commonly known as ST2L, and the IL-1R accessory protein. ST2L is expressed by endothelial cells, mast cells, basophils, Th2 cells, and DC. IL-33 has been associated with several immune-mediated disorders, including asthma, arthritis, and inflammatory bowel disease. In contrast, there is evidence that IL-33 can inhibit atherosclerosis development. A report in this issue of the European Journal of Immunology reveals a novel function of IL-33: the ability to promote myeloid DC generation in murine BM cell cultures, by triggering GM-CSF production by other BM cells, likely basophils. DC generated in the presence of IL-33 are maturation resistant, with only minimal T-cell stimulatory ability, associated with comparatively high levels of programmed death receptor ligand expression. This commentary discusses several questions raised by these findings, and provides a basis for further evaluation of IL-33 and ST2L in regulation of APC generation and function in both innate and adaptive immunity.

Rilonacept—CAPS and Beyond

Rilonacept is a dimeric fusion protein consisting of the extracellular domains of interleukin (IL)-1 type 1 receptor and IL-1 receptor accessory protein joined to the constant region (Fc) of human immunoglobulin G1. By incorporating both components of the IL-1 binding complex, rilonacept is able to tightly bind IL-1 with picomolar affinity. Although early clinical results in rheumatoid arthritis (RA) suggested that RA is not primarily an IL-1-driven disease, the discovery that the rare genetic conditions called cryopyrin-associated periodic syndromes (CAPS) were caused by overproduction of IL-1 led to clinical development and approval for these conditions. An assay that detects rilonacept:IL-1 complexes in plasma is helping to identify new indications, such as gout, in which IL-1 overproduction plays a key pathogenic role. The development of rilonacept for CAPS was achieved through collaboration between the pharmaceutical industry, academia, and government agencies, and demonstrates that knowledge gleaned in orphan indications can inform drug development for more common and heterogeneous diseases.

A Central Nervous System-Restricted Isoform of the Interleukin-1 Receptor Accessory Protein Modulates Neuronal Responses to Interleukin-1

Interleukin-1 (IL-1) has multiple functions in both the periphery and the central nervous system (CNS) and is regulated at many levels. We identified an isoform of the IL-1 receptor (IL-1R) accessory protein (termed AcPb) that is expressed exclusively in the CNS. AcPb interacted with IL-1 and the IL-1R but was unable to mediate canonical IL-1 responses. AcPb expression, however, modulated neuronal gene expression in response to IL-1 treatment in vitro. Animals lacking AcPb demonstrated an intact peripheral IL-1 response and developed experimental autoimmune encephalomyelitis (EAE) similarly to wild-type mice. AcPb-deficient mice were instead more vulnerable to local inflammatory challenge in the CNS and suffered enhanced neuronal degeneration as compared to AcP-deficient or wild-type mice. These findings implicate AcPb as an additional component of the highly regulated IL-1 system and suggest that it may play a role in modulating CNS responses to IL-1 and the interplay between inflammation and neuronal survival.

Differential gene expression profiles in the spontaneously hypertensive rats administrated with anti-hypertensive drugs (93.20)

Abstract To identify and characterize the genes involved in the functional regulation of hypertension and arteriosclerosis-specific genes, changes in gene expression profiles were examined by DNA microarray from the spontaneously hypertensive rats (SHR) and normal the Wistar-Kyoto (WKY) rats after administration with anti-hypertension drugs, including angiotensin I-converting enzyme (ACE) inhibitor, enalapril and the calcium channel blocker, nifedifine. Among the genes that were distinct and differentially expressed in brain, heart and liver of SHR rats administrated with the drugs, 113 were specifically up-regulated, and 102 were down-regulated genes compared to those of WKY or SHR rats. The differential gene expression profiles in DNA microarray were corroborated by semi-quantitative RT-PCR. Of these genes, expression of TNFSF4, 6, 10, IL-6 receptor, IL-18 receptor accessory protein and CD24 genes was extensively exhibited in a hypertension-specific manner, and patterns for hypertension-associated gene expression was regulated by changes of their expression in angiotensin ¥± or H2O2-treated vascular smooth muscle cells. These results will provide a fundamental basis to delineate the novel mechanisms, and a thorough investigation of the relationship between their expression and function will provide a better understanding in the development of new therapeutic drugs against cardiovascular diseases. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (KRF-2006-005-J03003)

IL‐1‐dependent, IL‐1R1‐independent resistance to gastrointestinal nematodes

IL-1 null mice are unable to expel the intestinal nematode Trichuris muris; whereas WT littermates exhibit sterile immunity. Intriguingly the essential signalling components IL-1R1 and IL-1R accessory protein (AcP) are dispensable for expulsion of this parasite. IL-1 is thus critical for CD4(+) Th2-mediated immunity to T. muris; however, this action is independent of the established IL-1 signalling receptor. We also present data demonstrating that both IL-1alpha and IL-1beta induce measurable effects on T. muris primed cells isolated from IL-1R1 or IL-1R AcP null mice. MLN cells from these mice restimulated with parasite antigen proliferated at a greater rate and produced more cytokines in response to exogenous IL-1. This ability to respond to IL-1 was restricted to these parasite-primed cells and importantly was not evident in cells from naïve gene null mice. These in vitro data are consistent with the observed ability of mice with compromised IL-1 signalling to expel the parasite, bolstering the premise that an alternative IL-1 signalling mechanism is accessible in the context of an intestinal helminth-driven Th2 immune response.

Differential expression of immunoregulatory genes in monocytes in response to Porphyromonas gingivalis and Escherichia coli lipopolysaccharide

Porphyromonas gingivalis lipopolysaccharide (LPS) (strain W50) interacts with Toll-like receptor 2 (TLR-2) leading to cytokine expression and inflammation, and thereby plays a key role in the pathogenesis of periodontal disease. The aims of this study were to investigate gene expression of key regulatory mediators of innate immune responses in a human monocytic cell line (THP-1) to P. gingivalis LPS and to compare these results with those obtained using the TLR-4 ligand, Escherichia coli LPS. Custom-made Taqman low-density arrays were used for expression profiling of 45 different cytokine-related genes. Both types of LPS highly up-regulated interleukin (IL)-1alpha and IL-1beta, IL-18 receptor (IL-18R), IL-18R accessory protein and IL-1 family (IL-1F)9. Expression levels of IL-1F6, IL-1F7 and caspase-1 were unaltered by either LPS. Genes for tumour necrosis factor-alpha, IL-6, leukaemia inhibitory factor and IL-32 were also highly induced by both LPS. For a subset of genes, including CXC chemokine ligand 5 (CXCL5), expression was induced only by E. coli LPS or was up-regulated more highly by E. coli compared with P. gingivalis LPS in THP-1 monocytes. A similar expression pattern was also observed in dendritic cells. Analysis of signalling pathways which lead to CXCL5 expression indicated that the mechanisms underpinning the differential responses did not involve the recruitment of different adaptor proteins by TLR-2 and TLR-4, and therefore occur downstream of the receptor-adaptor complex. We conclude that differences in signalling pathways activated by TLR-2 and TLR-4 ligands lead to differential innate immune responses which may be important in polymicrobial diseases such as periodontal disease.

The natural soluble form of IL-18 receptor β exacerbates collagen-induced arthritis via modulation of T-cell immune responses

Objective:IL-18 is a pluripotent cytokine that has been implicated in the development of rheumatoid arthritis. A soluble form of the IL-18 receptor accessory protein (sIL-18Rβ) with unknown function has recently...

The analysis of IL-1 beta and its naturally occurring inhibitors in multiple sclerosis: The elevation of IL-1 receptor antagonist and IL-1 receptor type II after steroid therapy

The aim of our investigation was to analyze the pattern of interleukin-1 (IL-1) family compounds: IL-1 beta, IL-1 receptor accessory protein (Acp), IL-1 receptor antagonist (IL-1Ra) and IL-1 receptor type II (IL-1RII) in the serum and cerebrospinal fluid (CSF) from 67 multiple sclerosis (MS) patients and 31 controls. We found significantly elevated CSF levels of IL-1 beta, IL-1Ra and Acp in MS patients compared to controls ( p = 0.001), while IL-1 beta and Acp were significantly elevated in MS sera ( p = 0.001). IL-1Ra and/or IL-1 RII increased in sera of all 10 investigated patients after the steroid treatment for relapse. Our findings suggest the important beneficial role of the induction of IL-1 RII and IL-1Ra in MS.

MMP-3 Response to Compressive Forces in vitro and in vivo

During orthodontic tooth movement, bone resorption occurs at the compression site. However, the mechanism underlying resorption remains unclear. Applying compressive force to human osteoblast-like cells grown in a 3D collagen gel, we examined gene induction by using microarray and RT-PCR analysis. Among 43 genes exhibiting significant changes, cyclo-oxygenase-2, ornithine decarboxylase, and matrix metalloproteinase-3 (MMP-3) were up-regulated, whereas membrane-bound interleukin-1 receptor accessory protein was down-regulated. The MMP-3 protein increases were further confirmed by Western blot. To ascertain whether MMP-3 is up-regulated in vivo by orthodontic force, we examined human bone samples at the compressive site by realigning the angulated molars. Immunohistochemical staining revealed MMP-3 distributed along the compressive site of the bony region within 3 days of compression. Since MMP-3 participates in degradation of a wide range of extracellular matrix molecules, we propose that MMP-3 plays an important role in bone resorption during orthodontic tooth movement.

Zebrafish orthologue of mental retardation protein IL1RAPL1 regulates presynaptic differentiation

IL1-receptor accessory protein-like 1 (IL1RAPL1), a member of interleukin-1/toll receptor (TIR) family, is responsible for a nonsyndromic form of mental retardation (MR). The zebrafish orthologue of mammalian IL1RAPL1, designated as Il1rapl1b, was expressed widely in the brain and in the olfactory placode. We employed an olfactory sensory neuron-specific gene manipulation system in combination with in vivo imaging of transparent zebrafish embryos to examine the functional role of Il1rapl1b in synaptic vesicle accumulation and subsequent morphological remodeling of axon terminals, the characteristic features of presynaptic differentiation of zebrafish olfactory sensory neurons during synapse formation. Antisense morpholino oligonucleotide against il1rapl1b suppressed both the synaptic vesicle accumulation and axon terminal remodeling. Consistently, the overexpression of Il1rapl1b stimulated synaptic vesicle accumulation. Swapping the carboxyl-terminal domain of Il1rapl1b with that of mouse IL-1 receptor accessory protein abolished the stimulatory effect. On the other hand, a substitution mutation in the TIR domain suppressed the morphological remodeling of axon terminals. Thus, the regulation of synaptic vesicle accumulation and subsequent morphological remodeling by Il1rapl1b appeared to be mediated by distinct domains. These results suggest that Il1rapl1b plays an important role in presynaptic differentiation during synapse formation.

Development of a Novel Noncompetitive Antagonist of IL-1 Receptor

IL-1 is a major proinflammatory cytokine which interacts with the IL-1 receptor I (IL-1RI) complex, composed of IL-1RI and IL-1R accessory protein subunits. Currently available strategies to counter pathological IL-1 signaling rely on a recombinant IL-1 receptor antagonist, which directly competes with IL-1 for its binding site. Presently, there are no small antagonists of the IL-1RI complex. Given this void, we derived 15 peptides from loops of IL-1R accessory protein, which are putative interactive sites with the IL-1RI subunit. In this study, we substantiate the merits of one of these peptides, rytvela (we termed "101.10"), as an inhibitor of IL-1R and describe its properties consistent with those of an allosteric negative modulator. 101.10 (IC(50) approximately 1 nM) blocked human thymocyte proliferation in vitro, and demonstrated robust in vivo effects in models of hyperthermia and inflammatory bowel disease as well as topically in contact dermatitis, superior to corticosteroids and IL-1ra; 101.10 did not bind to IL-1RI deficient cells and was ineffective in vivo in IL-1RI knockout mice. Importantly, characterization of 101.10, revealed noncompetitive antagonist actions and functional selectivity by blocking certain IL-1R pathways while not affecting others. Findings describe the discovery of a potent and specific small (peptide) antagonist of IL-1RI, with properties in line with an allosteric negative modulator.