The IL-1 receptor accessory protein is essential for PI 3-kinase recruitment and activation

IL-1RAP, a Key Therapeutic Target in Cancer

Cancer is a major cause of death worldwide and especially in high- and upper-middle-income countries. Despite recent progress in cancer therapies, such as chimeric antigen receptor T (CAR-T) cells or antibody-drug conjugate (ADC), new targets expressed by the tumor cells need to be identified in order to selectively drive these innovative therapies to tumors. In this context, IL-1RAP recently showed great potential to become one of these new targets for cancer therapy. IL-1RAP is highly involved in the inflammation process through the interleukins 1, 33, and 36 (IL-1, IL-33, IL-36) signaling pathways. Inflammation is now recognized as a hallmark of carcinogenesis, suggesting that IL-1RAP could play a role in cancer development and progression. Furthermore, IL-1RAP was found overexpressed on tumor cells from several hematological and solid cancers, thus confirming its potential involvement in carcinogenesis. This review will first describe the structure and genetics of IL-1RAP as well as its role in tumor development. Finally, a focus will be made on the therapies based on IL-1RAP targeting, which are now under preclinical or clinical development.

Bidirectional Regulation of Opioid and Chemokine Function

The opioid family of GPCRs consists of the classical opioid receptors, designated μ-, κ-, and δ-opioid receptors, and the orphanin-FQ receptor, and these proteins are expressed on both neuronal and hematopoietic cells. A number of laboratories have reported that an important degree of cross-talk can occur between the opioid receptors and the chemokine and chemokine receptor families. As a part of this, the opioid receptors are known to regulate the expression of certain chemokines and chemokine receptors, including those that possess strong pro-inflammatory activity. At the level of receptor function, it is clear that certain members of the chemokine family can mediate cross-desensitization of the opioid receptors. Conversely, the opioid receptors are all able to induce heterologous desensitization of some of the chemokine receptors. Consequently, activation of one or more of the opioid receptors can selectively cross-desensitize chemokine receptors and regulate chemokine function. These cross-talk processes have significant implications for the inflammatory response, since the regulation of both the recruitment of inflammatory cells, as well as the sensation of pain, can be controlled in this way.

Corneal surface glycosylation is modulated by IL-1R and Pseudomonas aeruginosa challenge but is insufficient for inhibiting bacterial binding

Cell surface glycosylation is thought to be involved in barrier function against microbes at mucosal surfaces. Previously we showed that the epithelium of healthy mouse corneas becomes vulnerable to Pseudomonas aeruginosa adhesion if it lacks the innate defense protein MyD88 (myeloid differentiation primary response gene 88), or after superficial injury by blotting with tissue paper. Here we explored their effect on corneal surface glycosylation using a metabolic label, tetra-acetylated N-azidoacetylgalactosamine (Ac₄GalNAz). Ac₄GalNAz treatment labeled the surface of healthy mouse corneas, leaving most cells viable, and bacteria preferentially associated with GalNAz-labeled regions. Surprisingly, corneas from MyD88^-/- mice displayed similar GalNAz labeling to wild-type corneas, but labeling was reduced and patchy on IL-1 receptor (IL-1R)-knockout mouse corneas (P < 0.05, ANOVA). Tissue paper blotting removed GalNAz-labeled surface cells, causing DAPI labeling (permeabilization) of underlying cells. MS of material collected on the tissue paper blots revealed 67 GalNAz-labeled proteins, including intracellular proteins. These data show that the normal distribution of surface glycosylation requires IL-1R, but not MyD88, and is not sufficient to prevent bacterial binding. They also suggest increased P. aeruginosa adhesion to MyD88^-/- and blotted corneas is not due to reduction in total surface glycosylation, and for tissue paper blotting is likely due to cell permeabilization.-Jolly, A. L., Agarwal, P., Metruccio, M. M. E., Spiciarich, D. R., Evans, D. J., Bertozzi, C. R., Fleiszig, S. M. J. Corneal surface glycosylation is modulated by IL-1R and Pseudomonas aeruginosa challenge but is insufficient for inhibiting bacterial binding.

The role of phosphoinositide 3-kinase signaling in intestinal inflammation

The phosphatidylinositol 3-kinase signaling pathway plays a central role in regulating the host inflammatory response. The net effect can either be pro- or anti-inflammatory depending on the system and cellular context studied. This paper focuses on phosphatidylinositol 3-kinase signaling in innate and adaptive immune cells of the intestinal mucosa. The role of phosphatidylinositol 3-kinase signaling in mouse models of inflammatory bowel disease is also discussed. With the development of new isoform specific inhibitors, we are beginning to understand the specific role of this complex pathway, in particular the role of the γ isoform in intestinal inflammation. Continued research on this complex pathway will enhance our understanding of its role and provide rationale for the design of new approaches to intervention in chronic inflammatory conditions such as inflammatory bowel disease.

Interleukin-1beta induces the novel adipokine chemerin in adipocytes in vitro

Chemerin has recently been characterized as a novel adipokine playing a crucial role in adipocyte differentiation and insulin signalling. In the current study, the impact of insulin resistance-inducing and proinflammatory interleukin (IL)-1beta on chemerin protein secretion and mRNA expression was determined in 3T3-L1 adipocytes. Interestingly, IL-1beta significantly induced chemerin protein secretion almost 1.3-fold from 5.89 ng/ml (basal) to 7.52 ng/ml. Furthermore, chemerin mRNA synthesis was significantly stimulated by IL-1beta in a dose-dependent fashion with 1.5-fold induction seen at IL-1beta concentrations as low as 0.07 ng/ml and maximal 2.6-fold upregulation found at 2 ng/ml effector. Induction of chemerin mRNA by IL-1beta was time-dependent in both 3T3-L1 adipocytes and brown fat cells. Signalling studies suggested that Janus kinase 2, nuclear factor kappa B, p44/42 mitogen-activated protein kinase, and phosphatidylinositol 3-kinase are involved in IL-1beta-induced chemerin mRNA expression. Furthermore, recombinant chemerin downregulated insulin-stimulated glucose uptake. Taken together, we show that chemerin is upregulated in fat cells by IL-1beta and might modulate the effects of IL-1beta on adipocyte metabolism and insulin sensitivity.

Differential pattern of inflammatory molecule regulation in intestinal epithelial cells stimulated with IL-1

To better predict the consequences of blocking signal transduction pathways as a means of controlling intestinal inflammation, we are characterizing the pathways up-regulated by IL-1 in intestinal epithelial cells (IEC). IL-1beta induced increased mRNA levels of MIP-2, MCP-1, RANTES, inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2) in the IEC-18 cell line. IL-1beta activated NF-kappaB but not ERK or p38. Infecting cells with adenovirus expressing a mutated gene for IkappaBalpha (IkappaBAA) blocked IL-1-induced mRNA increases in MIP-2, MCP-1, and iNOS but not COX-2 or RANTES. Expression of IkappaBAA attenuated the IL-1-induced increase in COX-2 protein. Unexpectedly, RANTES mRNA increased, and protein was secreted by cells expressing IkappaBAA in the absence of IL-1. Adenovirus-expressing IkappaBAA, blocking protein synthesis, and IL-1beta all resulted in activation of JNK. The JNK inhibitor SP600125 prevented the RANTES increases by all three stimuli. A human enterocyte line was similarly examined, and both NF-kappaB and JNK regulate IL-1-induced RANTES secretion. We conclude that in IEC-18, IL-1beta-induced increases in mRNA for MIP-2, MCP-1, and iNOS are NF-kappaB-dependent, whereas regulation of RANTES mRNA is independent of NF-kappaB but is positively regulated by JNK. IL-1beta-induced mRNA increases in COX-2 mRNA are both NF-kappaB- and MAPK-independent but the translation of COX-2 protein is NF-kappaB-dependent. This pattern of signaling due to a single stimulus exposed the complexities of regulating inflammatory genes in IEC.

A comprehensive map of the toll-like receptor signaling network

Recognition of pathogen-associated molecular signatures is critically important in proper activation of the immune system. The toll-like receptor (TLR) signaling network is responsible for innate immune response. In mammalians, there are 11 TLRs that recognize a variety of ligands from pathogens to trigger immunological responses. In this paper, we present a comprehensive map of TLRs and interleukin 1 receptor signaling networks based on papers published so far. The map illustrates the possible existence of a main network subsystem that has a bow-tie structure in which myeloid differentiation primary response gene 88 (MyD88) is a nonredundant core element, two collateral subsystems with small GTPase and phosphatidylinositol signaling, and MyD88-independent pathway. There is extensive crosstalk between the main bow-tie network and subsystems, as well as feedback and feedforward controls. One obvious feature of this network is the fragility against removal of the nonredundant core element, which is MyD88, and involvement of collateral subsystems for generating different reactions and gene expressions for different stimuli.

MyD88-dependent and -independent signaling by IL-1 in neurons probed by bifunctional Toll/IL-1 receptor domain/BB-loop mimetics

Interleukin (IL)-1beta is a pluripotent proinflammatory cytokine that signals through the type-I IL-1 receptor (IL-1RI), a member of the Toll-like receptor family. In hypothalamic neurons, binding of IL-1beta to IL-1RI mediates transcription-dependent changes that depend on the recruitment of the cytosolic adaptor protein myeloid differentiation primary-response protein 88 (MyD88) to the IL-1RI/IL-1 receptor accessory protein (IL-1RAcP) complex through homomeric Toll/IL-1 receptor (TIR)-TIR interactions. Through design and synthesis of bifunctional TIR mimetics that disrupt the interaction of MyD88 with the IL-1RI/IL-1RAcP complex, we analyzed the involvement of MyD88 in the signaling of IL-1beta in anterior hypothalamic neurons. We show here that IL-1beta-mediated activation of the protein tyrosine kinase Src depended on a MyD88 interaction with the IL-1RI/IL-1RAcP complex. The activation of the protein kinase Akt/PKB depended on the recruitment of the p85 subunit of PI3K to IL-1RI and independent of MyD88 association with the IL-1RI/IL-1RAcP complex. These bifunctional TIR-TIR mimetics represent a class of low-molecular-weight compounds with both an antiinflammatory and neuroprotective potential. These compounds have the potential to inhibit the MyD88-dependent proinflammatory actions of IL-1beta, while permitting the potential neuronal survival supporting actions mediated by the MyD88-independent activation of the protein kinase Akt.

Short-term interleukin-1β increases the release of secreted APPα via MEK1/2-dependent and JNK-dependent α-secretase cleavage in neuroglioma U251 cells

Several lines of neuroimmunological evidence correlate the development of the inflammatory responses of the brain with the formation of amyloid plaques associated with the pathogenesis of neurodegenerative disorders such as Alzheimer's disease. Within this context, we tested the ability of interleukin-1beta (IL-1beta) to regulate the processing of beta-amyloid precursor protein (beta-APP) in neuroglioma U251 cells. Our findings have shown that short-term treatment with IL-1beta (2 hr) resulted in a concentration-dependent decrease in the amount of the cell-associated form of beta-APP in U251 cells as compared to untreated cells, whereas a 2-hr treatment with IL-1beta led to increased release of secreted APP(alpha) fragment (sAPP(alpha)) into the conditioned media of the cells. The fact that sAPP(alpha) is an alpha-secretase cleavage metabolite of the cell-associated form of beta-APP, and the observation that IL-1beta-induced sAPP(alpha) release could be blocked by tissue inhibitors of metalloproteinases-1 (alpha-secretase inhibitors), suggested that alpha-secretase might be involved in IL-1beta-induced-sAPP(alpha) release. Moreover, to determine whether an intracellular signaling pathway mediates the IL-1beta-induced increase in sAPP(alpha) secretion, we used various specific signaling inhibitors and found that sAPP(alpha) release is significantly blocked by the mitogen-activated protein kinase (MEK1/2) inhibitor PD98059 and the c-Jun N-terminal kinase inhibitor SP600125. These findings suggested that the mechanism of IL-1beta-induced-sAPP(alpha) release is dependent on MEK1/2- and JNK-activated alpha-secretase cleavage in neuroglioma U251 cells.