IL-27 structural analysis demonstrates similarities with ciliary neurotrophic factor (CNTF) and leads to the identification of antagonistic variants.

IL-27, consisting of the subunits IL-27p28 and Epstein-Barr virus-induced gene 3 (EBI3), is a heterodimeric cytokine belonging to the IL-6/IL-12 family of cytokines. IL-27p28 is a four-helical cytokine requiring association with the soluble receptor EBI3 to be efficiently secreted and functionally active. Computational and biological analyses of the IL-27 binding site 1 to its receptor revealed important structural proximities with the ciliary neurotrophic factor group of cytokines and highlighted the contribution of p28 Trp(97), as well as of EBI3 Phe(97), Asp(210), and Glu(159), as key residues in the interactions between both cytokine subunits. WSX-1 (IL-27R) and gp130 compose the IL-27 receptor-signaling complex, recruiting the STAT-1 and STAT-3 pathways. A study of IL-27 binding site 3 showed that Trp(197) was crucial for the cytokine's interaction with gp130, but that the mutated cytokine still recognized IL-27R on the cell surface. IL-27 exerts both pro- and anti-inflammatory functions, promoting proliferation and differentiation of Th1 and inhibiting Th17 differentiation. Our results led us to develop mutated forms of human and mouse IL-27 with antagonistic activities. Using an in vivo mouse model of concanavalin A-induced Th1-cell-mediated hepatitis, we showed that the murine IL-27 antagonist W195A decreased liver inflammation by downregulating the synthesis of CXCR3 ligands and several acute phase proteins. Together, these data suggest that IL-27 antagonism could be of interest in down-modulating acute IL-27-driven Th1-cell-mediated immune response.

Lipidomic analysis of adipose-derived extracellular vesicles reveals specific EV lipid sorting informative of the obesity metabolic state.

Adipose extracellular vesicles (AdEVs) transport lipids that could participate in the development of obesity-related metabolic dysfunctions. This study aims to define mouse AdEV lipid signature by a targeted LC-MS/MS approach in either healthy or obesity context. Distinct clustering of AdEV and visceral adipose tissue (VAT) lipidomes by principal component analysis reveals specific AdEV lipid sorting when compared with secreting VAT. Comprehensive analysis identifies enrichment of ceramides, sphingomyelins, and phosphatidylglycerols species in AdEVs compared with source VAT whose lipid content closely relates to the obesity status and is influenced by the diet. Obesity moreover impacts AdEV lipidome, mirroring lipid alterations retrieved in plasma and VAT. Overall, our study identifies specific lipid fingerprints for plasma, VAT, and AdEVs that are informative of the metabolic status. Lipid species enriched in AdEVs in the obesity context may constitute biomarker candidates or mediators of the obesity-associated metabolic dysfunctions.

Extracellular vesicles are carriers of adiponectin with insulin-sensitizing and anti-inflammatory properties.

Recent evidence supporting that adipose tissue (AT)-derived extracellular vesicles (EVs) carry an important part of the AT secretome led us to characterize the EV-adipokine profile. In addition to evidencing a high AT-derived EV secretion ability that is further increased by obesity, we identify enrichment of oligomeric forms of adiponectin in small EVs (sEVs). This adipokine is mainly distributed at the EV external surface as a result of nonspecific adsorption of soluble adiponectin. EVs also constitute stable conveyors of adiponectin in the blood circulation. Adiponectin-enriched sEVs display in vitro insulin-sensitizing effects by binding to regular adiponectin receptors. Adoptive transfer of adiponectin-enriched sEVs in high-fat-diet-fed mice prevents animals from gaining weight and ameliorated insulin resistance and tissue inflammation, with major effects observed in the AT and liver. Our results therefore provide information regarding adiponectin-related metabolic responses by highlighting EVs as delivery platforms of metabolically active forms of adiponectin molecules.

Molecular dissection of human interleukin-31-mediated signal transduction through site-directed mutagenesis.

Interleukin (IL)-31 is a recently described cytokine, preferentially produced by T helper 2 lymphocytes and associated with skin diseases, such as atopic dermatitis. IL-31 is a member of the four alpha-helix bundle cytokine family and is related to the IL-6 subgroup. Its heterodimeric membrane receptor is composed of the gp130-like receptor (GPL) subunit associated to the oncostatin M receptor subunit. We identified critical amino acids implicated in the ligand receptor interaction by computational analysis combined with site-directed mutagenesis. Six IL-31 residues selected for their putative involvement in cytokine receptor contact sites were alanine-substituted, and the corresponding proteins were expressed in mammalian and bacterial systems. Biochemical, membrane binding, cell signaling, and cell proliferation analyses showed that mutation E44A, E106A, or H110A abolished IL-31 binding to GPL and the subsequent signaling events. A second ligand receptor-binding site involved Lys(134), with alanine substitution leading to a protein that still binds GPL, but is unable to recruit the second receptor subunit and the subsequent signaling pathways. The results indicate that IL-31 recognizes its receptor complex through two different binding sites, and we propose a three-dimensional model for IL-31.

Definition and characterization of an inhibitor for interleukin-31.

Interleukin-31 (IL-31) is a recently described T cell-derived cytokine, mainly produced by T helper type 2 cells and related to the IL-6 cytokine family according to its structure and receptor. IL-31 is the ligand for a heterodimeric receptor composed of a gp130-like receptor (GPL) associated with the oncostatin M receptor (OSMR). A link between IL-31 and atopic dermatitis was shown by studying the phenotype of IL-31 transgenic mice and IL-31 gene haplotypes in patients suffering from dermatitis. In this study, we generated a potent IL-31 antagonist formed by external portions of OSMR and GPL fused with a linker. This fusion protein, OSMR-L-GPL, consisting of 720 amino acids, counteracted the binding of IL-31 to its membrane receptor complex and the subsequent signaling events involving the STATs and MAPK pathways. Neutralizing effects were found in IL-31-sensitive cell lines, including brain-derived cells and primary cultures of keratinocytes.

The cys-loop ligand-gated ion channel gene superfamilies of the cockroaches Blattella germanica and Periplaneta americana.

BACKGROUND: Cockroaches are serious urban pests that can transfer disease-causing microorganisms as well as trigger allergic reactions and asthma. They are commonly managed by pesticides that act on cys-loop ligand-gated ion channels (cysLGIC). To provide further information that will enhance our understanding of how insecticides act on their molecular targets in cockroaches, we used genome and reverse transcriptase polymerase chain reaction (RT-PCR) data to characterize the cysLGIC gene superfamilies from Blattella germanica and Periplaneta americana. RESULTS: The B. germanica and P. americana cysLGIC superfamilies consist of 30 and 32 subunit-encoding genes, respectively, which are the largest insect cysLGIC superfamilies characterized to date. As with other insects, the cockroaches possess ion channels predicted to be gated by acetylcholine, γ-aminobutyric acid, glutamate and histamine, as well as orthologues of the drosophila pH-sensitive chloride channel (pHCl), CG8916 and CG12344. The large cysLGIC superfamilies of cockroaches are a result of an expanded number of divergent nicotinic acetylcholine receptor subunits, with B. germanica and P. americana, respectively, possessing eight and ten subunit genes. Diversity of the cockroach cysLGICs is also broadened by alternative splicing and RNA A-to-I editing. Unusually, both cockroach species possess a second glutamate-gated chloride channel as well as another CG8916 subunit. CONCLUSION: These findings on B. germanica and P. americana enhance our understanding of the evolution of the insect cysLGIC superfamily and provide a useful basis for the study of their function, the detection and management of insecticide resistance, and for the development of improved pesticides with greater specificity towards these major pests. © 2020 Society of Chemical Industry.

Exposure to sublethal doses of insecticide and their effects on insects at cellular and physiological levels.

Insecticides were used as pest management tools for a long time. The appearance of resistant insects has led the scientific community to rethink their use and to study the mechanisms underlying the resistance in order to circumvent it. However, we know now that sublethal doses of insecticide induce many effects which should be taken into account for pest control. In this review, we summarized current knowledge on mechanisms used by insects to deal with exposure to sublethal dose of insecticides. Physiological and cellular changes could contribute to the adaptation of the insect to its environment making the challenge of managing pests difficult.

Synergistic agent and intracellular calcium, a successful partnership in the optimization of insecticide efficacy.

Integrated Pest Management and Integrated Vector Management worldwide are developed in agriculture and public health to counteract and limit the exponential increasing development of insect resistance to insecticides. However, facing the predominance of some resistant populations, new strategies are urgently needed to target resistant insects. An innovative approach lies in the optimization of commonly used insecticides when combined with chemical or biological synergistic agents. By an increase of intracellular calcium concentration followed by activation of calcium-dependant signalling pathways, the synergistic agents are able to indirectly increase target sites sensitivity to insecticide by inducing conformational change. The synergistic agents are of great interest in optimizing the efficacy of insecticides and in overcoming resistance mechanisms.

Microbial Pest Control Agents: Are they a Specific And Safe Tool for Insect Pest Management?

Microorganisms (viruses, bacteria and fungi) or their bioactive agents can be used as active substances and therefore are referred as Microbial Pest Control Agents (MPCA). They are used as alternative strategies to chemical insecticides to counteract the development of resistances and to reduce adverse effects on both environment and human health. These natural entomopathogenic agents, which have specific modes of action, are generally considered safer as compared to conventional chemical insecticides. Baculoviruses are the only viruses being used as the safest biological control agents. They infect insects and have narrow host ranges. Bacillus thuringiensis (Bt) is the most widely and successfully used bioinsecticide in the integrated pest management programs in the world. Bt mainly produces crystal delta-endotoxins and secreted toxins. However, the Bt toxins are not stable for a very long time and are highly sensitive to solar UV. So genetically modified plants that express toxins have been developed and represent a large part of the phytosanitary biological products. Finally, entomopathogenic fungi and particularly, Beauveria bassiana and Metarhizium anisopliae, are also used for their insecticidal properties. Most studies on various aspects of the safety of MPCA to human, non-target organisms and environment have only reported acute but not chronic toxicity. This paper reviews the modes of action of MPCA, their toxicological risks to human health and ecotoxicological profiles together with their environmental persistence. This review is part of the special issue "Insecticide Mode of Action: From Insect to Mammalian Toxicity".

Predominant expression of the long isoform of GP130-like (GPL) receptor is required for interleukin-31 signaling.

Gp130-like receptor (GPL) is a newly identified cytokine receptor. A recent study reported the involvement of GPL, together with OSMR, in the formation of the receptor complex for IL-31, a novel immune cytokine with a skin tropism. In the present work, we analyzed the signaling properties of IL-31 in glioblastoma and melanoma tumor cells. We demonstrate that in response to IL-31, its receptor complex recruits Jak1, Jak2, STAT1, -3, -5 signaling pathways, as well as the Pi3 kinase / AKT cascade. SHP-2 and Shc adapter molecules are also recruited and contribute to an increased activation of the MAP kinase pathway in response to IL-31. Different responses were observed depending on the expression of short or long GPL receptor isoform within the studied cell lines. We show that the short form of GPL receptor exerts a profound inhibitory effect on the signaling of IL-31 and behaves as a dominant negative receptor.

Ciliary neurotrophic factor, cardiotrophin-like cytokine, and neuropoietin share a conserved binding site on the ciliary neurotrophic factor receptor alpha chain.

Ciliary neurotrophic factor, cardiotrophin-like cytokine, and neuropoietin are members of the four-helix bundle cytokine family. These proteins signal through a common tripartite receptor composed of leukemia inhibitory factor receptor, gp130, and ciliary neurotrophic factor receptor alpha. Binding to ciliary neurotrophic factor receptor alpha occurs through an interaction site located at the C terminus of the cytokine AB loop and alphaD helix, known as site 1. In the present study, we have generated a model of neuropoietin and identified a conserved binding site for the three cytokines interacting with ciliary neurotrophic factor receptor alpha. To identify the counterpart of this site on ciliary neurotrophic factor receptor alpha, its cytokine binding domain was modeled, and the physicochemical properties of its surface were analyzed. This analysis revealed an area displaying properties complementary to the site 1 of ciliary neurotrophic factor, cardiotrophin-like cytokine, and neuropoietin. Based on our computational predictions, residues were selected for their potential involvement in the ciliary neurotrophic factor receptor alpha binding epitope, and site-directed mutagenesis was carried out. Biochemical, cell proliferation, and cell signaling analyses showed that Phe(172) and Glu(286) of ciliary neurotrophic factor receptor alpha are key interaction residues. Our results demonstrated that ciliary neurotrophic factor, cardiotrophin-like cytokine, and neuropoietin share a conserved binding site on ciliary neurotrophic factor receptor alpha.

Oncostatin M secreted by skin infiltrating T lymphocytes is a potent keratinocyte activator involved in skin inflammation.

Cutaneous inflammatory diseases such as psoriasis vulgaris and atopic dermatitis are associated with altered keratinocyte function, as well as with a particular cytokine production profile of skin-infiltrating T lymphocytes. In this study we show that normal human epidermal keratinocytes express a functional type II oncostatin-M (OSM) receptor (OSMR) consisting of the gp130 and OSMRbeta components, but not the type I OSMR. The type II OSMR is expressed in skin lesions from both psoriatic patients and those with atopic dermatitis. Its ligand, OSM, induces via the recruitment of the STAT3 and MAP kinase pathways a gene expression profile in primary keratinocytes and in a reconstituted epidermis that is characteristic of proinflammatory and innate immune responses. Moreover, OSM is a potent stimulator of keratinocyte migration in vitro and increases the thickness of a reconstituted epidermis. OSM transcripts are enhanced in both psoriatic and atopic dermatitic skin as compared with healthy skin and mirror the enhanced production of OSM by T cells isolated from diseased lesions. Results from a microarray analysis comparing the gene-modulating effects of OSM with those of 33 different cytokines indicate that OSM is a potent keratinocyte activator similar to TNF-alpha, IL-1, IL-17, and IL-22 and that it acts in synergy with the latter cytokines in the induction of S100A7 and beta-defensin 2 expression, characteristic of psoriatic skin. Taken together, these results demonstrate that OSM and its receptor play an important role in cutaneous inflammatory responses in general and that the specific effects of OSM are associated with distinct inflammatory diseases depending on the cytokine environment.

Molecular and functional characterization of a soluble form of oncostatin M/interleukin-31 shared receptor.

Activation of the signaling transduction pathways mediated by oncostatin M (OSM) requires the binding of the cytokine to either type I OSM receptor (leukemia inhibitory factor receptor/gp130) or to type II OSM receptor (OSMR/gp130). In the present work we have developed an enzyme-linked immunosorbent assay detecting a soluble form of OSMR (sOSMR) secreted by glioblastoma, hepatoma, and melanoma tumor cell lines. sOSMR was also present in sera of healthy individuals, with increased levels in multiple myeloma. Molecular cloning of a corresponding cDNA was carried out, and it encoded for a 70-kDa protein consisting of a half cytokine binding domain containing the canonical WSXWS motif, an immunoglobulin-like domain, and the first half of a second cytokine binding domain with cysteines in fixed positions. Analysis of the soluble receptor distribution revealed a preferential expression in lung, liver, pancreas, and placenta. sOSMR was able to bind OSM and interleukin-31 when associated to soluble gp130 or soluble interleukin-31R, respectively, and to neutralize both cytokine properties. We have also shown that OSM could positively regulate the synthesis of its own soluble receptor in tumor cells.

Differential effects of IL-27 on human B cell subsets.

IL-27 is a novel heterodimeric cytokine of the IL-12 family that plays an important role in the regulation of T cell responses. Its role on human B cells has not been previously studied. In this study, we show that both chains of the IL-27 receptor complex, IL-27R and gp130, are constitutively expressed at the surface of naive and memory human tonsillar B cells, and are induced on germinal center B cells following CD40 stimulation. In naive B cells, IL-27 induced strong STAT1 and STAT3 phosphorylation, whereas it induced moderate STAT1 and low STAT3 activation in memory B cells. IL-27 induced T-bet expression in naive and memory B cells stimulated by CD40 or surface Ig engagement, but induced significant IL-12Rbeta2 surface expression in anti-Ig-stimulated naive B cells only. In anti-Ig-stimulated naive or memory B cells, IL-27 also induced CD54, CD86, and CD95 surface expression. In addition, IL-27 increased proliferation of anti-Ig-activated naive B cells and of anti-CD40-activated naive and germinal center B cells, but not of CD40-activated memory B cells. These data indicate that the B cell response to IL-27 is modulated during B cell differentiation and varies depending on the mode of B cell activation.

Inactivation of cardiotrophin-like cytokine, a second ligand for ciliary neurotrophic factor receptor, leads to cold-induced sweating syndrome in a patient.

Ciliary neurotrophic factor (CNTF) receptor controls a pathway supporting the differentiation and survival of a wide range of neural cell types during development and in adulthood. Cardiotrophin-like cytokine (CLC)-cytokine-like factor 1 (CLF) composite cytokine is a second ligand for the CNTF alpha-component receptor (CNTFRalpha). This composite cytokine is built on the structural model of IL-12, with a complex formed by a four-helix bundle type I cytokine, CLC (also referred to as CLCF1), bound to a soluble receptor subunit, CLF (also known as CRLF1). We have reported mutations in the chaperone soluble receptor CLF, causing cold-induced sweating syndrome (CISS). In this study, we studied the CLC-mutated alleles in a patient suffering from a similar disease. This patient was compound heterozygous for two different CLC mutations. The first allele was inactivated by a stop codon at position 107 (Y107X). In the second allele, a R197L mutation in the CLC-predicted binding site to the CNTFRalpha was detected. Functional analysis of the mutated protein revealed an incapacity for R197L CLC to bind to CNTFRalpha and activate the subsequent signaling events. Structural and docking interaction studies showed that the R197L substitution destabilized the contact site between CLC and CNTFRalpha.

Secretion of IL-6, IL-11 and LIF by human cardiomyocytes in primary culture.

Interleukin (IL)-6-type cytokines are multifunctional proteins involved in cardiac hypertrophy and myocardial protection. Recent studies, performed on animal models, report the production of these cytokines by heart. The aim of this study was to analyse the capacity of myocytes and fibroblasts isolated from human atrium to secrete IL-6, leukaemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), IL-11, oncostatin M (OSM), ciliary neurotrophic factor (CNTF) and the soluble receptor subunits sIL-6R and sgp130 during primary culture. We detected LIF, IL-11, sgp130 and a large amount of IL-6, but not OSM, CT-1, CNTF nor IL-6R in these culture supernatants. Both cardiomyocytes and fibroblasts are able to spontaneously produce IL-6. The increase of IL-6 production all along the culture period appears to be the consequence of fibroblast proliferation and gp130 stimulation. This is the first demonstration that human cardiac cells are able to secrete IL-6, but also LIF and IL-11 in vitro. These cytokines could be involved in an autocrine and/or a paracrine networks regulating myocardial cyto-protection, hypertrophy and fibrosis.

Leukemia inhibitory factor (LIF), cardiotrophin-1, and oncostatin M share structural binding determinants in the immunoglobulin-like domain of LIF receptor.

Leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), and oncostatin M (OSM) are four helix bundle cytokines acting through a common heterodimeric receptor composed of gp130 and LIF receptor (LIFR). Binding to LIFR occurs through a binding site characterized by an FXXK motif located at the N terminus of helix D (site III). The immunoglobulin (Ig)-like domain of LIFR was modeled, and the physico-chemical properties of its Connolly surface were analyzed. This analysis revealed an area displaying properties complementary to those of the LIF site III. Two residues of the Ig-like domain of LIFR, Asp214 and Phe284, formed a mirror image of the FXXK motif. Engineered LIFR mutants in which either or both of these two residues were mutated to alanine were transfected in Ba/F3 cells already containing gp130. The F284A mutation impaired the biological response induced by LIF and CT-1, whereas the response to OSM remained unchanged. The Asp214 mutation did not alter the functional responses. The D214A/F284A double mutation, however, totally impaired cellular proliferation to LIF and CT-1 and partially impaired OSM-induced proliferation with a 20-fold increase in EC50. These results were corroborated by the analysis of STAT3 phosphorylation and Scatchard analysis of cytokine binding to Ba/F3 cells. Molecular modeling of the complex of LIF with the Ig-like domain of LIFR provides a clue for the superadditivity of the D214A/F284A double mutation. Our results indicate that LIF, CT-1, and OSM share an overlapping binding site located in the Ig-like domain of LIFR. The different behaviors of LIF and CT-1, on one side, and of OSM, on the other side, can be related to the different affinity of their site III for LIFR.

Two different contact sites are recruited by cardiotrophin-like cytokine (CLC) to generate the CLC/CLF and CLC/sCNTFRalpha composite cytokines.

The cytokines of the interleukin-6 family are multifunctional proteins that regulate cell growth, differentiation, and other cell functions in a variety of biological systems including the immune, inflammatory, hematopoietic, and nervous systems. One member of this family, ciliary neurotrophic factor (CNTF), displays biological functions more restricted to the neuromuscular axis. We have recently identified two additional ligands for the CNTF receptor complex. Both are composite cytokines formed by cardiotrophin-like cytokine (CLC) associated to either the soluble type I cytokine receptor CLF or the soluble form of CNTF receptor alpha (CNTFRalpha). The present study was aimed at analyzing the interactions between the cytokine CLC and its different receptor chains. For this purpose, we modeled CLC/receptor interactions to define the residues potentially involved in the contact sites. We then performed site-directed mutagenesis on these residues and analyzed the biological interactions between mutants and receptor chains. Importantly, we found that CLC interacts with the soluble forms of CNTFRalpha and CLF via sites 1 and 3, respectively. For site 1, the most crucial residues involved in the interaction are Trp67, Arg170, and Asp174, which interact with CNTFRalpha. Surprisingly, the residues that are important for the interaction of CLC with CLF are part of the conserved FXXK motif of site 3 known to be the interaction site of LIFRbeta. Obtained results show that the Phe151 and Lys154 residues are effectively involved in the interaction of CLC with LIFRbeta. This study establishes the molecular details of the interaction of CLC with CLF, CNTFRalpha, and LIFRbeta and helps to define the precise role of each protein in this functional receptor complex.

Functionally active fusion protein of the novel composite cytokine CLC/soluble CNTF receptor.

The heterodimeric cytokine composed of the soluble ciliary neurotrophic factor receptor (sCNTFR) and the IL-6 family member cardiotrophin-like cytokine (CLC) was recently identified as a new ligand for gp130-leukemia inhibitory factor receptor (LIFR) complex [Plun-Favreau, H., Elson, G., Chabbert, M., Froger, J., deLapeyriere, O., Lelievre, E., Guillet, C., Hermann, J., Gauchat, J. F., Gascan, H. & Chevalier, S. (2001) EMBO J. 20, 1692-1703]. This heterodimer shows overlapping biological properties with LIF. Although CLC contains a putative signal peptide and therefore should enter into the classical secretory pathway, the protein has been shown to be retained within transfected mammalian cells, unless coexpressed with either sCNTFR or cytokine like factor (CLF) [Elson, G. C., Lelievre, E., Guillet, C., Chevalier, S., Plun-Favreau, H., Froger, J., Suard, I., de Coignac, A. B., Delneste, Y., Bonnefoy, J. Y., Gauchat, J. F. & Gascan, H. (2000) Nat. Neurosci. 3, 867-872]. In the present study, we demonstrate that a fusion protein comprising CLC covalently coupled through a glycine/serine linker to sCNTFR (CC-FP) is efficiently secreted from transfected mammalian cells. CC-FP shows enhanced activities in respect to the CLC/sCNTFR native complex, on a number of cells expressing gp130 and LIFR on their surface. In addition, CC-FP is able to compete with CNTF for cell binding, indicating that both cytokines share binding epitope(s) expressed by their receptor complex. Analysis of the downstream signaling events revealed the recruitment by CC-FP of the signal transducer and activator of transcription (STAT)-3, Akt and mitogen-activated protein (MAP) kinase pathways. The monomeric bioactive CLC/sCNTFR fusion protein is therefore a powerful tool to study the biological role of the recently described cytokine CLC.

GPL, a novel cytokine receptor related to GP130 and leukemia inhibitory factor receptor.

We describe a novel cytokine receptor named GP130 Like receptor, or GPL, that displays similarities with the interleukin-6 and interleukin-12 family of signaling receptors. Four different isoforms diverging in their carboxyl terminus were isolated, corresponding to proteins encompassing 560, 610, 626, and 745 amino acids. Sequences included a signal peptide of 32 amino acids, followed by a cytokine binding domain containing four conserved cysteines, a WSDWS motif, and a region consisting of three fibronectin type III domain repeats. No immunoglobulin-like module was identified in the GPL sequences. The intracellular part of longer isoforms contained a proline-rich region defining a box1 motif for interaction with the Janus kinases. The Gpl gene is organized in 15 exons and is located on 5q11.2 in tandem with the gp130 gene. Both genes were only separated by 24 kilobases, with opposite transcriptional orientations. The GPL receptor displayed a 28% identity with gp130. Specific GPL transcripts were observed in tissues involved in reproduction. Transcripts were also found in blood cells and in bone marrow, revealing expression of GPL in all of the myelomonocytic lineage, from hematopoietic stem cells to activated dendritic cells. In monocytes and dendritic cells, expression of GPL was strongly up-regulated by interferon-gamma, indicating a possible involvement of GPL in Th1-type immune responses. The molecular basis of cell signaling mediated by GPL was studied using chimeric receptors where external portions of alpha or beta interleukin-5 receptor subunits were fused to the internal portion of GPL or of related receptors. Results indicated that association of GPL to the intracellular portions of gp130, or LIF receptor, allowed the signaling cascade.