UNIPROT:P05231 - FACTA Search

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Query: UNIPROT:P05231 (interleukin-6)
23,907 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The product of the junB gene is a member of the AP-1 family of transcription factors that activate transcription by binding to TPA-responsive elements (TREs) within the promoters of target genes. Components of AP-1 are immediate-early genes whose expression is upregulated by a plethora of extracellular stimuli and are important in mediating cellular proliferation and differentiation. Such stimuli include the pleiotropic cytokine interleukin-6 (IL-6) which plays a role in immune and inflammatory responses and ciliary neurotrophic factor (CNTF) which enhances survival and differentiation of neurons and glia. We have analysed expression from junB promoter-CAT reporter constructs in HepG2 cells and found that a region between -196 and -91 can mediate response to IL-6 and CNTF and was able to confer responsiveness to a heterologous promoter. We further show by gel retardation analysis that distinct nuclear factors induced by IL-6 specifically bind to this interleukin-6 response element (IRE). This region contains both a putative ETS- and a STAT-transcription factor binding site. We show by mutational analysis and supershift data that the IL-6 induced complex indeed contains the transcription factor APRF/Stat3 that is both necessary and sufficient for activation. Interestingly this site does not appear to bind Stat1 itself, as shown by supershift analysis and a lack of response to IFN-gamma both at the DNA-binding and transcriptional level. Furthermore, we demonstrate that the junB IRE-binding activity induced by IL-6 requires tyrosine kinase activity, whereas induced transactivation of IRE-constructs additionally occurs through an H7-sensitive pathway that is p21ras-independent, implicating serine/threonine kinases in the transactivation of IRE-binding factors.
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PMID:Transcriptional regulation of the junB promoter: analysis of STAT-mediated signal transduction. 789 39

Mammary gland factor (MGF) is a transcription factor discovered initially in the mammary epithelial cells of lactating animals. It confers the lactogenic hormone response to the milk protein genes. We reported recently the isolation of the cDNA encoding MGF. MGF is a novel member of the cytokine-regulated transcription factor gene family. Members of this gene family mediate interferon alpha/beta and interferon gamma induction of gene transcription, as well as the response to epidermal growth factor and interleukin-6, and have been named signal transducers and activators of transcription (Stat). The name Stat5 has been assigned to MGF. We studied the mechanisms involved in the prolactin activation of Stat5 in COS cells co-transfected with cDNA encoding Stat5 and the prolactin receptor. Prolactin treatment of the transfected cells caused activation of Stat5 within 5-10 min. This activation does not require ongoing protein synthesis. Tyrosine kinase inhibitors prevent Stat5 activation in transfected COS cells. Treatment of recombinant Stat5 with a tyrosine-specific protein phosphatase in vitro abolishes its DNA binding activity. Prolactin stimulation of transfected cells induces Stat5 phosphorylation on tyrosine. Phosphorylation of in vitro transcribed and translated Stat5 with the Jak2 tyrosine kinase, but not with fyn, lyn or lck, confers DNA binding activity. The prolactin response of the beta-casein milk protein gene promoter can be observed in COS cells transfected with cDNA vectors encoding Stat5 and the long form of the prolactin receptor. The short form of the prolactin receptor is unable to promote Stat5 phosphorylation and confer transcriptional induction in COS cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Prolactin induces phosphorylation of Tyr694 of Stat5 (MGF), a prerequisite for DNA binding and induction of transcription. 792 80

Interleukin-6 (IL-6) is a multifunctional cytokine which is made by osteoblasts and has diverse effects on bone metabolism. We studied the interaction of IL-6 with the Ca2+ and cAMP signaling systems in the osteoblastic cell line UMR-106 and in primary osteoblastic cultures derived from neonatal rat calvariae. IL-6 did not alter basal intracellular calcium concentration ([Ca2+]i) but inhibited Ca2+ transients induced by parathyroid hormone (PTH), prostaglandin E2 (PGE2), and endothelin-1 in both dose- (100-400 U/ml) and time- (4-48 h) dependent manners. The effect of the cytokine was abolished by the tyrosine kinase inhibitor, herbimycin A (50 ng/ml). The IL-6 effect on the Ca2+ message system was related to suppressed production of hormonally induced inositol 1,4,5-triphosphate and inhibition of Ca2+ release from intracellular stores. Hormonally induced calcium entry pathways (estimated by using Mn2+ as a surrogate for Ca2+) were not, however, altered by the cytokine. IL-6 did not modulate cAMP generation in osteoblasts. With respect to osteoblast function, IL-6, although having no effect on cell proliferation by itself, greatly enhanced the antiproliferative effect of PGE2 and PTH. Because the production of IL-6 in osteoblasts is stimulated by calciotropic hormones (e.g., PTH and PGE2), the suppressive effect of the cytokine on hormonally induced Ca2+ transients may serve as an autocrine/paracrine mechanism for modulating the effect of hormones on bone metabolism.
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PMID:Interleukin-6 attenuates agonist-mediated calcium mobilization in murine osteoblastic cells. 820 Sep 68

Interleukin-6 (IL-6) may play an important role in human CG (hCG) production by activating the IL-6-receptor (-R) system on human trophoblasts. Trophoblasts produced hCG in response to rIL-6 as well as to 8-bromo cAMP (8-Br-cAMP), 12-O-tetradecanoyl phorbol-13-acetate (TPA), and calcium ionophore A23187. To determine whether the signal transduction pathway activated by the IL-6-R system depends on protein kinases such as protein kinase A, protein kinase C, and Ca2+/calmodulin-dependent kinase, trophoblasts were stimulated with recombinant (r-) IL-6 in the presence or absence of protein kinase inhibitors such as N(2-methyl-aminoethyl)-5-isoquinoline sulfonamide dihydrochloride (H8), and 1-(5-isoquinolinesulfomyl)-2-methylpiperazine (H7) and a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1- napthalenesulfonamide (W7), H8, H7, and W7 failed to suppress rIL-6-induced hCG production but completely inhibited hCG production induced by 8-Br-cAMP, TPA, and the GnRH agonist (GnRHa), respectively. In contrast, genistein, a tyrosine kinase inhibitor, completely suppressed rIL-6-induced hCG production but failed to inhibit hCG production induced by 8-Br-cAMP, TPA, and A23187. Genistein also did not suppress GnRH-induced hCG production. The addition of genistein to rIL-1- and rTNF-alpha-stimulated trophoblasts inhibited rIL-1-induced and rTNF-alpha induced hCG production but maintained rIL-1- and rTNF-alpha-induced IL-6 production. These results show that the IL-6/IL-6-R system-induced signal transduction pathway in the placenta probably stimulates hCG production by activating a tyrosine kinase pathway. The experiment with genistein shows that the GnRH/GnRH-R system activates a signal transduction pathway distinct from that activated by the IL-6/IL-6-R system.
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PMID:The interleukin-6 (IL-6)/IL-6-receptor system induces human chorionic gonadotropin production by activating tyrosine kinase-dependent signal transduction pathway different from pathways triggered by protein kinase activators including gonadotropin releasing hormone. 837 Jun 93

Interleukin-6 (IL-6) activation of the immediate-early gene junB has been shown to require both a tyrosine kinase and an unknown 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7)-sensitive pathway. Here we report the identification and characterization of an IL-6 immediate-early response element in the junB promoter (designated JRE-IL6) in HepG2 cells. The JRE-IL6 element, located at -149 to -124, contains two DNA motifs, an Ets-binding site (EBS) (CAGGAAGC) and a CRE-like site (TGACGCGA). Functional studies using variously mutated JRE-IL6 elements showed that both motifs were necessary and sufficient for IL-6 response of the promoter. The EBS of the JRE-IL6 element (JEBS) appears to bind a protein in the Ets family or a related protein which could also form a major complex with the EBSs of the murine sarcoma virus long terminal repeat or human T-cell leukemia virus type 1 long terminal repeat. The CRE-like site appears to weakly bind multiple CREB-ATF family proteins. Despite the similarity in the structure between the JRE-IL6 element and the polyomavirus enhancer PyPEA3, composed of an EBS and an AP1-binding site and known to be activated by a variety of oncogene signals, JRE-IL6 could not be activated by activated Ha-Ras, Raf-1, or 12-O-tetradecanoylphorbol-13-acetate. We show that IL-6 activates JRE-IL6 through an H7-sensitive pathway that does not involve protein kinase C, cyclic AMP-dependent kinase, Ca(2+)- or calmodulin-dependent kinases, Ras, Raf-1, or NF-IL6 (C/EBP beta). The combination of JEBS and the CRE-like site appears to form the basis for the selective and efficient response of JRE-IL6 to IL-6 signals, but not to signals generated by activated Ha-Ras, Raf-1, or protein kinase C.
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PMID:Identification of a novel interleukin-6 response element containing an Ets-binding site and a CRE-like site in the junB promoter. 838 18

The biological functions of interleukin-6 (IL-6) are mediated through a signal-transducing component of the IL-6 receptor, gp130, which is associated with the ligand-occupied IL-6 receptor (IL-6R) protein. Binding of IL-6 to IL-6R induced disulfide-linked homodimerization of gp130. Tyrosine kinase activity was associated with dimerized but not monomeric gp130 protein. Substitution of serine for proline residues 656 and 658 in the cytoplasmic motif abolished tyrosine kinase activation and cellular responses but not homodimerization of gp130. The IL-6-induced gp130 homodimer appears to be similar in function to the heterodimer formed between the leukemia inhibitory factor (LIF) receptor (LIFR) and gp130 in response to the LIF or ciliary neurotrophic factor (CNTF). Thus, a general first step in IL-6-related cytokine signaling may be the dimerization of signal-transducing molecules and activation of associated tyrosine kinases.
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PMID:IL-6-induced homodimerization of gp130 and associated activation of a tyrosine kinase. 851 89

Native PC12 cells respond differentially to nerve growth factor (NGF) but not interleukin-6 (IL-6); PC12-E2 cells, a stable variant, respond to both stimuli (and more rapidly to NGF). Neither responds to epidermal growth factor (EGF). NGF primarily induces the RAS/extracellular signal-regulated kinase (ERK) pathway and IL-6 activates a JAK (Janus tyrosine kinase)/STAT (signal transducers and activators of transcription) response. EGF also stimulates RAS/ERK but in a transient manner. When either cell type is treated with combinations of NGF, EGF, and IL-6, at concentrations that produce modest or no response, a substantial augmentation of neurite outgrowth is observed. With PC12-E2 cells, a subthreshold concentration of IL-6 increases NGF response by approximately 2-3-fold after 1-2 days; the increase with EGF is more pronounced. Native PC12 cells show even greater synergistic effects with NGF and IL-6. The most dramatic effect was observed with low levels of EGF, where IL-6 increased the percentage of responsive cells from zero to approximately 60% after 3 days. In addition, two neural-specific transcripts, GAP-43 and SCG-10, are synergistically increased by the combinations of growth factors. Importantly, IL-6 does not enhance ERK phosphorylation in the presence of either NGF or EGF. In contrast, NGF and EGF, in the presence or absence of IL-6, cause mobility shifts of Stat3 that are consistent with serine phosphorylations. Although these modifications do not lead to activation and translocation by themselves, in the presence of the tyrosine phosphorylation induced by IL-6, they may play a role in the synergistic responses. These observations suggest a differentially regulated two-stage mechanism for the differentiative response of PC12 cells to NGF.
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PMID:Synergistic induction of neurite outgrowth by nerve growth factor or epidermal growth factor and interleukin-6 in PC12 cells. 866 31

Most of the receptors for soluble factors functioning in the hematopoietic system belong to the class I cytokine receptor family. These receptors often share common signal transducing receptor components in the same family, which explains the functional redundancy of cytokines. One typical example is a group of receptor systems for interleukin-6 (IL-6) and related cytokines that share gp130 as a signal transducer. This subset of cytokines, i.e., IL-6, IL-11, leukemia inhibitory factor, oncostatin M, ciliary neurotrophic factor, and cardiotrophin-1, are all pleiotropic, exhibiting overlapping biological activities, and are known to function also in the neuronal system. In their receptor complexes, gp130 and ligand-specific chains possess no intrinsic tyrosine kinase domain but are associated with members of the Jak family of cytoplasmic tyrosine kinases. The Jak kinases become activated after ligand-induced homo- or heterodimerization of gp130. This activation appears to link the cell surface receptors to the nuclear genes through a series of biochemical changes, including tyrosine phosphorylation and activation of a latent cytoplasmic transcription factor called signal transducer and activator of transcription 3 (STAT3).
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PMID:Gp130, a shared signal transducing receptor component for hematopoietic and neuropoietic cytokines. 866 78

Interleukin-6 (IL-6) is a multifunctional cytokine that is produced not only by a variety of normal cells but also by cancer cells. IL-6 produced by cancer cells stimulates the proliferation of these cancer cells in an autocrine/ paracrine manner and causes paraneoplastic syndromes including hypercalcemia, cachexia, and leukocytosis. We have reported previously that a human oral squamous cancer associated with hypercalcemia produces large amounts of IL-6, that animals bearing this cancer exhibit elevated levels of plasma IL-6, and that neutralizing antibodies to human IL-6 reverse hypercalcemia in tumor-bearing animals, indicating an important role of IL-6 in the hypercalcemia in this model. Because these cancer cells overexpress epidermal growth factor receptors (EGFR) with intrinsic tyrosine kinase (TK) activity similar to many other squamous cancers, we examined the effects of herbimycin A, a tyrosine kinase inhibitor, on IL-6 production and hypercalcemia in animals bearing this cancer to develop a new approach to treat the hypercalcemia associated with malignancy. Intraperitoneal administration (once a day for 2 days) of herbimycin A to cancer-bearing hypercalcemic mice reduced the plasma levels of human IL-6 and impaired the hypercalcemia. During 2-day treatment with herbimycin A, no changes were observed in tumor size. Of interest, plasma levels of mouse, but not human, soluble IL-6 receptors were also elevated. However, herbimycin A showed no effects on plasma levels of mouse soluble IL-6 receptors. Herbimycin A suppressed the tyrosine autophosphorylation of EGFR and IL-6 mRNA expression and production, all of which were stimulated by EGF. The data raise the possibility that TK inhibitors may be potential mechanism-based therapeutic agents for the treatment of hypercalcemia associated with squamous cancers which overexpress EGFR.
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PMID:Herbimycin A, a tyrosine kinase inhibitor, impairs hypercalcemia associated with a human squamous cancer producing interleukin-6 in nude mice. 879 10

alpha 2-Macroglobulin (alpha 2M) is expressed at high levels in the corpus luteum of pregnant rats in response to PRL and rat placental lactogens. These studies document that PRL induction of alpha 2M mRNA occurs rapidly in granulosa cells differentiated to the preovulatory phenotype in the presence of FSH and steroid, is hormone specific [induced by PRL but not by LH or interleukin-6 (IL-6)], and involves tyrosine kinase activity. To analyze the cellular signaling events stimulated by PRL, transient transfections of granulosa cells and electrophoretic mobility shift assays were done using the IL-6 response element (IL-6RE) of the alpha 2M promoter. The IL-6RE consists of two gamma-activating like sequences (GAS) that bind the acute phase response factor (APRF/Stat 3) in rat liver and the mammary gland factor (MGF/Stat 5) from mammary tissue. By transfecting various alpha 2M promoter-luciferase reporter transgenes into the granulosa cell cultures, we show that the GAS-like sites together with the minimal -48 base pairs of the alpha 2M promoter can confer PRL inducibility to the luciferase reporter gene. These same GAS-like sequences of the alpha 2M promoter were used to analyze the DNA-binding activity of proteins in whole cell extracts prepared from differentiated granulosa cells exposed to PRL for 0.25, 0.5, 4, and 20 h. PRL rapidly stimulated the binding of a specific protein to labeled alpha 2M GAS-like oligonucleotide, and this PRL-induced binding activity was shown to contain Stat 5 but not Stat 1 or Stat 3, using specific antibodies in the electrophoretic mobility shift assays. Because both Stat 5 and Stat 3 proteins are present in the whole cell extracts of differentiated granulosa cells, PRL appears to activate detectable amounts of Stat 5 (and not Stat 3). Thus, the initial induction of the alpha 2M gene by PRL in differentiated rat granulosa cells involves, at least in part, the activation (tyrosine phosphorylation?) of Stat 5.
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PMID:Prolactin induction of the alpha 2-Macroglobulin gene in rat ovarian granulosa cells: stat 5 activation and binding to the interleukin-6 response element. 882 57

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