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)

Development of cytokine resistance is an important feature of melanoma cells during tumor progression. To study the mechanisms of interleukin-6 resistance, we examined an interleukin-6 sensitive (WM35) and an interleukin-6 unresponsive cell line (WM9). Interleukin-6 treatment resulted in rapid inhibition of cyclin-dependent kinase 2/cyclin E activity and accumulation of the hypophosphorylated retinoblastoma protein in WM35 but not in WM9 cells. In contrast to previous reports, no differences in the expression of the cyclin-dependent kinase 2 inhibitor p21Cip1/WAF1 upon interleukin-6 treatment were found in both cell lines. Interleukin-6-induced inhibition of cyclin-dependent kinase 2 was also not due to changes in protein expression of cyclin-dependent kinase 2, cyclin E, p27Kip1 and cdc25A, a phosphatase positively regulating cyclin-dependent kinase 2 activity. As it is established that interleukin-6 resistance of WM9 cells is not caused by differential interleukin-6 receptor expression, we studied whether this is due to defective interleukin-6 signaling in which activation of signal transducer and activator of transcription 3 is a critical step. WM9 cells showed reduced tyrosine phosphorylation, DNA binding, and delayed nuclear translocation of signal transducer and activator of transcription 3 as compared with WM35 cells. The kinase upstream of signal transducer and activator of transcription 3, Janus kinase 1, was constitutively tyrosine-phosphorylated in WM9 cells and did not respond to interleukin-6 with increased phosphorylation. As compared with WM35 cells, interleukin-6 treatment of WM9 cells was not paralleled by reduced activity of the mitogen-activated protein kinase kinase-1, which suppresses activation of signal transducer and activator of transcription 3. Our data suggest that resistance of advanced melanoma cells to interleukin-6 is associated with reduced inhibition of cyclin-dependent kinase 2, which appears to be a consequence of a complex alteration in interleukin-6 signal transduction.
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PMID:Interleukin-6-resistant melanoma cells exhibit reduced activation of STAT3 and lack of inhibition of cyclin E-associated kinase activity. 1144 60

Polyclonal lymphocyte activation and hypergammaglobulinemia characterize the acute phase of Chagas' disease, a debilitating condition caused by Trypanosoma cruzi. Such pathogenic hyper-reactivities not only compromise specific host defense against the pathogen, but may also contribute to infection-induced chronic autoimmune responses. Recent studies showed that T. cruzi trans-sialidase (TS) directly stimulates the polyclonal proliferation and Ig secretion of normal murine B cells in a T-independent, Bruton's tyrosine kinase (Btk)-dependent manner. Related to this observation, we now show that parasite-derived and recombinant TS potentiate the proliferation and cytokine secretion of normal T cells triggered by antigen-specific and non-specific stimuli. TS potentiates T cell activation through stimulating B cells and macrophages, independent of CD40/CD40L and CD43 pathways. In contrast, optimal TS potentiation requires interleukin-6 (IL-6) and Btk, as it is significantly reduced in splenocytes from IL-6-/- and Btk-defective Xid mice. The results suggest that TS, directly and indirectly, activates both antigen-presenting cell and T cell compartments, and that TS-induced IL-6 may further amplify such activation. These observations open up the possibility that TS drives the polyclonal lymphocyte activation in acute T. cruzi infection, a phenomenon contributing to the pathogenesis of Chagas' disease.
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PMID:Trypanosoma cruzi trans-sialidase potentiates T cell activation through antigen-presenting cells: role of IL-6 and Bruton's tyrosine kinase. 1146 7

Janus kinase 1 (Jak1) is a cytoplasmic tyrosine kinase that noncovalently associates with a variety of cytokine receptors. Here we show that the in vitro translated N-terminal domains of Jak1 are sufficient for binding to a biotinylated peptide comprising the membrane-proximal 73 amino acids of gp130, the signal-transducing receptor chain of interleukin-6-type cytokines. By the fold recognition approach amino acid residues 36-112 of Jak1 were predicted to adopt a beta-grasp fold, and a structural model was built using ubiquitin as a template. Substitution of Tyr(107) to alanine, a residue conserved among Jaks and involved in hydrophobic core interactions of the proposed beta-grasp domain, abrogated binding of full-length Jak1 to gp130 in COS-7 transfectants. By further mutagenesis we identified the loop 4 region of the Jak1 beta-grasp domain as essential for gp130 association and gp130-mediated signal transduction. In Jak1-deficient U4C cells reconstituted with the loop 4 Jak1 mutants L80A/Y81A and Delta(Tyr(81)-Ser(84)), the interferon-gamma, interferon-alpha, and interleukin-6 responses were similarly impaired. Thus, loop 4 of the beta-grasp domain plays a role in the association of Jak1 with both class I and II cytokine receptors. Taken together the structural model and the mutagenesis data provide further insight into the interaction of Janus kinases with cytokine receptors.
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PMID:Mapping of a region within the N terminus of Jak1 involved in cytokine receptor interaction. 1146 94

Previous studies demonstrate that interleukin-6 (IL-6) mediates growth and survival in human multiple myeloma (MM) cells via the MEK/MAPK and JAK/STAT signaling pathways, respectively. IL-6 also confers protection against Dexamethasone (Dex)-induced apoptosis via activation of protein tyrosine phosphatase (SHP2). In the current study, we characterized IL-6 triggered phophatidylinositol-3 kinase/Akt kinase (PI3-K/Akt) signaling in MM cells. IL-6 induces Akt/PKB phosphorylation in a time and dose dependent manner in MM.1S MM cells. IL-6 also induced phosphorylation of downstream targets of Akt, including Bad, GSK-3beta, and FKHR, confirming Akt activation. Inhibition of Akt activation by the PI3-K inhibitor LY294002 partially blocked IL-6 triggered MEK/MAPK activation and proliferation in MM.1S cells, suggesting cross-talk between PI3-K and MEK signaling. We demonstrate that Dex-induced apoptosis in MM.1S cells is mediated by downstream activation of caspase-9, with resultant caspase-3 cleavage; and conversely, that IL-6 triggers activation of PI3-K and its association with SHP2, inactivates caspase-9, and protects against Dex-induced apoptosis. LY294002 completely abrogates this signaling cascade, further confirming the importance of PI3-K/Akt signaling in conferring the protective effect of IL-6 against Dex-induced apoptosis. Finally, we show that IL-6 triggered PI3-K/Akt signaling in MM.1S cells inactivates forkhead transcriptional factor (FKHR), with related G1/S phase transition, whereas LY294002 blocks this signaling, resulting in upregulation of p27(KIP1) and G1 growth arrest. Our data therefore suggest that PI3-K/Akt signaling mediates growth, survival, and cell cycle regulatory effects of IL-6 in MM.
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PMID:Biologic sequelae of interleukin-6 induced PI3-K/Akt signaling in multiple myeloma. 1159 6

We previously showed that basic fibroblast growth factor (bFGF) stimulates release of vascular endothelial growth factor (VEGF) and synthesis of interleukin-6 (IL-6) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effects of leukemia inhibitory factor (LIF) on the release of VEGF and IL-6 in these cells. LIF did not affect the bFGF-stimulated VEGF release. On the contrary, LIF, which alone had little effect on IL-6 release, significantly enhanced the bFGF-stimulated IL-6 release. The amplifying effect of LIF on the IL-6 release was dose dependent in the range between 0.01 and 10 ng/ml. AG490, an inhibitor of JAK2, suppressed the amplifying effect of LIF. LIF induced the phosphorylation of STAT3. AG490 inhibited the LIF-induced STAT3 phosphorylation. Taken together, our results strongly suggest that LIF enhances bFGF-stimulated IL-6 synthesis via JAK2/STAT3 pathway in osteoblasts.
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PMID:Leukemia inhibitory factor enhances bFGF-induced IL-6 synthesis in osteoblasts: involvement of JAK2/STAT3. 1185 38

Oncostatin M (OSM) is a glycoprotein cytokine that is produced by activated T-lymphocytes, monocytes, and macrophages. In a DNA synthesis assay, OSM reduced tritiated thymidine incorporation by 53% in Calu-1 lung carcinoma cells. Radiolabeled cDNAs from untreated Calu-1 cells and 30-h OSM-treated cells were used to probe duplicate nylon membrane cDNA expression arrays. This study revealed OSM-mediated expression of mRNAs encoding tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1). Northern blot analysis showed that the steady-state level of tPA mRNA is nearly undetectable in Calu-1 cells. Exposure of these cells to OSM for 30 h increased tPA mRNA expression by 20-fold and PAI-1 mRNA expression by 5-fold. Exposure of these cells to other gp130 receptor family cytokines, including leukemia inhibitory factor (LIF), interleukin-6 (IL-6), and IL-11, do not significantly affect DNA synthesis or induction of tPA/PAI-1. Western blot studies demonstrated that OSM mediates a marked increase in secretion of the tPA protein. Secreted tPA was present in the conditioned medium almost exclusively as tPA/PAI-1 complexes. Inhibitor studies demonstrated that OSM-mediated induction of tPA and PAI-1 mRNAs is largely dependent upon activation of the MEK1/2 pathway. The JAK3/STAT3 pathway potentially serves a secondary role in these regulatory events.
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PMID:Oncostatin M induces tissue-type plasminogen activator and plasminogen activator inhibitor-1 in Calu-1 lung carcinoma cells. 1209 Jul 57

Signal transducers and activators of transcription (STAT) factors are cytoplasmic proteins that can be activated by Janus kinases (JAK) and that modulate gene expression in response to cytokine receptor stimulation. STAT proteins dimerize, translocate into the nucleus, and activate specific target genes. In the present study, we show for the first time that interleukin-6 (IL), in the presence of its soluble receptor (sIL-6R), induces activation of JAK1, JAK2, and STAT1/STAT3 proteins in bovine articular chondrocytes. Western blotting and mobility shift assays demonstrated that this effect is accompanied by the DNA binding of the STAT proteins. The mitogen-activated protein kinase pathway was also activated in response to IL-6/sIL-6R association, as reflected by phosphorylation of ERK1 and ERK2 proteins. In these conditions, the expression of cartilage-specific matrix genes, type II collagen, aggrecan core, and link proteins was found to be markedly down-regulated. This negative effect was abolished by addition of parthenolide, an inhibitor of the STAT activation, whereas blockade of the MAP kinases with PD098059 was without significant effect. Thus, activation of the STAT signaling pathways, but not ERK-dependent pathways, is essential for down-regulation of the major cartilage-specific matrix genes by IL-6. In addition, a parallel reduction of Sox9 expression, a key factor of chondrocyte phenotype, was found in these experimental conditions. These IL-6 effects might contribute to the phenotype loss of chondrocytes in joint diseases and the alteration of articular cartilage associated with this pathology.
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PMID:JAK/STAT but not ERK1/ERK2 pathway mediates interleukin (IL)-6/soluble IL-6R down-regulation of Type II collagen, aggrecan core, and link protein transcription in articular chondrocytes. Association with a down-regulation of SOX9 expression. 1241 23

As a c-fms-interacting protein, we cloned a novel adaptor molecule, signal-transducing adaptor protein-2 (STAP-2), which contains pleckstrin homology- and Src homology 2-like (PH and SRC) domains and a proline-rich region. STAP-2 is structurally related to STAP-1/BRDG1 (BCR downstream signaling-1), which we had cloned previously from hematopoietic stem cells. STAP-2 is a murine homologue of a recently identified adaptor molecule, BKS, a substrate of BRK tyrosine kinase. STAP-2 was tyrosine-phosphorylated and translocated to the plasma membrane in response to epidermal growth factor when overexpressed in fibroblastic cells. To define the function of STAP-2, we generated mice lacking the STAP-2 gene. STAP-2 mRNA was strongly induced in the liver in response to lipopolysaccharide and in isolated hepatocytes in response to interleukin-6. In the STAP-2(-/-) hepatocytes, the interleukin-6-induced expression of acute-phase (AP) genes and the tyrosine-phosphorylation level of STAT3 were reduced specifically at the late phase (6-24 h) of the response. These data indicate that STAP-2 plays a regulatory role in the AP response in systemic inflammation. STAP-2 contains a YXXQ motif in the C-terminal region that is a potential STAT3-binding site. Overexpression of wild-type STAP-2, but not of mutants lacking this motif, enhanced the AP response element reporter activity and an AP protein production. These data suggest that STAP-2 is a new class of adaptor molecule that modulates STAT3 activity through its YXXQ motif.
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PMID:STAP-2/BKS, an adaptor/docking protein, modulates STAT3 activation in acute-phase response through its YXXQ motif. 1254 Aug 42

Protein I/II, a pathogen-associated molecular pattern from oral streptococci, is a potent inducer of interleukin-6 (IL-6) and IL-8 synthesis and release from fibroblast-like synoviocytes (FLSs), cells that are critically involved in joint inflammation. This synthesis implicates ERK 1/2 and JNKs as well as AP-1-binding activity and nuclear translocation of NF-kappaB. The mechanisms by which protein I/II activates MAPKs remain, however, elusive. Because focal adhesion kinase (FAK) was proposed to play a role in signaling to MAPKs, we examined its ability to contribute to the MAPKs-dependent synthesis of IL-6 and IL-8 in response to protein I/II. We used FAK-/- fibroblasts as well as FAK+/+ fibroblasts and FLSs transfected with FRNK, a dominant negative form of FAK. The results demonstrate that IL-6 and IL-8 release in response to protein I/II was strongly inhibited in both protein I/II-stimulated FAK-/- and FRNK-transfected cells. Cytochalasin D, which inhibits protein I/II-induced phosphorylation of FAK (Tyr-397), had no effect either on activation of ERK 1/2 and JNKs or on IL-6 and IL-8 release. Taken together, these results indicate that IL-6 and IL-8 release by protein I/II-activated FLSs is regulated by FAK independently of Tyr-397 phosphorylation.
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PMID:ERK 1/2- and JNKs-dependent synthesis of interleukins 6 and 8 by fibroblast-like synoviocytes stimulated with protein I/II, a modulin from oral streptococci, requires focal adhesion kinase. 1276 Dec 29

We established hepatitis C virus (HCV) core-expressing cells and investigated whether HCV core would modify the Janus kinase (JAK)-signal transducer and activator transcription factor (STAT) pathway under interleukin-6 (IL-6) and interferon (IFN)-gamma stimuli. Phosphorylation of JAK1/2 and STAT3, and STAT3-mediated transcription, were prevented by HCV core under IL-6 stimulation. In contrast, HCV core increased phosphorylation of JAK1/2 and STAT1 and STAT1-mediated transcription under IFN-gamma stimulation. Immunoprecipitation/Western blot analysis showed that HCV core could bind to JAK1/2. The PGYPWP sequences at codons 79-84 within HCV core were important for interaction with JAKs by in vitro binding analysis. In the reporter gene assay, HCV core-mediated suppression of JAK-STAT pathway under IL-6 stimulation was not observed by abrogation of PGYPWP sequence, suggesting that HCV core/JAK interaction may directly affect the signal transduction. In contrast, augmentation of JAK-STAT pathway was still seen by HCV core without functional PGYPWP sequence under IFN-gamma stimulation. Flow cytometric analysis revealed that HCV core up-regulated of IFN-gamma receptor 2 expression, which may be responsible for HCV core-mediated enhancement of JAK-STAT pathway under IFN-gamma stimulation. In conclusion, HCV core has different effects on the JAK-STAT pathway under IL-6 and IFN-gamma stimuli. This may be exerted by these two independent mechanisms.
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PMID:Hepatitis C virus core protein differently regulates the JAK-STAT signaling pathway under interleukin-6 and interferon-gamma stimuli. 1276 55

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