UNIPROT:P05412 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UNIPROT:P05412 (c-Jun)
11,453 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transforming growth factor beta (TGF-beta) plays an important role in constraining cellular proliferation, but it is also a potent inducer of programmed cell death or apoptosis. Here, we demonstrate that TGF-beta can have an opposite effect, acting as a survival factor to prevent c-Myc-induced cell death in Rat-1 fibroblasts. However, in marked contrast to TGF-beta, Smad2, which is a critical intracellular mediator of the TGF-beta signaling pathway, functions as an antagonist to induce increased cell death. The protective activity of TGF-beta was associated with the activation of c-Jun N-terminal Kinase (JNK) and was not linked to the ability of TGF-beta to promote cell cycle progression. Expression of dominant-interfering forms of various components of the JNK signaling pathway, including Rac1, Cdc42, mitogen-activated protein kinase kinase 4 (MKK4), and c-Jun, abolished TGF-beta-mediated cell survival. Furthermore, overexpression of the constitutively activated mutant RacL61F37A, which selectively stimulates JNK cascade but not G1 cell cycle progression or actin polymerization, was sufficient to prevent apoptosis induced by c-Myc. These findings describe a differential effect of two separated signaling pathways of TGF-beta and indicate for the first time that Smad2 can act as antagonist to suppress TGF-beta-dependent cell survival. Oncogene (2000) 19, 1277 - 1287.
...
PMID:Differential roles of JNK and Smad2 signaling pathways in the inhibition of c-Myc-induced cell death by TGF-beta. 1071 69

The Sma and Mad related (Smad) family proteins are critical mediators of the transforming growth factor-beta (TGF-beta) superfamily signaling. After TGF-beta-mediated phosphorylation and association with Smad4, Smad2 moves to the nucleus and activates expression of specific genes through cooperative interactions with DNA-binding proteins, including members of the winged-helix family of transcription factors, forkhead activin signal transducer (FAST)-1 and FAST2. TGF-beta has also been described to activate other signaling pathways, such as the c-Jun N-terminal Kinase (JNK) pathway. Here, we show that activation of JNK cascade blocked the ability of Smad2 to mediate TGF-beta-dependent activation of the FAST proteins. This inhibitory activity is mediated through the transcriptional factor c-Jun, which enhances the association of Smad2 with the nuclear transcriptional corepressor TG-interacting factor (TGIF), thereby interfering with the assembly of Smad2 and the coactivator p300 in response to TGF-beta signaling. Interestingly, c-Jun directly binds to the nuclear transcriptional corepressor TGIF and is required for TGIF-mediated repression of Smad2 transcriptional activity. These studies thus reveal a mechanism for suppression of Smad2 signaling pathway by JNK cascade through transcriptional repression.
...
PMID:c-Jun interacts with the corepressor TG-interacting factor (TGIF) to suppress Smad2 transcriptional activity. 1137 41

Transforming growth factor (TGF)-beta plays a central role in fibrosis, contributing both to the influx and activation of inflammatory cells, as well as to activation of fibroblasts to elaborate extracellular matrix. In the past few years, new insight has been gained into signal transduction pathways downstream of the TGF-beta receptor serine-threonine kinases with the identification of a family of evolutionarily conserved Smad proteins. Two receptor-activated Smad proteins, Smad2 and Smad3, are phosphorylated by the activated TGF-beta type I receptor kinase, after which they partner with the common mediator, Smad4, and are translocated to the nucleus to where they participate in transcriptional complexes to control expression of target genes. We have shown in wound healing studies of mice null for Smad3, that loss of this key signaling intermediate interferes with the chemotaxis of inflammatory cells to TGF-beta as well as with their ability to autoinduce TGF-beta. Moreover, studies with mouse embryo fibroblasts null for Smad3 show that TGF-beta-dependent induction of c-Jun and c-Fos, important in induction of collagen as well as in autoinduction of TGF-beta, is mediated by Smad3. Based on these observations, we hypothesize that loss of Smad3 will confer resistance to fibrosis and result in reduced inflammatory cell infiltrates, reduced autoinduction of TGF-beta, important to sustain the process, and reduced elaboration of collagen. Preliminary observations in a model of radiation-induced fibrosis confirm this hypothesis and suggest that inhibitors of Smad3 might have clinical application both to improve wound healing and to reduce fibrosis.
...
PMID:Is Smad3 a major player in signal transduction pathways leading to fibrogenesis? 1145 11

The Smad proteins are key intracellular effectors of transforming growth factor-beta (TGF-beta) cytokines. The ability of Smads to modulate transcription results from a functional cooperativity with the coactivators p300/cAMP-response element-binding protein-binding protein (CBP), or the corepressors TGIF and Ski. The c-Jun N-terminal kinase (JNK) pathway, another downstream target activated by TGF-beta receptors, has also been suggested to inhibit TGF-beta signaling through interaction of c-Jun with Smad2 and Smad3. Here we show that c-Jun directly interacts with Ski to enhance the association of Ski with Smad2 in the basal state. Interestingly, TGF-beta signaling induces dissociation of c-Jun from Ski, thereby relieving active repression by c-Jun. Moreover, activation of JNK pathway suppressed the ability of TGF-beta to induce dissociation of c-Jun from ski. Thus, the formation of a c-Jun/Ski complex maintains the repressed state of Smad2-responsive genes in the absence of ligand and participates in negative feedback regulation of TGF-beta signaling by the JNK cascade.
...
PMID:c-Jun associates with the oncoprotein Ski and suppresses Smad2 transcriptional activity. 1203 30

Transforming growth factor (TGF)-beta1 acts as a potent growth inhibitor of prostate epithelial cells, and aberrant function of its receptor type I and II correlates with tumor aggressiveness. However, intracellular and serum TGF-beta1 levels are elevated in prostate cancer patients and further increased in patients with metastatic carcinoma, suggesting the oncogenic switch of TGF-beta1 role in prostate tumorigenesis. Recently, we reported the mitogenic conversion of TGF-beta1 effect by oncogenic Ha-Ras in prostate cancer cells. Here, we show that TGF-beta1 activates interleukin (IL)-6, which has been implicated in the malignant progression of prostate cancers, via multiple signaling pathways including Smad2, nuclear factor-kappaB (NF-kappaB), JNK, and Ras. TGF-beta1-induced IL-6 gene expression was strongly inhibited by DN-Smad2 but not by DN-Smad3 while it was further activated by wild-type Smad2 transfection. IL-6 activation by TGF-beta1 was accompanied by nuclear translocation of NF-kappaB, which was blocked by the p38 inhibitors SB202190 and SB203580 or by IkappaBalphaDeltaN transfection, indicating the crucial role for the p38-NF-kappaB signaling in TGF-beta1 induction of IL-6. TGF-beta1 activated c-Jun phosphorylation, and IL-6 induction by TGF-beta1 was severely impeded by DN-c-Jun and DN-JNK or AP-1 inhibitor curcumin, showing that the JNK-c-Jun-AP-1 signaling plays a pivotal role in TGF-beta1 stimulation of IL-6. It was also found that the Ras-Raf-MEK1 cascade is activated by TGF-beta1 and participates in the TGF-beta1 induction of IL-6 in an AP-1-dependent manner. Cotransfection assays demonstrated that TGF-beta1 stimulation of IL-6 results from the synergistic collaboration of the Smad2, p38-NF-kappaB, JNK-c-Jun-AP-1, or Ras-Raf-MEK1 cascades. In addition, a time course IL-6 decay revealed that mRNA stability of IL-6 is modestly increased by TGF-beta1, indicating that TGF-beta1 also regulates IL-6 at the post-transcriptional level. Intriguingly, IL-6 inactivation restored the sensitivity to TGF-beta1-mediated growth arrest and apoptosis, suggesting that elevated IL-6 in advanced prostate tumors might act as a resistance factor against TGF-beta1. Collectively, our data demonstrate that IL-6 expression is stimulated by tumor-producing TGF-beta1 in human prostate cancer cells through multiple signaling pathways including Smad2, p38, JNK, and Ras, and enhanced expression of IL-6 could contribute to the oncogenic switch of TGF-beta1 role for prostate tumorigenesis, in part by counteracting its growth suppression function.
...
PMID:Transforming growth factor-beta1 activates interleukin-6 expression in prostate cancer cells through the synergistic collaboration of the Smad2, p38-NF-kappaB, JNK, and Ras signaling pathways. 1285 69

In the course of screening for inhibitors of transforming-growth factor-beta (TGF-beta) functions we found that conophylline, a vinca alkaloid, inhibited TGF-beta-induced apoptosis in rat hepatoma cells. Because conophylline also inhibited TGF-b-induced promoter activity in mink lung cells, we studied the mechanism of the inhibition in this cell line. Conophylline did not inhibit nuclear translocation of Smad2. Instead, we found that conophylline increased the expression of c-Jun, which had been earlier shown to interact with the corepressor TGIF to suppress the transcriptional activity dependent on Smad2. Conophylline attenuated the interaction between the Smad2 complex and p300 but enhanced that between the Smad2 complex and TGIF. In cells overexpressing c-Jun, suppression of promoter activity induced by TGF-beta and the enhancement of the association of the Smad2 complex with TGIF were also observed. Thus, our data suggest that inhibition of TGF-beta-induced promoter activity by conophylline can be attributed to its potency in modulating the interaction of downstream transcriptional factors via upregulation of c-Jun expression.
...
PMID:Suppression of TGF-beta signaling by conophylline via upregulation of c-Jun expression. 1462 94

The role of transforming growth factor beta (TGF-beta) in carcinogenesis is complex, with tumor suppressor and pro-oncogenic activities depending on the particular tumor cell and its stage in malignant progression. We previously have demonstrated in breast cancer cell lines that Smad2/3 signaling played a dominant role in mediating tumor suppressor effects on well-differentiated breast cancer cell lines grown as xenografts and prometastatic effects on a more invasive, metastatic cell line. Our present data based on selective interference with activation of endogenous Smad2 and Smad3 by stable expression of a mutant form of the TGF-beta type I receptor (RImL45) unable to bind Smad2/3 but with a functional kinase again show that reduction in Smad2/3 signaling by expression of RImL45 enhanced the malignancy of xenografted tumors of the well-differentiated MCF10A-derived tumor cell line MCF10CA1h, resulting in formation of larger tumors with a higher proliferative index and more malignant histologic features. In contrast, expression of RImL45 in the more aggressive MCF10CA1a cell line strongly suppressed formation of lung metastases following tail vein injection. These results suggest a causal, dominant role for the endogenous Smad2/3 signaling pathway in the tumor suppressor and prometastatic activities of TGF-beta in these cells. Using an in vitro assay, we further show that non-Smad signaling pathways, including p38 and c-Jun NH(2)-terminal kinase, cooperate with TGF-beta/Smads in enhancing migration of metastatic MCF10CA1a cells, but that, although necessary for migration, these other pathways are not sufficient for metastasis.
...
PMID:Smad-binding defective mutant of transforming growth factor beta type I receptor enhances tumorigenesis but suppresses metastasis of breast cancer cell lines. 1523 62

TGF-beta 1 is an antiproliferative and apoptogenic factor for mammary epithelial cells (MEC) acting in an auto/paracrine manner and thus considered an important local regulator of mammary tissue involution. However, the apoptogenic signaling pathway induced by this cytokine in bovine MEC remains obscure. The present study was focused on identification of molecules involved in apoptogenic signaling of transforming growth factor-beta 1 (TGF-beta 1) in the model of bovine mammary epithelial cell line (BME-UV1). Laser scanning cytometry (LSC), Western blot and electrophoretic mobility shift assay (EMSA) were used for analysis of expression and activity of TGF-beta 1-related signaling molecules. The earliest response occurring within 1-2 h after TGF-beta 1 administration was an induction and activation of R-Smads (Smad2 and Smad3) and Co-Smad (Smad4). An evident formation of Smad-DNA complexes began from 2nd hour after MEC exposure to TGF-beta 1. Similarly to Smads, proteins of AP1 complex: phosphorylated c-Jun and JunD appeared to be early reactive molecules; however, an increase in their expression was detected only in cytosolic fraction. In the next step, an increase of IGF binding protein-3 (IGFBP-3) and IGFBP-4 expression was observed from 6th hour followed by a decrease in the activity of protein kinase B (PKB/Akt), which occurred after 24 h of MEC exposure to TGF-beta 1. The decrease in PKB/Akt activity coincided in time with the decline of phosphorylated Bad expression (inactive form). Present study supported additional evidence that stimulation of insulin-like growth factor I (IGF-I) was associated with complete abrogation of TGF-beta 1-induced activation of Bad and Bax and in the consequence protection against apoptosis. In conclusion, apoptotic effect of TGF-beta 1 in bovine MEC is mediated by IGFBPs and occurs through IGF-I sequestration, resulting in inhibition of PKB/Akt-dependent survival pathway.
...
PMID:IGF-binding proteins mediate TGF-beta 1-induced apoptosis in bovine mammary epithelial BME-UV1 cells. 1555 67

Conversion of normal epithelial cells to tumors is associated with a shift in transforming growth factor-beta (TGF-beta) function: reduction of tumor suppressor activity and increase of oncogenic activity. However, specific mechanisms of this functional alteration during human colorectal carcinogenesis remain to be elucidated. TGF-beta signaling involves Smad2/3 phosphorylated at linker regions (pSmad2/3L) and COOH-terminal regions (pSmad2/3C). Using antibodies specific to each phosphorylation site, we herein showed that Smad2 and Smad3 were phosphorylated at COOH-terminal regions but not at linker regions in normal colorectal epithelial cells and that pSmad2/3C were located predominantly in their nuclei. However, the linker regions of Smad2 and Smad3 were phosphorylated in 31 sporadic colorectal adenocarcinomas. In particular, late-stage invasive and metastatic cancers typically showed a high degree of phosphorylation of Smad2/3L. Their extent of phosphorylation in 11 adenomas was intermediate between those in normal epithelial cells and adenocarcinomas. Whereas pSmad2L remained in the cytoplasm, pSmad3L was located exclusively in the nuclei of Ki-67-immunoreactive adenocarcinomas. In contrast, pSmad3C gradually decreased as the tumor stage progressed. Activated c-Jun NH(2)-terminal kinase in cancers could directly phosphorylate Smad2/3L. Although Mad homology 2 region sequencing in the Smad4 gene revealed a G/A substitution at codon 361 in one adenocarcinoma, the mutation did not correlate with phosphorylation. No mutations in the type II TGF-beta receptor and Smad2 genes were observed in the tumors. In conclusion, pSmad3C, which favors tumor suppressor activity of TGF-beta, was found to decrease, whereas c-Jun NH(2)-terminal kinase tended to induce the phosphorylation of Smad2/3L in human colorectal adenoma-carcinoma sequence.
...
PMID:Acceleration of Smad2 and Smad3 phosphorylation via c-Jun NH(2)-terminal kinase during human colorectal carcinogenesis. 1566 91

Transforming growth factor beta (TGF-beta) is a multifunctional cytokine involved in the regulation of cell proliferation, differentiation and survival/or apoptosis of many cells. Knock-out experiments in mice for the three isoforms of TGF-beta have demonstrated their importance in regulating inflammation and tissue repair. TGF-beta is implicated in the pathogenesis of human diseases, including tissue fibrosis and carcinogenesis. TGF-beta receptors act through multiple intracellular pathways. Upon binding of TGF-beta with its receptor, receptor-regulated Smad2/3 proteins become phosphorylated and associate with Smad4. Such complex translocates to the nucleus, binds to DNA and regulates transcription of specific genes. Negative regulation of TGF-beta/Smad signalling may occur through the inhibitory Smad6/7. Furthermore, TGF-beta-activated kinase-1 (TAK1) is a component of TGF-beta signalling and activates stress-activated kinases: p38 through MKK6 or MKK3 and c-Jun N-terminal kinases (JNKs) via MKK4. In the brain TGF-beta, normally expressed at the very low level, increases dramatically after injury. Increased mRNA levels of the three TGF-beta isoforms correlate with the degree of malignancy of human gliomas. TGF-betas are secreted as latent precursors requiring activation into the mature form. TGF-beta may contribute to tumour pathogenesis by direct support of tumour growth and influence on local microenvironment, resulting in immunosuppression, induction of angiogenesis, and modification of the extracellular matrix. TGF-beta1,2 may stimulate production of vascular endothelial growth factor (VEGF) as well as plasminogen activator inhibitor (PAI-I), that are involved in vascular remodelling occurring during angiogenesis. Blocking of TGF-beta action inhibits tumour viability, migration, metastases in mammary cancer, melanoma and prostate cancer model. Reduction of TGF-beta production and activity may be a promising target of therapeutic strategies to control tumour growth.
...
PMID:TGF beta signalling and its role in tumour pathogenesis. 1599 Sep 18

1 2 3 4 5 Next >>