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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyclin-dependent kinase inhibitor p21(Cip1) regulates multiple cellular functions and protects cells from genotoxic and other cellular stresses. Activation of apoptosis signal-regulating kinase 1 (ASK1) induced by inhibition of mTOR signaling leads to sustained phospho-c-Jun that is suppressed in cells with functional p53 or by forced expression of p21(Cip1). Here we show that small deletions of p21(Cip1) around S98 abrogate its association with ASK1 but do not affect binding to Cdk1, hence distinguishing between the cell cycle-regulating functions of p21(Cip1) and its ability to suppress activation of the ASK1/Jun N-terminal protein kinase (JNK) pathway. p21(Cip1) is phosphorylated in vitro by both ASK1 and JNK1 at S98. In vivo phosphorylation of p21(Cip1), predominantly carried out by ASK1, is associated with binding to ASK1 and inactivation of ASK1 kinase function. Binding of p21(Cip1) to ASK1 requires ASK1 kinase function and may involve phosphorylation of S98.
Mol Cell Biol 2007 May
PMID:Negative regulation of ASK1 by p21Cip1 involves a small domain that includes Serine 98 that is phosphorylated by ASK1 in vivo. 1732 29

Dipyrithione (2, 2'-dithiobispyridine-1, 1'-dioxide, PTS2), a pyrithione derivate, is highly bactericidal and fungicidal. In this study we examined its apoptotic effect on HeLa cells. PTS2 induced HeLa cell death in a dose and time dependent manner. ERK1/2 and p38 were markedly activated, but little JNK1/2 activation was detected. Suppression of p38 activation by SB203580 reduced the extent of apoptosis of the HeLa cells and also prevented induction of p21, release of cytochrome c, and cleavage of caspase-3 and PARP. Inhibition of ERK1/2 with PD98059 increased apoptosis, indicating that ERK1/2 activation has an anti-apoptotic effect on PTS2-induced HeLa cell apoptosis. PTS2 also inhibited murine sarcoma 180 and hepatoma 22 tumor growth in an animal tumor model. Our findings indicate that PTS2 possesses anti-tumor activity, that caspase-3 and poly (ADP-ribose) polymerase (PARP) are involved in PTS2-induced HeLa cell apoptosis and that ERK1/2 and p38 have opposing effects on this apoptosis.
Mol Cells 2007 Feb 28
PMID:Opposing effects of ERK and p38 MAP kinases on HeLa cell apoptosis induced by dipyrithione. 1746 9

Shear stress at 1.2 dynes/cm(2) induces stress-activated protein kinase/jun kinase phosphorylation that precedes and causes apoptosis in embryos (Xie et al., 2006b, Biol Reprod). Pipetting embryos is necessary for many protocols, from in vitro fertilization to collecting embryos prior to analyzing gene expression by microarrays. We sought to determine if pipetting upregulates phosphorylated MAPK8/9 (formerly known as stress-activated protein kinase/jun kinase/SAPK/JNK1, 2). We found that phosphorylated MAPK8/9, a marker of MAPK8/9 activation, is upregulated in a dose-dependent manner by pipetting. Whereas embryos with the zona pellucida removed were more sensitive to stress-induced lethality mediated by 1.2 dynes/cm(2) shear force, phosphorylated MAPK8/9 was induced at lower numbers of pipet triturations in hatched embryos at E4.5. E4.5 embryos were more sensitive to induction of MAPK8/9 than unhatched embryos at E2.5 or E3.5. E3.5 embryos also showed a pipetting dose-dependent induction of FOS protein (formerly known as c-fos), a marker of shear stress in many cell types. Phosphorylated MAPK8/9 measured in ex vivo embryos from E1.5 to E4.5 were expressed at low levels. Embryos that had been pipetted sufficiently to induce phosphorylated MAPK8/9 and FOS had the same number of cells as untreated embryos 24 hr later. This suggests that rapid phosphorylation of MAPK8/9 due to transient shear stress does not mediate long-term negative biological outcomes. But, it is possible that techniques requiring multiple handling events would induce MAPK8/9 and cause biological outcomes or that other biological outcomes are affected by low amounts of transient shear stress. This study suggests that embryo handling prior to experimental measurement of signal transduction phosphoproteins, proteins and mRNA should be performed with care. Indeed, it is likely that shear stress may cause rapid transient changes in hundreds of proteins and mRNA.
Mol Reprod Dev 2007 Oct
PMID:Pipetting causes shear stress and elevation of phosphorylated stress-activated protein kinase/jun kinase in preimplantation embryos. 1749 77

Tumor necrosis factor (TNF)-receptor-associated-factor-6 (TRAF6) is an adaptor protein involved in Toll-like receptor (TLR) signaling. Recent studies using macrophages from TRAF6 knockout mice have revealed that TRAF6 is required for TLR7 signaling. However, an essential role of TRAF6 in TLR4 signaling and cytokine production is slightly controversial. Using an RNAi approach to reduce the cellular levels of TRAF6, we tested the role of this adaptor protein on the sensitivity of the various components of the ERK pathway mediated by TLR4 and -7 in Raw264.7, a mouse macrophage cell line. ERK activation in macrophages by TLR4 and -7 is mediated via a MAP3K, called TPL2/COT, which under unstimulated conditions is associated with NF kappa B1 p105, a member of the I kappa B family of proteins. Upon stimulation with TLR ligands, p105 is phosphorylated by I kappa B kinase (IKK) complex and partially degraded, which releases TPL2. The free TPL2 is active and stimulates the ERK pathway via MEK1/2. The free TPL2, however, is also unstable and is targeted for degradation. We demonstrate here that reduced level of TRAF6 ( approximately 80% decrease) in macrophages does not significantly affect any of the components of the TLR4-stimulated ERK pathway, including p105 phosphorylation, TPL2 degradation and ERK1/2 phosphorylation. Surprisingly, however, TLR4-induced JNK1/2 phosphorylation is significantly blocked by TRAF6 knockdown, suggesting that ERK and JNK pathways are differentially sensitive to TRAF6 levels. Furthermore, although TLR4-mediated IKK-induced p105 phosphorylation is not sensitive to TRAF6 knockdown, I kappa B alpha phosphorylation (also, IKK-induced) is significantly blocked, suggesting that TLR4 activation results in a TRAF6-sensitive and -insensitive IKK activation in macrophages. In contrast to TLR4 signaling, TLR7 activation of ERK, JNK pathways and phosphorylation of p105 and I kappa B alpha are completely inhibited in TRAF6 knockdown cells. Compared to the signaling data, while TLR4-induced TNFalpha mRNA expression is not significantly inhibited by TRAF6 knockdown, TLR7-induced TNFalpha mRNA is significantly blocked. In contrast, both TLR4- and TLR7-induced IL6 mRNA are significantly blocked by TRAF6 knockdown. These results suggest that while TRAF6 is absolutely essential for TLR7 activation of ERK, JNK and NF kappa B pathways, TLR4-induced ERK, JNK pathways and IKK-mediated phosphorylation of I kappa B family members as well as cytokine expression are differentially sensitive to the cellular levels of TRAF6. These results have important implications in terms of therapeutic targeting of TRAF6 complexes in diseases where TLR4 and -7 are involved.
Mol Immunol 2007 Jul
PMID:Sensitivity of TLR4- and -7-induced NF kappa B1 p105-TPL2-ERK pathway to TNF-receptor-associated-factor-6 revealed by RNAi in mouse macrophages. 1750 94

The JNK proteins are activated by multiple and diverse stimuli, leading to varied and seemingly contradictory cellular responses. In particular, JNKs have been reported to have a role in the induction of apoptosis, but have also been implicated in enhancing cell survival and proliferation. Thus the JNK proteins seem to represent an archetype of contrariety of intracellular signaling. The opposing roles of JNKs have been attributed to the observation that JNKs activate different substrates based on specific stimulus, cell type or temporal aspects. Because of their analogous expression in apparently almost every tissue, JNK1 and JNK2 have most often been considered to have overlapping or redundant functions. In spite of this assessment, research evidence suggests that the functions of JNKs should be addressed in a manner that differentiates between their precise contributions. Specifically in this review, we examine evidence regarding whether the JNKs proteins might play distinctive roles in cellular processes associated with carcinogenesis.
Mol Carcinog 2007 Aug
PMID:The functional contrariety of JNK. 1753 55

Low calcemic analogs of vitamin D are candidates for differentiation therapy of human myeloid leukemias. We report here that the seco-steroid synthesized to have resistance to intracellular degradation and low calcemia-inducing activity, 1alpha-hydroxymethyl-3beta-16-ene-24,24-difluoro-25-hydroxy-vitamin D(3) (JKF), induces monocytic differentiation in four established human myeloid leukemia cell lines, HL60, U937, THP-1, NB-4, and murine myeloid leukemia cells WEHI-3B D(-). JKF has differentiation-inducing potency which is slightly lower than the physiologically active form of vitamin D, 1,25(OH)(2)vitamin D(3) (1,25D). However, simultaneous addition of carnosic acid (CA), an antioxidant, and SB20190 (SB), an inhibitor of p38MAP kinase, increases the differentiation efficiency of JKF to a level similar to the level observed when 1,25D is used in such combinations. We also show for the first time that SB inhibits the phosphorylation of MAPKAPK2, a downstream target of p38MAPK, but upregulates the phosphorylation of at least one of the isoforms of JNK (p46 JNK1) and of c-jun in all four human myeloid cell lines studied here. These studies indicate that the JNK1 pathway is positively associated with monocytic differentiation of several subtypes of myeloid leukemia cells arrested at different developmental stages. Further, since JKF is less calcemic than 1,25D, the data suggest that JKF combined with CA and SB is likely to have a therapeutic advantage over 1,25D-based experimental regimens for myeloid leukemias.
J Steroid Biochem Mol Biol
PMID:Differentiation-inducing potency of the seco-steroid JK-1624F2-2 can be increased by combination with an antioxidant and a p38MAPK inhibitor which upregulates the JNK pathway. 1758 92

The mechanism of acacetin-induced apoptosis of human breast cancer MCF-7 cells was investigated. Acacetin caused 50% growth inhibition (IC50) of MCF-7 cells at 26.4% 0.7% M over 24 h in the MTT assay. Apoptosis was characterized by DNA fragmentation and an increase of sub-G1 cells and involved activation of caspase-7 and PARP (poly-ADP-ribose polymerase). Maximum caspase 7 activity was observed with 100 microM acacetin for 24 h. Caspase 8 and 9 activation cascades mediated the activation of caspase 7. Acacetin caused a reduction of Bcl-2 expression leading to an increase of the Bax:Bcl-2 ratio. It also caused a loss of mitochondrial membrane potential that induced release of cytochrome c and apoptosis inducing factor (AIF) into the cytoplasm, enhancing ROS generation and subsequently resulting in apoptosis. Pretreatment of cells with N-acetylcysteine (NAC) reduced ROS generation and cell growth inhibition, and pretreatment with NAC or a caspase 8 inhibitor (Z-IETD-FMK) inhibited the acacetin-induced loss of mitochondrial membrane potential and release of cytochrome c and AIF. Stress-activated protein kinase/c-Jun NH4-terminal kinase 1/2 (SAPK/ JNK1/2) and c-Jun were activated by acacetin but extracellular-regulated kinase 1/2 (Erk1/2) nor p38 mitogen-activated protein kinase (MAPK) were not. Our results show that acacetin-induced apoptosis of MCF-7 cells is mediated by caspase activation cascades, ROS generation, mitochondria-mediated cell death signaling and the SAPK/JNK1/2-c-Jun signaling pathway, activated by acacetin-induced ROS generation.
Mol Cells 2007 Aug 31
PMID:Acacetin-induced apoptosis of human breast cancer MCF-7 cells involves caspase cascade, mitochondria-mediated death signaling and SAPK/JNK1/2-c-Jun activation. 1784 3

The aim of this study was to investigate the activation of JNK1/2 signalling pathway and the respective cellular phenotype of H9c2 cardiac myoblasts during two distinct types of oxidative insult. We examined the dose- and time-dependent activation of JNK1/2 pathway by exogenous H2O2, both under transient and sustained stimulation. At 2 h of either sustained or transient treatment, maximal phosphorylation of c-Jun was observed, coincidently with the activation of nuclear JNK1/2; under sustained stress, these phosphorylation levels remained elevated above basal for up to 6 h, whereas under transient stress they declined to basal ones within 4 h of withdrawal. Furthermore, the JNK1/2 selective inhibitor SP600125 abolished the c-jun phosphorylation induced by oxidative stress. Our results using cell viability assays and light microscopy revealed that sustained H2O2 stimulation significantly and time-dependently decreased H9c2 viability, in contrast to transient stimulation; SP600125 (10 microM) abolished cell death induced by sustained as well as cell survival induced by transient oxidative stress. Hoechst staining showed an increase in DNA condensation during sustained, but not during transient stimulation. Moreover, from the antioxidants tested, catalase and superoxide dismutase prevented oxidative stress-induced cell death. Flow cytometry studies reconfirmed that sustained oxidative stress induced apoptosis, whereas transient resulted in the recovery of cardiac myoblasts within 24 h. We conclude that in H9c2 myoblasts, sustained activation of JNK1/2 signalling pathway during oxidative stimulation is followed by an apoptotic phenotype, while transient JNK1/2 activation correlates well with cell survival, suggesting a dual role of this signalling pathway in cell fate determination.
Mol Cell Biochem 2008 Feb
PMID:Transient and sustained oxidative stress differentially activate the JNK1/2 pathway and apoptotic phenotype in H9c2 cells. 1806 May 75

Although it is often assumed that the antitumor effects of nonsteroidal anti-inflammatory drugs (NSAIDs) are due to inhibition of cyclooxgenase (COX) activity, specifically COX-2, there is accumulating evidence that COX-2 independent mechanisms can also play an important role. Studies with sulindac sulfone (Aptosyn) and related derivatives have revealed a novel pathway of tumor growth inhibition and apoptosis mediated by activation of the guanosine 3',5' monophosphate (cGMP)-dependent enzyme protein kinase G (PKG). The present study indicates that concentrations of the NSAIDs celecoxib, indomethacin, and meclofenamic acid that inhibit growth of SW480 human colon cancer cells inhibit subcellular cGMP-phosphodiesterase (PDE) enzymatic activity and in intact cells induce a two- to threefold increase in intracellular levels of cGMP. This is associated with phosphorylation of the protein VASP, a marker of PKG activation, activation of JNK1 and a decrease in cellular levels of cyclin D1; effects seen with other agents that cause activation of PKG in these cells. On the other hand even a high concentration of the COX-2 specific inhibitor rofecoxib (500 microM) did not inhibit growth of SW480 cells. Nor did rofecoxib inhibit cGMP-PDE activity or cause other changes related to PKG activation in these cells. Since activation of the PKG pathways by celecoxib, indomethacin, and meclofenamic acid in this cell culture system required high concentrations of these compounds, it remains to be determined whether activation of this pathway contributes to the in vivo antitumor effects of specific NSAIDs.
Mol Carcinog 2008 Jul
PMID:Celecoxib-induced growth inhibition in SW480 colon cancer cells is associated with activation of protein kinase G. 1816 59

The transcription factor Sp1 is ubiquitously expressed in different cells and thereby regulates the expression of genes involved in many cellular processes. This study reveals that Sp1 was phosphorylated during the mitotic stage in three epithelial tumor cell lines and one glioma cell line. By using different kinase inhibitors, we found that during mitosis in HeLa cells, the c-Jun NH(2)-terminal kinase (JNK) 1 was activated that was then required for the phosphorylation of Sp1. In addition, blockade of the Sp1 phosphorylation via inhibition JNK1 activity in mitosis resulted in the ubiquitination and degradation of Sp1. JNK1 phosphorylated Sp1 at Thr278/739. The Sp1 mutated at Thr278/739 was unstable during mitosis, possessing less transcriptional activity for the 12(S)-lipoxygenase expression and exhibiting a decreased cell growth rate compared with wild-type Sp1 in HeLa cells. In N-methyl-N-nitrosourea-induced mammary tumors, JNK1 activation provided a potential relevance with the accumulation of Sp1. Together, our results indicate that JNK1 activation is necessary to phosphorylate Sp1 and to shield Sp1 from the ubiquitin-dependent degradation pathway during mitosis in tumor cell lines.
Mol Biol Cell 2008 Mar
PMID:Phosphorylation by c-Jun NH2-terminal kinase 1 regulates the stability of transcription factor Sp1 during mitosis. 1819 80


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