Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The extracellular microenvironment of tumors differs from most normal tissues. Many tumors have relatively acidic extracellular pH (pHe), although the intracellular pH (pHi) of tumor cells remains normal due to efficient maintenance of a large proton gradient across the membrane. This difference between tumors and normal tissues might be exploited therapeutically by disruption of the mechanisms which regulate pHi, so that tumor cells are killed by intracellular acid-induced injury. To investigate the mechanisms by which intracellular acidification leads to cell death, we have studied the roles of the anti-apoptotic gene bcl-2 and its pro-apoptotic binding partner bax, the Stress Activated Protein Kinases (SAPK/JNK), and the caspase proteases in mediating acid-induced cell death. While expression of bcl-2 in human bladder cancer MGH-U1 cells had no effect on acid-induced death, overexpression of bax enhanced cell death, consistent with its pro-apoptotic function. Inhibition of SAPK, through expression of a dominant negative mutant of its activator, SEK1 protected cells from acid-induced cell death. Caspase activation, as measured by poly (ADP-ribose) polymerase cleavage, was absent after lethal intracellular acidification. Consistent with this observation, inhibition of ICE proteases by the peptide z-VAD.fmk did not protect against acid-induced cell killing. We conclude that acid-induced cell death depends on bax and on SAPK signaling pathways but not on the caspase proteases. Therapeutic manipulation of bax and SAPK may enhance acid-induced tumor cell killing.
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PMID:Inhibition of apoptotic signaling pathways in cancer cells as a mechanism of chemotherapy resistance. 977 Jan 20

We have previously described the expression of a functional full-length trkC transcript for neurotrophin-3 (NT-3) receptor in oligodendroglia (OL) cells (Kumar and de Vellis, 1996). To date, the role of NT-3 and its signal transduction cascade in OL remains poorly defined. We report that the NT-3 responsive population of cells in the OL lineage are the progenitor cells and that the addition of NT-3 results in the autophosphorylation of p145TrkC. Furthermore, NT-3-mediated activation of p21ras and mitogen-activated protein kinase (MAPK), extracellular signal-regulated protein kinase2 (ERK2), were also observed in the progenitor OL cells. These protein tyrosine kinase (PTK)-induced responses were sensitive to the presence of K252a, an inhibitor for tyrosine kinase. We have determined that NT-3 promotes progenitor OL cell commitment to enter into S-phase of cell cycle to initiate DNA synthesis, in a manner similar to platelet-derived growth factor-AA (PDGF-AA). NT-3 thus plays a role in cell proliferation when present alone, while augmenting the proliferation capacity of PDGF-AA as indicated by the nuclear binding activity of the transcription factor, E2F-1. Both the initiation and progression of mitotic events were confirmed by the expression of c-myc and cdc2 in the presence of NT-3, PDGF-AA or NT-3 plus PDGF-AA. A cell survival assay examining interleukin 1-beta-converting enzyme (ICE)-like protease-mediated cleavage of poly (ADP-ribose) polymerase (PARP) revealed an increase in OL progenitor cell death in the absence of NT-3 or PDGF-AA. In corroboration with our in vitro studies, in vivo results show an increased expression of the progenitor OL cell marker, glycerol phosphate dehydrogenase (GPDH) within 48 hr following an intracranial injection of NT-3, PDGF-AA, or NT-3 plus PDGF-AA in PN4-5 rats. These novel findings suggest that PDGF-AA potentiates the OL progenitor cell's ability to enter into the S-phase of the cell cycle and that NT-3 can augment this activity. Furthermore, PDGF-AA and NT-3 can block ICE-like protease-mediated PARP fragmentation in progenitor OL cells. These results provide important information which further delineates the signal transduction cascades and the role of NT-3 and PDGF-AA on OL progenitor cells.
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PMID:NT-3-mediated TrkC receptor activation promotes proliferation and cell survival of rodent progenitor oligodendrocyte cells in vitro and in vivo. 985 59

Anchorage removal like growth factor removal induces apoptosis. In the present study we have characterized signaling pathways that can prevent this cell death using a highly growth factor- and anchorage-dependent line of lung fibroblasts (CCL39). After anchorage removal from exponentially growing cells, annexin V-FITC labeling can be detected after 8 h. Apoptosis was confirmed by analysis of sub-G1 DNA content and Western blotting of the caspase substrate poly (ADP-ribose) polymerase. Growth factor withdrawal accelerates and potentiates suspension-induced cell death. Activation of Raf-1 kinase in suspension cultures of CCL39 or Madin-Darby canine kidney cells stably expressing an estrogen-inducible activated-Raf-1 construct (DeltaRaf-1:ER) suppresses apoptosis induced by growth factor and/or anchorage removal. This protective effect appears to be mediated by the Raf, mitogen- or extracellular signal-regulated kinase kinase (MEK), and mitogen-activated protein kinase module because it is sensitive to pharmacological inhibition of MEK-1 and it can be mimicked by expression of constitutively active MEK-1 in CCL39 cells. Finally, apoptosis induced by disruption of the actin cytoskeleton with the Rho-directed toxin B (Clostridium difficile) is prevented by activation of the DeltaRaf-1:ER chimeric construct. These findings highlight the ability of p42/p44 mitogen-activated protein kinase to generate survival signals that counteract cell death induced by loss of matrix contact, cytoskeletal integrity, and extracellular mitogenic factors.
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PMID:The p42/p44 MAP kinase pathway prevents apoptosis induced by anchorage and serum removal. 1071 23

Tumor necrosis factor (TNF) is a multipotential cytokine that induces apoptosis and activates nuclear factor-kappa B (NF-kappaB), activation protein 1 (AP-1), mitogen-activated protein kinase (MAPK), and c-Jun N-terminal kinase (JNK). Several mechanisms have been suggested to explain these effects of TNF, one of them being the involvement of reactive oxygen intermediates (ROI). Because Bcl-2 family members are known to affect the redox status of the cell, we examined the effect of Bcl-x(L) expression on TNF signaling. Overexpression of Bcl-x(L) in human promyelocytic lymphoma HL-60 cells downregulated TNF-induced cytotoxicity. Cleavage of poly (ADP-ribose) polymerase by caspases, an early indicator of apoptosis, was also blocked by Bcl-x(L) overexpression. Activation of NF-kappaB was significantly suppressed in cells overexpressing Bcl-x(L), as was degradation of IkappaBalpha, the inhibitory subunit of NF-kappaB. NF-kappaB activation induced by serum-activated lipopolysaccharide (SALPS), ceramide, and okadaic acid was also inhibited by overexpression of Bcl-x(L), whereas that by phorbol myristate acetate (PMA) and H2O2 was unaffected. Besides NF-kappaB, the activation of AP-1 by TNF also was blocked by Bcl-x(L). The activation of JNK and MAPK kinase, which regulate these transcription factors, was reduced in Bcl-x(L)-transfected cells. Overall, our results demonstrate that Bcl-x(L) inhibits TNF signaling at an early step common to induction of activation of apoptosis, NF-kappaB, AP-1, MAPK, and JNK.
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PMID:Bcl-x(L) suppresses TNF-mediated apoptosis and activation of nuclear factor-kappaB, activation protein-1, and c-Jun N-terminal kinase. 1095 16

Oxidant-induced neuronal apoptosis has been shown to involve potassium and zinc dysregulation, energetic dysfunction, activation of stress-related kinases, and caspase cleavage. The temporal ordering and interdependence of these events was investigated in primary neuronal cultures exposed to the sulfhydryl oxidizing agent 2,2'-dithiodipyridine (DTDP), a compound that induces the intracellular release of zinc. We previously observed that tetraethylammonium (TEA), high extracellular potassium, or cysteine protease inhibitors block apoptosis induced by DTDP. We now report that both p38 and extracellular signal-regulated kinase phosphorylation are evident in neuronal cultures within 2 hr of a brief exposure to 100 microm DTDP. However, only p38 inhibition is capable of blocking oxidant-induced toxicity. Cyclohexamide or actinomycin D does not attenuate DTDP-induced cell death, suggesting that posttranslational modification of existing targets, rather than transcriptional activation, is responsible for the deleterious effects of p38. Indeed, an early robust increase in TEA-sensitive potassium channel currents induced by DTDP is attenuated by p38 inhibition but not by caspase inhibition. Moreover, we found that activation of p38 is required for caspase 3 and 9 cleavage, suggesting that potassium currents enhancement is required for caspase activation. Finally, we observed that DTDP toxicity could be blocked with niacinamide or benzamide, inhibitors of poly (ADP-ribose) synthetase. Based on these findings, we conclude that oxidation of sulfhydryl groups on intracellular targets results in intracellular zinc release, p38 phosphorylation, enhancement of potassium currents, caspase cleavage, energetic dysfunction, and translationally independent apoptotic cell death.
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PMID:p38 activation is required upstream of potassium current enhancement and caspase cleavage in thiol oxidant-induced neuronal apoptosis. 1133 59

Annonaceous acetogenins have potent antitumor effect in vitro and in vivo. Squamocin is one of the annonaceous acetogenins and has been reported to have antiproliferative effect on cancer cells. Our results from this study showed that squamocin inhibited proliferation of HL-60 cells with IC50 value of 0.17 microg/ml and induced apoptosis of HL-60 cells. Investigation of the mechanism of squamocin-induced apoptosis revealed that treatment of HL-60 cells with squamocin resulted in extensive nuclear condensation. DNA fragmentation, cleavage of the death substrate poly (ADP-ribose) polymerase (PARP) and induction of caspase-3 activity. Pretreatment of HL-60 cells with caspase-3 specific inhibitor DEVD-CHO prevented squamocin-induced DNA fragmentation, PARP cleavage and cell death. The expression levels of protein bcl-2, bax have no change in response to squamocin treatment in HL-60 cells, whereas stress-activated protein kinase (SAPK/JNK) was activated after treatment with squamocin in HL-60 cells. These results suggest that apoptosis of HL-60 cells induced by squamocin requires caspase-3 activation and is related to SAPK activation.
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PMID:Involvement of caspase-3 activation in squamocin-induced apoptosis in leukemia cell line HL-60. 1188 4

Bile acid-induced apoptosis plays an important role in the pathogenesis of cholestatic liver disease, and its prevention is of therapeutic interest. The effects of betaine were studied on taurolithocholate 3-sulfate (TLCS) and glycochenodeoxycholate (GCDC)-induced apoptosis in rat hepatocytes in vitro and in vivo. Hepatocyte apoptosis, caspase activation, and poly (ADP-ribose) polymerase (PARP) cleavage, which are normally observed in response to both bile acids, were largely prevented after preincubation of hepatocytes with betaine. Betaine uptake was required for this protective effect, which was already observed at betaine concentrations of 1 mmol/L. Betaine did not affect the TLCS-induced membrane trafficking of CD95 and tumor necrosis factor-related apoptosis inducing ligand (TRAIL) receptor 2 to the plasma membrane or the TLCS-induced recruitment of Fas-associated death domain (FADD) and caspase 8 to the CD95 receptor. However, betaine largely prevented cytochrome c release and oxidative stress exerted otherwise by TLCS. Inhibition of caspase 9 strongly blunted TLCS-induced caspase-8 activation. Further betaine did not prevent the TLCS-induced c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (Erk), and p38 mitogen-activated protein kinase (p38(MAPK)) activation or TLCS-induced protein kinase B (PKB) dephosphorylation. The protective betaine effect was insensitive to inhibition of Erks by PD089059, of p38(MAPK) by SB203580, or of phosphatidylinositol 3-kinase (PI3-kinase) by LY294002. Betaine supplementation in the drinking water significantly ameliorated in vivo hepatocyte apoptosis following bile duct ligation. In conclusion, this study identifies betaine as a potent protectant against bile acid-induced apoptosis in vivo and in vitro, and its antiapoptotic action largely resides on an inhibition of the proapoptotic mitochondrial pathway.
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PMID:Prevention of bile acid-induced apoptosis by betaine in rat liver. 1229 30

Herpes simplex virus type 1 (HSV-1) triggered apoptosis in hippocampal cultures, as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and immunohistochemistry with antibody specific for the large fragment of activated caspase 3. The levels of phosphorylated (activated) c-Jun N-terminal kinase (JNK) were also increased in HSV-1-infected hippocampal cultures as were the levels of activated c-Jun, its target. JNK activation was involved in HSV-1-induced apoptosis as evidenced by apoptosis inhibition with the JNK inhibitor SP600125. HSV-2 activated the mitogen-activated protein kinase/extracellular regulated protein kinase (MEK/ERK) survival pathway and did not trigger apoptosis in hippocampal cultures. The MEK specific inhibitor U0126 inhibited ERK activation and caused a significant increase in the percent TUNEL(+) cells in HSV-2-infected cultures, indicating that the failure of HSV-2 to trigger apoptosis is due to its ability to activate the MEK/ERK survival pathway. JNK was also activated in brain tissues from patients with HSV-associated acute focal encephalitis (HSE) that were positive for HSV-1 antigen. JNK activation correlated with apoptosis, as determined by immunohistochemistry with antibody to activated caspase 3 or cleaved poly (ADP-ribose) polymerase (PARP). The data suggest that HSE has an apoptotic component that may contribute to disease pathogenesis.
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PMID:Herpes simplex virus type 1-induced encephalitis has an apoptotic component associated with activation of c-Jun N-terminal kinase. 1258 73

Although tamoxifen (TAM), which is widely used in the treatment of breast cancer, also has a beneficial effect on cisplatin-refractory ovarian cancer, the biological mechanism of this effect has remained obscure. TAM, besides its action as an antiestrogen, also inhibits cell proliferation of estrogen receptor (ER)-negative cells by an unknown mechanism. Therefore, we examined the roles of the MAPK family in the antiproliferative effect of TAM on cisplatin-resistant Caov-3, which expresses ER and cisplatin-sensitive A2780, which does not express ER. The number of viable cells was reduced by TAM dose-dependently. TAM induced the activation of ERK, c-Jun N-terminal protein kinase (JNK), and p38 with different time courses. PD98059 canceled the reduction of the number of viable cells by 1 microM TAM and inhibited the TAM-induced cell-cycle arrest at the G(1) phase and dephosphorylation of the retinoblastoma protein. Either expression of dominant-negative JNK or pretreatment with SB203580 canceled the reduction of the number of viable cells by 5 microM TAM and inhibited the apoptotic nuclear changes and the cleavage of poly (ADP-ribose) polymerase induced by TAM. These results provide evidence that whereas the ERK cascade is involved in the induction of cell-cycle arrest at the G(1) phase by lower concentrations of TAM, the JNK or p38 cascade is involved in the induction of apoptosis by higher concentrations of TAM in both types of cells.
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PMID:Tamoxifen inhibits cell proliferation via mitogen-activated protein kinase cascades in human ovarian cancer cell lines in a manner not dependent on the expression of estrogen receptor or the sensitivity to cisplatin. 1464 10

In this study, we examined the effects of isoform-specific functional inhibitors of lysophosphatidic acid acyltransferase (LPAAT), which converts lysophosphatidic acid to phosphatidic acid, on multiple myeloma (MM) cell growth and survival. The LPAAT-beta inhibitors CT-32176, CT-32458, and CT-32615 induced >95% growth inhibition (P < 0.01) in MM.1S, U266, and RPMI8226 MM cell lines, as well as MM cells from patients (IC(50), 50-200 nM). We further characterized this LPAAT-beta inhibitory effect using CT-32615, the most potent inhibitor of MM cell growth. CT-32615 triggered apoptosis in MM cells via caspase-8, caspase-3, caspase-7, and poly (ADP-ribose) polymerase cleavage. Neither interleukin 6 nor insulin-like growth factor I inhibited CT-32615-induced apoptosis. Dexamethasone and immunomodulatory derivatives of thalidomide (IMiDs), but not proteasome inhibitor PS-341, augmented MM cell apoptosis triggered by LPAAT-beta inhibitors. CT-32615-induced apoptosis was associated with phosphorylation of p53 and c-Jun NH(2)-terminal kinase (JNK); conversely, JNK inhibitor SP600125 and dominant-negative JNK inhibited CT-32615-induced apoptosis. Importantly, CT-32615 inhibited tumor necrosis factor-alpha-triggered nuclear factor-kappaB activation but did not affect either tumor necrosis factor-alpha-induced p38 mitogen-activated protein kinase phosphorylation or interleukin 6-triggered signal transducers and activators of transcription 3 phosphorylation. Finally, although binding of MM cells to bone marrow stromal cells augments MM cell growth and protects against dexamethasone-induced apoptosis, CT-32615 induced apoptosis even of adherent MM cells. Our data therefore demonstrate for the first time that inhibiting LPAAT-beta induces cytotoxicity in MM cells in the bone marrow milieu, providing the framework for clinical trials of these novel agents in MM.
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PMID:Antitumor activity of lysophosphatidic acid acyltransferase-beta inhibitors, a novel class of agents, in multiple myeloma. 1467 6


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