Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.62 (caspase-9)
 7,507 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many pro-apoptotic signals activate caspase-9, an initiator protease that activates caspase-3 and downstream caspases to initiate cellular destruction. However, survival signals can impinge on this pathway and suppress apoptosis. Activation of the Ras-Raf-MEK-ERK mitogen-activated protein kinase (MAPK) pathway is associated with protection of cells from apoptosis and inhibition of caspase-3 activation, although the targets are unknown. Here, we show that the ERK MAPK pathway inhibits caspase-9 activity by direct phosphorylation. In mammalian cell extracts, cytochrome c-induced activation of caspases-9 and -3 requires okadaic-acid-sensitive protein phosphatase activity. The opposing protein kinase activity is overcome by treatment with the broad-specificity kinase inhibitor staurosporine or with inhibitors of MEK1/2. Caspase-9 is phosphorylated at Thr 125, a conserved MAPK consensus site targeted by ERK2 in vitro, in a MEK-dependent manner in cells stimulated with epidermal growth factor (EGF) or 12-O-tetradecanoylphorbol-13-acetate (TPA). Phosphorylation at Thr 125 is sufficient to block caspase-9 processing and subsequent caspase-3 activation. We suggest that phosphorylation and inhibition of caspase-9 by ERK promotes cell survival during development and tissue homeostasis. This mechanism may also contribute to tumorigenesis when the ERK MAPK pathway is constitutively activated.
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PMID:Inhibition of caspase-9 through phosphorylation at Thr 125 by ERK MAPK. 1279 50

Sphingolipids are putative intracellular signal mediators in cell differentiation, growth inhibition, and apoptosis. Sphingosine, sphinganine, and phytosphingosine are structural analogs of sphingolipids and are classified as long-chain sphingoid bases. Sphingosine and sphinganine are known to play important roles in apoptosis. In the present study, we examined the phytosphingosine-induced apoptosis mechanism, focusing on mitochondria in human T-cell lymphoma Jurkat cells. Phytosphingosine significantly induced chromatin DNA fragmentation, which is a hallmark of apoptosis. Enzymatic activity measurements of caspases revealed that caspase-3 and caspase-9 are activated in phytosphingosine-induced apoptosis, but there is little activation of caspase-8 suggesting that phytosphingosine influences mitochondrial functions. In agreement with this hypothesis, a decrease in DeltaPsi(m) and the release of cytochrome c to the cytosol were observed upon phytosphingosine treatment. Furthermore, overexpression of mitochondria-localized anti-apoptotic protein Bcl-2 prevented phytosphingosine apoptotic stimuli. Western blot assays revealed that phytosphingosine decreases phosphorylated Akt and p70S6k. Dephosphorylation of Akt was partially inhibited by protein phosphatase inhibitor OA and OA attenuated phytosphingosine-induced apoptosis. Moreover, using a cell-free system, phytosphingosine directly reduced DeltaPsi(m). These results indicate that phytosphingosine perturbs mitochondria both directly and indirectly to induce apoptosis.
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PMID:Phytosphingosine induced mitochondria-involved apoptosis. 1572 52

Recent studies indicate that caspase-2 is involved in the early stage of apoptosis before mitochondrial damage. Although the activation of caspase-2 has been shown to occur in a large protein complex, the mechanisms of caspase-2 activation remain unclear. Here we report a regulatory role of Bcl-2 on caspase-2 upstream of mitochondria. Stress stimuli, including ceramide and etoposide, caused caspase-2 activation, mitochondrial damage followed by downstream caspase-9 and -3 activation, and cell apoptosis in human lung epithelial cell line A549. When A549 cells were pretreated with the caspase-2 inhibitor benzyloxycarbonyl-Val-Asp(-OMe)-Val-Ala-Asp(-OMe)-fluoromethyl ketone or transfected with caspase-2 short interfering RNA, both ceramide- and etoposide-induced mitochondrial damage and apoptosis were blocked. Overexpression of Bcl-2 prevented ceramide- and etoposide-induced caspase-2 activation and mitochondrial apoptosis. Furthermore, caspase-2 was activated when A549 cells were introduced with Bcl-2 short interfering RNA or were treated with Bcl-2 inhibitor, which provided direct evidence of a negative regulatory effect of Bcl-2 on caspase-2. Cell survival was observed when caspase-2 was inhibited in Bcl-2-silencing cells. Blockage of the mitochondrial permeability transition pore and caspase-9 demonstrated that Bcl-2-modulated caspase-2 activity occurred upstream of mitochondria. Further studies showed that Bcl-2 was dephosphorylated at serine 70 after ceramide and etoposide treatment. A protein phosphatase inhibitor, okadaic acid, rescued Bcl-2 dephosphorylation and blocked caspase-2 activation, mitochondrial damage, and cell death. Taken together, ceramide and etoposide induced mitochondria-mediated apoptosis by initiating caspase-2 activation, which was, at least in part, regulated by Bcl-2.
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PMID:Bcl-2 rescues ceramide- and etoposide-induced mitochondrial apoptosis through blockage of caspase-2 activation. 1581 79

Rocaglaol is a cytotoxic cyclopenta[b]benzofuran isolated from the bark of Aglaia crassinervia. It exhibited in vitro cytotoxic activity against Lu1, LNCaP and MCF-7 cells with ED50 values of 13.8, 23.0 and 9.2 nM, respectively. DAPI staining indicated that LNCaP cells treated with rocaglaol underwent apoptosis. In order to determine whether rocaglaol-induced apoptosis is mediated by the mitochondrial pathway, apoptosis-related mitochondrial-associated proteins were studied. Rocaglaol treatment induced Bax expression through 12 to 72 h of exposure, while Bcl-xl expression was slightly decreased through 48 h, and decreased more significantly by 72 h. Cleaved caspase-9 expression was detected at 72 h, and cleaved caspase-7 was increased through 48 to 72 h. Consequently, the large fragment (89 kDa) of PARP resulting from caspase cleavage was detected at 12, 24 and 48 h, and especially at 72 h. Cleaved PARP expression was also detected at 72 h. Since rocaglaol caused dose-dependent G2/M phase arrest of LNCaP cells as indicated by flow cytometric analysis, the protein levels of cell cycle-related genes were measured. Rocaglaol treatment (230 nM) did not change cyclin B after 24- to 60-h treatment. The expression of cdc2 was not changed and phospho-cdc2 (Tyr 15) increased after 36-, 48- and 60-h treatment. In addition, protein phosphatase Cdc25C, which functions as a mitotic activator by dephosphorylation of Cdc2, decreased in a time-dependent manner after rocaglaol treatment. Taken together, these results suggest that rocaglaol is a potent anticancer drug that induces apoptosis of LNCaP cells through the mitochondrial pathway and its G2/M-phase cell cycle arrest is associated with the down-regulation of Cdc25C and the dephosphorylation of Cdc2.
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PMID:Rocaglaol induces apoptosis and cell cycle arrest in LNCaP cells. 1661 91

Survivin, an important member of inhibitor-of-apoptosis (IAP) family, can be up-regulated by various pro-apoptotic stimuli, such as UV, photodynamic therapy (PDT) and cisplatin. High fluence low-power laser irradiation (HF-LPLI) is a newly discovered pro-apoptotic stimulator. The anti-apoptotic mechanism of survivin during HF-LPLI-induced apoptosis is still not investigated. Here, we report that HF-LPLI up-regulates survivin activity through reactive oxygen species (ROS)/cdc25c protein phosphatase (cdc25c)/cyclin-dependent kinase (CDK1) signaling pathway in human lung adenocarcinoma cells (ASTC-a-1). The up-regulation of survivin activity can reduce HF-LPLI-induced apoptosis, while down-regulation of the activity can promote the apoptosis. In addition, activated survivin delays mitochondrial depolarization, cytochrome c release, caspase-9 and Bax activation, all of which are typical pro-apoptotic events of cell apoptosis induced by HF-LPLI. On the basis of the present studies, we conclude that survivin can mediate self-protection during tumor cell apoptosis caused by HF-LPLI.
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PMID:Survivin mediates self-protection through ROS/cdc25c/CDK1 signaling pathway during tumor cell apoptosis induced by high fluence low-power laser irradiation. 2057 6

Gefitinib, a selective epidermal growth factor receptor tyrosine kinase inhibitor, is under clinical testing and use in cancer patients, including glioma. However, the molecular mechanisms involved in gefitinib-mediated anticancer effects against glioma remain largely uncharacterized. Gefitinib inhibits cell growth and induces apoptosis in human glioma cells. Gefitinib also induces death of H4 cells with characteristics of the intrinsic apoptotic pathway, including Bax mitochondrial translocation, mitochondrial outer membrane permeabilization, cytochrome c cytosolic release, and caspase-9/caspase-3 activation. The importance of Bax in mediating gefitinib-induced apoptosis was confirmed by the attenuation of apoptosis by Bax siRNA and Bax channel blocker. Gefitinib caused Bad dephosphorylation, particularly in serine-112, and increased its binding preference to Bcl-2 and Bcl-xL. The dephosphorylation of Bad in gefitinib-treated cells was accompanied by reduced intracellular cyclic AMP content and protein kinase A (PKA) activity. Adenylyl cyclase activator forskolin attenuated, but PKA inhibitor H89 augmented, gefitinib-induced Bad dephosphorylation, Bax mitochondrial translocation, caspase-9/caspase-3 activation, and viability loss. Intriguingly, a nonselective protein phosphatase inhibitor okadaic acid alleviated gefitinib-induced alterations, except Bad dephosphorylation. In parallel with the higher basal PKA activity, response of U87 cells to gefitinib treatment was delayed and relatively resistant compared with that of H4 and T98G cells. Inactivation of PKA sensitized H4, T98G, and U87 cells to gefitinib cytotoxicity, Bad dephosphorylation in serine-112, and caspase-9/caspase-3 activation. Our findings suggest the involvement of the Bad/Bax signaling pathway in gefitinib-induced glioma apoptosis. Furthermore, the inactivation of PKA was shown to play a role in triggering the proapoptotic function of Bad.
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PMID:Gefitinib induces apoptosis in human glioma cells by targeting Bad phosphorylation. 2174 78

Tautomycetin (TMC), originally isolated from Streptomyces griseochromogenes, has been suggested as a potential drug retaining specificity toward colorectal cancer. However, we found that TMC exhibited inhibitory effects on cell proliferation of many cancer cell lines including adriamycin-resistant human breast adenocarcinoma. We investigated its anti-tumor activity and mechanisms in human breast cancer cells for the first time. In this study, we showed that TMC effectively inhibited breast cancer cell proliferation, migration, and invasion. TMC also induced apoptosis in MCF-7 cells. This apoptotic response was in part mediated by Bcl-2 cleavage, leading to the release of cytochrome c, which facilitates binding of Apaf-1 to caspase-9 in its presence and subsequent activation of caspase-7 in apoptosis induction signaling pathways. Furthermore, we identified that TMC induced apoptosis by suppressing Akt signaling pathway activation, which is independent of protein phosphatase PP1 inhibition. The levels of downstream targets of Akt, including phospho-forkhead transcription factor and Bad, were also reduced after TMC treatment. Overall, our results indicate that TMC could be used as a potential drug candidate for breast cancer therapy. More importantly, our study provides new mechanisms for the anticancer effects of TMC.
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PMID:Tautomycetin induces apoptosis by inactivating Akt through a PP1-independent signaling pathway in human breast cancer cells. 2326 38

The aim of the present study was to investigate the effect of Huaier on the proliferation and apoptosis of the MKN45 and SGC7901 gastric cancer cell lines. The MTT assay was used to measure the effects of Huaier on the growth of the cells, while cell cycle distribution and apoptosis levels were analyzed using flow cytometry. Western blotting was used to assess the levels of proteins associated with the apoptotic pathway. It was found that cell survival decreased with the increase in the concentration of Huaier, and the apoptosis rates were increased in a dose-dependent manner both in MKN45 and SGC7901 cells. The number of cells in the G2/M phase in the Huaier-treated groups was increased in a dose-dependent manner compared with that in the control group. Huaier inhibited phosphorylated- (p-)AKT1, phosphatidylinositol 3-kinase (PI3K), pyruvate dehydrogenase kinase isoform 1, p-phosphatidylinositol 3,4,5-trisphosphate 3-phosphatase and dual-specificity protein phosphatase and B-cell lymphoma 2 expression and upregulated cleaved-caspase-9 expression in a dose-dependent manner. In conclusion, Huaier can strongly inhibit gastric cancer cell proliferation by inhibiting cyclin B1 expression, promoting G2/M-phase arrest and modulating the PI3K/AKT signaling pathway, and can induce gastric cancer cell apoptosis by modulating the PI3K/AKT signaling pathway in dose-dependent manner.
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PMID:Effect of Huaier on the proliferation and apoptosis of human gastric cancer cells through modulation of the PI3K/AKT signaling pathway. 2662 67