Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.56 (caspase-3)
 35,750 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dibutyryl cyclic AMP (DBcAMP) was previously reported to enhance the down-regulation of the retinoblastoma (RB) protein during G1 phase in proliferating primary rat hepatocytes, but to inhibit their entry into S phase and RB phosphorylation. In the present study, DBcAMP was also found to enhance the down-regulation of RB protein in the human hepatoma cells PLC/PRF/5 after hydroxyurea-induced synchronization at G1/S phase. One hour after synchronization, CPP32 activity was detected in the cells and was further enhanced in the presence of DBcAMP. CPP32-specific cleavage of the RB protein was also detected and enhanced by the addition of DBcAMP in a dose-dependent manner. DNA analysis by flow cytometry after serum starvation-induced synchronization at G0/G1 phase revealed that DBcAMP elicited an apoptotic peak after the S phase. Based on these findings, DBcAMP was suspected of inducing apoptosis by RB protein degradation during G1/S transition and thereby inhibit the growth of PLC/PRF/5 cells. Under serum-deficient culture conditions, addition of the CPP32 inhibitor DEVD or the ICE inhibitor YVAD enhanced cell growth but did not abolish the DBcAMP-induced growth inhibition. On the other hand, antisense oligodeoxynucleotides against Bcl-2 mRNA showed a growth inhibitory effect on PLC/PRF/5 cells, but did not show an additive effect on the DBcAMP-induced growth inhibition. DBcAMP itself inhibited bcl-2 protein expression. DBcAMP-induced growth inhibition may be mediated by different mechanisms, including apoptosis.
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PMID:Dibutyryl cyclic AMP-induced enhancement of RB protein degradation in human hepatoma cells. 1069 31

Apoptosis is a cell suicide mechanism that requires the activation of cellular death proteases for its induction. We examined whether the progress of apoptosis involves cleavage of phospholipase C-gamma1 (PLC-gamma1), which plays a pivotal role in mitogenic signaling pathway. Pretreatment of T leukemic Molt-4 cells with PLC inhibitors such as U-73122 or ET-18-OCH(3) potentiated etoposide-induced apoptosis in these cells. PLC-gamma1 was fragmented when Molt-4 cells were treated with several apoptotic stimuli such as etoposide, ceramides, and tumor necrosis factor alpha. Cleavage of PLC-gamma1 was blocked by overexpression of Bcl-2 and by specific inhibitors of caspases such as Z-DEVD-CH(2)F and YVAD-cmk. Purified caspase-3 and caspase-7, group II caspases, cleaved PLC-gamma1 in vitro and generated a cleavage product of the same size as that observed in vivo, suggesting that PLC-gamma1 is cleaved by group II caspases in vivo. From point mutagenesis studies, Ala-Glu-Pro-Asp(770) was identified to be a cleavage site within PLC-gamma1. Epidermal growth factor receptor (EGFR) -induced tyrosine phosphorylation of PLC-gamma1 resulted in resistance to cleavage by caspase-3 in vitro. Furthermore, cleaved PLC-gamma1 could not be tyrosine-phosphorylated by EGFR in vitro. In addition, tyrosine-phosphorylated PLC-gamma1 was not significantly cleaved during etoposide-induced apoptosis in Molt-4 cells. This suggests that the growth factor-induced tyrosine phosphorylation may suppress apoptosis-induced fragmentation of PLC-gamma1. We provide evidence for the biochemical relationship between PLC-gamma1-mediated signal pathway and apoptotic signal pathway, indicating that the defect of PLC-gamma1-mediated signaling pathway can facilitate an apoptotic progression.
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PMID:Proteolytic cleavage of phospholipase C-gamma1 during apoptosis in Molt-4 cells. 1083 29

Arsenic trioxide has recently been shown to inhibit growth and induce apoptosis in acute promyelocytic leukemia (APL), but little is known about the molecular mechanisms mediating these effects. Here we demonstrate that treatment of promonocytic U937 cells with arsenic trioxide leads to G2/M arrest which was associated with a dramatic increase in the levels of cyclin B and cyclin B-dependent kinase and apoptosis. We further show that apoptosis occurs after bcl-2 phosphorylation and caspase-3 activation followed by cleavage of PARP and PLC-gamma1 degradation and DNA fragmentation. The arsenic trioxide-induced apoptosis could be blocked by the protein synthesis inhibitor cycloheximide. In addition, pretreatment of U937 cells with the DNA polymerase inhibitor aphidicolin also blocked apoptosis, but did not cause the arrest of cells in the G2/M phase. The findings suggest that arsenic trioxide exerts its growth-inhibitory effects by modulating expression and/or activity of several key G2/M regulatory proteins. Furthermore, arsenic trioxide-mediated G2/M arrest correlates with the onset of apoptosis.
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PMID:Arsenic trioxide induces G2/M growth arrest and apoptosis after caspase-3 activation and bcl-2 phosphorylation in promonocytic U937 cells. 1152 58

Resveratrol has been shown to induce anti-proliferation and apoptosis of human cancer cell lines. In the present study, we determined the effect of high intracellular levels of the anti-apoptosis protein Bcl-2 on caspase-3 activation, PLC-gamma1 degradation and cytochrome c release during resveratrol-induced apoptosis. For this, we used U937/vector and U937/Bcl-2 cells, which were generated by transfection of the cDNA of the Bcl-2 gene. As compared with U937/vector, U937/Bcl-2 cells exhibited a 4-fold greater expression of Bcl-2. Treatment with 60 or 100 microM resveratrol for 24 h produced morphological features of apoptosis and DNA fragmentation in U937/vector cells, respectively. This was associated with caspase-3 activation and PLC-gamma1 degradation. In contrast, resveratrol-induced caspase-3 activation and PLC-gamma1 degradation and apoptosis were significantly inhibited in U937/Bcl-2 cells. Bcl-2 overexpressing cells exhibited less cytochrome c release and sustained expression levels of the IAP proteins during resveratrol-induced apoptosis. In addition, these findings indicate that Bcl-2 inhibits resveratrol-induced apoptosis by a mechanism that interferes with cytochrome c release and activity of caspase-3 that is involved in the execution of apoptosis.
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PMID:Bcl-2 overexpression attenuates resveratrol-induced apoptosis in U937 cells by inhibition of caspase-3 activity. 1157 2

We observed that N-(4-hydroxyphenyl)retinamide (4HPR), a chemopreventive and chemotherapeutic agent, effectively induced apoptosis in hepatoma cells. Interestingly, Fas-negative (Hep 3B and PLC/PRF/5) hepatoma cells were shown to be more susceptible to apoptosis induced by 4HPR than were Fas-positive (Hep G2 and SK-HEP-1) hepatoma cells. Thus, we explored the mechanisms underlying 4HPR-induced apoptosis in Fas-defective hepatoma cells. Hep 3B cells stably expressing the dominant-negative Fas-associated death domain (dnFADD) showed no alteration in 4HPR drug susceptibility, but when stably expressing E1B19K, Crm A, or dominant-negative FLICE (dnFLICE), Hep 3B cells were resistant, suggesting that 4HPR-induced apoptosis was mediated by caspase-8 activation. Furthermore, apoptosis could be completely blocked by Z-VAD-FMK (a general caspase inhibitor) or by IETD-CHO (a caspase-8 inhibitor), but was only partially blocked by Ac-DEVD-CMK (a caspase-3 inhibitor), by N-acetyl-L-cysteine (NAC) (an antioxidant), by N-acetyl-leucyl-leucyl-norleucinal (ALLN) (a calpain inhibitor I), or by Z-LEHD-FMK (a caspase-9 inhibitor). Time-sequence analysis of the induction of apoptosis by 4HPR revealed that an initial caspase-8 activation was followed by late mitochondrial cytochrome c release and minor caspase-9 activation, which suggested that caspase-8 activation is the primary upstream regulatory point. Activation of Bid or induction of proapoptotic Bax was not observed during apoptosis. In contrast, Bcl-xL expression was decreased during 4HPR-induced apoptosis. Taken together, these results indicate that 4HPR may be a potential chemotherapeutic drug, which is able to induce apoptosis in Fas-defective hepatoma cells through caspase-8 activation.
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PMID:Activation of caspase-8 during N-(4-hydroxyphenyl)retinamide-induced apoptosis in Fas-defective hepatoma cells. 1173 1

Phospholipase C-gamma1 (PLC-gamma1) activation has been reported to enhance cell survival during the cellular response to oxidative stress. We studied the role of protein kinase C (PKC) pathways in mediating PLC-gamma1 survival signalling in oxidative stress by using mouse embryonic fibroblasts genetically deficient in PLC-gamma1 (Plcg1(-/-)) and its wild type (Plcg1(+/+)). PLC-gamma1 was activated by H(2)O(2) treatment in a dose- and time-dependent manner. Activation of PKC was also markedly increased in both cell lines treated with H(2)O(2) (1-5 mM), but with low doses (50-200 microM), PKC activation was considerably decreased in Plcg1(-/-) cells. After treatment with H(2)O(2), PKC-dependent phosphorylation of Bcl-2 and cell viability of Plcg1(-/-) cells decreased dramatically and caspase-3-like activity increased significantly compared with that of the wild-type cells. Furthermore, pretreatment of Plcg1(+/+) cells with PKC-specific inhibitor decreased levels of PKC-dependent Bcl-2 phosphorylation, enhanced caspase-3 activity and their sensitivity to H(2)O(2). On the contrary, treatment of Plcg1(-/-) cells with PKC-specific activator increased the Bcl-2 phosphorylation, decreased caspase-3 activity and improved their survival. These results suggest that PLC-gamma1 mediates survival signalling in oxidative-stress response by PKC-dependent phosphorylation of Bcl-2 and inhibition of caspase-3.
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PMID:Phospholipase C-gamma1 is required for cell survival in oxidative stress by protein kinase C. 1193 70

Glucocorticoid hormones (GCHs) regulate normal and neoplastic lymphocyte development by exerting antiproliferative and/or apoptotic effects. We have previously shown that dexamethasone (DEX)-activated thymocyte apoptosis requires a sequence of events including interaction with the glucocorticoid receptor (GR), phosphatidylinositol-specific phospholipase C (PI-PLC), and acidic sphingomyelinase (aSMase) activation. We analyzed the mechanisms of GCH-activated apoptosis by focusing on GR-associated Src kinase, cytochrome c release, and caspase-8, -9, and -3 activation. We show here that PI-PLC binds to GR-associated Src kinase, as indicated by coimmunoprecipitation experiments. Moreover, DEX treatment induces PI-PLC phosphorylation and activation. DEX-induced PI-PLC phosphorylation, activation, and apoptosis are inhibited by PP1, a Src kinase inhibitor, thus suggesting that Src-mediated PI-PLC activation is involved in DEX-induced apoptosis. Caspase-9, -8, and -3 activation and cytochrome c release can be detected 1 to 2 hours after DEX treatment. Caspase-9 inhibition does not counter cytochrome c release, caspase-8 and caspase-3 activation, and apoptosis. Caspase-8 inhibition counters cytochrome c release, caspase-9 and caspase-3 activation, and apoptosis, thus suggesting that caspase-8 inhibitor can directly inhibit caspase-9 and/or that DEX-induced caspase-8 activation is upstream to mitochondria and can regulate caspase-3 directly or through cytochrome c release and the consequent caspase-9/caspase-3 activation. DEX-induced caspase-8 activation, like ceramide-induced caspase-8 activation, correlates with the formation of Fas-associated death domain protein (FADD)/caspase-8 complex. Caspase-8 activation is countered by the inhibition of macromolecular synthesis and of Src kinase, PI-PLC, and aSMase activation, suggesting it is downstream in the DEX-activated apoptotic pathway of thymocytes.
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PMID:Dexamethasone-induced apoptosis of thymocytes: role of glucocorticoid receptor-associated Src kinase and caspase-8 activation. 1239 59

Previous experiments have shown that emodin is highly active in suppressing the proliferation of several tumor cell lines. However, it is not clear that emodin can induce growth inhibition of hepatoma cells. We have found that emodin induces apoptotic responses in the human hepatocellular carcinoma cell lines (HCC) Mahlavu, PLC/PRF/5 and HepG2. The addition of emodin to these three cell lines led to inhibition of growth in a time- and dose-dependent manner. Emodin generated reactive oxygen species (ROS) in these cells which brought about a reduction of the intracellular mitochondrial transmembrane potential (DeltaPsim), followed by the activation of caspase-9 and caspase-3, leading to DNA fragmentation and apoptosis. Our findings demonstrate that ROS and the resulting oxidative stress play a pivotal role in apoptosis. Preincubation of hepatoma cell lines with the hydrogen peroxide-scavenging enzyme, catalase (CAT) and cyclosporin A (CsA), partially inhibited apoptosis. These results demonstrate that enhancement of generation of ROS, DeltaPsim disruption and caspase activation may be involved in the apoptotic pathway induced by emodin.
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PMID:Induction of apoptosis in hepatocellular carcinoma cell lines by emodin. 1271 64

Genistein, biochanin-A, and daidzein, the predominant soy isoflavones, have been reported to lower the risk of cancer, but it is not known whether they protect against human hepatoma cancer. This study was designed to investigate their effects on cell growth, the cell cycle, and apoptosis induction in the human hepatoma cell lines, HepG2, Hep3B, Huh7, PLC, and HA22T. Genistein, biochanin-A, and daidzein inhibited growth of all five lines in a dose-dependent manner. DNA fragmentation studies and the TUNEL assay demonstrated that isoflavones caused tumor cell death by induction of apoptosis. Activation of caspase-3 and cleavage of the caspase-3 substrate, poly(ADP-ribose)polymerase, was seen in hepatoma cells after 24 hours' exposure to isoflavones. In addition, isoflavone cytotoxicity correlated with downregulation of Bcl-2 and Bcl-XL expression. Synergistic effects of the three isoflavones were observed on cell growth inhibition, apoptosis induction, and anti-apoptotic protein expression. Flow cytometry showed that genistein, but not biochanin-A or daidzein, induced progressive and sustained accumulation of hepatoma cancer cells in the G2/M phase as a result of inhibition of Cdc2 kinase activity. Coapplication of caffeine prevented this cell cycle arrest, but not apoptosis, showing that cell cycle arrest was not necessary for apoptosis. Furthermore, the isoflavones combination also had a significant tumor-suppressive effect in nude mice. These results suggest that isoflavones might be promising agents for the treatment of human hepatoma.
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PMID:Effects of soy isoflavones on apoptosis induction and G2-M arrest in human hepatoma cells involvement of caspase-3 activation, Bcl-2 and Bcl-XL downregulation, and Cdc2 kinase activity. 1279 11

Daunorubicin (DNR) induces apoptosis in the human myeloid leukemia cells by activation of neutral sphingomyelinease and ceramide production. In the present study, we determined the effect of the antiapoptosis protein Bcl-2 on caspase-3 activation, phospholipase C-gamma 1 (PLC-gamma 1) degradation and cytochrome c release during the DNR-induced apoptosis. Treatment with 3 microM DNR for 12 hr produced morphological features of apoptosis and DNA fragmentation in U937 cells, which was associated with caspase-3 activation and PLC-gamma 1 degradation. Induction of apoptosis was also accompanied by release of cytochrome c, down-regulation of X-linked inhibitor of apoptosis protein (XIAP), and inactivation of Akt, which was blocked by the pan-caspase inhibitor z-VAD-fmk. DNR-induced caspase-3 activation, PLC-gamma 1 degradation and apoptosis were significantly attenuated in Bcl-2 overexpressing U937/Bcl-2 cells. Ectopic expression of Bcl-2 appeared to inhibit DNR-induced apoptosis by interfering with inhibition of XIAP and Akt degradation.
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PMID:Bcl-2 overexpression prevents daunorubicin-induced apoptosis through inhibition of XIAP and Akt degradation. 1456 88


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