Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P42574 (caspase-3)
 45,978 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

Okadaic acid is a specific inhibitor of serine/threonine protein phosphatase 1 (PP-1) and 2A (PP-2A). The phosphorylation and dephosphorylation at the serine/threonine residues on proteins play important roles in regulating gene expression, cell cycle progression, and apoptosis. In this study, phosphatase inhibitor okadaic acid induces apoptosis in U937 cells via a mechanism that appears to involve caspase 3 activation, but not modulation of Bcl-2, Bax, and Bcl-X(L) expression levels. Treatment with 20 or 40 nM okadaic acid for 24 h produced DNA fragmentation in U937 cells. This was associated with caspase 3 activation and PLC-gamma1 degradation. Okadaic acid-induced caspase 3 activation and PLC-gamma1 degradation and apoptosis were dose-dependent with a maximal effect at a concentration of 40 nM. Moreover, PMA (phorbol myristate acetate), PKC (protein kinase C) activator, protected U937 cells from okadaic acid-induced apoptosis, abrogated okadaic acid-induced caspase 3 activation, and specifically inhibited downregulation of XIAP (X-linked inhibitor of apoptosis) by okadaic acid. PMA cotreated U937 cells exhibited less cytochrome c release and sustained expression levels of the IAP (inhibitor of apoptosis) proteins during okadaic acid-induced apoptosis. In addition, these findings indicate that PMA inhibits okadaic acid-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:Phorbol myristate acetate inhibits okadaic acid-induced apoptosis and downregulation of X-linked inhibitor of apoptosis in U937 cells. 1154 66

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

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. In the present study, we determined the molecular pathways that lead to apoptosis after treatment of cells with arsenic trioxide. Arsenic trioxide treatment of U937 cells leads to apoptosis, which is accompanied by activation of caspase 3 (as measured by decreased levels of the 32 kDa inactive form and increased proteolytic cleavage of PLC-gamma1). The broad-range caspase inhibitor z-VAD-fmk inhibits this induction of apoptosis, supporting a direct link between caspase activation and arsenic trioxide induction of apoptosis. This activation of apoptosis is accompanied by release of cytochrome c, down-regulation of cIAP1, and inactivation of Akt. Bcl-2 overexpression attenuates arsenic trioxide-induced apoptosis in U937 cells by inhibition of caspase 3 activity, but not inhibition of Akt. In addition, arsenic trioxide-induced apoptosis was caused by the generation of reactive oxygen species, which was prevented by antioxidant NAC (N-acetyl-cysteine). Co-treatment with NAC markedly prevented dephosphorylation of Akt, activation of caspase 3, and down-regulation of cIAP1. These data indicate that arsenic trioxide can cause cell damage by inactivating the Akt-related cell survival pathway and generating the reactive oxygen species, providing a new mechanism for arsenic trioxide-induced apoptosis.
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PMID:Arsenic trioxide-induced apoptosis in U937 cells involve generation of reactive oxygen species and inhibition of Akt. 1216 6

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

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a wide range of malignant cells. However, several cancers, including human hepatoma, are resistant to TRAIL. In this study, we analyzed TRAIL-induced pro- and antiapoptotic signaling pathways in human hepatoma cells. Nuclear factor kappa B (NF-kappaB) was found to be a critical TRAIL-induced antiapoptotic factor in the PLC/PRF/5, HepG2, and Hep3B cell lines. TRAIL-induced NF-kappaB activation was preceded by IkappaBalpha kinase (IKK) activation and IkappaBalpha degradation and depended on TRAF2, NF-kappaB-inducing kinase (NIK), IKK1, and IKK2. Accordingly, inhibition of NF-kappaB by adenoviral dominant negative (dn) TRAF2, NIKdn, IKK1dn, IKK2dn, or IkappaBsr sensitized PLC/PRF/5 cells to rhTRAIL, resulting in 40% to 50% cell death after 48 hours as compared with <10% with rhTRAIL alone. Agonistic anti-TRAIL receptor 1 and anti-TRAIL receptor 2 antibodies or combinations of both were equally efficient in inducing apoptosis as rhTRAIL, indicating that decoy receptors did not contribute to resistance toward TRAIL under the conditions of our study. TRAIL-mediated apoptosis depended on FADD, caspase 8 and 3 as demonstrated by the ability of FADDdn, CrmA, and pharmacologic caspase inhibitors to prevent apoptosis. Confocal microscopy showed the onset of the mitochondrial permeability transition (MPT) 5 hours after rhTRAIL plus actinomycin D, which was followed by cytochrome c release. The MPT was critical for TRAIL-induced apoptosis as demonstrated by the ability of pharmacologic MPT inhibitors to completely protect PLC/PRF/5 cells. In conclusion, NF-kappaB prevents TRAIL-induced apoptosis in human hepatoma through a TRAIL-activated TRAF2-NIK-IKK pathway. Inhibition of NF-kappaB unmasks a TRAIL-induced apoptotic signaling cascade that involves FADD, caspase 8, the MPT, and caspase 3.
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PMID:TRAIL-mediated apoptosis requires NF-kappaB inhibition and the mitochondrial permeability transition in human hepatoma cells. 1244 76

Onset of the mitochondrial permeability transition (MPT) causes both necrotic and apoptotic cell death in cultured hepatocytes. Salicylate lowers the threshold for onset of the MPT. In this study, our aim was to determine whether nontoxic concentrations of salicylate potentiate MPT-mediated cell killing. In necrotic killing models to rat hepatocytes, salicylate (1 mM) enhanced calcium ionophore (Br-A23187)- and tert-butylhydroperoxide (t-BuOOH)-induced cell death, which was blocked or delayed by cyclosporin A (CsA, 2 microM), a specific inhibitor of the MPT. In hepatocyte apoptosis induced by tumor necrosis factor-alpha (TNF-alpha), salicylate accelerated cell killing after low-dose TNF-alpha (1 ng/ml), which by itself induced little apoptosis. Salicylate enhancement of apoptosis was associated with onset of the MPT and accelerated caspase 3 activation. Salicylate also augmented killing of MCF-7 human breast tumor cells by etoposide and PLC/PRF/5 human hepatoma cells by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In conclusion, salicylate potentiates both necrotic and apoptotic cell killing by promoting onset of the MPT. Enhancement by salicylate of MPT-dependent apoptosis may play a role in protection by aspirin and other nonsteroidal anti-inflammatory drugs against colon, lung, and breast cancer.
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PMID:Salicylate enhances necrosis and apoptosis mediated by the mitochondrial permeability transition. 1270 Apr 12


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