• Journal of Integrative Natural Science
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• v.7 no.1
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• pp.25-38
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• 2014

Amyloid-${\beta}$-peptide ($A{\beta}$) is important in the pathogenesis of Alzheimer's disease (AD). Calpain ($Ca^{2+}$-dependent protease) and caspase-8 (the initiating caspase for the extrinsic, receptor-mediated apoptosis pathway) have been implicated in $AD/A{\beta}$ toxicity. We found that $A{\beta}$ promoted degradation of calpastatin (the specific endogenous calpain inhibitor); calpastatin degradation was prevented by inhibitors of either calpain or caspase-8. The results implied a cross-talk between the two proteases and suggested that one protease was responsible for the activity of the other one. In neuron-like differentiated PC12 cells, calpain promotes active caspase-8 formation from procaspase-8 via the $A{\beta}$ and CD95 pathways, along with degradation of the procaspase-8 processing inhibitor caspase-8 (FLICE)-like inhibitory protein, short isoform (FLIPS). Inhibition of calpain (by pharmacological inhibitors and by overexpression of calpastatin) prevents the cleavage of procaspase-8 to mature, active caspase-8, and inhibits FLIPS degradation in the $A{\beta}$-treated and CD95-triggered cells. Increased cellular Ca2+ per se results in calpain activation but does not lead to caspase-8 activation or FLIPS degradation. The results suggest that procaspase-8 and FLIPS association with cell membrane receptor complexes is required for calpain-induced caspase-8 activation. The results presented here add to the understanding of the roles of calpain, caspase- 8, and CD95 pathway in $AD/A{\beta}$ toxicity. Calpain-promoted activation of caspase-8 may have implications for other types of CD95-induced cell damage, and for nonapoptotic functions of caspase-8. Inhibition of calpain may be useful for modulating certain caspase-8-dependent processes.

• Journal of Life Science
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• v.27 no.2
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• pp.164-171
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• 2017

Our previous study suggested that S-allylcysteine (SAC) inhibits the proliferation of the human cervical cancer cell line, HeLa, at least in part through the induction of apoptosis and cell cycle arrest. To further analyze the specific molecular mechanism(s) by which SAC mediates its antiproliferative effects, this study examined the role of SAC in regulating the protein expression of initiator caspase (caspase-9), effector caspases (caspase-3 and caspase-7), and poly-ADP-ribose polymerase (PARP) in HeLa. Western blot analysis showed that when cells were treated with 50 mM SAC for 48 hr, the expression of procaspase-3, -7, and -9 and PARP was reduced by 94%, 38%, 95%, and 64%, respectively, as compared to the untreated control. In contrast, the expression of caspase-3, -7, and -9 and cleaved-PARP was markedly increased by SAC treatment. The SAC-mediated changes in the expression of these proteins were correlated with the concomitant inhibition of cellular proliferation by SAC. The cell proliferation assay showed that HeLa treatment with more than 20 mM SAC for 6-48 hr resulted in both concentration- and time-dependent inhibition of cellular proliferation. These results indicate that the SAC-induced antiproliferative effect in HeLa may be mediated at least in part through the activation of caspase-9, followed by the activation of caspase-3 and caspase-7 as well as the inactivation of PARP, thus leading to cellular apoptosis.

• Journal of Microbiology and Biotechnology
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• v.24 no.5
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• pp.719-723
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• 2014

Caspases are a family of cysteine proteases that play an important role in the apoptotic pathway. Caspase-6 is an apoptosis effector that cleaves a variety of cellular substrates. The active form of the enzyme is required for use in research. However, it has been difficult to obtain sufficient quantities of active caspase-6 from Escherichia coli. In the present study, we constructed a caspase-6 with a 23-amino-acid deletion in the pro-domain. This engineered enzyme was expressed as a soluble protein in E. coli and was purified using affinity resin. In vitro enzyme assay and cleavage analysis revealed that the engineered active caspase-6 protein had characteristics similar to those of wild-type caspase-6. This novel method can be a valuable tool for obtaining active caspase-6 that can be used for screening caspase-6-specific substrates, which in turn can be used to elucidate the function of caspase-6 in apoptosis.

• BMB Reports
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• v.37 no.4
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• pp.445-453
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• 2004

We identified apoptosis as being a significant mechanism of toxicity following the exposure of HeLa cell cultures to abrin holotoxin, which is in addition to its inhibition of protein biosynthesis by N-glycosidase activity. The treatment of HeLa cell cultures with abrin resulted in apoptotic cell death, as characterized by morphological and biochemical changes, i.e., cell shrinkage, internucleosomal DNA fragmentation, the occurrence of hypodiploid DNA, chromatin condensation, nuclear breakdown, DNA single strand breaks by TUNEL assay, and phosphatidylserine (PS) externalization. This apoptotic cell death was accompanied by caspase-9 and caspase-3 activation, as indicated by the cleavage of caspase substrates, which was preceded by mitochondrial cytochrome c release. The broad-spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk), prevented abrin-triggered caspase activation and partially abolished apoptotic cell death, but did not affect mitochondrial cytochrome c release. These results suggest that the release of mitochondrial cytochrome c, and the sequential caspase-9 and caspase-3 activations are important events in the signal transduction pathway of abrin-induced apoptotic cell death in the HeLa cell line.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.10
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• pp.5027-5031
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• 2012

This study was conducted to investigate the expression of survivin and caspase 3 in oral squamous cell carcinoma and peritumoral tissue, and possible pathogenesis mechanisms. We used ELISA and western blotting to detect the protein expression levels of survivin and caspase 3 in tissue. In situ hybridization and real-time PCR were applied to assess mRNA expression levels. In this study, 13 tumor samples and 13 peritumoral tissue samples were collected from oral squamous cell carcinoma patients and 10 normal tissue samples obtained from patients without tumor. The result showed that the protein and mRNA expression of survivin in carcinoma was the highest among three types of tissue; following was that in peritumoral tissue. No difference in caspase 3 zymogen between peritumoral tissue and normal tissue could be found, while it was evidently decreased in carcinoma tissue. Activated caspase 3 was detected in normal tissue but could not be identified in peritumoral or carcinoma tissue. Our results indicate that the expression of survivin is apparently elevated in tumoral and peritumoral tissue. Expression of activated caspase 3 was not detected in tumoral tissue and the expression of caspase 3 zymogen was decreased in tumoral tissue. Our findings suggest that survivin may inhibit both synthesis and activation of caspase 3, hence inhibiting cell apoptosis and facililitating eventual development of oral squamous cell carcinoma.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.10
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• pp.5895-5900
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• 2013

Dictamnine (Dic) has the ability to exert cytotoxicity in human cervix, colon, and oral carcinoma cells and dihydroartemisinin (DHA) also has potent anticancer activity on various tumour cell lines. This report explores the molecular mechanisms by which Dic treatment and combination treatment with DHA and Dic cause apoptosis in human lung adenocarcinoma A549 cells. Dic treatment induced concentration- and time-dependent cell death. FCM analysis showed that Dic induced S phase cell cycle arrest at low concentration and cell apoptosis at high concentration in which loss of mitochondrial membrane potential (${\Delta}{\Psi}m$) was not involved. In addition, inhibition of caspase-3 using the specific inhibitor, z-DQMD-fmk, did not attenuate Dic-induced apoptosis, implying that Dic-induced caspase-3-independent apoptosis. Combination treatment with DHA and Dic dramatically increased the apoptotic cell death compared to Dic alone. Interestingly, pretreatment with z-DQMD-fmk significantly attenuated DHA and Dic co-induced apoptosis, implying that caspase-3 plays an important role in Dic and DHA co-induced cell apoptosis. Collectively, we found that Dic induced S phase cell cycle arrest at low concentration and cell apoptosis at high concentration in which mitochondria and caspase were not involved and DHA enhanced Dic induced A549 cell apoptosis via a caspase-dependent pathway.

• Molecules and Cells
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• v.38 no.4
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• pp.349-355
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• 2015

EphA7 has been implicated in the regulation of apoptotic cell death in neural epithelial cells. In this report, we provide evidence that EphA7 interacts with caspase-8 to induce apoptotic cell signaling. First, a pull-down assay using biotinylated ephrinA5-Fc showed that EphA7 co-precipitated with wild type caspase-8 or catalytically inactive caspase-8 mutant. Second, co-transfection of EphA7 with caspase-8 significantly increased the number of cleaved caspase-3 positive apoptotic cells under an experimental condition where transfection of EphA7 or caspase-8 alone did not affect cell viability or apoptosis. EphA4 also had a causative role in inducing apoptotic cell death with caspase-8, whereas EphA8 did not. Third, caspase-8 catalytic activity was essential for the apoptotic signaling cascade, whereas tyrosine kinase activity of the EphA4 receptor was not. Interestingly, we found that kinase-inactive EphA4 was well co-localized at the plasma membrane with catalytically inactive caspase-8, suggesting that an interaction between these mutant proteins was more stable. Finally, we observed that the extracellular region of the EphA7 receptor was critical for interacting with caspase-8, whereas the cytoplasmic region of EphA7 was not. Therefore, we propose that Eph receptors physically associate with a transmembrane protein to form an apoptotic signaling complex and that this unidentified receptor-like protein acts as a biochemical linker between the Eph receptor and caspase-8.

• Journal of Life Science
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• v.10 no.2
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• pp.21-26
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• 2000

Cytokine deprivation-induced apoptosis can abrogate by the appropriate survival factors. Because the mechanism of Interleukin (IL)-2 deprived apoptotic cell death remains unclear, we here show the apoptosis in CTLL2 cells correlates with an increase of the activity of caspase3-like protease(s). Inhibition of caspase3-like protease(s) with caspase protease inhibitors (Z-VAD, Z-EVD, and Z-LPD) blocks typical apoptotic morphological abnormalities in CTLL2 cells. Interestingly, Bcl-{TEX}$X_{L}${/TEX} protein was decreased by IL-2 deprivation in the cells. These results suggest that caspase3-like protease(s), not caspase1, plays an important role in apoptosis execution of CTLL2 cell death.

• Journal of Microbiology and Biotechnology
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• v.24 no.5
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• pp.714-718
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• 2014

Apoptosis is the process of programmed cell death executed by specific proteases, the caspases, which mediate the cleavage of various vital proteins. Elucidating the consequences of this endoproteolytic cleavage is crucial to understanding cell death and other related biological processes. Although a number of possible roles for caspase-6 have been proposed, the identities and functions of proteins that interact with caspase-6 remain uncertain. In this study, we established a cell line expressing tandem affinity purification (TAP)-tagged caspase- 6 and then used LC-MS/MS proteomic analysis to analyze the caspase-6 interactome. Eight candidate caspase-6-interacting proteins were identified. Of these, five proteins (hnRNP-M, DHX38, ASPP2, MTA2, and UACA) were subsequently examined by co-immunoprecipitation for interactions with caspase-6. Thus, we identified two novel members of the caspase-6 interactome: hnRNP-M and MTA2.

• Journal of Integrative Natural Science
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• v.7 no.2
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• pp.87-91
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• 2014

Amyloid beta ($A{\beta}$) peptide has been implicated in the pathogenesis of Alzheimer's disease and has been reported to induce apoptotic death in cell culture. Cysteine Proteases, a family of enzymes known as caspases, mediate cell death in many models of apoptosis. In the present study, we examined the caspase activity and cell death in $A{\beta}$-treated SHSY5Y cells, as an attempt to elucidate the relationship between the type of caspase and $A{\beta}$-induced cell death. $A{\beta}$ at 20 ${\mu}M$ induce activation of caspase-3, 8 and 9 activity, but not the caspase-1. Caspase-3, 8 and 9 were processed by Ab treatment, consistent with the activity assay. Inhibition of the caspase activities by the selective inhibitors, however, marginally affected the cell death induced by $A{\beta}$. Taken together, the results indicate that $A{\beta}$-induced cell death may be independent of caspase activity and rather, the enzymes might be activated as a result of the cell death.