共查询到20条相似文献,搜索用时 15 毫秒
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We investigated the role of some key regulators of cell cycle in the activation of caspases during apoptosis of insulin-secreting cells after sustained depletion of GTP by a specific inosine 5'-monophosphate dehydrogenase inhibitor, mycophenolic acid (MPA). p21(Waf1/Cip1) was significantly increased following MPA treatment, an event closely correlated with the time course of caspase activation under the same conditions. MPA-induced p21(Waf1/Cip1) was not mediated by p53, since p53 mass was gradually reduced over time of MPA treatment. The increment of p21(Waf1/Cip1) by MPA was further enhanced in the presence of a pan-caspase inhibitor, indicating that the increased p21(Waf1/Cip1) may occur prior to caspase activation. This notion of association of p21(Waf1/Cip1) accumulation with caspase activation and apoptosis was substantiated by using mimosine, a selective p21(Waf1/Cip1) inducer independent of p53. Mimosine, like MPA, also increased p21(Waf1/Cip1), promoted apoptosis and simultaneously increased the activity of caspases. Furthermore, knocking down of p21(Waf1/Cip1) transfection of siRNA duplex inhibited caspase activation and apoptosis due to GTP depletion. In contrast to p21(Waf1/Cip1), a reduction in p27(Kip1) occurred in MPA-treated cells. These results indicate that p21(Waf1/Cip1) may act as an upstream signal to block mitogenesis and activate caspases which in turn contribute to induction of apoptosis. 相似文献
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Induced N- and C-terminal cleavage of p53: a core fragment of p53, generated by interaction with damaged DNA, promotes cleavage of the N-terminus of full-length p53, whereas ssDNA induces C-terminal cleavage of p53. 总被引:7,自引:0,他引:7 下载免费PDF全文
p53 is able to recognize and bind sites of DNA damage and, in some way, damage to cellular DNA activates a p53 response leading to G1 arrest or apoptosis. We have previously shown that 'damaged DNA' induces N-terminal cleavage of p53 to generate p40(DeltaN) and p35 (core) protein products. We now show that the p35 product has protease activity and is able to cleave between residues 23 and 24 of full-length p53 to generate a novel product, p50(DeltaN23). This activity was inhibited by bestatin, an aminopeptidase inhibitor. Residues 23 and 24 lie within the mdm-2 binding domain of p53 and the possibility that p50(DeltaN23) may be resistant to feedback regulation by mdm-2 is discussed. Unexpectedly, interaction with ssDNA induced two further cleavage products of p53, generated by C-terminal cleavage and designated p50(DeltaC) and p40(DeltaC). In vivo generation of a C-terminal cleavage product of endogenous p53 similar in size to p50(DeltaC) correlated with up-regulation of p21 expression in ML-1 cells exposed to either adriamycin or cisplatin. The possible significance of the various p53 cleavage products in relation to the cellular response to DNA damage is discussed. 相似文献
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p53 dephosphorylation and p21Cip1/Waf1 translocation correlate with caspase-3 activation in TGF-β1-induced apoptosis of HuH-7 cells 总被引:3,自引:0,他引:3
Fan G Ma X Wong PY Rodrigues CM Steer CJ 《Apoptosis : an international journal on programmed cell death》2004,9(2):211-221
The p53 tumor suppressor gene product plays an important role in the regulation of apoptosis. Transforming growth factor beta1 (TGF-beta1)-induced apoptosis in hepatic cells is associated with reduced expression of the retinoblastoma protein (pRb) and subsequent E2F-1-activated expression of apoptosis-related genes. In this study, we explored the potential role of p53 in TGF-beta1-induced apoptosis. HuH-7 human hepatoma cells were either synchronized in G1, S and G2/M phases, or treated with 1 nM TGF-beta1. The results indicated that greater than 90% of the TGF-beta1-treated cells were arrested in G1 phase of the cell cycle. This was associated with enhanced p53 dephosphorylation and p21(Cip1/Waf1) expression, which coincided with decreased Cdk2, Cdk4, and cyclin E expression, compared with synchronized G1 cells. In addition, p53 dephosphorylation coincided with caspase-3 activation, and translocation of p21(Cip1/Waf1) and p27(Kip1) into the cytoplasm, all of which were suppressed by caspase inhibition of TGF-beta1-induced apoptosis. Finally, phosphatase inhibition and pRb overexpression partially inhibited p53-mediated apoptosis. In conclusion, the results demonstrated that TGF-beta1-induced p53 dephosphorylation is associated with caspase-3 activation, and cytosolic translocation of p21(Cip1/Waf1) and p27(Kip1), resulting in decreased expression of Cdks and cyclins. Further, p53 appears to mediate TGF-beta1-induced apoptosis downstream of the pRb/E2F-1 pathway. 相似文献
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To examine the p53-mediated biological activities and signalling pathways, we generated stable transfectants of the p53-null IW32 murine erythroleukemia cells expressing the temperature-sensitive p53 mutant DNA, tsp53(val135). Two clones with different levels of p53 protein expression were selected for further characterization. At permissive temperature, clone 1-5 cells differentiated along the erythroid pathway, and clone 3-2 cells that produced greater levels (3.5-fold) of p53 underwent apoptosis. Apoptosis of 3-2 cells was accompanied by mitochondrial cytochrome c release and caspase activation as well as by cleavage of caspase substrates. Bax protein was induced to a similar extent in these clones by wild-type p53; expression of p21(Cip1/Waf1) and p27(Kip1) proteins was also increased. However, significantly lesser extent of induction for both CDK inhibitors was detected in the apoptotic 3-2 clone. The general caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (z-VAD.fmk) blocked the p53-induced apoptosis in 3-2 cells, with a concomitant elevation of p27(Kip1), suggesting that p27(Kip1) protein underwent caspase-dependent proteolysis in the apoptotic 3-2 cells. Together these results linked a pathway involving cytochrome c release, caspase activation and p27(Kip1) degradation to the p53-induced apoptosis in IW32 erythroleukemia cells. 相似文献
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Huang S Shu L Dilling MB Easton J Harwood FC Ichijo H Houghton PJ 《Molecular cell》2003,11(6):1491-1501
Under serum-free conditions, rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), induces apoptosis of cells lacking functional p53. Cells expressing wild-type p53 or p21(Cip1)arrest in G1 and remain viable. In cells lacking functional p53, rapamycin or amino acid deprivation induces rapid and sustained activation of apoptosis signal-regulating kinase 1 (ASK1), c-Jun N-terminal kinase, and elevation of phosphorylated c-Jun that results in apoptosis. This stress response depends on expression of eukaryotic initiation factor 4E binding protein 1 and is suppressed by p21(Cip1) independent of cell cycle arrest. Rapamycin induces p21(Cip1) binding to ASK1, suppressing kinase activity and attenuating cellular stress. These results suggest that inhibition of mTOR triggers a potentially lethal response that is prevented only in cells expressing p21(Cip1). 相似文献
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《Cell cycle (Georgetown, Tex.)》2013,12(10):1305-1311
The functional significance of the cyclin-dependent kinase inhibitor (CDKI) p21Cip1/WAF1 in paclitaxel-mediated lethality was examined in p53-null human leukemia cells (U937 and Jurkat). In these cells, paclitaxel exposure failed to induce p21Cip1/Waf1 expression. Nevertheless, stable expression of U937 cells with a p21Cip1/WAF1 antisense construct blocked paclitaxel-induced G2M arrest and significantly, albeit modestly, increased mitochondrial injury, caspase activation, apoptosis, and loss of clonogenic potential. These protective effects were less than those observed in cells exposed to the antimetabolite ara-C. Consistent with these results, enforced expression of p21Cip1/WAF1 in Jurkat cells transfected with a construct driven by a doxycycline-responsive promoter increased the percentage of cells arrested in G2M, but attenuated paclitaxel-mediated mitochondrial injury and apoptosis. Unexpectedly, enforced expression of p21Cip1/WAF1 diminished paclitaxel-mediated inactivation of ERK, and reduced paclitaxel-induced activation of JNK as well as Bcl-2 phosphorylation. Together, these findings suggest that the CDKI p21Cip1/WAF1 modestly but significantly protects p53-null human leukemia cells from paclitaxel-mediated lethality, and raise the possibility that p21Cip1/WAF1-associated perturbations in signal transduction pathways as well as Bcl-2 phosphorylation status may play a role in this phenomenon. 相似文献
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K Mitsui A Matsumoto S Ohtsuka M Ohtsubo A Yoshimura 《Biochemical and biophysical research communications》1999,264(2):457-464
p21(Cip1/Waf1) inhibits cell-cycle progression by binding to G1 cyclin/CDK complexes and proliferating cell nuclear antigen (PCNA) through its N- and C-terminal domains, respectively. Here, we report a novel p21(Cip1/Waf1)-interacting protein, Ciz1 (for Cip1 interacting zinc finger protein), which contains polyglutamine repeats and glutamine-rich region in the N-terminus as well as three zinc-finger motifs and one MH3 (matrin 3-homologous domain 3) in the C-terminal region. Ciz1 bound to the N-terminal, the CDK2-interacting part of p21(Cip1/Waf1), and the interaction was disrupted by the overexpression of CDK2. A region of about 150 amino acids containing the first zinc-finger motif in Ciz1 was the binding site for p21(Cip1/Waf1). When Ciz1 and p21(Cip1/Waf1) were individually overexpressed in U2-OS cells, they mostly localized in the nucleus. However, coexpression of Ciz1 induced cytoplasmic distribution of p21(Cip1/Waf1). These data indicate that Ciz1 is a unique nuclear protein that regulates the cellular localization of p21(Cip1/Waf1). 相似文献
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Chloramphenicol-induced mitochondrial stress increases p21 expression and prevents cell apoptosis through a p21-dependent pathway 总被引:2,自引:0,他引:2
Pretreatment of HepG2 and H1299 cells with chloramphenicol rendered the cells resistant to mitomycin-induced apoptosis. Both mitomycin-induced caspase 3 activity and PARP activation were also inhibited. The mitochondrial DNA-encoded Cox I protein, but not nuclear-encoded proteins, was down-regulated in chloramphenicol-treated cells. Cellular levels of the p21(waf1/cip1) protein and p21(waf1/cip1) mRNA were increased through a p53-independent pathway, possibly because of the stabilization of p21(waf1/cip1) mRNA in chloramphenicol-treated cells. The p21(waf1/cip1) was redistributed from the perinuclear region to the cytoplasm and co-localized with mitochondrial marker protein. Several morphological changes and activation of the senescence-associated biomarker, SA beta-galactosidase, were observed in these cells. Both p21(waf1/cip1) antisense and small interfering RNA could restore apoptotic-associated caspase 3 activity, PARP activation, and sensitivity to mitomycin-induced apoptosis. Similar effects were seen with other antibiotics that inhibit mitochondrial translation, including minocycline, doxycycline, and clindamycin. These findings suggested that mitochondrial stress causes resistance to apoptosis through a p21-dependent pathway. 相似文献
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Tzu-Yue Shiu Shih-Ming Huang Yu-Lueng Shih Heng-Cheng Chu Wei-Kuo Chang Tsai-Yuan Hsieh 《PloS one》2013,8(4)
Background
Hepatitis C virus (HCV) has been reported to regulate cellular microRNAs. The HCV core protein is considered to be a potential oncoprotein in HCV-related hepatocellular carcinoma, but HCV core-modulated cellular microRNAs are unknown. The HCV core protein regulates p21Waf1/Cip1 expression. However, the mechanism of HCV core-associated p21Waf1/Cip1 regulation remains to be further clarified. Therefore, we attempted to determine whether HCV core-modulated cellular microRNAs play an important role in regulating p21Waf1/Cip1 expression in human hepatoma cells.Methods
Cellular microRNA profiling was investigated in core-overexpressing hepatoma cells using TaqMan low density array. Array data were further confirmed by TaqMan real-time qPCR for single microRNA in core-overexpressing and full-length HCV replicon-expressing cells. The target gene of microRNA was examined by reporter assay. The gene expression was determined by real-time qPCR and Western blotting. Apoptosis was examined by annexin V-FITC apoptosis assay. Cell cycle analysis was performed by propidium iodide staining. Cell proliferation was analyzed by MTT assay.Results
HCV core protein up- or down-regulated some cellular microRNAs in Huh7 cells. HCV core-induced microRNA-345 suppressed p21Waf1/Cip1 gene expression through targeting its 3′ untranslated region in human hepatoma cells. Moreover, the core protein inhibited curcumin-induced apoptosis through p21Waf1/Cip1-targeting microRNA-345 in Huh7 cells.Conclusion and Significance
HCV core protein enhances the expression of microRNA-345 which then down-regulates p21Waf1/Cip1 expression. It is the first time that HCV core protein has ever been shown to suppress p21Waf1/Cip1 gene expression through miR-345 targeting. 相似文献18.
Bo Gao Hai-Lian Shi Xiang Li Shui-Ping Qiu Hui Wu Bei-Bei Zhang Xiao-Jun Wu Zheng-Tao Wang 《Life sciences》2014
Aims
This study aims to investigate the effect and the mechanisms of notoginsenoside Ft1, a natural compound exclusively found in P. notoginseng, on the proliferation and apoptosis of human neuroblastoma SH-SY5Y cells.Main methods
CCK-8 assay was used to assess the cell proliferation. Flow cytometry was performed to measure the cell cycle distribution and cell apoptosis. Hoechst 33258 staining was conducted to confirm the morphological changes of apoptotic cells. Protein expression was detected by western blot analysis and caspase 3 activity was measured by colorimetric assay kit.Key findings
Among the saponins examined, Ft1 showed the best inhibitory effect on cell proliferation of SH-SY5Y cells with IC50 of 45 μM. Ft1 not only arrested the cell cycle at S, G2/M stages, but also promoted cell apoptosis, which was confirmed by Hoechst 33258 staining. Further studies demonstrated that Ft1 up-regulated the protein expressions of cleaved caspase 3, phospho-p53, p21, and cyclin B1, but down-regulated that of Bcl-2. Moreover, Ft1 enhanced the phosphorylation of ERK1/2, JNK and p38 MAPK. However, the phosphorylation of Jak2 and p85 PI3K was reduced by Ft1. Inhibitors of p38 MAPK and ERK1/2 but not JNK abrogated the up-regulated protein expressions of cleaved caspase 3, p21 and down-regulated protein expression of Bcl-2 as well as elevated caspase 3 activity induced by Ft1.Significance
Ft1 arrested the proliferation and elicited the apoptosis of SH-SY5Y cells possibly via p38 MAPK and ERK1/2 pathways, which indicates the potential therapeutic effect of it on human neuroblastoma. 相似文献19.
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