Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.25.1 (proteasome)
 28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ubiquitin-proteasome pathway is the principal mechanism for the degradation of short-lived proteins in eukaryotic cells. Recently, proteasome inhibitors have been shown to induce apoptosis in many kinds of human malignant cells. In this study, the mechanism of apoptosis induced by proteasome inhibitor in leukemic cells was examined. Evaluated by MTT assay, treatment of leukemic cells with Z-LLL-CHO, a reversible proteasome inhibitor, induced cell death in a dose-dependent manner. Appearance of the sub G(0)/G(1) fraction of cell cycle observed in flow cytometry assay suggested the induction of apoptosis, which was further proved by typical DNA ladder and morphological study. Western blot displayed the cleavage of bcl-2 into a shortened 22 kD fragment and the decrease in the levels of caspase-3 precursor. A highly sensitive colorimetric assay was employed and the elevation of caspase-3 activity was detected in both cell lines after treatment with Z-LLL-CHO. By comparison, these results showed that the leukemic cell line M-07e and KG-1a, which both express bcl-2 at a relative high level, had different susceptibility to undergo apoptosis induced by Z-LLL-CHO, which possibly due to their different levels of expression and activation of caspase-3 precursor, as well as their different degree of bcl-2 cleavage after treated by Z-LLL-CHO.
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PMID:[Induction of Apoptosis in Leukemic Cells by Inhibiting the Ubiquitin-Proteasome Pathway and Its Possible Mechanism] 1257 13

We report that the expression of mutant G93A copper/zinc superoxide dismutase (SOD1), associated with familial amyotrophic lateral sclerosis, specifically causes a decrease in MTT reduction rate and ATP levels and an increase in both cytosolic and mitochondrial reactive oxygen species (ROS) production in human neuroblastoma SH-SY5Y cells compared to cells overexpressing wild-type SOD1 and untransfected cells. Exposure to N-acetylcysteine lowers ROS production and returns mitochondrial functional assays to control levels. No large aggregates of human SOD1 are detectable under basal growth conditions in any of the investigated cell lines. After proteasome activity inhibition, SOD1 aggregates can be detected exclusively in G93A-SOD1 cells, even though they do not per se enhance cell death compared to control cell lines. Our findings indicate that mitochondrial homeostasis is affected by mutant SOD1-generated ROS independently from the formation of aggregates and that this alteration is reversed by antioxidants.
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PMID:Mitochondrial dysfunction due to mutant copper/zinc superoxide dismutase associated with amyotrophic lateral sclerosis is reversed by N-acetylcysteine. 1290 35

Recent researches indicate that ubiquitin-protea some pathway plays an important role in apoptosis regulation. Proteasome inhibitors induce apoptosis in many kinds of neoplastic cells, thus provide a great opportunity for exploring synergy of proteasome inhibitors and other apoptosis-inducing agents. In this study, the effect of the proteasome inhibitor Z-LLL-CHO combined with etoposide (VP16) on leukemic cell lines M-07e and TF-1 was investigated by MTT assay, trypan blue exclusion, flow cytometry and Western blot. The results showed that the combination of Z-LLL-CHO and VP16 was much more effective than either agents alone in promoting cytotoxicity in both cell lines evaluated. Accumulation of cells in S + G2/M phase of the cell cycle was observed in the cells treated with VP16 and Z-LLL-CHO alone, while apparent increase of sub-G0/G1 fraction was detected in cells treated with combination of the agents. The cleavage of Bcl-2 into a shortened 22 kD fragment was detected in M-07e cells exposed to either agents alone, and the fraction of 22 kD fragment was increased in the cells treated with combination of the agents. In conclusion, the combination of Z-LLL-CHO and VP16 enhanced their individual cytotoxic effect by inducing apoptosis, in which increase of S + G2/M fraction in cell cycle as well as the enhanced cleavage of Bcl-2 are the possible mechanism of the additive effect on leukemic cells by Z-LLL-CHO and VP16.
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PMID:[Enhanced apoptosis-inducing effect of etoposide on leukemic cell lines M-07e and TF-1 by the proteasome inhibitor Z-LLL-CHO]. 1457 42

The aim of this work was to determine whether Hsp70 overexpression via proteasome inhibitor MG132 was able to protect chondrocytes towards mono-iodoacetate (MIA) cytotoxicity both in vitro and in vivo. In vitro, overexpression of Hsp70 via MG132 was significantly able to protect chondrocytes from MIA toxicity (MTT/LDH analyses). Hsp70 essentially mediated this chondroprotective effect as demonstrated by antisense strategy. In vivo, chondrocytic overexpression of Hsp70, after a preventive intra-articular injection of MG132 in rat knee, was sufficient to decrease the severity of OA-induced MIA lesions, as demonstrated histologically and biochemically. In conclusion, intracellular overexpression of Hsp70, through proteasome inhibition, could be an interesting tool in protecting chondrocytes from cellular injuries, either necrotic or apoptotic in nature, and thus might be a novel chondroprotective modality in rat experimental OA.
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PMID:Induction of heat shock protein 70 (Hsp70) by proteasome inhibitor MG 132 protects articular chondrocytes from cellular death in vitro and in vivo. 1529 83

Lithium fluoride thermoluminescent (TL) detectors, with Li-7 isotope and various activators (MTS-7 LiF:Mg,Ti, MTT-7 LiF:Mg,Ti with enhanced Ti concentration and MCP-7 LiF:Mg,Cu,P) were used for dosimetry of heavy charged particles, within the ICHIBAN experiment. The microdosimetric model has been applied to calculate detection efficiency, eta, relative to gamma-ray dose, of these detectors after proton and heavy charged particle (HCP) irradiation for ion charges ranging from Z = 1 to Z = 6 and in the energy range from 0.3 to 20 MeV amu(-1). The calculated ratio eta(MCP-7)/eta(MTS-7) lies in the range between 0.2 and 1.0 for protons and between 0.2 and 0.4 for HCP with Z > 1. The calculated value of eta(MTT-7)/eta(MTS-7) for protons was found range between 1.0 and 1.45 and, for Z > 1, between 1.3 and 2. These relationships can be applied to derive information about the 'effective LET' in an unknown HCP field and to correct the TLD readings for dose evaluation.
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PMID:Dosimetry of heavy charged particles with thermoluminescence detectors--models and applications. 1535 66

Pancreatic cancer remains a highly chemoresistant malignancy. Gemcitabine, the most effective first-line agent available, acts by disrupting cellular replication. Caspases belong to a family of proteases that function as key components of the apoptotic death machinery. We investigated the mechanisms by which gemcitabine blocks proliferation and whether it can induce apoptosis in pancreatic cancer cells. Quiescent pancreatic cancer cells (BxPC-3) were stimulated to proliferate (10% fetal calf serum) with or without gemcitabine, PS-341 (26S proteasome inhibitor), or both. Proliferation was measured by MTT assay and apoptosis by propidium iodine staining. To determine activation of the apoptotic regulatory cell proteins, caspase-3 and cleavage of poly(ADP-ribose)polymerase (PARP) into its 85-kDa fragment were assessed by Western blotting. Gemcitabine at even low doses (10 micromol/L) significantly inhibited cellular proliferation, whereas PS-341 (10 nmol/L) had no effect. With combined treatment, PS-341 potentiated the antiproliferative effects of gemcitabine (P=0.001). At 48 hours, the apoptotic fraction was greatly enhanced by the presence of PS-341 compared with gemcitabine alone. Caspase-3 accumulated as early as 30 minutes and was associated with cleavage of PARP to its apoptotic fragment. Gemcitabine, a nucleoside analogue, may in part exert its antiproliferative effects by directing pancreatic cancer cells to a default pathway of apoptosis. 26S proteasome inhibition potentiates this effect, suggesting its potential clinical value against chemoresistance in pancreatic cancer.
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PMID:Caspase-3 drives apoptosis in pancreatic cancer cells after treatment with gemcitabine. 1558 96

Tetrandrine is an antitumor alkaloid isolated from the root of Stephania tetrandra. We find that micromolar concentrations of tetrandrine irreversibly inhibit the proliferation of human colon carcinoma cells in MTT and clonogenic assays by arresting cells in G(1). Tetrandrine induces G(1) arrest before the restriction point in nocodazole- and serum-starved synchronized HT29 cells, without affecting the G(1)-S transition in aphidicolin-synchronized cells. Tetrandrine-induced G(1) arrest is followed by apoptosis as shown by fluorescence-activated cell sorting, terminal deoxynucleotidyl transferase-mediated nick end labeling, and annexin V staining assays. Tetrandrine-induced early G(1) arrest is mediated by at least three different mechanisms. First, tetrandrine inhibits purified cyclin-dependent kinase 2 (CDK2)/cyclin E and CDK4 without affecting significantly CDK2/cyclin A, CDK1/cyclin B, and CDK6. Second, tetrandrine induces the proteasome-dependent degradation of CDK4, CDK6, cyclin D1, and E2F1. Third, tetrandrine increases the expression of p53 and p21(Cip1) in wild-type p53 HCT116 cells. Collectively, these results show that tetrandrine arrests cells in G(1) by convergent mechanisms, including down-regulation of E2F1 and up-regulation of p53/p21(Cip1).
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PMID:Tetrandrine induces early G1 arrest in human colon carcinoma cells by down-regulating the activity and inducing the degradation of G1-S-specific cyclin-dependent kinases and by inducing p53 and p21Cip1. 1560 77

Treatment of transected distal axons of rat sympathetic neurons in compartmented cultures with MG132 (5 microM) and other inhibitors of proteasome activity, preserved axonal mitochondrial function, assessed by Mitotracker-Orange and MTT staining, for at least 24 h. MG132 similarly protected axons from undergoing branch elimination (pruning) in response to local NGF deprivation. Axons protected by MG132 displayed persistent phosphorylation of Erk1/2, and pharmacological inhibition of MEK activity with U0126 (50 microM) restored rapid axonal degeneration. Therefore, the proteasome does not appear to be necessary as a general effector of protein degradation during axonal degeneration. Rather, the proteasome functions in the regulation of signaling pathways that control axonal survival and degeneration. Specifically, the down-regulation of the MEK/Erk pathway by the proteasome plays roles in Wallerian degeneration of severed axons and axonal pruning in response to local NGF deprivation. Identification of the pathways that regulate axonal survival and degeneration will provide possible target sites for pharmacological treatments of neurodegenerative diseases and traumatic injury.
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PMID:Regulation of Wallerian degeneration and nerve growth factor withdrawal-induced pruning of axons of sympathetic neurons by the proteasome and the MEK/Erk pathway. 1573 34

Polyamines are powerful modulators of both growth and survival in mammalian cells. In this study, we investigated the possibility of attenuating the process of apoptosis in bone marrow stromal cells (BMSCs), which comprise mesenchymal stem cells, by reducing the intracellular levels of polyamines. BMSCs were isolated from rat femurs and expanded for 12 days. At this time, BMSCs were CD34neg, CD45neg, and mostly CD90pos. BMSCs were grown for an additional 2 days in the presence of 1 mM alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, which reduced the content of both putrescine and spermidine by nearly 90%. DFMO treatment progressively slowed down BMSC proliferation, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay, without arresting their growth completely. The effect of polyamine depletion on caspase-3 activity was evaluated in BMSCs after treatment with 500 U/ml tumor necrosis factor-alpha (TNFalpha) and 5 microM MG132, an inhibitor of proteasome. Caspase-3 activity increased linearly over a period of 24-hour stimulation (p<.01), but this augmentation was blunted by 50% after DFMO administration (p<.05). The effect of DFMO on TNFalpha/MG132-induced upregulation of caspase-3 activity was reversed by the addition of 100 microM putrescine, confirming that polyamines were really involved in the apoptotic process. Also, the number of apoptotic BMSCs after TNFalpha/MG132 treatment, as determined by terminal transferase-mediated dUTP nick end-labeling (TUNEL) assay, were threefold reduced after polyamine depletion (p<.05). On the contrary, DFMO did not affect the MG132-mediated increase in p53 abundance, nor its translocation to the nucleus. Thus, polyamine depletion can be considered a useful tool for counteracting programmed cell death in BMSCs without involving the p53 proapoptotic protein.
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PMID:Polyamine depletion reduces TNFalpha/MG132-induced apoptosis in bone marrow stromal cells. 1594 55

The ubiquitin-proteasome system plays a critical role in the regulation of programmed cell death. Proteasome inhibitors induce apoptosis in various cancer cells and have antitumor effects in murine tumor models. In the present study, we investigated whether the cell-permeable proteasome inhibitor MG132 (carbobenzoxyl-L-leucyl-L-leucyl-L-leucinal) reduced the growth of a human pancreatic cancer cell line through induction of apoptosis in vitro. The effects of MG132 (0.125-1.000 microM) on the growth of the human pancreatic cancer cell line BxPC-3 were analyzed by cell count and MTT assay. Apoptosis was determined by FACS analysis after annexin V and propidium iodide staining and the enrichment of intracellular nucleosomes. The proteasome inhibitor MG132 decreased cell growth of the human pancreatic cancer cell line BxPC-3 in a dose- and time-dependent manner. This effect was at least in part mediated by the induction of apoptosis. A combination therapy with standard cytotoxic agents and proteasome inhibitors could potentially be a novel therapeutic strategy in treatment of pancreatic cancer.
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PMID:The proteasome inhibitor MG132 induces apoptosis in human pancreatic cancer cells. 1627 69


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