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 effects of combining histone deacetylase (HDAC) inhibitors and proteasome inhibitors were evaluated in both established glioblastoma multiforme (GBM) cell lines and short-term cultures derived from the Mayo Clinic xenograft GBM panel. Coexposure of LBH589 and bortezomib at minimally toxic doses of either drug alone resulted in a striking induction of apoptosis in established U251, U87, and D37 GBM cell lines, as well as in GBM8, GBM10, GBM12, GBM14, and GBM56 short-term cultured cell lines. Synergism of apoptosis induction was also observed in U251 cells when coexposing cells to other HDAC inhibitors, including LAQ824 and trichostatin A, with the proteasome inhibitor MG132, thus demonstrating a class effect. In U251 cells, bortezomib alone or in combination with LBH589 decreased Raf-1 levels and suppressed Akt and Erk activation. LBH589 or bortezomib alone increased expression of the cell cycle regulators p21 and p27. Additionally, the combination, but not the individual agents, markedly enhanced JNK activation. Synergistic induction of apoptosis after exposure to LBH589 and bortezomib was partially mediated by Bax translocation from the cytosol to the mitochondria resulting from Bax conformational changes. Bax translocation precedes cytochrome c release and apoptosis, and selective down-regulation of Bax using siRNA significantly mitigates the cytotoxicity of LBH589 and bortezomib. This combination regimen warrants further preclinical and possible clinical study for glioma patients.
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PMID:Mitochondrial Bax translocation partially mediates synergistic cytotoxicity between histone deacetylase inhibitors and proteasome inhibitors in glioma cells. 1844

Proteasome inhibitors display potent anti-neoplastic and anti-angiogenic properties both in vitro and in vivo. The mechanisms, however, by which proteasome inhibitors kill tumor cells are still fairly elusive as is the molecular basis of resistance to treatment. To address these questions, we employed a high-throughput Western blotting procedure to analyze changes in a subproteome of approximately 800 proteins in the promyelocytic leukemia cell line HL-60 upon treatment with the proteasome inhibitor PSI (Z-Ile-Glu(OtBu)-Ala-Leu-aldehyde) and correlated the changes of selected target proteins with the changes in two multidrug-resistant HL-60 variants. In total, 105 proteins were upregulated more than 1.5-fold after PSI treatment, while 79 proteins were downregulated. Activation of caspases-3 and -8, modulation of members of the Bcl-2 family as well as stimulation of stress signaling pathways was prominent during HL-60 apoptosis. We also identified changes in the abundance of proteins previously not known to be affected by proteasome inhibitors. In contrast, two multidrug-resistant HL-60 cell lines, overexpressing either MRP1 or P-glycoprotein were largely resistant to PSI-induced apoptosis and could not be resensitized by the pharmacological inhibitors of the drug efflux pumps MK571 or PSC833. Drug resistance was also independent of the upregulation of Bad. Overexpression of multidrug resistance proteins, P-glycoprotein and MRP-1 is thus not sufficient to explain resistance of HL-60 cells to treatment with proteasome inhibitor PSI, which remains more closely related to a low level of Bax expression and to the inability to activate JNK. Alternative routes to the acquisition of resistance to PSI have therefore to be considered.
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PMID:Analysis of changes in the proteome of HL-60 promyeloid leukemia cells induced by the proteasome inhibitor PSI. 1846 79

Sodium 4-phenylbutyrate (4-PBA) has attracted a great deal of attention in cystic fibrosis (CF) pathology due to its capacity to traffic DeltaF508-cystic fibrosis transmembrane conductance regulator (CFTR) to the cell membrane and restore CFTR chloride function at the plasma membrane of CF lung cells in vitro and in vivo. Using two different DeltaF508-CFTR lung epithelial cell lines (CFBE41o- and IB3-1 cells, characterized with DeltaF508-homozygous and heterozygous genotype, respectively) in vitro, 4-PBA induced an increase of proinflammatory cytokine interleukin (IL)-8 production in a concentration-dependent manner. This 4-PBA-induced IL-8 production was associated with a strong reduction of proteasome and nuclear factor-kappaB transcriptional activities in the two DeltaF508-CFTR lung cells either in a resting state or after tumor necrosis factor-alpha stimulation. In contrast, a strong increase of activator protein-1 transcriptional activity was observed. The inhibition of extracellular signal-regulated protein kinase 1/2 (ERK1/2) by 1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio] butadiene (U0126) and 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one (PD98059) and c-Jun-NH(2)-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) by anthra[1,9-cd] pyrazol-6 (2H)-one (SP600125), respectively, was associated with a reduction (2-3.5-fold) of IL-8 production in both DeltaF508-CFTR lung cell lines treated with 4-PBA. No significant change of IL-8 production was observed after an inhibition of p38 MAPK with 4-[4-(4-fluorophenyl)-5-(4-pyridinyl)-1H-imidazol-2-yl] phenol (SB202190). Therefore, we suggest that inhibition of both ERK1/2 and JNK signaling may be a means to strongly reduce 4-PBA-induced IL-8 production in combination with 4-PBA treatment to restore CFTR Cl(-) channel function in lung epithelial cells of patients with CF.
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PMID:Proinflammatory effect of sodium 4-phenylbutyrate in deltaF508-cystic fibrosis transmembrane conductance regulator lung epithelial cells: involvement of extracellular signal-regulated protein kinase 1/2 and c-Jun-NH2-terminal kinase signaling. 1857 3

The conditional kinase DeltaMEKK3:ER allows activation of JNK, p38 and ERK1/2 without overt cellular stress or damage and has proved useful in understanding how these pathways regulate apoptosis and cell cycle progression. We have previously shown that activation of DeltaMEKK3:ER causes a sustained G(1) cell cycle arrest which requires p21(CIP1), with ERK1/2 and p38 cooperating to promote p21(CIP1) expression. In cells lacking p21(CIP1), DeltaMEKK3:ER causes only a transient delay in cell cycle re-entry. We now show that this delay in cell cycle re-entry is due to a reduction in cyclin D1 levels. Activation of DeltaMEKK3:ER promotes the proteasome-dependent turnover of cyclin D1; this requires phosphorylation of threonine 286 (T(286)) and expression of cyclin D1T(286)A rescues the delay in G(1)/S progression. DeltaMEKK3:ER-dependent phosphorylation of T(286) does not appear to be mediated by GSK3beta but requires activation of the ERK1/2 and p38 pathways. ERK1/2 can physically associate with cyclin D1 but activation of ERK1/2 alone is not sufficient for phosphorylation of T(286). Rather, cyclin D1 phosphorylation appears to require coincident activation of ERK1/2 and p38. Thus activation of DeltaMEKK3:ER promotes a sustained G(1) cell cycle arrest by a bipartite mechanism involving the rapid destruction of cyclin D1 and the slower more prolonged expression of p21(CIP1). This has parallels with the bipartite response to ionizing radiation and p53-independent mechanisms of G(1) cell cycle arrest in simple organisms such as yeast.
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PMID:ERK1/2 and p38 cooperate to delay progression through G1 by promoting cyclin D1 protein turnover. 1866 82

The significance of impairment of proteasome activity in PC12 cells was examined in connection with nitrative/nitrosative stress and apoptotic cell death. Treatment of differentiated PC12 cells with MG132, a proteasome inhibitor, elicited a dose- and time-dependent increase in neuronal nitric oxide synthase (nNOS) protein levels, decreased cell viability, and increased cytotoxicity. Viability and cytotoxicity were ameliorated by L-NAME (a broad NOS inhibitor). Nitric oxide/peroxynitrite formation was increased upon treatment of PC12 cells with MG132 and decreased upon treatment with the combination of MG132 and 7-NI (a specific inhibitor of nNOS). The decreases in cell viability appeared to be effected by an activation of JNK and its effect on mitochondrial Bcl-x(L) phosphorylation. These effects are strengthened by the activation of caspase-9 along with increased caspase-3 activity upon treatment of PC12 cells with MG132. These results suggest that impairment of proteasome activity and consequent increases in nNOS levels lead to a nitrative stress that involves the coordinated response of JNK cytosolic signaling and mitochondrion-driven apoptotic pathways.
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PMID:Compromised proteasome degradation elevates neuronal nitric oxide synthase levels and induces apoptotic cell death. 1870 82

Heat shock protein 90 (Hsp90) is an abundantly and ubiquitously expressed chaperone with majority of client proteins which act as signal molecules. Transforming growth factor beta-activated kinase 1 (TAK1) is a mitogen-activated protein kinase kinase kinase (MAPKKK), and is essential in interleukin-1beta (IL-1beta) triggered signaling pathways. In the present study, we found that Hsp90 plays an important role in regulating IL-1beta signaling by keeping TAK1 stability. The results showed that the specific inhibitor geldanamycin (GA) of Hsp90 dramatically inhibited IL-1beta stimulated TAK1-MAPKs and TAK1-nuclear factor-kappaB (NF-kappaB) activation, resulting in the decrease of cyclooxygenase-2 (COX-2) protein expression. Silencing Hsp90 expression through RNA interference (RNAi) also down-regulated TAK1, as well as attenuated IL-1beta induced phosphorylation of c-Jun NH(2)-terminal kinase (JNK) and p38 MAPKs, and degradation of IkappaBalpha. The same results were obtained in T6RZC stable cells which initiated IL-1beta-induced cell signaling at the level of the oligomerization and ubquitination of TNF receptor-associated factor 6 (TRAF6). We further found that Hsp90 formed a complex with TAK1 via its N-terminal domain and GA destabilized TAK1 and induced TAK1 degradation through proteasome pathway. Taken together our results demonstrate that Hsp90 regulates IL-1beta-induced signaling by interacting with TAK1 and maintaining the stability of TAK1, suggesting that Hsp90 might act as the chaperone of TAK1 in immune and inflammatory responses related with IL-1 signal cascades.
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PMID:Heat shock protein 90 (Hsp90) regulates the stability of transforming growth factor beta-activated kinase 1 (TAK1) in interleukin-1beta-induced cell signaling. 1895 Aug 63

Tumor necrosis factor-alpha (TNFalpha) stimulation of hepatocytes induces either cell survival or apoptosis, which seems to be regulated by the ubiquitin-proteasome system. Here we investigated the role of TNFalpha-induced down-modulation of the de-ubiquitinating enzyme USP2 for hepatocyte survival. Inhibition of hepatocyte apoptosis by pre-treatment with TNFalpha (TNFalpha tolerance) was analyzed in the mouse model of galactosamine/TNFalpha-induced liver injury and in actinomycin D/TNFalpha-treated primary mouse hepatocytes. The role of USP2 for TNFalpha-induced hepatocyte survival was studied using small interference RNA or an expression clone. Injection of mice or preincubation of hepatocytes with TNFalpha caused a rapid down-regulation of hepatic USP2-41kD, the predominant USP2 isoform in the liver. In vitro an artificial knockdown of USP2 inhibited actinomycin D/TNFalpha-induced hepatocyte apoptosis, which was associated with elevated levels of the anti-apoptotic protein c-Flip(L/S) and a concomitant decrease of cellular levels of the ubiquitinligase Itch, a negative regulator of c-Flip. USP2-41kD overexpression abrogated TNFalpha tolerance in vitro, prevented accumulation of c-Flip(L/S) and resulted in elevated levels of Itch. Accordingly, c-Flip(L/S) protein levels were elevated in livers of TNFalpha-tolerant mice, which correlated to a switch from JNK and ERK to p38 signaling after galactosamine/TNF re-challenge. Our results indicate that TNFalpha-induced USP2 down-regulation is an effective cytoprotective mechanism in hepatocytes. Hence, USP2 could be a novel pharmacological target, and specific USP2 inhibitors might be potential candidates for the treatment of inflammation-related apoptotic liver damage.
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PMID:Down-regulation of the de-ubiquitinating enzyme ubiquitin-specific protease 2 contributes to tumor necrosis factor-alpha-induced hepatocyte survival. 1900 62

The flexible heteroarotinoid, SHetA2, is a novel compound with apoptosis-inducing and anticancer activities in vitro and in vivo. Our previous research showed that up-regulation of death receptor 5 plays a critical role in the mechanism of SHetA2-induced apoptosis in human lung cancer cells. The hypothesis of this study was that the mechanism of SHetA2-induced apoptosis requires modulation of additional proteins critical for regulation of apoptosis, including cellular FLICE-inhibitory protein (c-FLIP), survivin, X-linked inhibitor of apoptosis, Bcl-2, Bcl-X(L), Bax, and Bim. Western blot analysis showed that c-FLIP and survivin were substantially reduced in all of the tested cell lines exposed to SHetA2 compared with other proteins that were reduced only in a subset of the cell lines tested. Strikingly, overexpression of c-FLIP, but not survivin, protected cells from SHetA2-induced apoptosis and enhancement of TRAIL-initiated apoptosis, although knockdown of endogenous survivin did slightly sensitize cells to SHetA2-induced apoptosis. Consistent with these results, small interfering RNA-mediated reduction of c-FLIP was more effective than survivin down-regulation in triggering apoptosis in these cell lines. SHetA2 increased ubiquitination of c-FLIP and the consequent degradation was abrogated by the proteasome inhibitor MG132. Although SHetA2 treatment led to increased c-Jun phosphorylation, the JNK inhibitor SP600125 did not prevent c-FLIP down-regulation by SHetA2. Thus, it appears that SHetA2 down-regulates c-FLIP levels by facilitating its ubiquitin/proteasome-mediated degradation independent of JNK activation. Collectively, the present study indicates that, in addition to death receptor 5 up-regulation, c-FLIP down-regulation is another important component of flexible heteroarotinoid (SHetA2)-induced apoptosis as well as enhancement of TRAIL-induced apoptosis.
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PMID:Involvement of c-FLIP and survivin down-regulation in flexible heteroarotinoid-induced apoptosis and enhancement of TRAIL-initiated apoptosis in lung cancer cells. 1900 38

Atrogin-1/MAFbx is a major atrophy-related E3 ubiquitin ligase that is expressed specifically in striated muscle. Although the contribution of atrogin-1 to cardiac and muscle hypertrophy/atrophy has been examined extensively, it remains unclear whether atrogin-1 plays an essential role in the simulated ischemia/reperfusion-induced apoptosis of primary cardiomyocytes. Here we showed that atrogin-1 markedly enhanced ischemia/reperfusion-induced apoptosis in cardiomyocytes via activation of JNK signaling. Overexpression of atrogin-1 increased phosphorylation of JNK and c-Jun and decreased phosphorylation of Foxo3a. In addition, atrogin-1 decreased Bcl-2, increased Bax, and enhanced the activation of caspases. Furthermore, JNK inhibitor SP600125 markedly blocked the effect of atrogin-1 on cell apoptosis and the expression of apoptotic-related proteins and caspases. Importantly, atrogin-1 induced sustained activation of JNK through a mechanism that involved degradation of MAPK phosphatase-1 (MKP-1) protein. Atrogin-1 interacted with and triggered MKP-1 for ubiquitin-mediated degradation. In contrast, proteasome inhibitors markedly blocked the degradation of MKP-1. Taken together, these results demonstrate that atrogin-1 promotes degradation of MKP-1 through the ubiquitin-proteasome pathway, thereby leading to persistent activation of JNK signaling and further cardiomyocyte apoptosis following ischemia/reperfusion injury.
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PMID:Atrogin-1/MAFbx enhances simulated ischemia/reperfusion-induced apoptosis in cardiomyocytes through degradation of MAPK phosphatase-1 and sustained JNK activation. 1911 50

Inhibitors of the ubiquitin-proteasome system (UPSIs) promote apoptosis of cancer cells and show encouraging anti-tumor activities in vivo. In this study, we evaluated the death activities of two different UPSIs: bortezomib and the isopeptidase inhibitor G5. To unveil whether these compounds elicit different types of death, we compared their effect both on apoptosis-proficient wild type mouse embryo fibroblasts and on cells defective for apoptosis (double-deficient Bax/Bak mouse embryo fibroblasts) (double knockout; DKO). We have discovered that (i) both inhibitors induce apoptosis in a Bax and Bak-dependent manner, (ii) both inhibitors elicit autophagy in WT and DKO cells, and (iii) only G5 can kill apoptosis-resistant DKO cells by activating a necrotic response. The induction of necrosis was confirmed by different experimental approaches, including time lapse analysis, HMGB1 release, and electron microscopy studies. Neither treatment with antinecrotic agents, such as antioxidants, poly(ADP-ribose) polymerase and JNK inhibitors, necrostatin, and the intracellular Ca(2+) chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester, nor overexpression of Bcl-2 and Bcl-xL prevented necrosis induced by G5. This necrotic death is characterized by the absence of protein oxidation and by the rapid cyclosporin A-independent dissipation of the mitochondrial membrane potential. Notably, a peculiar feature of the G5-induced necrosis is an early and dramatic reorganization of the actin cytoskeleton, coupled to an alteration of cell adhesion. The importance of cell adhesion impairment in the G5-induced necrotic death of DKO cells was confirmed by the antagonist effect of the extracellular matrix-adhesive components, collagen and fibronectin.
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PMID:The Isopeptidase Inhibitor G5 Triggers a Caspase-independent Necrotic Death in Cells Resistant to Apoptosis: A COMPARATIVE STUDY WITH THE PROTEASOME INHIBITOR BORTEZOMIB. 1913 5


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