Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 Nuclear Factor (NF)-kappaB family of transcription factors controls expression of genes which promote cell growth, survival, and neoplastic transformation. Recently we demonstrated aberrant constitutive activation of NF-kappaB in primary human and rat breast cancer specimens and in cell lines. Overexpression of the epidermal growth factor receptor (EGFR) family member Her-2/neu, seen in approximately 30% of breast cancers, is associated with poor prognosis. Previously, Her-2/neu has been shown to signal via a phosphatidylinositol 3 (PI3)-kinase to Akt/protein kinase B (PKB) pathway. Since this signaling pathway was recently shown to activate NF-kappaB, here we have tested the hypothesis that Her-2/neu can activate NF-kappaB in breast cancer. Overexpression of Her-2/neu and EGFR-4 in Ba/F3 cells led to constitutive PI3- and Akt kinase activities, and induction of classical NF-kappaB (p50/p65). Similarly, a tumor cell line and tumors derived from MMTV-Her-2/neu transgenic mice displayed elevated levels of classical NF-kappaB. Engagement of Her-2/neu receptor downregulated the level of NF-kappaB. NF-kappaB binding and activity in the cultured cells was reduced upon inhibition of the PI3- to Akt kinase signaling pathway via ectopic expression of kinase inactive mutants, incubation with wortmannin, or expression of the tumor suppressor phosphatase PTEN. Inhibitors of calpain, but not the proteasome, blocked IkappaB-alpha degradation. Inhibition of Akt did not affect IKK activity. These results indicate that Her-2/neu activates NF-kappaB via a PI3- to Akt kinase signaling pathway that can be inhibited via the tumor suppressor PTEN, and is mediated by calpain rather than the IkappaB kinase complex.
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PMID:Her-2/neu overexpression induces NF-kappaB via a PI3-kinase/Akt pathway involving calpain-mediated degradation of IkappaB-alpha that can be inhibited by the tumor suppressor PTEN. 1131 73

Our previous studies indicated that an alternatively spliced variant mRNA of p40-phox, a cytosolic component of NADPH oxidase, is expressed but its protein is hardly detected in myeloid cells such as promyelocytic HL-60 cells and neutrophils. Here, we have examined the stability of p40-phox variant protein in undifferentiated HL-60 cells. When in vitro-translated proteins were incubated with subcellular fractions of HL-60 cells, p40-phox variant protein but not native p40-phox was degraded by the cytosol and granule fractions. The degradation of variant protein by the granule fraction was observed using sonicated but not intact granules, suggesting that the variant protein is unlikely to be degraded by the granules in intact cells. To identify the enzyme(s) involved, we examined the effects of various enzyme inhibitors on the degradation of variant protein by the cytosol fraction. Degradation was completely inhibited by proline-specific serine protease (prolyl endopeptidase) inhibitors but not by proteasome, calpain, and metalloprotease inhibitors. Furthermore, the variant protein was degraded by a purified prolyl endopeptidase, and the degradation was protected by treating HL-60 cells with a cell-permeable inhibitor (S17092-1) for prolyl endopeptidase. These observations suggest that a cytosolic prolyl endopeptidase is involved in the degradation of p40-phox variant protein in myeloid cells.
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PMID:Involvement of cytosolic prolyl endopeptidase in degradation of p40-phox splice variant protein in myeloid cells. 1140 83

The basic treatment of leishmaniasis consists in the administration of pentavalent antimonials. The mechanisms that contribute to pentavalent antimonial toxicity against the intracellular stage of the parasite (i.e., amastigote) are still unknown. In this study, the combined use of several techniques including DNA fragmentation assay and in situ and cytofluorometry terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling methods and YOPRO-1 staining allowed us to demonstrate that potassium antimonyl tartrate, an Sb(III)-containing drug, was able to induce cell death associated with DNA fragmentation in axenic amastigotes of Leishmania infantum at low concentrations (10 microg/ml). This observation was in close correlation with the toxicity of Sb(III) species against axenic amastigotes (50% inhibitory concentration of 4.75 microg/ml). Despite some similarities to apoptosis, nuclease activation was not a consequence of caspase-1, caspase-3, calpain, cysteine protease, or proteasome activation. Altogether, our results demonstrate that the antileishmanial toxicity of Sb(III) antimonials is associated with parasite oligonucleosomal DNA fragmentation, indicative of the occurrence of late events in the overall process of apoptosis. The elucidation of the biochemical pathways leading to cell death could allow the isolation of new therapeutic targets.
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PMID:Antimonial-mediated DNA fragmentation in Leishmania infantum amastigotes. 1140 24

Dihydrotestosterone (DHT) decreases rat liver alcohol dehydrogenase (ADH) due principally to an increased rate of degradation of the enzyme. The pathway of degradation of ADH was investigated. Exposure of hepatocytes in culture to lactacystin or to MG132, which are inhibitors of the ubiquitin-proteasome pathway of protein degradation, resulted in higher ADH. Furthermore, both lactacystin and MG132 prevented the decrease in ADH caused by DHT. By contrast, the lysosomal proteolytic inhibitors 3-methyladenine and leupeptin as well as inhibitors of the calcium-activated neutral protease calpain system had no effect on ADH in the absence or presence of DHT. ADH isolated by immunoprecipitation from hepatocytes exposed to DHT reacted specifically with anti-ubiquitin antibody. Ubiquitinated ADH was also demonstrated in hepatocytes exposed to MG132. The combination of DHT and MG132 resulted in more ubiquitinated ADH than exposure to either compound alone. These results suggest that the ubiquitin-proteasome pathway plays a role in the degradation of ADH and in the enhanced degradation of this enzyme by DHT.
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PMID:Liver alcohol dehydrogenase is degraded by the ubiquitin-proteasome pathway. 1145 41

Early preneoplastic cells (sup+) exhibit increased susceptibility to apoptosis, which is lost in late stage preneoplastic cells (sup-). Sup+ cells, which undergo apoptosis when cultured in low serum, show little or no DNA binding activity to nuclear factor (NF)-kappa B either in 10% or 0.2% serum. In contrast sup- cells, which are resistant to apoptosis in low serum, show a sustained constitutive activation of NF-kappa B. The constitutive activation of NF-kappa B observed in sup- cells is not due to loss of I kappa B alpha. We considered that the activation of NF-kappa B in sup- cells might be secondary to an increase in cytosolic Ca(2+), since sup- cells have a cytosolic Ca(2+) level that is double that in sup+ cells. In support of a role for Ca(2+), lowering cytosolic Ca(2+) in sup- cells by addition of the cell-permeable Ca(2+) chelator 1,2 bis(O-aminophenoxy)ethane-N, N, N', N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM) reduced cytosolic Ca(2+) by approximately 31% relative to untreated sup- cells, concomitant with a 65% reduction in NF-kappa B DNA binding activity and a reduction in I kappa B kinase (IKK) activity. In sup- cells in low serum, addition of BAPTA-AM also resulted in a significant ( approximately 50%) increase in caspase-3 activity. Raising extracellular Ca(2+) in sup+ cells resulted in a slight activation of I kappa B kinase and in enhanced NF-kappa B DNA binding activity. Using proteasome and calpain inhibitors, we determined that the basal activity of NF-kappa B in sup- cells is largely proteasome-independent, but sensitive to calpain inhibitors. Taken together these data suggest that the elevated Ca(2+) in sup- cells causes a modest activation of IKK, which likely contributes to the enhanced basal activation of NF-kappa B in sup- cells; however, the predominant effect of Ca(2+) appears to be mediated by Ca(2+)-enhanced degradation by calpain.
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PMID:Elevated calcium in preneoplastic cells activates NF-kappa B and confers resistance to apoptosis. 1147 82

Moloney murine leukemia virus (MoMuLV)-ts1-mediated neuronal degeneration in mice is likely due to loss of glial support and release of inflammatory cytokines and neurotoxins from surrounding ts1-infected glial cells including astrocytes. NF-kappaB is a transcription factor that participates in the transcriptional activation of a variety of immune and inflammatory genes. We investigated whether ts1 activates NF-kappaB in astrocytes and examined the mechanism(s) responsible for the activation of NF-kappaB by ts1 infection in vitro. Here we present evidence that ts1 infection of astrocytes in vitro activates NF-kappaB by enhanced proteolysis of the NF-kappaB inhibitors, IkappaBalpha and IkappaBbeta. In in vitro studies using protease inhibitors, IkappaBalpha proteolysis in ts1-infected astrocytes was significantly blocked by a specific calpain inhibitor calpeptin but not by MG-132, a specific proteasome inhibitor, whereas rapid IkappaBbeta proteolysis was blocked by MG-132. Furthermore, treatment with MG-132 increased levels of multiubiquitinated IkappaBbeta protein in ts1-infected astrocytes. These results indicate that the calpain proteolysis is a major mechanism of IkappaBalpha proteolysis in ts1-infected astrocytes. Additionally, ts1 infection of astrocytes in vitro increased expression of inducible nitric oxide synthase (iNOS), a NF-kappaB-dependent gene product. Our results suggest that NF-kappaB activation in ts1-infected astrocytes is mediated by enhanced proteolysis of IkappaBalpha and IkappaBbeta through two different proteolytic pathways, the calpain and ubiquitin-proteasome pathways, resulting in increased expression of iNOS, a NF-kappaB-dependent gene.
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PMID:Enhanced proteolysis of IkappaBalpha and IkappaBbeta proteins in astrocytes by Moloney murine leukemia virus (MoMuLV)-ts1 infection: a potential mechanism of NF-kappaB activation. 1158 19

The goal of the current study was to examine the role of the ubiquitin-proteasome system (UPS), a pathway of intracellular degradation, in the regulation of fetal fibronectin (FFN) expression in human placenta. Primary cultures of cytotrophoblasts (CTs) and placental mesenchymal cells (PMCs) were isolated from human term placentas and were maintained in serum-free medium (SFM) in the presence of inhibitors of proteasome-mediated degradation (e.g., MG132) as well as inhibitors of other proteases. Levels of secreted FFN and interleukin (IL)-8 in culture media were quantitated by enzyme-linked immunosorbent assay (ELISA), and cell viability was assessed by trypan blue exclusion. Intracellular levels of FFN and ubiquinated proteins were measured by Western blotting, and levels of fibronectin mRNA were determined following Northern blotting. We found that proteasome inhibitors (MG132, MG262, and PSI) potently suppressed levels of secreted FFN in cultures of CTs, but they not did affect levels of IL-8. Lysosomal, calpain, and serine protease inhibitors as well as the anti-inflammatory compound sulfasalazine did not markedly affect levels of secreted FFN in CT cultures. Proteasome inhibitors did not compromise cell viability during the initial 16-18 hours of treatment and did not affect intracellular levels of FFN protein or fibronectin mRNA. The efficacy of suppression of FFN in CT culture media by proteasome inhibitors reflected their effects on intracellular accumulation of ubiquinated proteins. By contrast, the presence of proteasome inhibitors did not alter levels of secreted FFN in cultures of PMCs. We conclude that inhibitors of proteasome-mediated degradation potently and specifically suppressed extracellular expression of FFN in CTs through a cell type-specific pathway that did not involve alterations in FFN synthesis. This suggests that accumulation of ubiquinated proteins in the presence of proteasome inhibitors blocks FFN secretion or promotes the extracellular degradation of FFN. This experimental paradigm will be useful for dissecting the role of the UPS in regulating CT function.
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PMID:Role of the proteasome in the regulation of fetal fibronectin secretion in human placenta. 1159 54

The proteasome pathway is important for the turnover of many regulatory proteins. This pathway has recently become a target for antitumor agents and several research groups have demonstrated that inhibitors with specificities for the proteasome are potent apoptosis-inducing agents. Many mechanisms by which proteasome inhibitors exert their effects have been suggested, including inhibition of NF-kappa B activity and stabilization of the p53 tumor suppressor protein. We investigated the ability of inhibitors with specificities for the proteasome and for another protein degradation enzyme, calpain, to sensitize a murine B-cell lymphoma with constitutive NF-kappa B1 homodimer activity and high expression of Bcl-2 protein to radiation-induced apoptosis. Protease inhibitors tested were calpain inhibitor I, calpain inhibitor II, calpeptin, MG132, and Lactacystin. All five inhibitors induced apoptosis and sensitized cells to radiation despite the maintenance of Bcl-2 protein levels throughout the course of treatment. An electrophoretic migration shift assay for NF-kappa B1 activity provided evidence that reversal of NF-kappa B activity was not required for induction of cell death; however, p53 levels were elevated for all inhibitors tested. HL-60 cells, devoid of p53, could not be sensitized to radiation by MG132 treatment, suggesting that p53 was important for cell death induced by combined treatment with protease inhibitors and radiation. We concluded that protease inhibitors are capable of overcoming the protective effects of Bcl-2 to induce apoptosis and suggest that protease inhibitor treatment, when combined with ionizing radiation, leads to p53-mediated apoptosis.
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PMID:Protease inhibitors restore radiation-induced apoptosis to Bcl-2-expressing lymphoma cells. 1174 2

Within 24 h of hormonally stimulated 3T3-L1 adipocyte differentiation, there are dramatic changes in the protein levels of p130 and p107, two members of the retinoblastoma tumor suppressor gene family. Designated the "p103:p107" switch, this alteration is characterized by a rapid and transient drop in p130 protein levels accompanied by a transient increase in both p107 mRNA and protein levels. Using protease inhibitors, the specific proteolytic pathway involved in degradation of p130 was examined. Treatment of cells with N-acetyl-leu-leu-norleucinal, an inhibitor that blocks proteolytic activity of type I calpain and the 26S proteasome, resulted in a complete block in the degradation of p130 protein, as well as adipocyte differentiation, suggesting that one of these pathways is involved in regulating p130 protein levels. Similar analysis with lactacystin, a specific inhibitor of the 26S proteasome, also resulted in a complete block in both differentiation and p130 degradation. Furthermore, both inhibitors blocked the increase in p107 protein levels normally observed on Day 1, suggesting that the p130:p107 switch is required for adipocyte differentiation and one of the early molecular events involved in activating the p130:p107 switch is the specific degradation of p130 by the 26S proteasome.
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PMID:Proteasomal degradation of retinoblastoma-related p130 during adipocyte differentiation. 1179 83

Tumor necrosis factor-alpha (TNF) is well known for its cytotoxic effect on malignant cells. Its role in cell cycle control is relatively less known. In this study, we found that TNF induced G(1) arrest of TF-1 and MV4-11 cells while simultaneously causing apoptosis. Treatment of the cells with TNF for 48 h caused cell cycle arrest, accompanied by dephosphorylation of pRb and reduction in D-type cyclin expression. The down-regulation of the D-type cyclins resulted in approximately 50-80% decrease of the cyclin-dependent kinase activities. Cells treated with calpain-dependent inhibitor ALLN and apoptosis inhibitor zVAD-FMK suppressed degradation of IkappaBalpha and activation of caspase 3, respectively. However, treatment of cells with these two inhibitors was not able to prevent TNF-induced down-regulation of the D-type cyclins. In contrast, proteasome inhibitor MG-132 and lactacystin blocked both TNF-induced degradation of IkappaBalpha and down-regulation of D-type cyclins. These data suggest that down-regulation of D-type cyclins by TNF may be proteasome-proteolysis dependent. Additional support for this conclusion was obtained from experiments showing an increase of proteasome activity in TNF-treated cells and in vitro degradation of cyclin D3 by 26 S proteasome.
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PMID:Ubiquitin/proteasome-dependent degradation of D-type cyclins is linked to tumor necrosis factor-induced cell cycle arrest. 1186 73


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