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)

We established several swine endothelial cell (SEC) lines, expressing human MCP (CD46), DAF (CD55), and MCP/DAF hybrid by transfection of cDNA, and assessed the function of these transfectant molecules on complement-mediated cell lysis as an in vitro hyperacute rejection model of swine to human discordant xenograft. Discordant organ xenografts are hyperacutely rejected by complement activation. Amelioration of complement-mediated lysis by these transfectant molecules was tested in each SEC line by lactate dehydrogenase assay. Naive swine endothelial cells were markedly damaged by human complement mainly via the classical pathway, activating only minimally the alternative pathway of human complement. Both MCP and DAF protected SEC from human complement attack in parallel with the expression density, with DAF being more effective than MCP. The MCP/DAF hybrid was more effective than MCP alone, and as effective as DAF in this system. The results suggest that the transfection of DAF or the MCP/DAF hybrid cDNA into organs to be transplanted could protect against hyperacute rejection.
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PMID:Effects of transfected complement regulatory proteins, MCP, DAF, and MCP/DAE hybrid, on complement-mediated swine endothelial cell lysis. 752 6

Extensively oxidized low density lipoprotein (ox-LDL), a modulator of atherogenesis, down-regulates the lipopolysaccharide (LPS)-induced activation of transcription factor NF-kappaB. We investigated whether 4-hydroxynonenal (HNE), a prominent aldehyde component of ox-LDL, represents one of the inhibitory substances. NF-kappaB activation by stimuli such as LPS, interleukin (IL)-1beta, and phorbol ester, but not tumor necrosis factor (TNF), was reversibly inhibited by HNE in a dose-dependent manner in human monocytic cells, whereas AP-1 binding was unaffected. Using similar HNE concentrations, LPS-induced kappaB- and TNF or IL-8 promoter-dependent transcription was prevented. Furthermore, pretreatment with HNE suppressed TNF production but not lactate dehydrogenase levels. Under these conditions the binding of LPS to monocytic cells was not significantly affected. However, induced proteolysis of the inhibitory proteins IkappaB-alpha, IkappaB-beta, and, at a later time point, IkappaB-epsilon was prevented. This is not due to inhibition of the proteasome, the major proteolytic activities of which remain unaffected, but rather to a specific prevention of the activation-dependent phosphorylation of IkappaB-alpha. This is the first report which demonstrates that HNE specifically inhibits the NF-kappaB/Rel system. Down-modulation of NF-kappaB-regulated gene expression may contribute at certain stages of atherosclerosis to low levels of chronic inflammation and may also be involved in other inflammatory/degenerative diseases.
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PMID:4-Hydroxynonenal prevents NF-kappaB activation and tumor necrosis factor expression by inhibiting IkappaB phosphorylation and subsequent proteolysis. 1020 70

Interleukin-1beta is a secreted protein that accumulates in the cytosol as an inactive precursor (pIL-1beta) before processing and release of biologically active protein. To understand the impact of this property on IL-1beta production, we examined the intracellular stability of pIL-1beta in lipopolysaccharide (LPS)-stimulated human monocytes. Precursor IL-1beta was degraded with a relatively short half-life of 2.5 h in the promonocytic cell line, THP-1, and in primary monocytes. MG132 (carbobenzoxyl-leucinyl-leucinyl-leucinal) stabilized pIL-1beta levels in THP-1 cells, suggesting that degradation was proteasome-mediated, but this inhibitor was toxic for primary monocytes, causing release of pIL-1beta as well as the cytoplasmic enzyme, lactate dehydrogenase (LDH) into supernatants. In contrast, clasto-lactacystin beta-lactone, a specific inhibitor of the proteasome, caused a dose-dependent stabilization of intracellular pIL-1beta, and this led to a corresponding increase in mIL-1beta and pIL-1beta but not LDH release into culture supernatants. Therefore, by regulating intracellular levels of precursor IL-1beta, the proteasome plays an important and previously unrecognized role in controlling the amount of biologically active IL-1beta that is exported by activated monocytes.
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PMID:Proteasome-mediated regulation of interleukin-1beta turnover and export in human monocytes. 1091

Age-related sarcopenia could partly result from cumulative repeated episodes of incomplete repair and regeneration. We hypothesized that mitotic and metabolic events associated with satellite cell activation and proliferation could be altered with aging. Muscle-derived cells (mdc) were isolated from gastrocnemius and quadriceps muscles of young (3 wk old), adult (9 mo old), and old (24 mo old) Sprague-Dawley male rats (n = 10/group). The mdc from young growing rats started to proliferate earlier compared with adult and old animals. Cell cycle duration was significantly reduced with aging from 36.5 +/- 3.2 to 28.0 +/- 2.2 h. However, the proportion of noncycling (G0 phase) and cycling (G1 + S + G2 + M phases) cultured mdc was statistically unchanged among the three age groups. Significantly lower increase in c-met and proliferating cell nuclear antigen expression were observed in cultured mdc of old rats upon serum stimulation. Major changes in the expression of citrate synthase, lactate dehydrogenase, proteasome, caspase 3, plasminogen activators (PAs), and matrix metalloproteinase 2-9 (MMP2-9) were observed upon serum stimulation, but no age-related difference was noted. However, when measured on crushed muscle extracts, PAs and MMP2-9 enzyme activities were significantly decreased with aging. Our results show that cellular and biochemical events associated with the control of mdc activation and proliferation occur with aging. These alterations may participate in the accumulation of repeated episodes of incomplete repair and regeneration throughout the life span, thus contributing to the loss of skeletal muscle mass and function with aging.
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PMID:Age-related changes in the mitotic and metabolic characteristics of muscle-derived cells. 1455 72

High-dose treatment (HDT) with autologous stem cell transplant(s) (ASCT) improved survival, when compared to standard treatment, in multiple myeloma patients. Although the superiority of HDT is clearly recognized by the medical community, what is less appreciated is the disproportionate benefit enjoyed (as a result of this approach) by various patient subgroups. As the clinical heterogeneity of myeloma can be currently traced to its underlying genetic features, prognostically different patient groups can be identified largely based on the presence of adverse cytogenetic abnormalities and high serum levels of lactate dehydrogenase at baseline (high-risk features). While HDT applied to high-risk patients leads to modest survival gains, the same treatment, as the backbone of a comprehensive approach, can be curative in a minority of low-risk patients. A third group of low-risk patients will enjoy rather prolonged (10-year) survival, interrupted, however, by responsive relapses. In a manner analogous to follicular lymphoma, this latter group may transform to a more aggressive disease, characterized by the new acquisition of adverse cytogenetic abnormalities. Improving the complete response rate in these patients, by integrating newer therapeutic agents, may increase their cure rate. Currently non-myeloablative, allogeneic transplants (and possibly proteasome inhibitors) are the most promising approaches for high-risk patients.
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PMID:Cure of myeloma: hype or reality? 1554 96

Extracellular ATP (ATPe) binds to P2X7 receptors (P2X7R) expressed on the surface of cells of hematopoietic lineage, including murine thymocytes. Activation of P2X7R by ATPe results in the opening of cation-specific channels, and prolonged ATPe exposure leads to the formation of non-selective pores enabling transmembrane passage of solutes up to 900 Da. In the presence of ATPe, P2X7R-mediated thymocyte death is due primarily to necrosis/lysis and not apoptosis, as measured by the release of lactate dehydrogenase indicative of a loss of plasma membrane integrity. The present study is focused on the identification of P2X7R signaling mediators in ATP-induced thymocyte necrosis/lysis. Thus, extracellular signal-regulated protein kinase 1/2 (Erk1/2) phosphorylation was found to be required for cell lysis, and both events were independent of ATP-induced calcium influx. P2X7R-dependent thymocyte death involved the chronological activation of Src family tyrosine kinase(s), phosphatidylinositol 3-kinase, the mitogen-activated protein (MAP) kinase(Erk1/2) module, and the proteasome. Although independent of this signaling cascade, non-selective pore formation may modulate ATP-mediated thymocyte death. These results therefore suggest a role for both activation of MAP kinase(Erk1/2) and non-selective pore opening in P2X7R-induced thymocyte death.
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PMID:A role for mitogen-activated protein kinase(Erk1/2) activation and non-selective pore formation in P2X7 receptor-mediated thymocyte death. 1593 34

HepG2 cells were transfected with recombinant plasmids, one carrying the murine alcohol dehydrogenase (ADH) gene and the other containing the gene encoding human cytochrome P450 2E1 (CYP2E1). One of recombinant clones called VL-17A exhibited ADH and CYP2E1 specific activities comparable to those in isolated rat hepatocytes. VL-17A cells oxidized ethanol and generated acetaldehyde, the levels of which depended upon the initial ethanol concentration. Compared with unexposed VL-17A cells, ethanol exposure increased the cellular redox (lactate:pyruvate ratio) and caused cell toxicity, indicated by increased leakage of lactate dehydrogenase into the medium,. Exposure of VL-17A cells to 100mM ethanol significantly elevated caspase 3 activity, an indicator of apoptosis, but this ethanol concentration did not affect caspase 3 activity in parental HepG2 cells. Because ethanol consumption causes a decline in hepatic protein catabolism, we examined the influence of ethanol exposure on proteasome activity in HepG2, VL-17A, E-47 (CYP2E1(+)) and VA-13 (ADH(+)) cells. Exposure to 100mM ethanol caused a 25% decline in the chymotrypsin-like activity of the proteasome in VL-17A cells, but the enzyme was unaffected in the other cell types. This inhibitory effect on the proteasome was blocked when ethanol metabolism was blocked by 4-methyl pyrazole. We conclude that recombinant VL-17A cells, which express both ADH and CYP2E1 exhibit hepatocyte-like characteristics in response to ethanol. Furthermore, the metabolism of ethanol by these cells via ADH and CYP2E1 is sufficient to bring about an inhibition of proteasome activity that may lead to apoptotic cell death.
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PMID:Recombinant Hep G2 cells that express alcohol dehydrogenase and cytochrome P450 2E1 as a model of ethanol-elicited cytotoxicity. 1618

Antimicrobial peptides have received increasing attention not only as potential candidates to their administration as antimicrobial agents, but also as potential drugs applied in cancer therapy. Here, we have examined the action of both nisin and magainin on human promyelocytic leukemia HL-60 cells. Cells were cultured in presence of either nisin or magainin 1 as well as in combination with both nisin and magainin 1. Results have revealed that magainin, but not nisin, produces a loss of cell viability in HL-60 cells, and a minor increase of hemolysis, whereas it is not responsible for cell membrane disruption and lactate dehydrogenase (LDH) leakage. In addition, magainin is involved in a significant generation of reactive oxygen species (ROS), as well as in an augment of caspase-3 activity. Magainin-induced apoptosis was verified by DNA fragmentation and annexin V-FITC/propidium iodide (PI) staining of the cells. Promotion of cell death by magainin occurs via cytochrome c release accompanied by a substantial increase of proteasome activity. These results underline the importance of magainin as a drug capable of exerting an in vitro antitumoral activity by triggering apoptosis.
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PMID:In vitro biological activities of magainin alone or in combination with nisin. 1635 89

Although the structure of an enzyme is often depicted as static, it is dynamic. Hence, a population of chemically identical enzymes has not one, but a distribution of structures at any moment in time. Does this have an effect on the activity of the enzyme? This article reviews experiments designed to test the hypothesis that this distribution of structures results in a distribution of enzyme activities. The experiments reviewed here use different enzymes, falvin adenine dinucleotide, beta-galactosidase, alkaline phosphatase, exonuclease I, lactate dehydrogenase I, alpha-chymotrypsin, the 20S proteasome, and horseradish peroxidase. All experiments come to the same conclusion, when measured individually, apparently identical enzymes show a distribution in rates of activity.
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PMID:Diversity in the activity of individual enzymes. 1637 26

Gentamicin accumulates in the lysosomes of kidney proximal tubular cells and causes apoptosis at clinically relevant doses. Gentamicin-induced apoptosis can be reproduced with cultured renal cells, but only at high extracellular concentrations (1 to 3 mM; 0.4 to 1.2 g/liter) because of its low level of uptake. We recently showed that gentamicin-induced apoptosis in LLC-PK1 cells involves a rapid (2-h) permeabilization of lysosomes and activation of the mitochondrial pathway of apoptosis (10 h). We now examine whether the delivery of gentamicin to the cytosol by electroporation would sensitize LLC-PK1 cells to apoptosis. Cells were subjected to eight pulses (1 ms) at 800 V/cm (square waves) in the presence of gentamicin (3 microM to 3 mM; 1.2 mg/liter to 1.2 g/liter); returned to gentamicin-free medium; and examined at 8 h for their Bax (a marker of mitochondrial pathway activation) contents by Western blotting and competitive reverse transcriptase PCR and at 24 h for apoptosis by 4',6'-diamidino-2'-phenylindole staining (confirmed by electron microscopy) and for necrosis (by determination of lactate dehydrogenase release). Nonelectroporated cells were incubated with gentamicin for 8 and 24 h. Significant increases in Bax levels (8 h) and apoptosis (24 h) were detected with 0.03 mM (13.2 mg/liter) gentamicin in electroporated cells compared with those achieved with 2 mM (928 mg/liter) in incubated cells. The increase in the Bax level was not associated with an increase in the level of its mRNA but was associated with the accumulation of ubiquitinated forms (probably as a result of impairment of its degradation by the proteasome). Assay of cell-associated gentamicin showed a marked, immediate, but transient accumulation in electroporated cells, whereas a slow, steady uptake was detected in incubated cells. The data indicate that cytosolic gentamicin triggers apoptosis. Sequestration of gentamicin in lysosomes would, to some extent, protect against apoptosis.
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PMID:Gentamicin causes apoptosis at low concentrations in renal LLC-PK1 cells subjected to electroporation. 1656 31


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