Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The proteolytic degradation of the inhibitory protein MAD3/I kappa B alpha in response to extracellular stimulation is a prerequisite step in the activation of the transcription factor NF-kappa B. Analysis of the expression of human I kappa B alpha protein in stable transfectants of mouse 70Z/3 cells shows that, as for the endogenous murine protein, exogenous I kappa B alpha is degraded in response to inducers of NF-kappa B activity, such as phorbol myristate acetate or lipopolysaccharide. In addition, pretreatment of the cells with the proteasome inhibitor N-Ac-Leu-Leu-norleucinal inhibits this ligand-induced degradation and, in agreement with previous studies, stabilizes a hyperphosphorylated form of the human I kappa B alpha protein. By expressing mutant forms of the human protein in this cell line, we have been able to delineate the sequences responsible for both the ligand-induced phosphorylation and the degradation of I kappa B alpha. Our results show that deletion of the C terminus of the I kappa B alpha molecule up to amino acid 279 abolishes constitutive but not ligand-inducible phosphorylation and inhibits ligand-inducible degradation. Further analysis reveals that the inducible phosphorylation of I kappa B alpha maps to two serines in the N terminus of the protein (residues 32 and 36) and that the mutation of either residue is sufficient to abolish ligand-induced degradation, whereas both residues must be mutated to abolish inducible phosphorylation of the protein. We propose that treatment of 70Z/3 cells with either phorbol myristate acetate or lipopolysaccharide induces a kinase activity which phosphorylates serines 32 and that these phosphorylations target the protein for rapid proteolytic degradation, possibly by the ubiquitin-26S proteasome pathway, thus allowing NF-kappa B to translocate to the nucleus and to activate gene expression.
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PMID:N- and C-terminal sequences control degradation of MAD3/I kappa B alpha in response to inducers of NF-kappa B activity. 756 83

The objective of this study was to elucidate the role of the proteasome pathway or multicatalytic proteinase complex in the induction of immunologic nitric oxide (NO) synthase (iNOS) in rat alveolar macrophages activated by lipopolysaccharide. Macrophages were incubated in the presence of lipopolysaccharide plus test agent for up to 24 hr. Culture media were analyzed for accumulation of stable oxidation products of NO (NO2- + N03-, designated as NOX-), cellular RNA was extracted for determination of iNOS mRNA levels by Northern blot analysis, and nuclear extracts were prepared for determination of NF-kappa B by electrophoretic mobility-shift assay. Inhibitors of calpain (alpha-N-acetyl-Leu-Leu-norleucinal; N-benzyloxycarbonyl-Leu-leucinal) and the proteasome (N-benzyloxycarbonyl-Ile-Glu-(O-t-Bu)-Ala-leucinal) markedly inhibited or abolished the induction of iNOS in macrophages. The proteinase inhibitors interfered with lipopolysaccharide-induced NOX- production by macrophages, and this effect was accompanied by comparable interference with the appearance of both iNOS mRNA and NF-kappa B. Calpain inhibitors elicited effects at concentrations of 1-100 microM, whereas the proteasome inhibitor was 1000-fold more potent, producing significant inhibitory effects at 1 nM. The present findings indicate that the proteasome pathway is essential for lipopolysaccharide-induced expression of the iNOS gene in rat alveolar macrophages. Furthermore, the data support the view that the proteasome pathway is directly involved in promoting the activation of NF-kappa B and that the induction of iNOS by lipopolysaccharide involves the transcriptional action of NF-kappaB.
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PMID:Inhibitors of the proteasome pathway interfere with induction of nitric oxide synthase in macrophages by blocking activation of transcription factor NF-kappa B. 862 34

Regulation of the transcription factor NF-kappaB involves proteasome-mediated processing of the NF-kappaB1 p105 precursor protein, which generates the p50 subunit of NF-kappaB. The processing of p105 occurs constitutively in vivo but can be markedly enhanced by various cellular activation agents, although the underlying regulatory mechanism is not yet clear. In the present study, we demonstrate that signal-mediated induction of p105 processing in human T cells is associated with de novo synthesis of this precursor protein. Transient transfection studies performed in COS7 cells revealed that the newly synthesized p105 protein appears to be more rapidly processed compared to its accumulated form that is already associated with the processed product p50. Interestingly, the processing rate of p105 is markedly inhibited in cells co-transfected with p50 or other NF-kappaB subunits, including RelA and c-Rel, that physically interact with p105. These findings suggest that the processing of p105 is subject to negative regulation by the various NF-kappaB subunits. We further demonstrate that p105 undergoes degradation in lipopolysaccharide-stimulated human monocytic cells. However, the inducible degradation of p105 is not coupled with the generation of p50. Together, these studies demonstrate that the processing and inducible degradation of p105 are differentially regulated.
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PMID:Inhibition of p105 processing by NF-kappaB proteins in transiently transfected cells. 864 79

We previously reported cDNA cloning of a novel oxidative stress protein termed A170 from murine macrophages. Further experiments have demonstrated that exposure of the cells to low levels of H2O2 produced by glucose/glucose oxidase markedly induced the 60-kDa A170 protein. This result suggests that the level of A170 protein can also be controlled at posttranscriptional levels, because we showed previously that H2O2 hardly increased the level of A170 mRNA. We have found that proteasome inhibitors markedly induced the A170 protein after 2 to 8 h similarly to glucose/glucose oxidase, suggesting rapid degradation of the A170 protein by proteasome under normal conditions. Activation of cellular signaling pathways either by epidermal growth factor, lipopolysaccharide or tumor necrosis factor-alpha did not enhance the level of the A170 protein. The levels of glucose oxidase-induced A170 protein did not decrease after the addition of cycloheximide. These results suggest that low levels of H2O2 may stabilize the A170 protein, allowing it to accumulate within cells.
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PMID:Low micromolar levels of hydrogen peroxide and proteasome inhibitors induce the 60-kDa A170 stress protein in murine peritoneal macrophages. 912 46

Cyclosporine A is an immunosuppressive agent that is used clinically in the prevention of transplant rejection and development of graft-versus-host disease. Recently, cyclosporine A has been shown to possess anti-inflammatory properties and is capable of inhibiting lipopolysaccharide-induced NF-kappaB activation. Ubiquitin-mediated proteasomal proteolysis plays a critical role in signal-induced NF-kappaB activation since it regulates both IkappaB degradation and p105 processing, it is also involved in the production of peptides for the assembly of MHC class I molecules. We report here that cylcosporine A acts as an uncompetitive inhibitor of the chymotrypsin-like activity of the 20S proteasome in vitro and that it suppresses lipopolysaccharide-induced IkappaB degradation and p105 processing in vivo demonstrating that inhibition of proteasome proteolysis is the mechanism by which cyclosporine A prevents NF-kappaB activation. A structurally unrelated immunosuppressant, rapamycin, did not inhibit the 20S proteasome in vitro.
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PMID:Cyclosporine A is an uncompetitive inhibitor of proteasome activity and prevents NF-kappaB activation. 928 Mar 12

Intercellular adhesion molecule 1 (ICAM-1) is an important molecule in promotion of polymorphonuclear neutrophil transendothelial migration during inflammation. Coincident with many inflammatory diseases is tissue hypoxia. Thus we hypothesized that combinations of hypoxia and inflammatory stimuli may differentially regulate expression of endothelial ICAM-1. Human endothelial cells were exposed to hypoxia in the presence or absence of added lipopolysaccharide (LPS) and examined for expression of functional ICAM-1. Although hypoxia alone did not induce ICAM-1, the combination of LPS and hypoxia enhanced (3 +/- 0.4-fold over normoxia) ICAM-1 expression. Combinations of hypoxia and LPS significantly increased lymphocyte binding, and such increases were inhibited by addition of anti-ICAM-1 antibodies or antisense oligonucleotides. Hypoxic endothelia showed a > 10-fold increase in sensitivity to inhibitors of proteasome activation, and combinations of hypoxia and LPS enhanced proteasome-dependent cytoplasmic-to-nuclear localization of the nuclear transcription factor-kappa B p65 (Rel A) subunit. Such proteasome activation correlated with hypoxia-evoked decreases in both extracellular and intracellular pH. We conclude from these studies that endothelial hypoxia provides a novel, proteasome-dependent stimulus for ICAM-1 induction.
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PMID:Hypoxia enhances induction of endothelial ICAM-1: role for metabolic acidosis and proteasomes. 937 42

We investigated the effect of proteasome inhibitors on the lipopolysaccharide (LPS)-induced expression of several monocytic cytokines, which may be dependent on the transcription factor, nuclear factor-kappaB (NF-kappaB). Exposure of human monocytic THP-1 cells to ALLN and Mu873 prevented the LPS-induced degradation of IkappaB-alpha and -beta, as did the more potent proteasome inhibitor, PSI, whereas several calpain inhibitors were ineffective. This was accompanied by the inhibition of nuclear NF-kappaB binding activity and NF-kappaB transcriptional activation. At the mRNA level, the inhibitors blocked the expression of tumor necrosis factor (TNF) and interleukin-1beta (IL-1beta), whereas IL-8 remained unaffected by ALLN and was only partially reduced by the highest dose of PSI. The latter effect appears to be due to an increase in IL-8 mRNA stability in the presence of proteasome inhibitors. Furthermore, the production of TNF was efficiently suppressed by ALLN and PSI, less by Mu873, and not at all by calpain inhibitors. In primary human blood monocytes ALLN also prevented the LPS-induced degradation of IkappaB-alpha and -beta, efficiently blocked the production of TNF and, to a lesser extent, IL-1beta, whereas that of IL-8 was not inhibited. The expression of NF-kappaB-dependent monocytic cytokines may be selectively controlled by the proteasome, offering a potential therapeutic target in inflammatory disease.
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PMID:Effect of proteasome inhibitors on monocytic IkappaB-alpha and -beta depletion, NF-kappaB activation, and cytokine production. 950 May 29

Rat C6 glioma cells were stably transfected with a human cDNA encoding heat shock protein (HSP)70. Immunostaining revealed the presence of largely cytosolic HSP70 in C6-hsp70 cells, but not in control (vector transfected) C6-pTK cells. Induction of nitric oxide synthase (NOS-2) expression in C6-hsp70 cells, assessed by nitrite accumulation, was significantly reduced compared to control C6-pTK cells (25+/-8% of control cell induction, P < 0.005), when induced with a maximally stimulatory combination of bacterial endotoxin lipopolysaccharide (LPS) plus a mixture of three cytokines ("CM:" TNF-alpha, IL1-beta, and IFN-gamma). Immunostaining for the transcription factor NFkappaB p65 subunit revealed decreased cytokine-dependent nuclear uptake in HSP70 expressing cells compared to control cells. Activation of C6 cell NFkappaB by LPS plus CM required IkappaB degradation by the 20S proteasome, since NOS-2 expression was blocked by a selective proteasome inhibitor. In parental C6 cells, the presence of LPS plus CM caused a rapid (within 30 min) decrease in inhibitory IkappaB-alpha protein levels, and this loss was abolished by prior heat shock of the cells. In contrast, IkappaB-alpha levels in transfected cells were not modified by the expression of HSP70. These results demonstrate that constitutive HSP70 expression in glial cells can reduce NOS-2 induction, presumably due to inhibition of NFkappaB nuclear uptake. Furthermore, whereas prevention of decreases in IkappaB-alpha can account for the suppressive effects of heat shock, the results suggest that HSP70 blocks NOS-2 induction by interfering at a later step in the NFkappaB activation pathway.
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PMID:Suppression of glial nitric oxide synthase induction by heat shock: effects on proteolytic degradation of IkappaB-alpha. 970 Oct 55

The multicatalytic proteinase or proteasome is a highly conserved cellular structure that is responsible for the ATP-dependent proteolysis of many proteins involved in important regulatory cellular processes. We have identified a novel class of inhibitors of the chymotrypsin-like proteolytic activity of the 20S proteasome that exhibit IC50 values ranging from 0.1 to 0.5 microgram/mL (0.1 to 1 microM). In cell proliferation assays, these compounds inhibit growth with an IC50 ranging from 5 to 10 micrograms/mL (10-20 microM). A representative member of this class of inhibitors was tested in other biological assays. CVT-634 (5-methoxy-1-indanone-3-acetyl-leu-D-leu-1-indanylamide) prevented lipopolysaccharide (LPS), tumor necrosis factor (TNF)-, and phorbol ester-induced activation of nuclear factor kappa B (NF-kappa B) in vitro by preventing signal-induced degradation of I kappa B-alpha. In these studies, the I kappa B-alpha that accumulated was hyperphosphorylated, indicating that CVT-634 did not inhibit I kappa B-alpha kinase, the enzyme responsible for signal-induced phosphorylation of I kappa B-alpha. In vivo studies indicated that CVT-634 prevented LPS-induced TNF synthesis in a murine macrophage cell line. In addition, in mice pretreated with CVT-634 at 25 and 50 mg/kg and subsequently treated with LPS, serum TNF levels were significantly lower (225 +/- 59 and 83 +/- 41 pg/mL, respectively) than in those mice that were treated only with LPS (865 +/- 282 pg/mL). These studies suggest that specific inhibition of the chymotrypsin-like activity of the proteasome is sufficient to prevent signal-induced NF-kappa B activation and that the proteasome is a novel target for the identification of agents that may be useful in the treatment of diseases whose etiology is dependent upon the activation of NF-kappa B.
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PMID:A new structural class of proteasome inhibitors that prevent NF-kappa B activation. 1007 30

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


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