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

Rip1 is required for IkappaB kinase activation in response to tumor necrosis factor alpha (TNF-alpha) and has been implicated in the Toll-like receptor 3 (TLR3) response to double-stranded RNA. Cytokine production is impaired when rip1-/- cells are treated with TNF-alpha, poly(I-C), or lipopolysaccharide, implicating Rip1 in the Trif-dependent TLR3 and TLR4 pathways. To examine the role of Rip1 in the Trif-dependent TLR4 pathway, we generated rip1-/- MyD88-/- cells. Lipopolysaccharide failed to stimulate NF-kappaB activation in rip1-/-MyD88-/- cells, revealing that Rip1 is also required for the Trif-dependent TLR4-induced NF-kappaB pathway. In addition to activating NF-kappaB, TLR3/4 pathways also stimulate interferon regulatory factor 3 activation. However, we find that Rip1 expression stimulates NF-kappaB but not interferon regulatory factor 3 activity. In the TNF-alpha pathway, Rip1 interacts with the E3 ubiquitin ligase Traf2 and is modified by polyubiquitin chains. Upon TLR3 activation, Rip1 is also modified by polyubiquitin chains and is recruited to TLR3 along with Traf6 and the ubiquitin-activated kinase Tak1. These studies suggest that Rip1 uses a similar, ubiquitin-dependent mechanism to activate IkappaB kinase-beta in response to TNF-alpha and TLR3 ligands.
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PMID:Rip1 mediates the Trif-dependent toll-like receptor 3- and 4-induced NF-{kappa}B activation but does not contribute to interferon regulatory factor 3 activation. 1611 77

Increasing evidence suggests that abnormal iron handling may be involved in the pathogenesis of Parkinson's disease. The present study investigates the role of iron and the iron-storage protein ferritin in inflammation-induced degeneration of dopaminergic neurons of the substantia nigra pars compacta. Injection of lipopolysaccharide into the globus pallidus of young and middle-aged rats substantially decreased tyrosine hydroxylase immunostaining in substantia nigra pars compacta four weeks after injection. Loss of tyrosine hydroxylase expression was accompanied by increased iron and ferritin levels in glial cells of the substantia nigra pars reticulata. Despite greater increases in nigral iron levels, ferritin induction was less pronounced in older rats, suggesting the regulation of ferritin was compromised with age. Automated movement tracking analyses showed that young rats recovered from LPS-induced locomotor deficits within four weeks, yet older rats failed to improve on measures of speed and total distance moved. Intrapallidal lipopolysaccharide injection also increased expression of alpha-synuclein and ubiquitin in tyrosine hydroxylase-positive neurons of the substantia nigra pars compacta. These results suggest that pallidal inflammation significantly increases stress on dopamine-containing neurons in the substantia nigra pars compacta. Alterations in nigral iron levels and protein handing may increase the vulnerability of nigral neurons to degenerative processes.
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PMID:Intrapallidal lipopolysaccharide injection increases iron and ferritin levels in glia of the rat substantia nigra and induces locomotor deficits. 1616 92

The apicomplexan parasite, Theileria annulata, dedifferentiates and induces continuous division of infected bovine myeloid cells. Re-expression of differentiation markers and a loss of proliferation occur upon treatment with buparvaquone, implying that parasite factors actively maintain the altered status of the infected cell. The factors that induce this unique transformation event have not been identified. However, parasite polypeptides (TashAT family) that are located in the infected leucocyte nucleus have been postulated to function as modulators of host cell phenotype. In this study differential RNA display and proteomic analysis were used to identify altered mRNA and polypeptide expression profiles in a bovine macrophage cell line (BoMac) transfected with TashAT2. One of the genes identified by differential display was found to encode an ubiquitin-like protease (bUBP43) belonging to the UBP43 family. The bUBP43 gene and the gene encoding its ubiquitin-like substrate, bISG15, were expressed at a low level in T. annulata-infected cells. However, infected cells were refractory to induction of elevated bISG15 expression by lipopolysaccharide or type 1 interferons while TashAT2-transfected cells showed no induction when treated with camptothecin. Modulation of the ISGylation system may be of relevance to the establishment of the transformed infected host cell, as ISGylation is associated with resistance to intracellular infection by pathogens, stimulation of the immune response and terminal differentiation of leukaemic cells.
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PMID:Infection of bovine cells by the protozoan parasite Theileria annulata modulates expression of the ISGylation system. 1644 38

Immune responses are initiated when molecules of microbial origin are sensed by the Toll-like receptors (TLRs). We now report the identification of essential molecular components for the trafficking of the lipopolysaccharide (LPS) receptor complex. LPS was endocytosed by a receptor-mediated mechanism dependent on dynamin and clathrin and colocalized with TLR4 on early/sorting endosomes. TLR4 was ubiquitinated and associated with the ubiquitin-binding endosomal sorting protein hepatocyte growth factor-regulated tyrosine kinase substrate, Hrs. Inhibition of endocytosis and endosomal sorting increased LPS signaling. Finally, the LPS receptor complex was sorted to late endosomes/lysosomes for degradation and loading of associated antigens onto HLA class II molecules for presentation to CD4+ T cells. Our results show that endosomal trafficking of the LPS receptor complex is essential for signal termination and LPS-associated antigen presentation, thus controlling both innate and adaptive immunity through TLR4.
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PMID:Endocytic pathways regulate Toll-like receptor 4 signaling and link innate and adaptive immunity. 1646 47

MNSFbeta is a ubiquitously expressed member of the ubiquitin-like family that has been implicated in various biological functions. Previous studies have demonstrated that MNSFbeta covalently binds to intracellular proapoptotic protein Bcl-G in mitogen-activated murine T cells. In this study, we further investigated the intracellular mechanism of action of MNSFbeta in macrophage cell line, Raw 264.7 cells. We present evidence that MNSFbeta.Bcl-G complex associates with ERKs in non-stimulated Raw 264.7. We found that MNSFbeta.Bcl-G directly bound to ERKs and inhibited ERK activation by MEK1. In Raw 264.7 cells treated with MNSFbeta small interfering RNA (siRNA) lipopolysaccharide (LPS)-induced ERK1/2 activation was enhanced and LPS-induced JNK and p38 activation was unaffected. SiRNA-mediated knockdown of MNSFbeta increased tumor necrosis factor alpha (TNFalpha) expression at mRNA and protein levels in LPS-stimulated Raw 264.7 cells. Finally, we found that transfection with MNSFbeta expression construct resulted in a significant inhibition of LPS-induced ERK activation and TNFalpha production. Co-transfection experiments with MNSFbeta and Bcl-G greatly enhanced this inhibition. Collectively, these findings indicate that MNSFbeta might be implicated in the macrophage response to LPS.
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PMID:The ubiquitin-like protein MNSFbeta regulates ERK-MAPK cascade. 1662 90

The serine anti-protease elafin is expressed by monocytes, alveolar macrophages, neutrophils, and at mucosal surfaces and possesses antimicrobial activity. It is also known to reduce lipopolysaccharide-induced neutrophil influx into murine alveoli as well as to abrogate lipopolysaccharide-induced production of matrix metalloprotease 9, macrophage inhibitory protein 2, and tumor necrosis factor-alpha by as-yet unidentified mechanisms. In this report we have shown that elafin inhibits the lipopolysaccharide-induced production of monocyte chemoattractant protein-1 in monocytes by inhibiting AP-1 and NF-kappaB activation. Elafin prevented lipopolysaccharide-induced phosphorylation of AP-1, c-Jun, and JNK but had no effect on phosphorylation of p38. The lipopolysaccharide-induced degradation of IL-1R-associated kinase 1, IkappaBalpha, and IkappaBbeta was inhibited by elafin but phosphorylation of IkappaBalpha was unaffected. Polyubiquitinated protein including polyubiquitinated IkappaBalpha was shown to accumulate in the presence of elafin. These results suggest that inhibition by elafin of lipopolysaccharide-induced AP-1 and NF-kappaB activation occurs via an effect on the ubiquitin-proteasome pathway.
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PMID:Elafin prevents lipopolysaccharide-induced AP-1 and NF-kappaB activation via an effect on the ubiquitin-proteasome pathway. 1698 Mar 10

ISG15 is one of the most strongly induced genes upon viral infection, interferon (IFN) stimulation, and lipopolysaccharide (LPS) stimulation, and only one copy has been found in mammals so far. Here two fish ISG15 genes, termed CaISG15-1 and CaISG15-2, have been cloned and sequenced from UV-inactivated GCHV (grass carp haemorrhagic virus)-infected and IFN-produced CAB cells (crucian carp Carassius auratus blastulae embryonic cells) by suppression subtractive hybridization. The full-length cDNA sequences of two crucian carp ISG15 encode a 155-amino-acid protein and a 161-amino-acid protein, both of which show 78.9% identity overall and possess the characteristic structures of mammalian ISG15 proteins including two tandem ubiquitin-like domains and the C-terminal canonical LRLRGG motif. In CAB cells treated with different stimuli including active virus, UV-inactivated GCHV and IFN containing supernatant (ICS), the expression of both CaISG15-1 and CaISG15-2 was upregulated but displayed different kinetics. Poly I:C and LPS were also able to induce an increase in mRNA for both genes. In CAB cells responsive to active GCHV, UV-inactivated GCHV, CAB ICS, Poly I:C and LPS, CaISG15-1 was upregulated more significantly than CaISG15-2. These results suggest that there are two ISG15 homologues in crucian carp, both of which might play distinct roles in innate immunity against viral and bacterial infection.
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PMID:Identification and characterization of two homologues of interferon-stimulated gene ISG15 in crucian carp. 1735 Aug 61

Members of the Pellino family are interleukin-1 receptor-associated kinase (IRAK)-interacting proteins that possess RING-like domains. The presence of these domains led to the suggestion that Pellino proteins are ubiquitin-protein isopeptide ligases (E3). However, no conclusive data currently exist to prove this proposal. This study provides the first direct evidence that Pellino proteins possess E3 activity. Recombinant forms of Pellino1 and Pellino2 and both spliced variants of Pellino3 are shown in an in vitro ubiquitination assay to be E3 ligases that catalyze Lys(63)-linked polyubiquitination, with Pellino3 exhibiting the greatest ligase activity. Whereas the Pellino proteins cause polyubiquitination of IRAK-1, we also show that kinase-active members of the IRAK family (IRAK-1 and IRAK-4) promote reciprocal polyubiquitination of the Pellino proteins and that this is associated with IRAK-induced degradation of the Pellino family. In contrast, IRAK-2 (which lacks a functional kinase domain) and kinase-dead forms of IRAK-1 and IRAK-4 fail to degrade the Pellino proteins. We show that these kinase-inactive IRAK proteins can associate with Pellino proteins, thus excluding the possibility that their inability to regulate Pellino degradation is due to lack of association with the Pellino proteins. The physiological relevance of IRAK-induced degradation of Pellino proteins is confirmed by the demonstration that lipopolysaccharide causes degradation of endogenous forms of Pellino3 in peripheral blood mononuclear cells. In summary, this study not only demonstrates Pellino proteins to be E3 ligases that can catalyze Lys(63)-linked polyubiquitination but also shows bidirectional signaling between the IRAK and Pellino families and highlights a novel function for IRAK kinase activity.
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PMID:Kinase-active interleukin-1 receptor-associated kinases promote polyubiquitination and degradation of the Pellino family: direct evidence for PELLINO proteins being ubiquitin-protein isopeptide ligases. 1767 97

The NF-kappaB transcription factor is normally transiently activated by proinflammatory cytokines and bacterial lipopolysaccharide (LPS); however, persistent NF-kappaB activation is commonly observed in inflammatory disease and malignancy. The ubiquitin editing enzyme A20 serves an essential role in the termination of TNF-alpha- and LPS-mediated NF-kappaB signaling by inactivating key signaling molecules. However, little is known about how A20 is regulated and if other molecules play a role in the termination of NF-kappaB signaling. Here we demonstrate that Tax1-binding protein 1 (TAX1BP1) is essential for the termination of NF-kappaB and JNK activation in response to TNF-alpha, IL-1 and LPS stimulation. In TAX1BP1-deficient mouse fibroblasts, TNF-alpha-, IL-1- and LPS-mediated IKK and JNK activation is elevated and persistent owing to enhanced ubiquitination of RIP1 and TRAF6. Furthermore, in the absence of TAX1BP1, A20 is impaired in RIP1 binding, deubiquitination of TRAF6 and inhibition of NF-kappaB activation. Thus, TAX1BP1 is pivotal for the termination of NF-kappaB and JNK signaling by functioning as an essential regulator of A20.
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PMID:Essential role for TAX1BP1 in the termination of TNF-alpha-, IL-1- and LPS-mediated NF-kappaB and JNK signaling. 1770 91

The blood-brain barrier (BBB), a communicating interface for inflammation, transports cytokines through its endothelial cells. This study shows how tumor necrosis factor alpha (TNF) regulates the expression of the leukemia inhibitor factor receptor (LIFR) gp190 in RBE4 cells. The high expression of LIFR was rapidly downregulated by the proinflammatory agents lipopolysaccharide, TNF, and LIF. Downregulation by TNF affected LIFR endocytosis and lysosomal degradation, preceding decreased LIFR mRNA. Lysosomal inhibitors reversed the rapid disappearance of LIFR, whereas inhibition of the ubiquitin-proteasome pathway did not. Rather, blockade of proteasome activity, as well as inhibition of NFkappaB activation, reduced the basal expression of LIFR. Thus, NFkappaB activity and proteasome degradation of IkappaB stabilized LIFR and prevented its rapid lysosomal degradation. By a non-NFkappaB-mediated mechanism, TNF facilitated LIFR degradation and reduced LIFR activation indicated by pStat3. The novel opposite effects of proteasomes and lysosomes in controlling receptor expression shows the functional implications and interactions of circulating inflammatory cytokines in acutely modulating BBB activity.
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PMID:Opposing effects of proteasomes and lysosomes on LIFR: modulation by TNF. 1787 91


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