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)

Endotoxin, also known as lipopolysaccharide (LPS), is the major mediator of septic shock due to Gram-negative bacterial infection. Chemically synthesized S3 peptide, derived from Sushi3 domain of Factor C, which is the endotoxin-sensitive serine protease of the limulus coagulation cascade, was previously shown to bind and neutralize LPS activity. For large-scale production of this peptide and to mimick other pathogen-recognizing molecules, tandem multimers of the S3 gene were constructed and expressed in Escherichia coli. The recombinant tetramer of S3 (rS3-4mer) was purified by anion exchange and digested into monomers (rS3-1mer). Both the rS3-4mer and rS3-1mer were functionally analyzed for their ability to bind LPS by an ELISA-based method and surface plasmon resonance. The LAL inhibition and TNFalpha-release test showed that rS3-1 mer can neutralize the LPS activity as effectively as the synthetic S3 peptide, while rS3-4mer displays an enhanced inhibitory effect on LPS-induced activities. Both recombinant peptides exhibited low cytotoxicity and no haemolytic activity on human cells. This evidence suggests that the recombinant sushi peptides have potential use for the detection, removal of endotoxin and/or anti-endotoxin strategies.
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PMID:Tandem repeats of Sushi3 peptide with enhanced LPS-binding and -neutralizing activities. 1296 81

The prophenoloxidase (proPO) cascade is a major innate immune response in invertebrates, which is triggered into its active form by elicitors, such as lipopolysaccharide, peptidoglycan, and 1,3-beta-D-glucan. A key question of the proPO system is how pattern recognition proteins recognize pathogenic microbes and subsequently activate the system. To investigate the biological function of 1,3-beta-D-glucan pattern recognition protein in the proPO cascade system, we isolated eight different 1,3-beta-D-glucan-binding proteins from the hemolymph of large beetle (Holotrichia diomphalia) larvae by using 1,3-beta-D-glucan immobilized column. Among them, a 20- and 17-kDa protein (referred to as Hd-PGRP-1 and Hd-PGRP-2) show high sequence identity with the short forms of peptidoglycan recognition proteins (PGRPs-S) from human and Drosophila melanogaster. To be able to characterize the biochemical properties of these two proteins, we expressed them in Drosophila S2 cells. Hd-PGRP-1 and Hd-PGRP-2 were found to specifically bind both 1,3-beta-D-glucan and peptidoglycan. By BIAcore analysis, the minimal 1,3-beta-D-glucan structure required for binding to Hd-PGRP-1 was found to be laminaritetraose. Hd-PGRP-1 increased serine protease activity upon binding to 1,3-beta-D-glucan and subsequently induced the phenoloxidase activity in the presence of both 1,3-beta-D-glucan and Ca(2+), but no phenoloxidase activity was elicited under the same conditions in the presence of peptidoglycan and Ca(2+). These results demonstrate that Hd-PGRP-1 can serve as a receptor for 1,3-beta-D-glucan in the insect proPO activation system.
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PMID:Peptidoglycan recognition proteins involved in 1,3-beta-D-glucan-dependent prophenoloxidase activation system of insect. 1458 8

Bacterial lipopolysaccharide (LPS)-induced exocytosis of granular hemocytes is a key component of the horseshoe crab's innate immunity to infectious microorganisms; stimulation by LPS induces the secretion of various defense molecules from the granular hemocytes. Using a previously uncharacterized assay for exocytosis, we clearly show that hemocytes respond only to LPS and not to other pathogen-associated molecular patterns, such as beta-1,3-glucans and peptidoglycans. Furthermore, we show that a granular protein called factor C, an LPS-recognizing serine protease zymogen that initiates the hemolymph coagulation cascade, also exists on the hemocyte surface as a biosensor for LPS. Our data demonstrate that the proteolytic activity of factor C is both necessary and sufficient to trigger exocytosis through a heterotrimeric GTP-binding protein-mediating signaling pathway. Exocytosis of hemocytes was not induced by thrombin, but it was induced by hexapeptides corresponding to the tethered ligands of protease-activated G protein-coupled receptors (PARs). This finding suggested the presence of a PAR-like receptor on the hemocyte surface. We conclude that the serine protease zymogen on the hemocyte surface functions as a pattern-recognition protein for LPS.
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PMID:A serine protease zymogen functions as a pattern-recognition receptor for lipopolysaccharides. 1472 55

HtrA1, a member of the mammalian HtrA serine protease family, has a highly conserved protease domain followed by a PDZ domain. Because HtrA1 is a secretory protein and has another functional domain with homology to follistatin, we examined whether HtrA1 functions as an antagonist of Tgfbeta family proteins. During embryo development, mouse HtrA1 was expressed in specific areas where signaling by Tgfbeta family proteins plays important regulatory roles. The GST-pulldown assay showed that HtrA1 binds to a broad range of Tgfbeta family proteins, including Bmp4, Gdf5, Tgfbetas and activin. HtrA1 inhibited signaling by Bmp4, Bmp2, and Tgfbeta1 in C2C12 cells, presumably by preventing receptor activation. Experiments using a series of deletion mutants indicated that the binding activity of HtrA1 required the protease domain and a small linker region preceding it, and that inhibition of Tgfbeta signaling is dependent on the proteolytic activity of HtrA1. Misexpression of HtrA1 near the developing chick eye led to suppression of eye development that was indistinguishable from the effects of noggin. Taken together, these data indicate that HtrA1 protease is a novel inhibitor of Tgfbeta family members.
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PMID:HtrA1 serine protease inhibits signaling mediated by Tgfbeta family proteins. 1497 87

Mild acid degradation of the lipopolysaccharide (LPS) of Proteus mirabilis O20 resulted in depolymerisation of the O-polysaccharide to give a repeating-unit pentasaccharide. A polysaccharide was obtained by O-deacylation of the LPS followed by nitrous acid deamination. The derived pentasaccharide and polysaccharide were studied by NMR spectroscopy, including 2D 1H,1H COSY, TOCSY, ROESY, 1H,13C HMQC and HMQC-TOSCY experiments, along with chemical methods, and the following structure of the repeating unit of the O-polysaccharide was established: [Carbohydrate structure: see text]. As opposite to most other P. mirabilis O-polysaccharides studied, that of P. mirabilis O20 is neutral. A week serological cross-reactivity was observed between anti-P. mirabilis O20 serum and LPS of a number of Proteus serogroups with known O-polysaccharide structure. The ability of LPS of P. mirabilis O20 to activate the serine protease cascade was tested in Limulus amoebocyte lysate and in human blood plasma and compared with that of P. mirabilis O14a,14c having an acidic O-polysaccharide. The LPS of P. mirabilis O20 was found to be less active in both assays than the LPS of P. mirabilis O14a,14c and, therefore, the structurally variable O-polysaccharide may influenced the biological activity of the conserved lipid A moiety of the LPS.
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PMID:Structure of the neutral O-polysaccharide and biological activities of the lipopolysaccharide of Proteus mirabilis O20. 1501 99

S3 peptide, derived from the Sushi 3 domain of Factor C, which is the lipopolysaccharide (LPS)-sensitive serine protease of the horseshoe crab coagulation cascade, was shown previously to harbor antimicrobial activity against Gram-negative bacteria. However, the mechanism of action remains poorly understood at the molecular level. Here we demonstrate that the intermolecular disulfide bonding of S3 resulting in S3 dimers is indispensable for its interaction with LPS. The binding properties of the S3 monomer and dimer to LPS were analyzed by several approaches including enzyme-linked immunosorbent assay (ELISA)-based assay, surface plasmon resonance, and fluorescence correlation spectroscopy (FCS). It is evident that the S3 dimer exhibits stronger binding to LPS, demonstrating 50% LPS-neutralizing capability at a concentration of 1 mum. Circular dichroism spectrometry revealed that the S3 peptide undergoes conformational change in the presence of a disulfide bridge, transitioning from a random coil to beta-sheet structure. Using a fluorescence correlation spectroscopy monitoring system, we describe a novel approach for examining the mechanism of peptide interaction with LPS in the native environment. The strategy shows that intermolecular disulfide bonding of S3 into dimers plays a critical role in its propensity to disrupt LPS micelles and consequently neutralize LPS activity. S3 dimers display detergent-like properties in disrupting LPS micelles. Considering intermolecular disulfide bonds as an important parameter in the structure-activity relationship, this insight provides clues for the future design of improved LPS-binding and -neutralizing peptides.
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PMID:Perturbation of Lipopolysaccharide (LPS) Micelles by Sushi 3 (S3) antimicrobial peptide. The importance of an intermolecular disulfide bond in S3 dimer for binding, disruption, and neutralization of LPS. 1532 39

Cathepsin G (CatG) is a serine protease found in the azurophilic granules of monocytes that is known to have antimicrobial properties, but its role in Mycobacterium tuberculosis infection is unknown. We found that M. tuberculosis infection of human THP-1 monocytic cells induced the down-regulation of CatG mRNA expression, as demonstrated by gene array analysis and reverse transcription-PCR. This was associated with a concomitant decrease in CatG protein and enzymatic activity. In contrast, the expression of lysosomal cathepsins B and D was up-regulated in infected cells. This effect was also observed when THP-1 cells were induced to differentiate into adherent macrophages by exposure to bacterial lipopolysaccharide (LPS). In agreement with this, CatG expression was null in adherent macrophages isolated from bronchoalveolar lavages and normal blood. We wanted to determine if the down-regulation of CatG would be relevant to M. tuberculosis infection. First, we found that addition of CatG to THP-1 cells prior to infection resulted in decreased bacillary viability, presumably due to extracellular killing of bacilli. However, pretreatment of cells with LPS, which decreases intracellular CatG expression, resulted in increased bacillary viability. Second, we found that CatG cationic peptides killed M. tuberculosis bacilli and were five- to sevenfold more bactericidal than full-length CatG. These observations suggest that M. tuberculosis infection of human monocytic cells results in a "cathepsin switch" with down-regulation of CatG rendering M. tuberculosis bacilli more viable. Therefore, the down-regulation of CatG in macrophages is advantageous to M. tuberculosis bacilli and possibly is an important mechanism by which M. tuberculosis is able to evade the host immune defenses.
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PMID:The down-regulation of cathepsin G in THP-1 monocytes after infection with Mycobacterium tuberculosis is associated with increased intracellular survival of bacilli. 1538 70

Urinary trypsin inhibitor (UTI), a serine protease inhibitor, has been widely used as a drug for patients with acute inflammatory disorders such as disseminated intravascular coagulation, shock, and pancreatitis in Japan. Recent studies have demonstrated that serine protease inhibitors may play an anti-inflammatory role beyond merely an inhibitory action on neutrophil elastase at the site of inflammation at least in vitro. To clarify the direct contributions of UTI to inflammatory condition in vivo, we analyzed its roles in experimental systemic inflammatory response induced by intraperitoneal administration of lipopolysaccharide (LPS) using UTI deficient (-/-) mice and corresponding wild-type (WT) mice. After LPS (1 mg/kg) challenge, UTI (-/-) mice revealed a significant elevation of plasma fibrinogen and fibrinogen/fibrin degradation products and a decrease in white blood cell counts compared with WT mice. LPS treatment induced more severe neutrophilic inflammation in the lung and the kidney obtained from UTI (-/-) mice than in those from WT mice, which was confirmed by histological examination. The protein levels of proinflammatory mediators, such as macrophage chemoattractant protein (MCP)-1 in the lungs, MCP-1 and keratinocyte chemoattractant (KC) in the kidneys, and interleukin-1beta, macrophage inflammatory protein-2, MCP-1, and KC in the liver, were significantly greater in UTI (-/-) mice than in WT mice after LPS challenge. Our results suggest that UTI protects against systemic inflammatory response and subsequent organ injury induced by bacterial endotoxin, at least partly through the inhibition of the enhanced expression of proinflammatory cytokines and chemokines.
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PMID:Urinary trypsin inhibitor protects against systemic inflammation induced by lipopolysaccharide. 1557 31

One innate immune response pathway of insects is a serine protease cascade that activates prophenol oxidase (pro-PO) in plasma. However, details of this pathway are not well understood, including the number and order of proteases involved. Protease inhibitors from the serpin superfamily appear to regulate the proteases in the pathway. Manduca sexta serpin-4 and serpin-5 suppress pro-PO activation in plasma, apparently by inhibiting proteases upstream of the direct activator of pro-PO. To identify plasma proteases inhibited by these serpins, we used immunoaffinity chromatography with serpin antibodies to isolate serpin-protease complexes that formed after activation of the cascade by exposure of plasma to bacteria or lipopolysaccharide. Covalent complexes of serpin-4 with hemolymph proteases HP-1 and HP-6 appeared in plasma activated by Gram-positive or Gram-negative bacteria, whereas serpin-4 complexes with HP-21 and two unidentified proteases were unique to plasma treated with Gram-positive bacteria. HP-1 and HP-6 were also identified as target proteases of serpin-5, forming covalent complexes after bacterial activation of the cascade. These results suggest that HP-1 and HP-6 may be components of the pro-PO activation pathway, which are activated in response to infection and regulated by serpin-4 and serpin-5. HP-21 and two unidentified proteases may participate in a Gram-positive bacteria-specific branch of the pathway. Several plasma proteins that co-purified with serpin-protease complexes, most notably immulectins and serine protease homologs, are known to be components of the pro-PO activation pathway. Our results suggest that after activation by exposure to bacteria, components of the pro-PO pathway associate to form a large noncovalent complex, which localizes the melanization reaction to the surface of invading microorganisms.
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PMID:Identification of plasma proteases inhibited by Manduca sexta serpin-4 and serpin-5 and their association with components of the prophenol oxidase activation pathway. 1569 6

Exposure of blood to tissue factor (TF) rapidly initiates the coagulation serine protease cascades. TF is expressed by macrophages and other types of cell within atherosclerotic lesions and plays an important role in thrombus formation after plaque rupture. Macrophage TF expression is induced by pro-inflammatory stimuli including lipopolysaccharide (LPS), interleukin-1beta and tumor necrosis factor-alpha. Here we demonstrate that activation of liver X receptors (LXRs) LXRalpha and LXRbeta suppresses TF expression. Treatment of mouse peritoneal macrophages with synthetic LXR agonist T0901317 or GW3965 reduced TF expression induced by pro-inflammatory stimuli. LXR agonists also suppressed TF expression and its activity in human monocytes. Human and mouse TF promoters contain binding sites for the transcription factors AP-1, NFkappaB, Egr-1 and Sp1, but no LXR-binding sites could be found. Cotransfection assays with LXR and TF promoter constructs in RAW 264.7 cells revealed that LXR agonists suppressed LPS-induced TF promoter activity. Analysis of TF promoter also showed that inhibition of TF promoter activity by LXR was at least in part through inhibition of the NFkappaB signaling pathway. In addition, in vivo, LXR agonists reduced TF expression within aortic lesions in an atherosclerosis mouse model as well as in kidney and lung in mice stimulated with LPS. These findings indicate that activation of LXR results in reduction of TF expression, which may influence atherothrombosis in patients with vascular disease.
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PMID:Liver X receptor agonists inhibit tissue factor expression in macrophages. 1575 69


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