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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The adsorption to human erythrocytes of Escherichia coli lipopolysaccharide treated by mild alkaline hydrolysis (h-LPS) stimulated an increase in the intracellular Na+ concentration and a decrease in the intracellular K+ concentration of the erythrocytes. Erythrocytes treated by h-LPS remained responsive to the membrane adenosine triphosphatase inhibitors ouabain and ethacrynic acid, indicating that hLPS did not alter erythrocyte cations be depleting energy intermediates or uncoupling energy metabolism from active cation transport. The h-LPS-treated erythrocytes became non-agglutinable by the lectin concanavalin A prior to the development of changes in intracellular cations. In addition, h-LPS-treated erythrocytes demonstrated a three-fold greater cation response to ethacrynic acid than the untreated erythrocytes; this greater response was probably due to local membrane effects by h-LPS on the ethacrynic acid-sensitive adenosine triphosphatase. It is suggested that the h-LPS-induced alteration of erythrocyte cation content was secondary to an increase in ion permeability localized to the concanavalin A receptor regions of the erythrocyte membrane, possibly combined with indirect effects of membrane-bound h-LPS on ethacrynic acid-sensitive adenosine triphosphatase.
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PMID:Effect of alkali-treated lipopolysaccharide on the intracellular cations of human erythrocytes. 33 Apr 8

The high sensitivity of rough mutants of Salmonella typhimurium, S. minnesota, and Escherichia coli 08 (i.e. with defects in the carbohydrate core of the lipopolysaccharide) to several antibiotics and to the dye gentian violet could be substantially reduced by the addition of cations (Mg2+, Na+) into the growth medium. One heptoseless mutant of S. typhimurium (chemotype Re) and its isogenic smooth parent strain were studied in more detail. The uptake of gentian violet was about 20% in the smooth strain, about 60% in the Re strain grown without additional cations, but decreased to about 15% in the same strain, when cations had been present during growth. In all cases, almost 50% of the gentian violet taken up by the cells was membrane-bound. The total membranes of the Re strain grown in nutrient broth without additional Mg2+ ions were reduced in the 36K and 34K major outer membrane proteins compared with the smooth strain; when grown with added cations the Re total membranes (and even whole cells) did not revert to the protein pattern of the smooth strain.
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PMID:The influence of cations on the permeability of the outer membrane of Salmonella typhimurium and other gram-negative bacteria. 38 29

Highly purified preparations of cytoplasmic and outer membrane were isolated from aerobically grown Rhodospirillum rubrum lysed by sequential treatment with lysozyme, ethylenediaminetetraacetate, and Brij 58. The membranes were resolved and separated from other cellular constitutents by a combination of velocity and isopyknic sedimentation in sucrose density gradients. On the basis of their appearance in electron micrographs and their protein profiles in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, these preparations appear to be quite similar to those obtained from other gram-negative bacteria. The cytoplasmic membrane fraction contained the majority of the total membrane-bound succinic dehydrogenase activity and was 10-fold enriched in b- and c-type cytochrome with respect to the outer membrane. The latter fraction was characterized by a much greater carbohydrate content and the presence of arachidic acid, which is typical of R. rubrum lipopolysaccharide. Their protein fatty acid, and overall chemical compositions suggested that these preparations were freer from cross-contamination than those obtained from R. rubrum with currently available methods.
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PMID:Membranes of Rhodospirillum rubrum: isolation and physicochemical properties of membranes from aerobically grown cells. 82 Jun 89

Both the synthesis of lipopolysaccharide O-antigen and the synthesis of peptidoglycan in Salmonella typhimurium proceed via membrane-bound glycosylated lipid intermediates. The first enzyme of each pathway transfers a sugar phosphate from a nucleotide sugar to the glycosyl carrier lipid (P-GCL). Each enzyme catalyzes an exchange reaction between the reaction product urine monophosphate, and the nucleotide sugar substrate. Several strains of S. typhimurium defective in lipopolysaccharide synthesis accumulate glycosylated lipid intermediates under appropriate conditions. In addition, strains lysogenic for phage P22 synthesize a glucose derivative of the carrier lipid. These strains were used to demonstrate the P/GCL requirement of the exchange reaction catalyzed by galactose-diphosphoglycosyl carrier lipid (GCL-PP-Gal) synthetase, the first enzyme of O-antigen synthesis. Enzyme activity is greatly reduced when glycosylated P-GCL accumulates on the cytoplasmic membrane. The exchange reaction catalyzed by the first enzyme of peptidoglycan synthesis is unaffected by the accumulation of O-antigen fragments on the carrier lipid and may interact with a different pool of P-GCL within the membrane. GCL-PP-Gal synthetase activity cannot be detected in the membranes of two rfa mutants that synthesize incomplete lipopolysaccharide core. Either the synthesis of GCL-PP-Gal synthetase or the stable integration of the enzyme into the membrane structure may be disrupted in the rfa mutants. Peptidoglycan synthesis is unaffected by the mutations affecting the core glycosyltransferases.
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PMID:Membrane-associated nucleotide sugar reactions: influence of mutations affecting lipopolysaccharide on the first enzyme of O-antigen synthesis. 109 85

CD14 is a 53-kd glycoprotein that is mainly expressed in myeloid cells and exists in two forms. The membrane-bound form represents the receptor for complexes of lipopolysaccharide (LPS) with LPS binding protein. The function and regulation of the soluble form are unknown. In the present study we investigated the release of soluble CD14 (sCD14) in cultures of human mononuclear leukocytes, elutriated monocytes, and monocyte-derived macrophages. The release of sCD14 into the medium of the cells cultured for 15 and 45 h was investigated in the absence or presence of selected cytokines. sCD14 release occurred constitutively and correlated with cell number. In monocytes differentiating into macrophages, cumulative release of sCD14 was linear from day 1 to day 7. Spontaneous sCD14 release after 15 h of culture (2 x 10(6) cells/ml) was higher in the supernatant from monocytes (314 +/- 58 ng/ml) than that from mononuclear leukocytes (68 +/- 10 ng/ml) and similar to that from macrophages (469 +/- 79 ng/ml). Cycloheximide and actinomycin D inhibited sCD14 release. Recombinant interferon-gamma (rIFN-gamma) and recombinant interleukin-4 (rIL-4) directly decreased sCD14 release in mononuclear leukocyte, monocyte, and macrophage cultures. rIL-2 and rIFN-alpha reduced sCD14 release into the supernatants of mononuclear leukocytes only. Use of anti-IFN-gamma antibodies indicated that the down-regulation of sCD14 release by rIL-2 and rIFN-alpha was partially due to induction of endogenous IFN-gamma. The down-regulation of sCD14 release by all four cytokines was both time and dose dependent. rIFN-gamma and rIL-4 added simultaneously had a synergistic effect on sCD14 down-regulation. In conclusion, sCD14 release may have an immunomodulatory role in circulating monocytes, is apparently not related to the process of macrophage differentiation, and is selectively down-regulated during an immune response when levels of IFN-gamma and IL-4 are high.
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PMID:Interferon-gamma and interleukin-4 down-regulate soluble CD14 release in human monocytes and macrophages. 138 44

Coagulation disorders have been associated with the use of chemotherapeutic drugs. Pharmacological doses of cisplatin and adriamycin directly induced low levels of procoagulant on normal human blood monocytes and on a human myelomonocytic cell line, RC2a. Activity was maximal after 24 h and was not due to cell lysis as increasing drug doses which decreased cell viability were less effective. Procoagulant induction was markedly enhanced in the presence of bacterial lipopolysaccharide (LPS), with as little as 10-100 pg/ml LPS potentiating the cisplatin response by 2-5-fold and more than doubling the adriamycin response. Greater than 90% of the procoagulant activity was membrane-bound tissue factor as indicated by the factor VII-dependent generation of factor Xa by viable cells and by the neutralization of this activity by a monoclonal antibody to tissue factor. Tissue factor antigen was measured simultaneously by immunohistochemical staining and by cell ELISA. Blood monocytes activated with LPS expressed high levels of tissue factor antigen; by contrast, adriamycin and cisplatin did not appear to induce antigen expression, but to enhance the specific activity of that already present. Results suggest that membrane alterations which occur following treatment with DNA/RNA intercalating drugs, may result in a highly active form of monocyte/macrophage tissue factor which may contribute to the complications caused by activated coagulation. Secondary Gram-negative infection or cytokines released by an active immune response to a tumour may contribute to the procoagulant potential of these cytotoxic drugs.
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PMID:Modulation of tissue factor on human monocytes by cisplatin and adriamycin. 139 Feb 32

A series of immunoglobulin (Ig)-transgenic mice were generated to study the functional capabilities of the IgM and IgD classes of B lymphocyte antigen receptor in regulating both cellular development and responses to specific antigen. B cells from Ig-transgenic mice expressing either hen-egg lysozyme (HEL)-specific IgM or IgD alone were compared with B cells from mice that coexpressed IgM and IgD of the same anti-HEL specificity. In all three types of Ig-transgenic mice, conventional B cells specific for HEL exhibited exclusion of endogenous Ig expression and matured to populate the usual microenvironments in peripheral lymphoid tissues. These peripheral B cells could be stimulated by HEL through either IgM or IgD antigen receptors to generate T cell dependent antibody production in vivo or to enhance T cell independent proliferative responses to lipopolysaccharide in vitro. Conversely, when HEL was encountered in vivo as a self-antigen, B cells expressing HEL-specific IgM or IgD alone were both rendered tolerant. In each case this occurred by clonal anergy in response to soluble autologous HEL, and clonal deletion when HEL was recognized as a membrane-bound self-antigen. Taken together, these findings indicate that IgM and IgD antigen receptors expressed alone on conventional B cells can support normal differentiation, antigen-dependent activation, and induction of self-tolerance, the only overt difference lying in a greater degree of receptor downregulation for IgM relative to IgD after induction of clonal anergy by soluble HEL.
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PMID:Immunoglobulin M and D antigen receptors are both capable of mediating B lymphocyte activation, deletion, or anergy after interaction with specific antigen. 140 69

When B cells are stimulated with lipopolysaccharide (LPS) they start to proliferate and mature into immunoglobulin (Ig)-secreting cells. Co-stimulation with F(ab')2 fragments of antibodies directed against the B cell antigen receptor leads to an inhibition of Ig secretion but not of proliferation. This effect can be mimicked by phorbol esters alone or by a combination of phorbol esters and the Ca2+ ionophore ionomycin, which activate protein kinase C. Here we report that co-stimulation with phorbol esters and ionomycin differentially affects a group of genes normally up-regulated during the course of LPS-dependent B cell activation. Thus, the mRNA coding for the membrane-bound form of IgM and the interleukin 2 receptor (55-kDa protein) continue to be expressed at the levels typical of LPS-stimulated cells, while the mRNA coding for the secreted form of IgM (mu S) and for the J chain are reduced. The loss of mu S mRNA is attributable to an altered processing behavior with respect to the mu precursor and/or a decreased stability of the mRNA itself.
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PMID:Regulation of immunoglobulin gene expression in normal lymphocytes. II. Mechanisms of down-regulation of immunoglobulin secretion after engagement of the B cell antigen receptor. 153 86

Tissue factor (TF) is the membrane-bound glycoprotein whose cofactor activity with factor VIIa causes activation of the extrinsic pathway of coagulation. The transition of endothelium to a procoagulant state by agents such as bacterial lipopolysaccharide (LPS) is the result of TF expression by these cells. The mechanism of TF induction in human umbilical vein endothelial cells (HUVEC) was investigated in response to LPS and phorbol 12-myristate 13-O-acetate (PMA). Northern blot analysis of total RNA from HUVEC showed a rapid rise in TF mRNA levels which was maximal at 2 h and had fallen to low levels by 6 h following both LPS (10 micrograms/ml) and PMA (10 ng/ml) stimulation. Nuclear-run on experiments showed at most a 2-fold increase in transcription of the TF gene following LPS stimulation but a 10-fold increase following PMA stimulation. In addition 24-h pre-incubation with PMA desensitized HUVEC to further PMA exposure, but caused no alteration in the response to LPS. Cycloheximide (10 micrograms/ml) alone caused induction of TF mRNA. Treatment of cells previously exposed to LPS for 1 or 4 h with actinomycin D indicated a 12-fold difference in the TF mRNA half-life. Therefore the rapid accumulation of TF mRNA in HUVEC stimulated by LPS is largely a result of an increase in mRNA stability rather than an increased rate of transcription of the gene.
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PMID:The regulation of tissue factor mRNA in human endothelial cells in response to endotoxin or phorbol ester. 169 17

Nitric oxide (.NO) synthase (NOS) activity in subcellular fractions from cultured endothelial cells (EC) and lipopolysaccharide-activated J774.2 monocyte/macrophages was investigated by monitoring the .NO-mediated increase in intracellular cyclic GMP in LLC-PK1 pig kidney epithelial cells. The constitutive NOS in EC (NOSc) was largely membrane-bound, whereas the inducible NOS in J774.2 cells (NOSi) was equally distributed among cytosol and membrane(s). Both the cytosolic NOSc in EC and the membrane-bound NOSi in J774.2 cells were strictly Ca(2+)-dependent, whereas the membrane-bound NOSc in EC and the cytosolic NOSi in J774.2 cells were not. L-Homoarginine and L-arginine-containing small peptides, such as L-arginyl-L-phenylalanine, replaced L-arginine as a substrate for the NOSc in EC and the Ca(2+)-independent NOSi in J774.2 cells, but not the Ca(2+)-dependent NOSi. Thus, irrespective of their intracellular localisation, at least three isoforms of NOS exist, which can be differentiated by their substrate specificity and Ca(2+)-dependency.
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PMID:On the substrate specificity of nitric oxide synthase. 172 80


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