Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The pattern of proteins in the soluble fraction of the cytoplasm of the rat epididymis was studied by acrylamide gel electrophoresis. The components of five distinct bands, labelled A, B, C, D and E, were found to be sensitive to changes in androgen in the blood. Castration for 14 days produced a sharp decrease in the colour intensity of bands B-E when stained with Amido black. After 21 days of castration, bands D and E were undetectable, bands B and C were severely diminished and band A was more intense. Seven days of replacement with testosterone (1 mg/day) induced a return towards a normal pattern. The degree of restoration was inversely proportional to the duration of castration. Quantitation by densitometry showed that the relative contributions of bands B-E to the region A-E were 61% in the control rat, only 27% after 21 days of castration and 35% when testosterone was given between days 14 and 21 of castration. The components of bands A-E are presumed to be proteins since the electrophoretic pattern was altered by digestion with pronase but not by ribonuclease, phospholipase C or neuraminidase. Epididymides from castrated and androgen-treated castrated rats were incubated with 14C- and 3H-labelled mixed amino acids respectively. After co-electrophoresis the ratio 3H: 14C rose from a baseline of 2-5 in band B, 32 in band C and 7 in bands D and E. Molecular weights were estimated as 27900 for B, 23100 for C and 34400 for D. Band A had the same electrophoretic mobility as serum albumin. Bands B and C were also present in testicular cytosol. Bands D and E were only found in the epididymis, localized mainly within the lumen of the tubules. Bands B-E increased with age during sexual maturation, bands D and E became detectable in the 20-day-old rats. Preliminary evidence indicates that the proteins in bands C, D and E can be removed from caput spermatozoa by washing.
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PMID:Androgen-controlled specific proteins in rat epididymis. 127 Sep 59

The attachment of lymphocytic choriomeningitis virus (LCMV) to murine and primate cell lines was quantitated by a fluorescence-activated cell sorter assay in which binding of biotinylated virus was detected with streptavidin-fluorescein isothiocyanate. Cell lines that were readily infected by LCMV (e.g., MC57, Rin, BHK, Vero, and HeLa) bound virus in a dose-dependent manner, whereas no significant binding was observed to lymphocytic cell lines (e.g., RMA and WIL 2) that were not readily infected. Binding was specific and competitively blocked by nonbiotinylated LCMV. It was also blocked by LCMV-specific antiserum and a neutralizing monoclonal antibody to the virus glycoprotein GP-1 but not by antibodies specific for GP-2, indicating that attachment was likely mediated by GP-1. Treatment of cells with any of several proteases abolished LCMV binding, whereas phospholipases including phosphatidylinositol-specific phospholipase C had no effect, indicating that one or more membrane proteins were involved in virus attachment. These proteins were characterized with a virus overlay protein blot assay. Virus bound to protein(s) with a molecular mass of 120 to 140 kDa in membranes from cell lines permissive for LCMV but not from nonpermissive cell lines. Binding was specific, since unlabeled LCMV, but not the unrelated enveloped virus herpes simplex virus type 1, competed with 125I-labeled LCMV for binding to the 120- to 140-kDa band. The proteinaceous nature of the LCMV-binding substance was confirmed by the lack of virus binding to proteinase K-treated membrane components. By contrast, glycosidase treatment of membranes did not abolish virus binding. However, in membranes treated with endoglycosidase F/N-glycosidase F, and/or neuraminidase and in membranes from cells grown in tunicamycin, the molecular mass of the LCMV-binding entity was reduced. Hence, LCMV attachment to rodent fibroblastic cell lines is mediated by a glycoprotein(s) with a molecular mass of 120 to 140 kDa, with complex N-linked sugars that are not involved in virus binding.
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PMID:Characterization of lymphocytic choriomeningitis virus-binding protein(s): a candidate cellular receptor for the virus. 133 20

Incubation of either C3a, C3ades Arg, or synthetic analogues of the C-terminal sequence of C3a with purified rat peritoneal mast cells resulted in a rapid and dose-dependent histamine release. The natural factors C3a and C3ades Arg were the most active of the factors tested exhibiting EC50 values of 3.3 and 2.2 microM, respectively. The corresponding 21- and 22-residue C-terminal analogues of C3a (Y21R and Y21) were less potent than intact factor exhibiting EC50 values of 10.9 and 25.1 microM, respectively. Histamine was released in a nonlytic manner and the mast cell stimulation by both natural and synthetic factors was sensitive to pertussis toxin, neuraminidase, benzalkonium chloride, and to an excess of calcium. C3a stimulated the generation of inositol polyphosphates that was inhibited by either pertussis toxin or benzalkonium chloride. The C3a anaphylatoxin also directly stimulates purified G proteins (i.e., GTPase activity) in a dose-dependent manner. The evident correlation between efficiency of C3a and C3a analogues to stimulate purified G proteins and their capacity to induce cellular histamine release led us to conclude that C3a fails to activate mast cells via a mechanism involving specific receptors on the cell. Instead, we propose that C3a either causes direct activation of G proteins of the Gi subtype, with a subsequent activation of phospholipase C, or interacts with a binding site of the cell surface specific for cationic molecules that is coupled to the G protein cascade.
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PMID:A mechanism of action for anaphylatoxin C3a stimulation of mast cells. 137 70

The specificity and properties of a novel IgA receptor expressed on the surface of a tissue culture-adapted B cell lymphoma, T560, that originated in murine gut-associated lymphoid tissue, have been explored. Like the IgA receptors of murine T and splenic B cells studied by others, the T560 IgA receptor is trypsin sensitive and neuraminidase resistant and is up-regulated on T560 cells by exposing them overnight to high concentrations of polymeric IgA. Unlike them, the T560 IgA receptor is inhibited by low concentrations of IgM and high concentrations of IgG2a and IgG2b, binds at pH 4.0 but not at pH 8.0, is down-regulated by activation of protein kinase C and is sensitive to phosphatidylinositol-specific phospholipase C, indicating that it is glycosyl phosphatidylinositol-linked to the cell membrane. It is not a cell-bound form of galactosyl transferase, does not appear to bind to Ig through carbohydrate residues and does not react specifically with antibody to secretory component. It may be a completely new, cross-reactive receptor, perhaps related in some way to the polymeric Ig receptor or to the receptor for IgA expressed on the apical surface of Peyer's patch M cells, which is known to cross-react with IgG. Alternatively, it may be homologous to the highly IgA-specific Fc alpha R of T cells but, perhaps because of its glycosyl phosphatidylinositol linker, may have an ability to move and interact with other Ig receptors on the cell surface such that Ig bound to them are cross-inhibitory.
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PMID:A novel IgA receptor expressed on a murine B cell lymphoma. 137 46

Previous studies have shown that thrombin-activated platelets interact through the P-selectin with neutrophils and monocytes. To identify other types of leukocytes capable of such an interaction, eosinophils, basophils, and lymphocytes were isolated from whole blood. Binding of these cells to activated platelets was examined in a double immunofluorescence assay and the results show that activated platelets not only bind to neutrophils and monocytes, but also to eosinophils, basophils, and subpopulations of T lymphocytes. Using monoclonal antibodies (MoAbs) specific for subsets of T cells, we could further demonstrate that the T cells which bind activated platelets are natural killer (NK) cells and an undefined subpopulation of CD4+ and CD8+ cells. All these interactions were dependent on divalent cations and were completely inhibited by an MoAb against P-selectin. Thus, P-selectin mediates the binding of activated platelets to many different types of leukocytes. Studies with leukocytes treated with proteases or neuraminidase have shown that the structures recognized by P-selectin are glycoproteins carrying sialic acid residues. Because the loss of binding of activated platelets to neuraminidase-treated neutrophils was almost complete, but only partial to treated eosinophils, basophils, and monocytes, the latter cell types may have different P-selectin ligands in addition to those present on neutrophils. We found that two previously identified ligands for P-selectin, the oligosaccharides Le(x) and sialyl-Le(x), had little or no inhibitory effect on adhesion of activated platelets to leukocytes and that binding was not inhibited by MoAbs against these oligosaccharides. In addition, there was no correlation between the expression of Le(x) on several cell types and their capacity to bind activated platelets. In contrast, the expression of sialyl-Le(x) on cells was almost perfectly correlated with their ability to bind activated platelets. Thus, while Le(x) cannot be a major ligand for P-selectin, a possible role for sialyl-Le(x) in P-selectin-mediated adhesion processes cannot be dismissed. Finally, activated platelets were found to bind normally to monocytes and neutrophils of patients with paroxysmal nocturnal hemoglobulinuria (PNH) and to neutrophils from which phosphatidyl inositol (PI)-linked proteins had been removed by glycosylphosphatidyl inositol-specific phospholipase C (GPI-PLC) digestion. This suggests that at least part of the P-selectin ligands on these cells are not GPI-anchored.
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PMID:P-selectin mediates Ca(2+)-dependent adhesion of activated platelets to many different types of leukocytes: detection by flow cytometry. 137 47

Trypanosoma cruzi enters host cells via formation of an acidic vacuole which is subsequently disrupted, allowing the parasite access to the cytoplasm. We show that in an acid environment, release of the parasite surface neuraminidase is enhanced, and this release is likely mediated by a phosphatidylinositol-specific phospholipase C (PIPLC), since antibodies to a carbohydrate epitope (CRD) revealed in glycosylphosphatidylinositol (GPI)-anchored proteins after PIPLC cleavage remove the great majority of the soluble neuraminidase activity from culture supernatants. The neuraminidase is active at acidic pH, and is capable of desialylating known vacuolar constituents, i.e., lysosomal membrane glycoproteins. Parasite escape into the cytoplasm is significantly facilitated in terminal sialylation-defective mutant Lec 2 cells, and enzymatically desialylated membranes are more susceptible to lysis by a parasite hemolysin previously implicated in vacuole membrane rupture. These findings provide evidence that terminal sialylation on carbohydrate moieties contributes to maintaining lysosomal membrane integrity, and indicate a role for a protozoan-derived neuraminidase in facilitating parasite entry into host cells. These observations raise the possibility that other microbial neuraminidases may serve a similar function in acidic intracellular compartments.
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PMID:Desialylation of lysosomal membrane glycoproteins by Trypanosoma cruzi: a role for the surface neuraminidase in facilitating parasite entry into the host cell cytoplasm. 150 Aug 49

125I-epsilon-toxin showed high affinity to rat brain homogenates and synaptosomal membrane fractions, having single binding phases with dissociation constants (Kds) of 2.5 and 3.3 nM, respectively. Treatment of synaptosomal membrane fractions with pronase and neuraminidase lowered the binding of the labeled toxin, whereas treatment with trypsin and phospholipase C did not. Heating of the fractions resulted in a decrease in the binding of the toxin. These data suggest that interaction of epsilon-toxin with cell membranes in the brain is facilitated by a sialoglycoprotein. On the other hand, treatment of the membrane fractions with lipase resulted in complete loss of binding, suggesting that the interaction may require an appropriate lipid environment. These data suggest the presence of specific binding sites in brain tissue for epsilon-toxin.
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PMID:High-affinity binding of Clostridium perfringens epsilon-toxin to rat brain. 154 39

gp65 and gp55 are glycoprotein components of CNS synapses that are recognised by a single monoclonal antibody, SMgp65. This antibody has now been used to investigate the molecular properties of these two glycoproteins and the structural relationship between them. Both gp65 and gp55 occur in most brain regions as doublets of apparent molecular masses of 63 and 67 kDa, and 52 and 57 kDa, respectively. Striatal samples, however, are enriched in a novel gp65 isoform of 69 kDa. Removal of oligosaccharide residues from gp65 and gp55 with trifluoromethanesulphonic acid shows that gp65 and gp55 are composed of single polypeptide chains of 40 and 28 kDa, respectively. Removal of sialic acid residues with neuraminidase lowers the apparent molecular mass of both glycoproteins by 5-6 kDa. Triton X-114 phase partitioning and alkaline extraction of synaptic membranes indicate that both gp65 and gp55 are integral membrane glycoproteins. Treatment of synaptic membranes with phosphatidylinositol-specific phospholipase C does not solubilise either glycoprotein. One-dimensional peptide and epitope maps obtained by digestion of gp65 and gp55 with endoproteinase lys C or subtilisin are consistent with a close structural relationship between the two molecules. Tryptic digestion of samples enriched in gp65 and/or gp55 results in the formation of a novel immunoreactive 53-kDa species that is resistant to further trypsin degradation except in the presence of 0.1% (wt/vol) sodium dodecyl sulphate. Trypsin treatment of cultures of forebrain neurones in situ lowers the apparent molecular mass of gp65 to 53 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Molecular characterisation and structural relationship of the synapse-enriched glycoproteins gp65 and gp55. 157 91

The adherence of Pseudomonas aeruginosa PAO1 to primary cultures of cystic fibrosis nasal polyp (CFNP), normal human nasal polyp (NHNP), and immortalized CF and normal cell lines was studied. PAO1 bound significantly more to primary CFNP cells than to NHNP cells as the mean adherence +/- standard deviation of 5 x 10(7) CFU of 35S-labeled bacteria per ml per well was 15.09 x 10(6) +/- 4.25 x 10(6) CFU/ml per well and 7.62 x 10(6) +/- 2.11 x 10(6) CFU/ml per well, respectively (Mann-Whitney U test, P less than 0.0001). There was no significant difference in PAO1 adherence to the immortalized CF and normal cell lines. The primary CFNP cells had more receptors (115 per cell) than did NHNP cells (34 per cell). P. aeruginosa binding to CFNP was blocked by GlcNAc, NeuAc, L-Fuc, and D-Gal, while binding to NHNP was blocked only by GlcNAc, suggesting that receptors on the two cell types were qualitatively different. Pseudomonas supernatants containing protease, phospholipase C, and neuraminidase activity increased adherence to CFNP and NHNP cells. The Pseudomonas exoproducts modified epithelial cell glycoconjugates, as characterized by binding of fluorescein isothiocyanate-labeled lectins and the release of sialic acid. There was minimal release of fibronectin by the bacterial supernatants. The affinity of P. aeruginosa for CF epithelial cells appeared to be due to an increased number of receptors and modification of the epithelial cell surface by P. aeruginosa exoproducts that exposed asialoganglioside binding sites.
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PMID:Comparison of adherence of Pseudomonas aeruginosa to respiratory epithelial cells from cystic fibrosis patients and healthy subjects. 161 46

Pseudorabies virus hemagglutinin was readily adsorbed on mouse erythrocytes at 4, 22, or 37 degrees C, but not on cattle erythrocytes. The adsorbed hemagglutinin could not be eluted from the cells by resuspending in phosphate-buffered saline (PBS), by incubating at 37 or 50 degrees C, or by incubating in the presence of neuraminidase. The receptor on mouse erythrocytes for the hemagglutinin was inactivated by trypsin, but not by neuraminidase, sodium deoxycholate (DOC), potassium periodate (KIO4), dithiothreitol (DTT), 2-mercaptoethanol (2-ME) and formalin. The hemagglutinin was inactivated by trypsin, alpha-amylase, pepsin, DOC, KIO4, and ethylendiamine-tetraacetic acid (EDTA), but not by papain, beta-glucosidase, phospholipase C, neuraminidase, DTT, 2-ME, Tween-80, ethylether, chloroform, trichloro-trifluoroethane, beta-propiolactone and formalin, suggesting that the hemagglutinin active component involved glycoproteins. The hemagglutinin was stable at 37 degrees C for lower temperatures but not at 60 degrees C or higher. The hemagglutinin activity was resistant to ultraviolet irradiation, while the infectivity was very susceptible. The hemagglutinin and the infectivity were readily sedimented by ultracentrifugation at 48,000 x g for 3 hr. In rate zonal centrifugation of the preparation on a sucrose density gradient, the hemagglutination (HA) activity showed a sharp peak at 1.22 g/ml coinciding with the peak of infectivity. The HA activity in the peak fraction seemed to be structually associated with virus particles. After fractionation of the virus by Nonidet P-40, the HA activity was found only in the fraction of the envelope material, indicating that the hemagglutinin is situated in the viral envelop.
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PMID:Physicochemical properties of pseudorabies virus hemagglutinin. 166 85


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