Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.1.53 (sialidase)
 2,694 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cerebral neurons in monolayer cultures, subjected to 25 micrograms/ml trypsin, lose after 10 min about 43.5% and 40.5% of the ability to bind 125I-labeled tetanotoxin as measured at 0-4 degrees C and 37 degrees C respectively. These losses are maximal by 30 min and can be prevented by 1.5 mg/ml soybean trypsin inhibitor. Chymotrypsin but not collagenase or hyaluronidase is also effective in reducing binding of toxin to cells. The trypsin-insensitive toxin-binding activity can be further eliminated by treatment with sialidase or by cell extraction with methanol. Fixation of cells with 3.5% paraformaldehyde or 2% glutaraldehyde also results in a marked decrease of 52.4% and 25% respectively in the toxin-cell association. Methanol or sialidase but not trypsin removes the remaining binding activity. About one-third of the lipid-linked and protein-linked sialic acid is removed after sialidase treatment whereas 1% and 9.4% respectively are removed after trypsin treatment. The data are consistent with the possibility that, in addition to a sialic acid component, binding of tetanotoxin to nerve cells is facilitated by a trypsin-removable and formaldehyde-inactivated component. There was no evidence for a polypeptide to substitute gangliosides as receptors for tetanotoxin. On the contrary, solubility in organic solvents and interaction of the extracted products with labeled toxin remain the major proof that gangliosides are the putative receptors for tetanotoxin.
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PMID:Tetanus toxin receptors on nerve cells contain a trypsin-sensitive component. 394 36

Somatic neurohybrid SB21B1 cells grown in serum exhibit limited capacity to bind 125I-labeled tetanus toxin and cannot synthesize gangliosides higher than GM2. By 6 h after supplementing the culture medium with pure or mixtures of brain gangliosides, binding of 125I-labeled tetanus toxin to cells increases approximately 8-fold compared to that of nonsupplemented cells. The uptake of added gangliosides is a saturable process and is facilitated by serum removal (2.1-fold) or substitution of growth factors for serum (3.8-fold). Enhancement of tetanus toxin binding to cells depends on the ganglioside species and concentration; GT1b (25 micrograms/ml) is, respectively, two and three times as effective as GD1b and GM1 in increasing toxin binding. Reconstitution of ganglioside-mediated tetanus toxin binding activity is a reversible phenomenon; removal of medium gangliosides causes a 3-fold drop in toxin binding by 24 h, after which an apparent plateau for at least 3 days above the basal level is established. As in cerebral cultures, binding of toxin to ganglioside-supplemented neurohybrid cells exhibits salt and sialidase sensitivity and is enhanced 2.6-fold at 37 degrees C compared to 0-4 degrees C. The resultant temperature-dependent toxin-cell association is sialidase insensitive. Fixation of cells by formaldehyde or treatment of ganglioside-supplemented cells with trypsin has no substantial effect on ganglioside-mediated binding of the toxin. Methanol/chloroform treatment of cells causes a 91.4% loss of binding activity.
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PMID:Gangliosides mediate association of tetanus toxin with neural cells in culture. 671 26

The nature of the receptors for four lectins specific for D-galactosyl residues was examined in human lymphocytes. The cells were fixed with formaldehyde to avoid subsequent cell lysis, treated with pronase, sialidase and organic solvents, and the binding of the lectins to the treated cells measured. The results show that the bulk of the receptors for peanut agglutinin (PNA) and ricin (RCA 60) are glycoproteins, whereas those for Ricinus communis agglutinin (RCA 120) and soybean agglutinin (SBA) are distributed nearly equally between membrane glycoproteins and glycolipids.
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PMID:Nature of the receptor sites for galactosyl-specific lectins on human lymphocytes. 672 99

In situ binding of (chimeric) proteins to tissue sections is a widely used method to identify ligands and their localization. Many different protocols for the fixation of frozen tissue sections are used for in situ binding studies. We report the effects of different fixation protocols on the binding pattern observed using in situ binding of an L-selectin-IgM chimeric protein to both rat lymph node and kidney tissue sections. L-selectin is a C-type lectin, expressed on leukocytes and is involved in both lymphocyte homing and migration upon inflammation. We show that different in situ binding patterns in rat kidney are observed using different fixation protocols, including glutaraldehyde, methanol, formaldehyde and acetone fixation. The observed staining is specific, as it can be blocked in the presence of EGTA, an L-selectin blocking antibody or by ligand competition. Enzymatic pre-treatment of the tissue sections using sialidase, heparitinase I or chondroitinase ABC has differential effects on in situ binding depending on tissue type and fixation protocol. These data indicate that special attention should be paid in choosing a fixation protocol for in situ binding studies, especially when using lectins. This could prevent biologically relevant ligands remaining undetected or wrong conclusions being drawn based on the localization of observed binding.
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PMID:Effect of fixation protocols on in situ detection of L-selectin ligands. 1584 5