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Production and purification of active snowdrop lectin in Escherichia coli.

Recombinant snowdrop lectin was produced in Escherichia coli from a cDNA clone encoding mature Galanthus nivalis agglutinin. After induction with isopropylthio-beta-D-galactoside, inclusion bodies from E. coli were solubilised and the G. nivalis agglutinin purified by metal-affinity chromatography using a carboxy-terminal hexahistidine tag. The protein was refolded on the metal-affinity column prior to elution. After purification, the recombinant G. nivalis agglutinin agglutinated rabbit erythrocytes to a dilution similar to that determined for 'native' lectin purified from snowdrop, and showed similar specific binding to mannose. The toxicity of the recombinant G. nivalis agglutinin towards rice brown planthopper (Nilaparvata lugens) was shown to be similar to that of 'native' G. nivalis agglutinin when incorporated into an artificial diet. The recombinant G. nivalis agglutinin is thus functionally similar to 'native' snowdrop lectin.

Amino Acid Sequence↗

Interaction between plant agglutinins and Legionella species.

Serogroups of Legionella pneumophila exhibited differential reactivities with plant agglutinin. Agglutination patterns were modified by growing the organisms in different media. The passage of four strains through guinea pigs did not result in altered reactivities with lectins or with plant agglutinins.

Alkalies↗

Stimulating effect of mercuric chloride and nickel sulfate on DNA synthesis of thymocytes and peripheral lymphoid cells from newborn guinea pigs.

The metal allergens mercuric chloride and nickel sulfate were found to stimulate DNA synthesis of different in vitro cultured lymphoid cells from newborn guinea pigs. In contrast to earlier findings in adult animals (where spleen cells were most consistently stimulated), in newborn animals thymocytes were the most clearly stimulated lymphoid cells. When separating thymocytes by peanut agglutinin agglutination, both agglutinated and nonagglutinated cells were stimulated, indicating that both functionally immature and mature thymocytes are the target cells for this effect of metal allergens.

Agglutinins↗

Carbohydrates may play an important role in the interaction between phagocytic vesicles and lysosomes.

Agglutination of phagocytic vesicles by plant lectins and lysosomes from guinea pig polymorphonuclear leukocytes (PMNs) were examined in vitro. PMNs were allowed to phagocytize paraffin oil emulsion, and phagocytic vesicles were isolated from the cells. First, the vesicles were suspended in isotonic sucrose or lactose with or without lectins, and then they were incubated at 0 degrees C for 20 min and photographed under a phase-contrast microscope. In sucrose, lectins such as Ricinus communis agglutinin, wheat germ agglutinin, Phaseolus vulgalis agglutinin-P and Ulex europeus agglutinin agglutinated the vesicles, while the vesicles without lectins remained dispersed. Concanavalin A agglutinated the vesicles in lactose solution, but the other lectins did not. These results suggest that the phagocytic vesicles have lectin receptors (carbohydrate moieties) on their cytoplasmic side, as galactosyl-, N-acetyl-galactosaminyl-, mannosyl-, glucosyl-, N-acetylglucosaminyl- and di-N-acetylchitobiose residues. Second, the phagocytic vesicles were incubated with lysosomes. Lysosomes induced agglutination of the vesicles immediately after incubation and this agglutination was inhibited by simultaneous addition of 50 mM mannose, fucose, N-acetylglucosamine, lactose and maltose, and 7 mM N-acetylneuraminic acid and 1.25 mg/ml fetuin. The results show that lysosomes agglutinated the phagocytic vesicles in vitro, and suggest that this interaction is mediated by recognition of the carbohydrate moieties on the vesicles.

Agglutination↗

Purification and characterization of a Neu5Acalpha2-6Galbeta1-4Glc/GlcNAc-specific lectin from the fruiting body of the polypore mushroom Polyporus squamosus.

A lectin has been purified from the carpophores of the mushroom Polyporus squamosus by a combination of affinity chromatography on beta-D-galactosyl-Synsorb and ion-exchange chromatography on DEAE-Sephacel. Gel filtration chromatography, SDS-polyacrylamide gel electrophoresis, and N-terminal amino acid sequencing indicated that the native lectin, designated P. squamosus agglutinin, is composed of two identical 28-kDa subunits associated by noncovalent bonds. P. squamosus agglutinin agglutinated human A, B, and O and rabbit red blood cells but precipitated only with human alpha(2)-macroglobulin, of many glycoproteins and polysaccharides tested. The detailed carbohydrate binding properties of the purified lectin were elucidated using three different approaches, i.e. precipitation inhibition assay (in solution binding assay), fluorescence quenching studies, and glycolipid binding by lectin staining on high-performance thin layer chromatography (solid-phase binding assay). Based on the results obtained by these assays, we conclude that although the P. squamosus lectin binds beta-D-galactosides, it has an extended carbohydrate-combining site that exhibits highest specificity and affinity toward nonreducing terminal Neu5Acalpha2, 6Galbeta1,4Glc/GlcNAc (6'-sialylated type II chain) of N-glycans (2000-fold stronger than toward galactose). The strict specificity of the lectin for alpha2,6-linked sialic acid renders this lectin a valuable tool for glycobiological studies in biomedical and cancer research.

ABO Blood-Group System↗

An endogenous carbohydrate-binding agglutinin of BHK cells. Purification, specificity and interaction with normal and ricin-resistant cell lines.

Several lectin-like activities were detected on the surface of unfixed, viable BHK cells by reaction with FITC-labelled glycosylated albumin derivatives. A prominent surface staining was obtained with the beta-lactosyl, beta-N-acetylgalactosaminyl, alpha-mannosyl and beta-N-acetylglucosaminyl derivatives. Endogenous lectin-like activities were also detected in BHK cell homogenates by haemagglutination of glutaraldehyde-fixed rabbit erythrocytes. Haemagglutinating activity was purified by chromatography of sodium deoxycholate-extracts of BHK cell microsomal fractions on Sepharose 4B and asialofetuin-Sepharose 4B. A purified agglutinin was eluted from the latter column with 0.2 M thiodigalactoside. The haemagglutination mediated by the purified factor was inhibited by thiodigalactoside, N-acetylgalactosamine, galactosyl-beta 1-4-N-acetylglucosamine and several glycoproteins. The purified agglutinin agglutinated trypsinised, fixed normal BHK cells more readily than several ricin-resistant cell lines. By contrast, a mannose-binding lectin from rabbit serum reacted equally well with normal and mutant cells. These results are in general agreement with models of cell-cell adhesion involving the interaction of surface located lectins with carbohydrate sequences of normal BHK cell surface glycoproteins.

Animals↗

Establishment of a murine thymic epithelial cell line capable of inducing both thymic nurse cell formation and thymocyte apoptosis.

A thymic epithelial cell (TEC) line (B/c. TEC-L1) was established from a normal thymus of a 4-week BALB/c mouse. The B/c. TEC-L1 had an epithelial morphology showing a contact-inhibited cobblestone-like arrangement with occasional desmosome-like structures at the adjacent cellular membranes. B/c.TEC-L1 cells showed positive staining for desmosomal glycoprotein, cytokeratin, thymosin alpha 1 beta 3, and I-Ad, and MHC class I antigens. The doubling time was 24 hours, and the chromosome number ranged from 52 to 78 with the mode of 70. Coculture of B/c.TEC-L1 cells with syngeneic, peanut agglutinin-agglutinated (PNA+) thymocytes in suspension at 37 degree C was followed by the formation of TEC thymocyte rosettes, after which the reconstitution of thymic nurse cells ensued. At 4 degrees C, PNA+ thymocytes bound to the B/c.TEC-L1 cell but did not form thymic nurse cells. PNA- thymocytes, although to a lesser degree than PNA+ cells, bound to the TECs at 37 degrees C, but at 4 degrees C few cells bound to the TECs. Allogeneic thymocytes also bound to the TECs at 37 degrees C. When the PNA+ thymocytes were cultured on the B/c.TEC-L1 monolayer, the small ones chiefly adhered on the surface of the TECs, while underneath the TECs the relatively large thymocytes (including cells in mitosis) predominated. Although the PNA- thymocytes bound to the surface of the monolayer within a few hours after coculture, by 24 hours nearly all cells disappeared. It is presumed that the thymocytes creeping underneath the B/c.TEC-L1 monolayer and those enveloped within the thymic nurse cell reconstituted in the suspension culture; both may be placed in circumstances analogous to the thymic microenvironment, wherein immature thymocytes appear to contact TECs directly and to be exposed to higher concentrations of thymic hormones and other soluble factors. Additionally, cell death in the PNA+ thymocytes was also observed in the coculture with B/c.TEC-L1 cells. The PNA+ cells revealed the morphological changes termed "apoptosis" characterized by chromatin condensation and nuclear fragmentation.

Animals↗

Interleukins 2 and 3 regulate the in vitro proliferation of two distinguishable populations of 20-alpha-hydroxysteroid dehydrogenase-positive cells.

The ability of interleukin 2 (IL 2), interleukin 3 (IL 3), and granulocyte/macrophage colony-stimulating factor (GM-CSF) to induce the proliferation of cells from thymus, spleen, or bone marrow was examined and compared with their ability to induce expression of the enzyme 20-alpha-hydroxysteroid dehydrogenase (20 alpha SDH). In the thymus, the peanut agglutinin agglutinated cells (PNA+) lacked 20 alpha SDH and showed no detectable response to IL 2, IL 3, or GM-CSF in either proliferation or induction of 20 alpha SDH. In contrast, the PNA nonagglutinated (PNA-) subpopulation expressed 20 alpha SDH and proliferated in response to Con A and/or IL 2. The responding cells that could be expanded in vitro with IL 2 expressed high levels of 20 alpha SDH. Neither IL 3 nor GM-CSF in the presence or absence of Con A had a demonstrable effect on the PNA- population. In cultures of bone marrow cells, both IL 3 and GM-CSF induced proliferation, whereas IL 2 had no effect on proliferation in the presence or absence of Con A. Thy-1-depleted bone marrow cells, expanded in tissue culture with IL3, contained cells that co-expressed Thy-1 and 20 alpha SDH. In contrast, cells proliferating in vitro to GM-CSF did not expressed Thy-1 or 20 alpha SDH. In cultures of normal splenic lymphocytes, two populations of cells capable of expressing 20 alpha SDH were detected. One population could be expanded in vitro with IL 2 and Con A, whereas the second was responsive to IL 3. In spleens from athymic mice, only the latter cells were detected. These results demonstrate that IL 3 and IL 2 responsiveness distinguishes two populations of 20 alpha SDH cells. The relevance of these observations to the possible relationship of IL 3 and IL 2 in T cell differentiation is discussed.

20-Hydroxysteroid Dehydrogenases↗

Differential agglutination by soybean agglutinin of human leukemia and neuroblastoma cell lines: potential application to autologous bone marrow transplantation.

Normal human bone marrow cells were mixed with radioactively labeled tumor cells from different leukemia and neuroblastoma cell lines, and the cell mixtures were separated by differential agglutination with soybean agglutinin. It is shown that the cell fraction unagglutinated by soybean agglutinin, which was previously found to be capable of reconstituting the hematopoietic system of lethally irradiated recipients, can be purged of tumor cells with varying efficiency depending on the tumor cell expression of soybean agglutinin receptors as detected by flow cytofluorimetry with fluoresceinated soybean agglutinin.

Animals↗

Receptor distribution and the mechanism of enhanced erythrocyte agglutination by soybean agglutinin.

We have examined the role of receptor clustering in intact erythrocyte membranes exhibiting enhanced lectin-mediated cell agglutination by analyzing freeze-fracture and freeze-etch images of human erythrocytes labeled with ferritin-conjugated soybean agglutinin. We find that trypsinization and fixation of intact erythrocytes, in either order, causes no alteration of the random distribution of ferritin-conjugated soybean agglutinin on the surfaces of these cells as compared to their distribution on the surfaces of fixed erythrocytes and untreated erythrocyte ghosts. Furthermore, clustering of the intramembranous particles in the membrane of intact erythrocytes was not found with any of the cells described above. We conclude that clustering of the soybean agglutinin receptors is not a major factor involved in the enhanced agglutination of intact trypsinized erythrocytes. Caution is necessary in transferring information obtained with erythrocyte ghosts, where clustering can be induced, to intact erythrocytes.

Agglutinins↗

Isolation and characterization of mutants of Streptococcus mutans using selective removal of wild-type cells by agglutination with an agglutinin from Persea americana.

Persea americana agglutinin (PAA), a substance known to bind basic proteins and inhibit the sucrose-independent adherence of Streptococcus mutants to saliva = coated hydroxyapatite (Staat et al., 1980) was used to selectively enrich for mutants defective in a variety of cell surface associated virulence characteristics from cultures UAB62 (PS14 Riff, serotype c), UAB66 (6715 Strr Spcr, serotype g) and UAB77 (GS5, serotype c). Following mutagenesis and growth for segregation and phenotypic expression, washed cells of each strain were exposed to PAA overnight at 37 degrees C. Aggregated cells were removed by low-speed centrifugation and cells remaining in the supernatant fluids were concentrated, grown to stationary phase and the enrichment with PAA repeated. Mutants isolated following enrichment were phenotypically diverse and included strains defective in one or more of the following characteristics: adherence to glass in a sucrose-containing medium, aggregation with sucrose, dextran or PAA. dextranase production, colony morphology, cell or chain morphology, fermentation of sorbitol, lactose, galactose, raffinose, melibiose, or fructose, and production of surface protein antigen A (SpaA). The diversity of mutant phenotypes identified along with the observation that PAA could still cause aggregation (with a lower efficiency) of all mutants leads us to infer that the interaction of this agglutinin with proteins on the S. mutans cell surface is relatively nonspecific and that the observed inhibition of S. mutants attachment to saliva-coated hydroxyapatite caused by PAA is not due to a highly specific unique interaction of PAA with the protein(s) responsible for sucrose-independent adherence.

Agglutination↗