The fucosyl specific lectins of Ulex europaeus and Sarothamnus scoparius. Biochemical characteristics and binding properties to human B-lymphocytes

Determination of the glycosylation-pattern of the middle ear mucosa in guinea pigs

In the present study the glycosylation pattern of the middle ear mucosa (MEM) of guinea pigs, an approved model for middle ear research, was characterized with the purpose to identify bioadhesive ligands which might prolong the contact time of drug delivery systems with the middle ear mucosa (MEM). To assess the utility of five fluorescein labeled plant lectins with different carbohydrate specificities as bioadhesive ligands, viable MEM specimens were incubated at 4°C and the lectin binding capacities were calculated from the MEM-associated relative fluorescence intensities. Among all lectins under investigation, fluorescein-labeled wheat germ agglutinin (F-WGA) emerged as the highest bioadhesive lectin. In general, the accessibility of carbohydrate moieties of the MEM followed the order: sialic acid and N-acetyl-d-glucosamine (WGA)>>mannose and galactosamine (Lensculinaris agglutinin)>N-acetyl-d-glucosamine (Solanumtuberosum agglutinin)>fucose (Ulexeuropaeus isoagglutinin I)>>terminal mannose α-(1,3)-mannose (Galanthusnivalis agglutinin). Competitive inhibition studies with the corresponding carbohydrate revealed that F-WGA-binding was inhibited up to 90% confirming specificity of the F-WGA-MEM interaction. The cilia of the MEM were identified as F-WGA binding sites by fluorescence imaging as well as a z-stack of overlays of transmission, F-WGA- and nuclei-stained images of the MEM. Additionally, co-localisation experiments revealed that F-WGA bound to acidic mucopolysaccharides of the MEM. All in all, lectin-mediated bioadhesion to the MEM is proposed as a new concept for drug delivery to prolong the residence time of the drug in the tympanic cavity especially for successful therapy for difficult-to-treat diseases such as otitis media.

Characterization of lectin isolated from Momordica charantia seed as a B cell activator

Lectin isolated from the seeds of Momordica charantia (MCL) is a galactose-specific glycoprotein. To investigate the effects of MCL on cell activation, we analyzed the responses of BALB/c splenocytes, thymocytes, T cells and B cells on MCL stimulation. Proliferation assays showed that MCL selectively stimulates the B cell subset of splenocytes (p<0.05) in a dose and time dependent manner and that this activation proceeds without the involvement of T cells. Flow cytometric analysis revealed that the fluorescein isothiocyanate (FITC)-labeled MCL binds to B cells, which was inhibited by specific sugars, including galactose. Mouse immunoglobulin (Ig) was able to inhibit MCL-induced proliferation of mouse B cells, suggesting MCL stimulates B cell activation via membrane Ig in the B cell surface. Moreover, after 96-h co-culture, MCL triggered splenocytes to produce a large amount of non-specific IgM in culture supernatants (p<0.01). Additionally, MCL was shown to up-regulate the cell activation marker CD86, in a B cell subpopulation distinct from that affected by LPS. These data suggest that MCL is a T cell-independent B cell activator and a polyclonal Ig inducer, and provide further information on the immunomodulatory effect of MCL.

Correlation between carbohydrate-binding specificity and amino acid sequence of carbohydrate-binding regions of Cytisus-type anti-H(O) lectins

A carbohydrate-binding peptide of the di-N-acetylchitobiose-binding Cytisus sessilifolius anti-H(O) lectin I (CSA-I) was isolated from the endoproteinase Asp-N digest of CSA-I by affinity chromatography on a column of N-acetyl-D-glucosamine oligomer-Sepharose (GlcNAc oligomer-Sepharose). The amino acid sequence of the carbohydrate-binding peptide of CSA-I was determined to be DTYFGKTYNPW using a gas-phase protein sequencer. This sequence corresponds to the sequence from Asp-129 to Trp-139 based on the primary structure of CSA-I, and shows a high degree of homology to those of the putative carbohydrate-binding peptide of the Laburnum alpinum lectin I (LAA-I) (DTYFGKAYNPW) and of the Ulex europaeus lectin II (UEA-II) (DSYFGKTYNPW). The binding of these three anti-H(O) lectins is known to be inhibited by di-N-acetylchitobiose but not by L-fucose. These results strongly suggest that there is a good correlation between the carbohydrate-binding specificity and the amino acid sequence of the carbohydrate-binding regions of di-N-acetylchitobiose-binding lectins.

Purification and characterization of carbohydrate-binding peptides from Lotus tetragonolobus and Ulex europeus seed lectins using affinity chromatography

Carbohydrate-binding peptides of several anti-H(O) leguminous lectins were obtained from endoproteinase Asp-N or Lys-C digests of L-fucose-binding Lotus tetragonolobus lectin (LTA) and Ulex europeus lectin I (UEA-I) and from that of a di-N-acetylchitobiose-binding Ulex europeus lectin II (UEA-II) by affinity chromatography on columns of Fuc-Gel (for LTA and UEA-I) and on a column of a mixture of several oligomers of N-acetyl-D-glucosamine (GlcNAc) coupled to Sepharose 4B (GlcNAc oligomer-Sepharose 4B) (for UEA-II). These peptides were retained on the Fuc-Gel or GlcNAc oligomer-Sepharose 4B column and were presumed to have an affinity for the columns. The amino acid sequences of the retarded peptides were determined using a protein sequencer.

Purification and characterization of a new type lactose-binding Ulex europaeus lectin by affinity chromatography

A new type lactose-binding lectin was purified from extracts of Ulex europaeus seeds by affinity chromatography on a column of galactose-Sepharose 4B, followed by gel filtration on Sephacryl S-300. This lectin, designated as Ulex europaeus lectin III (UEA-III), was found to be inhibited by lactose. The dimeric lectin is a glycoprotein with a molecular mass of 70,000 Da; it consists of two apparently identical subunits of a molecular mass of 34,000 Da. Compositional analysis showed that this lectin contains 30% carbohydrate and a large amount of aspartic acid, serine and valine, but no sulfur-containing amino acids. The N-terminal amino-acid sequences of L-fucose-binding Ulex europaeus lectin I (UEA-I) and di-N-acetylchitobiose-binding Ulex europaeus lectin II (UEA-II), both of which we have already purified and characterized, and that of UEA-III were determined and compared.

Flow cytometric analysis of the binding of eleven lectins to human T- and B-cells and to human T- and B-cell lines

The relative surface binding of 11 lectins to human peripheral blood T- and B-lymphocytes, to Molt-4 and JM T-cell lines, and to 6410 and NC37 B-cell lines was determined by flow cytometry. The lectins from Lens culinaris (LCA), Ricinus communis (RCA), Arachis hypogaea (PNA), Abrus precatorius (APA), Ulex europaeus (UEA-F), Sarothamnus scoparius (SAS-F), Helix pomatia (HPA), Phaseolus coccineus (L-PHA), Glycine max (SBA), and Triticum vulgare (WGA) were fluoresceinated and incubated with living, formaldehyde-fixed, or neuraminidase-treated cells. Except LCA, which preferentially bound to the two B-cell lines tested in this study, none of the other lectins exhibited selective binding to the undifferentiated cells of the cell lines. The T-cell lines and, in part, the peripheral blood T-cells bound less WGA, APA, LCA, and L-PHA than the B-cell lines and the peripheral blood B-cells. Binding of PNA was found only after neuraminidase treatment of the cells; the binding of PNA, HPA, and UEA-F after neuraminidase treatment was higher for the T-cells than the B-cells from peripheral blood. No significant differences were detected between both cell types for RCA, ConA, SBA, and SAS-F.

A comparative study of vitreous-body and zonular glycoconjugates that bind to the lectin from Ulex europaeus

Eyes from adult rodents, rabbits and humans were fixed in formalin, embedded in paraffin and incubated with a horseradish peroxidase-conjugated lectin from Ulex europaeus to localize vitreous-body and zonular glycoconjugates. Rodent eyes had reaction product for peroxidase activity in fibrous structures in the posterior chamber, vitreous base and vitreous cortex. The zonules and the internal limiting membrane region of the retina also were stained. Rabbit eyes had more stained fibrous material in the vitreous base than rodent eyes and the attachment region of the zonules on the lens capsule, the anterior hyaloid membrane and tracts in the vitreous cortex were more heavily stained in rabbits. There was heavy staining of the thick vitreous base in the human eyes as well as staining of zonules, anterior hyaloid membrane and vitreous cortex. The localization of this lectin may be specific for fucose in glycoproteins or other glycoconjugates, although this was not demonstrated here. However, the location of lectin binding sites correlates well with known sites of uptake of tritiated fucose and tritiated glucosamine in rabbit eyes. Eyes from the larger species studied had more lectin-binding glycoconjugates in fibrous structures in the vitreous body than those from smaller species. The amount of glycoconjugate identified in some of the lectin-binding sites may be related to some extent to the degree of stress incident upon those sites.

Partial isolation and characterization of Gp 220, the Ulex europaeus binding glycoprotein of the B-lymphocyte plasma membrane

Using affinity chromatography on Sepharose 4B coupled with Ulex europaeus lectin, a partially purified gp 220 was isolated from the RAJI cell membrane. This protein could not be isolated from the membranes of the T-cell line MOLT-4 nor from human erythrocytes. Gp 220 is composed of three subunits gp 85, 70 and 65 held together by disulfide bridges. Gp 85 contains fucosyl residues, gp 70 contains galactosyl residues, and gp 65 contains both sugars. Gp 220 is different from fibronectin and spectrin, proteins which also show binding to the Ulex europaeus lectin.

Purification and characterization of a Cytisus-type Ulex europeus hemagglutinin II by affinity chromatography

Ulex europeus hemagglutinin II [Cytisus-type anti-H(O) hemagglutinin] inhibited most by di-N-acetylchitobiose has been purified by affinity chromatography on a column of chitobiose-Sepharose 4B, followed by gel filtration on Sephacryl S-300. The purified hemagglutinin was homogeneous by ultracentrifugal analysis and gave a single band by electrophoresis on polyacrylamide gel, and had a molecular weight of 105 000 by sedimentation equilibrium and an isoelectric point of pH 6.66. This hemagglutinin was found to be composed of four, apparently identical, subunits of a molecular weight of 25 000 +/- 2 000 by dodecyl sulphate-polyacrylamide gel electrophoresis, and to contain 10.3% carbohydrate in which mannose (3.7%) was the predominant sugar, with smaller amounts of glucose, glucosamine, xylose, fucose and galactose. Amino acid analysis of the purified hemagglutinin II showed a large amount of aspartic acid and serine, but as little as 0.1 mol/100 mol of cystine or methionine could be detected.

Glycolipid and p 40 are the binding sites in the sheep erythrocyte and T-lymphocyte membrane responsible for rosette formation

By coupling the major glycoprotein and total glycolipid of the sheep erythrocyte membrane to agarose beads it could be demonstrated that only lipid-beads formed rosettes with peripheral blood lymphocytes. Lipid-beads and sheep erythrocytes formed double rosettes with peripheral blood lymphocytes. Trypsinization of lymphocytes destroyed the rosette formation with lipid-beads. Subfractionation of the lipid by thin-layer chromatography revealed 8 different subfractions, 3 of them when coupled to agarose beads showed rosette formation. When the lipid was coupled to radioactive albumin, a protection of molecular weight 40,000 was labeled in two T-lymphocyte plasma membranes but not in B-lymphocyte plasma membranes. It is concluded that a lipid-protection interaction, involving the lipid of the erythrocyte and the p40 of the lymphocyte membrane, is responsible for rosette formation of T-lymphocytes.

Binding of lectins to leukemic cell lines

The binding of 12 different fluorescein-conjugated lectins to 10 ALL (acute lymphoblastic leukemia) cell lines and two cell lines derived from patients in blast crisis of myeloid leukemia was examined. The specificity of the membrane fluorescence was demonstrated by inhibition with various saccharides. Three of the lectins bound to all cell lines, four bound to only some of the lines, and five were not bound. There was no correlation between the binding pattern and the immunological phenotype of the cultured lymphoblasts. The lectin from Lens culinaris, however, in the experimental condition used (incubation at 4 degrees C, fluorescein conjugation at pH 8.5), bound only to the cell membranes of 'Ia-like antigen, positive cell lines. Although three lectins (Lens culinaris, Pisum sativum, concanavalin A) had an identical monosaccharide specificity, they bound to different cell lines. Membrane fluorescence with the lectins from Helix pomatia, Arachis hypogea, and Ricinus communis (MW 60,000) was achieved after treatment with neuraminidase. It was shown that binding of the lectins from Helix pomatia and Ricinus communis 60 was effected by enzymatically exposed glycoproteins, whereas the lectin Arachis hypogea was bound via neuraminidase which stuck to the cell membrane.

The lectin binding sites on the plasma membrane components of human lymphoblastoid cell lines

The plasma membrane components of five human B-cell lines and three human T-cell lines were separated by dodecyl sulfate polyacrylamide gel electrophoresis, incubated with the radioactive labeled lectins from lentil, castor bean, wheat germ, Phaseolus bean, peanut, gorse and the Roman snail and the molecular weights of the binding sites determined. The lentil, castor bean and wheat germ lectin bound to multiple components from molecular weights (Mr) 20 000 to 200 000 within the plasma membranes, whereas peanut lectin bound preferentially to glycoproteins of Mr 150 000 and 83 000 in B-cells, and 150 000 and 130 000 in T-cells. The gorse lectin bound to a 220 000 component in B-cells which was not labeled in T-cells.