Carbohydrate-binding specificity of the so-called galactose-specific phytohemagglutinins

Mechanistic insight into pertussis toxin and lectin signaling using T cells engineered to express a CD8α/CD3ζ chimeric receptor

Mammalian cell-surface receptors typically display N- or O-linked glycans added post-translationally. Plant lectins such as phytohemagluttinin (PHA) can activate the T cell receptor (TCR) and other cell-surface receptors by binding to glycans and initiating receptor cross-linking. Pathogenic microorganisms such as Bordetella pertussis also express proteins with lectin-like activities. Similar to plant lectins, pertussis toxin (PTx) can activate the TCR and bind to a variety of glycans. However, whether the lectin-like activity of PTx is responsible for its ability to activate TCR signaling has not been formally proven. Here we examined the ability of PTx and a panel of lectins to activate the TCR or a CD8α/CD3ζ chimeric receptor (termed CD8ζ). We demonstrate that CD8ζ rescues PTx-induced signaling events lacking in TCR null cells. This result indicates that CD8ζ can substitute for TCR and supports the hypothesis that PTxB (functioning as a lectin) stimulates signaling via receptor cross-linking rather than by binding to a specific epitope on the TCR. Moreover, PTx is able to activate signaling by binding either N-linked or O-linked glycan-modified receptors as the TCR displays N-linked glycans while CD8ζ displays O-linked glycans. Finally, studies with a diverse panel of lectins indicate that the signaling activity of the lectins does not always correlate with the biochemical reports of ligand preferences. Comparison of lectin signaling through TCR or CD8ζ allows us to better define the structural and functional properties of lectin-glycan interactions using a biologically based signaling readout.

Variability of soya-bean lectin binding sites in the brush border membranes of calf intestinal epithelium

An enzyme-linked lectin sorbent assay (ELLSA) has been used to determine quantitatively the amount of soya-bean agglutinin (SBA) binding sites in and the sialic acid contents of small intestinal brush border membranes (BBM) of a group of 14 clinically healthy veal calves. Computer analysis of the results indicated 704 (s.e. 27) nmol SBA binding sites per mg of BBM protein with a Kj of 2·63 (s.e. 0·15) × 10-5mol/l; the sialic acid contents were 2·67 (s.e. 0·43) mg/g BBM protein. We could not demonstrate a correlation between the amount of binding sites and the sialic acid contents of the BBM.

Incubation with neuraminidase did not alter the number of SBA binding sites.

Interactions between ricinus agglutinin and human IgA

By affinity chromatography on Sepharose columns containing insolubilized ricinus agglutinin, all immunoglobulins of the IgA2 subclass and the polymers of IgA1 were retained and could be eluted with lactose. Monomeric IgA1 showed a more heterogeneous reaction with ricinus agglutinin. The major part was unretarded, whereas some of it was weakly bound to the column and could be eluted with lactose.

Presence of beta-linked GalNAc residues on N-glycans of human thyroglobulin

Hepatic asialoglycoprotein receptor, which may mediate the clearance of circulating thyroglobulin, is known to have a high affinity for GalNAc. Recently, the receptor has been reported to be present also in the thyroid, implicating interaction with thyroglobulin. Here, mammalian thyroglobulins were analyzed for GalNAc termini by Western blotting with GalNAc-recognizing lectins labeled with peroxidase or (125)I. Wistaria floribunda lectin was found to bind human thyroglobulin and, to some extent, bovine, but not porcine thyroglobulin. After desialylation, the lectin bound all of the thyroglobulins tested. The binding was inhibited by competitive inhibitor GalNAc. Peptide N-glycanase treatment of human desialylated thyroglobulin resulted in the complete loss of reactivity with W. floribunda lectin, indicating that the binding sites are exclusively on N-glycans. The binding sites on human desialylated thyroglobulin were partly sensitive to beta-galactosidase, and the remainder was essentially sensitive to beta-N-acetylhexosaminidase. On the other hand, the binding sites of bovine and porcine desialylated thyroglobulins were totally sensitive to beta-galactosidase. Thus the lectin binds beta-Gal termini, as well as beta-GalNAc. GalNAc-specific Dolichos biflorus lectin also bound human thyroglobulin weakly. In contrast to W. floribunda lectin, desialylation diminished binding, suggesting that these two lectins recognize different GalNAc-terminated structures. Again, the binding was inhibited by GalNAc and by treatment with peptide N-glycanase. These results strongly indicate the presence of distinct GalNAc termini of N-glycans on human thyroglobulin.

Stochastic molecular dynamics of peanut lectin PNA complex with T-antigen disaccharide

The stochastic boundary molecular dynamics simulation method was applied to investigate the structure of a complex comprised of a tetrameric peanut lectin and the tumour-associated disaccharide, Galbeta1-3GalNAc (T-antigen). Only a small region encompassing the active site was explicitly included in the calculations, but the electrical contribution of most outer atoms was taken into account by adding to the effective potential a term coming from an electrostatic potential grid that was pre-calculated and used to approximate the electrostatic energy and the force at any point in the interacting site. Results of simulating the intermolecular hydrogen bond network agree fairly well with X-ray experiments. An estimation of the direct and water-mediated interaction mean lifetimes and mean water residence times around the T-antigen oxygen atoms was computed over 400 ps. Monitoring the behaviour of water molecules within the active site revealed that there is a constant exchange of water with the bulk, especially in the proximity of ASN41, ASN127 and GLU129. The temporal evolution of the glycosidic linkage was also investigated and compared with simulations of T-antigen in solution. These studies of peanut lectins-sugar complexes clearly emphasize the importance of bound water molecules in generating carbohydrate specificity.

Correlation between the sialylation of cell surface Thomsen-Friedenreich antigen and the metastatic potential of colon carcinoma cells in a mouse model

The cell surface glycosylation profiles of a liver metastatic colon carcinoma variant cell line, SL4 cells previously selected from colon 38 cells in vivo for liver colonization were investigated. Flowcytometric analysis was performed with 7 plant lectins and 10 carbohydrate specific monoclonal antibodies. The results showed that peanut agglutinin (PNA), Sambucus nigra agglutinin, Ulex europeus agglutinin-I, anti-LeX, anti-LeY, and anti-Le(b) antibodies bound to the parental colon 38 cells but not to SL4 cells. Another variant cell line was selected in vitro for the paucity of cell surface PNA-binding sites using a magnetic cell sorter and was designated as 38-N4 cells. The binding profiles of plant lectins and carbohydrate-specific antibodies to 38-N4 cells were very similar to those of SL4 cells. After intrasplenic injections, metastatic ability of 38-N4 cells was higher than that of colon 38 cells. PNA binding to SL4 cells and 38-N4 cells was detected after sialidase treatment of these cells, indicating increased sialylation of Thomsen-Friedenreich antigen in these cells. The mRNA levels of sialyltransferases, ST3Gal I, ST3Gal II, ST6GalNAc I, and ST6GalNAc II, were compared. The level of ST3Gal II mRNA was elevated in both SL4 cells and 38-N4 cells, whereas the level of ST6GalNAc II mRNA was elevated in 38-N4 cells compared with colon 38 cells. According to the expression array analysis, there are other glycosyltransferase genes differentially expressed between SL4 and colon 38 cells, yet their involvement in the altered glycosylation in these cells is unclear.

Ultrastructural and ultracytochemical features of secretory granules in the ampullary epithelium of the hamster oviduct

The epithelium of mammalian oviducts consists mainly of ciliated and non-ciliated secretory cells. In some mammals, secretory products originating from oviductal secretory cells have been shown to bind to the surface of, or accumulate within, ovulated eggs and/or developing embryos. These findings suggest that the secretions of the oviductal epithelial cells may play an important role in reproductive and developmental events that occur in the oviduct. In the present study, ultrastructural and cytochemical features of secretory cells in the hamster ampullary epithelium were shown by routine electron microscopy, lectin-gold cytochemistry and both conventional freeze-fracture and rapid-freezing techniques with special reference to the organizational aspects of their secretory granules. The use of ferrocyanide-reduced osmium tetroxide as a post-fixative in the Epon embedment of ampullary tissue samples also proved to be advantageous especially in revealing the carbohydrate contents of certain cellular compartments. The most conspicuous characteristic of the secretory cells, based on their staining property, was the presence of two types of secretory granules: those with a homogeneous electron-dense matrix and those with an electron-lucent matrix. Under favorable conditions, distinct features of the organizational arrangement of a crystalline lattice inside the secretory granules were also revealed. This well organized crystalline lattice shown in sections of Epon-embedded oviductal tissue was confirmed by examination of replicas of freeze-fractured oviducts prepared by the rapid-freezing technique. We also demonstrated with high resolution lectin-gold cytochemistry the intracellular distribution of lectin-binding glycoconjugates in the secretory cells of the hamster oviductal ampulla often in a linear array following the crystalline lattice. The results obtained in this study, taken together, provide insight into a possible link of the internal topographical features of oviductal secretory granules along with the cytochemical properties of their contents to the anticipated regulatory mechanism underlying their process of secretions.

Analysis of lectin binding properties on human Burkitt's lymphoma cell lines that show high spontaneous metastasis to distant organs in SCID mice: the binding sites for soybean agglutinin lectin masked by sialylation are closely associated with metastatic lymphoma cells

Alterations in cell surface carbohydrates on human lymphoma cell lines with different spontaneous metastatic potential in the severe combined immunodeficiency (SCID) mouse model were analyzed. A difference in cell surface carbohydrates between high- (HBL-2, HBL-7 and HBL-8) and no- or low-(HBL-4, HBL-6, Daudi and Raji) spontaneous metastatic human lymphoma cell lines were analyzed on a FACScan using fluorescein-isothiocyanate (FITC)-conjugated lectins. The most consistent difference in lectin binding properties was found with soybean agglutinin (SBA) lectin. High-metastatic lymphoma cells (HBL-7 and HBL-8 cells) in vitro were found to bind the SBA lectin, but the cells in vivo (in primary tumors and metastatic tumors of SCID mice) showed considerably reduced SBA lectin binding. In addition, HBL-2 cells that almost did not bind SBA lectin in vitro and in vivo showed high spontaneous metastasis. Neuraminidase treatment revealed that SBA lectin binding sites were masked by sialic acid. On the other hand, no- or low-metastatic lymphoma cells in vitro and in vivo were found to bind SBA lectin. HBL-8 cell clones without SBA lectin binding showed high spontaneous metastasis to distant organs in SCID mice but HBL-8 cell clones with SBA lectin binding showed very low spontaneous metastasis. Sophora Japonica agglutinin (SJA) lectin is able to recognize the carbohydrates in common with SBA lectin, but it does not appear to be associated with metastatic capacity. These results suggest that the sialylation of particular carbohydrate residues on human lymphoma cells that are recognized by SBA lectin may be associated with the spontaneously metastatic capacity of human lymphoma cell lines in our SCID mouse model.

Imparting exquisite specificity to peanut agglutinin for the tumor-associated Thomsen-Friedenreich antigen by redesign of its combining site

Lectins from legumes constitute one of the most thoroughly studied families of proteins, yet the absence of a rigorous framework to explain their carbohydrate binding specificities appears to have prevented a rational approach to alter their ligand binding activity. Studies reported here deal with the redesign of the recognition propensity of peanut agglutinin (PNA), an important member of the family. PNA is extensively used as a tool for recognition of the tumor-associated Thomsen-Friedenrich antigen (T-antigen; Galbeta1-3GalNAc) on the surfaces of malignant cells and immature thymocytes. PNA also recognizes N-acetyllactosamine (LacNAc; Galbeta1-4GlcNAc), which is present at the termini of several cell-surface glycoproteins. The crystal structure of the PNA-lactose complex revealed, in addition to the expected interactions with the residues constituting the binding site, the presence of leucine 212 at a position close enough to be in steric contact with the acetamido group on LacNAc. We report here two leucine mutants, one to asparagine (L212N) and the other to alanine (L212A), that exhibit distinct preference for T-antigen and N-acetyllactosamine, respectively. Carbohydrate binding studies reveal that mutant L212N does not recognize LacNAc at high concentrations, thus making it an exquisitely specific cell-surface marker compared with its wild-type counterpart.

Cloning by genomic PCR and production of peanut agglutinin in Escherichia coli

Using the polymerase chain reaction, the coding sequence for peanut agglutinin (PNA) was cloned and expressed in Escherichia coli. Amplified PNA is identical to previously reported cDNA, suggesting the absence of any introns in PNA gene. Recombinant (re-) PNA forms inclusion bodies in E. coli. Production of PNA was confirmed by probing Western blots with polyclonal anti-PNA immunoglobulin G. Inclusion bodies were solubilized with 6 M guanidine-HCl and renatured by rapid dilution in the presence of metal ions. The renatured lectin was then purified by affinity chromatography. The re-lectin shows carbohydrate-binding properties similar to the natural PNA. This expression system provides a model for future mutagenesis studies of the carbohydrate-binding site and thus facilitates ongoing efforts to explore the molecular basis for the specificity of lectin-carbohydrate interaction.

Homogeneity in the distribution of matrix components in the hamster zona pellucida as revealed by backscattered electron imaging fracture-label

BACKGROUND

Backscattered electron imaging fracture-label (BEI-FL), an adaptation of the fracture-label method for scanning electron microscopy, offers the advantage of providing information about the distribution of antigenic and receptor sites with respect to the three-dimensional organization of tissues and cells over relatively large surfaces. Recently, using post-embedding cytochemistry on thin-sections of Lowicryl-embedded oocytes, a homogenous distribution of glycoproteins in the zona pellucida (ZP) was demonstrated (Kan et al., 1989. Biol. Reprod., 40:585-598, Anat. Rec., 226:37-47; Roux and Kan, 1991. Anat. Rec., 230:347-360). However, it can be argued that the chemical nature of resins and the physical conditions of tissue processing required for post-embedding cytochemistry may introduce changes in the tissue components and result in altered distribution of components. On the other hand, freeze-fracture exposes constituents in a minimally denaturing manner and, since no embedding media are used, binding sites are sterically available to the probe. We have, therefore, applied BEI-FL to examine the distribution of matrix glycoproteins in the ZP of hamster oocytes.

METHODS

Ovaries and cumulus masses obtained from superovulated female golden hamsters were fixed by immersion in 2.5% glutaraldehyde and processed for fracture-label. Tissues were labeled, respectively, with Wheat germ agglutinin (WGA) followed by ovomucoid-colloidal gold, Ricinus communis agglutinin I (RCA I)-colloidal gold or a monoclonal antibody against Hamster Oviductin-1 followed by protein A-gold, and then examined in the scanning electron microscope.

RESULTS

Backscattered electron imaging revealed a homogenous distribution of WGA and RCA I binding sites throughout the cross-fractured matrix of the ZP of ovarian and postovulatory oocytes. Hamster Oviductin-1, an oviductal glycoprotein which is transferred to the ZP of oocytes during oviductal transit, was also found to be uniformly distributed throughout the ZP of postovulatory oocytes.

CONCLUSIONS

Our results indicate that BEI-FL can be advantageously used to examine extracellular matrices and are consistent with the concept that glycoproteins are uniformly distributed throughout the ZP of the hamster oocyte.

Inhibitory effects of sialic acid- or N-acetylglucosamine-specific lectins on histamine release induced by compound 48/80, bradykinin and a polyethylenimine in rat peritoneal mast cells

The effects of seven lectins with various sugar-specificities on histamine release from rat peritoneal mast cells induced by non-immunologic stimuli were studied. The non-immunologic stimuli used were three basic secretagogues, compound 48/80, bradykinin and PEI6 (polyethylenimine with a molecular weight of 600). In this study, we observed inhibition of the histamine release by Macckia amurensis mitogen and Solanum tuberosum agglutinin (100 micrograms/ml at 37 degrees C for 10 min), which are specific for sialic acid-alpha 2,3-N-acetyl galactosamine (Sia alpha 2,3GalNAc) and N-acetyl glucosamine (GlcNAc) oligomers, respectively. The effects of Phytolacca americana mitogen and Sambucus sieboldiana agglutinin were different. Three lectins specific for mucin type oligosaccharides inhibited the histamine release induced by compound 48/80 but not that induced by bradykinin or PEI6. Since bradykinin and PEI6 additively enhanced the histamine release induced by compound 48/80, they partially shared the same signalling pathways. Glycoproteins with bisecting GlcNAc and Sia residues, as described previously (Jpn. J. Pharmacol. 57, 79-90, 1991), seemed to be one of the action sites for compound 48/80, bradykinin and PEI6. In addition to the direct activation of the pertussis toxin-sensitive G proteins, we propose another mechanism of non-immunologic stimuli via specific glycoproteins on rat peritoneal mast cells. The apparent sugar residues involved were asparagine-linked oligosaccharides with Sia (especially Sia alpha 2,3Gal), GlcNAc oligomers and/or bisecting GlcNAc.

Purification and characterization of novel lectins from Great Northern bean, Phaseolus vulgaris L

Two lectins, GNL-1 and 2, were isolated from extracts of Great Northern bean powder through fractionation with ammonium sulfate, ion-exchange chromatographies on CM- and DEAE-celluloses, and gel filtration chromatography on Sephacryl S-200 HR. These lectins were shown to be homogenous by gel electrophoresis, gel filtration, and isoelectric focusing. The lectins (GNL-1 and 2) have molecular masses of 175 and 145 kDa on gel filtration, respectively. They yield three bands having the respective same molecular masses on SDS-PAGE (GNL-1; alpha-subunit of 34.5 kDa, beta of 37.0, and gamma of 39.0: GNL-2; alpha' of 34.5 kDa, beta' of 37.0, and gamma' of 39.0). Two lectins are shown to be glycoproteins and the carbohydrate contents of GNL-1 and 2 are 5.1 and 4.5%, respectively. The isoelectric points are 5.5 and 5.1 and the extinction coefficients (A 1cm 1%) at 280 nm are 11.37 and 11.45, respectively. These lectins are nonspecific in agglutination for rabbit and any types of human erythrocytes. Inhibition study shows no specificity against mono and disaccharides. On the other hand, binding assay of horseradish peroxidase-glycoproteins to the bands electroblotted onto PVDF membrane reveals that all of the subunits can bind to sugar moieties in fetuin, asialofetuin, and porcine thyroglobulin specifically. Moreover, assay of mitogenic activity shows that GNL-1 is a strong mitogen, but GNL-2 is lack of the activity.

Defining carbohydrate specificity of Ricinus communis agglutinin as Gal beta 1-->4GlcNAc (II) > Gal beta 1-->3GlcNAc (I) > Gal alpha 1-->3Gal (B) > Gal beta 1-->3GalNAc (T)

To define carbohydrate specificity of Ricinus communis agglutinin (RCA1), the combining site of RCA1 was further characterized by quantitative precipitin (QPA) and precipitin-inhibition assays (QPIA). Among the oligosaccharides tested for QPIA, Gal beta 1-->4GlcNAc (II, human blood group type II precursor sequence) was found to be 7.1 times more active than Gal beta 1-->3GalNAc (T, Thomsen-Friedenreich sequence) and about 1.7 times more active than the other three disaccharides tested--Gal beta 1-->4Man, Gal beta 1-->3DAra and Gal beta 1-->6GalNAc. Gal alpha 1-->4Gal, the receptor of the uropathogenic E. coli ligand was 3.6 times less active than the II sequence. These results indicate that the beta 1-->4 linkage of the terminal Gal to subterminal GlcNAc is important as this beta 1-->4GlcNAc sequence is at least 1.6 times more active than other types of disaccharides. Among the glycoproteins examined for QPA, native and desialized bovine submandibular glycoproteins, native and desialized human plasma alpha 1-acid glycoproteins, as well as crude hog stomach mucin and its three mild acid hydrolyzed products reacted well with the lectin. These glycoproteins precipitated over 75% of the lectin nitrogen added indicating that RCA1 has the ability to recognize Gal beta 1-->4/3GlcNAc and/or the related residues at the non-reducing ends and at positions in the interior of the chains. However, Tn (GalNAc alpha 1-->Ser/Thr sequence) rich glycoproteins such as desialized ovine submandibular glycoprotein and desialized armadillo salivary glycoprotein, in which over 90% of the carbohydrate side chains are Tn determinants with none or only a trace of I/II or T determinants, precipitated poorly with RCA1. From the present and previous results obtained, the carbohydrate specificity of RCA1 can be constructed and summarized in decreasing order by lectin determinants as follows: II (Gal beta 1-->4GlcNAc) > I (Gal beta 1-->3GlcNAc) > E (Gal alpha 1-->4Gal) and B (Gal alpha 1-->3Gal) > T (Gal beta 1-->3GalNAc), while Tn (GalNAc alpha 1-->Ser/Thr) is a poor inhibitor.

Changes of glycoconjugate contents of the zona pellucida during oocyte growth and development in the golden hamster: a quantitative cytochemical study

We demonstrated here with the high resolution lectin-gold approach and quantitative analysis, changes of glycoconjugates in the hamster zona pellucida (ZP) during oocyte growth and development in the ovary and the oviduct. Glycoconjugates which contain N-acetyl-D-galactosamine as terminal sugar residues are absent in the ovary but are secreted by secretory cells in the oviduct and are added to the ZP of superovulated oocytes during oviductal transit. Glycoconjugates which carry sialic acid as terminal sugar residues appear to be acquired mainly from the ovary. The oviduct contributes little of this particular component to the ZP during the transit of oocytes in the oviduct. On the contrary D-galactose and N-acetylglucosamine associated glycoconjugates, added to the ZP in ovarian follicles, are also secreted by non-ciliated oviductal epithelial cells and these secretory products are transferred to the ZP in significant amount during passage of the oocyte through the oviduct. Lectin-gold labeling of the ZP of superovulated oocytes reveals homogeneous distribution of gold particles throughout the zona matrix. Thus, we conclude that the ZP of hamster superovulated oocytes consists of glycoconjugates that may derive from different origins. Deposition of ZP glycocomponents begins in the ovary. Similar and new glycoconjugates, secreted by oviductal non-ciliated secretory cells, are added to the ZP of oocytes during oviductal transit. At this stage the ZP is made up of a homogeneous matrix of glycoconjugates.

Further characterization of the saccharide specificity of peanut (Arachis hypogaea) agglutinin

2-Dansylamino-2-deoxy-D-galactose (GalNDns) has been shown to bind to peanut (Arachis hypogaea) agglutinin (PNA) in a saccharide-specific manner. This binding was accompanied by a five-fold increase in the fluorescence of GalNDns. The interaction was characterized by an association constant of 0.15 mM at 15 degrees and delta H and delta S values of -57.04 kJ.mol-1 and -118.1J.mol-1.K-1, respectively. Binding of a variety of other mono-, di- and oligo-saccharides to PNA, studied by monitoring their ability to dissociate the PNA GalNDns complex, revealed that PNA interacts with several T-antigen-related structures, such as beta-D-Galp-(1----3)-D-GalNAc, beta-D-Galp-(1----3)-alpha-D-GalpNAcOMe, and beta-D-Galp-(1----3)-alpha-D-GalpNAc-(1----3)-Ser, as well as the asialo-GM1 tetrasaccharide, with comparable affinity, thus showing that this lectin does not discriminate between saccharides in which the penultimate sugar of the beta-D-Galp-(1----3)-D-GalNAc unit is the alpha or beta anomer, in contrast to jacalin (Artocarpus integrifolia agglutinin), another anti T-lectin which preferentially binds to beta-D-Galp-(1----3)-alpha-D-GalNAc and does not recognize beta-D-Galp-(1----3)-beta-D-GalNAc or the related asialo-GM1 oligosaccharide. These studies also indicated that, in the extended combining region of PNA which accommodates a disaccharide, the primary subsite (subsite A) is highly specific for D-galactose, whereas the secondary subsite (subsite B) is less specific and can accommodate various structures, such as D-galactose, 2-acetamido-2-deoxy-D-galactose, D-glucose, and 2-acetamido-2-deoxy-D-glucose.

Oligosaccharide-related epitope specific for a brain-specific glycoprotein, 1D4 antigen

The characteristics of glycosylation of a brain-specific glycoprotein, 1D4 antigen, and the epitope recognized by its monoclonal antibody were studied. Removal of high-mannose and hybrid types of N-linked oligosaccharides by treatment with endoglycosidase H converted the molecular mass of the 1D4 antigen from 89 kDa to 78 kDa, but did not affect its reactivity with the 1D4 monoclonal antibody. Removal of all types of N-linked oligosaccharides by treatment with glycopeptidase F or removal of both N- and O-linked oligosaccharides by chemical treatment caused both reduction of the molecular mass of the antigen to 63 kDa and loss of its reactivity with the monoclonal antibody. These results suggest that the 1D4 monoclonal antibody recognizes a complex-type oligosaccharide-related epitope specific for the 1D4 antigen. Results also showed that N-linked glycosylation was not responsible for the charge heterogeneity of the 1D4 antigen. The oligosaccharide chain-related epitope was detected in rat brain but not in mouse, rabbit, or bovine brain, but the 1D4 antigen was recognized in rat and mouse brains with antiserum (polyclonal antibodies). These findings indicate that the oligosaccharide-related epitope is species specific. Furthermore, results with neuraminidase-treated 1D4 antigen indicated that sialic acids were not involved in the oligosaccharide-related epitope. These findings suggest that the 1D4 antigen may have the oligosaccharide structure specific for rat brain and itself.

Mucin-specific bark lectin from elderberry Sambucus sieboldiana and its applications to the affinity chromatography of mucin

Three bark lectins were isolated from elderberry Sambucus sieboldiana using fetuin-Sepharose 4B and mucin-Sepharose 4B, and were studied comparatively for their binding to glycoprotein and to clarify various physicochemical features. For each, a unique pattern on isoelectric focusing was noted and their affinity toward various glycoproteins differed, indicating the structures of their carbohydrate binding sites possibly differ. One bark lectin showed specific binding toward porcine mucin. The purity of mucin from a crude porcine stomach mucin or an extract of porcine submaxillary glands could be improved by affinity chromatography on immobilized lectin having binding specificity toward mucin.

Comparison of the carbohydrate-binding specificities of seven N-acetyl-D-galactosamine-recognizing lectins

Seven plant lectins, Dolichos biflorus agglutinin (DBA), Griffonia simplicifolia agglutinin (GSA, isolectin A4), Helix pomatia agglutinin (HPA), soybean (Glycine max) agglutinin (SBA), Salvia sclarea agglutinin (SSA), Vicia villosa agglutinin (VVA, isolectin B4) and Wistaria floribunda agglutinin (WFA), known to be specific for N-acetyl-D-galactosamine-(GalNAc) bearing glycoconjugates, have been compared by the binding of their radiolabelled derivatives, to eight well-characterized synthetic oligosaccharides immobilized via a spacer on an inert silica matrix (Synsorb). The eight oligosaccharides included the Forssman, the blood group A and the T antigens, as well as alpha GalNAc coupled directly to the support (Tn antigen) and also structures with GalNAc linked alpha or beta to positions 3 or 4 of an unsubstituted Gal. The binding studies clearly distinguished the lectins into alpha GalNAc-specific agglutinins like DBA, GSA and SSA, and lectins which recognize alpha- as well as beta-linked GalNAc residues like HPA, VVA, WFA and SBA. HPA was the only lectin which bound to the beta Gal1----3 alpha GalNAc-Synsorb adsorbent (T antigen) indicating that it also recognizes internal GalNAc residues. Among the alpha GalNAc-specific lectins, DBA strongly recognized blood group A structures while GSA displayed weaker recognition, and SSA bound only slightly to this affinity matrix. In addition, DBA and SSA were able to distinguish between GalNAc linked alpha 1----3 and GalNAc linked alpha 1----4, to the support, the latter being a much weaker ligand. These results were corroborated by the binding of the lectins to biological substrates as determined by their hemagglutination titers with native and enzyme-treated red blood cells carrying known GalNAc determinants, e.g. blood group A, and the Cad and Tn antigens. For SSA, the binding to the alpha GalNAc matrix was inhibited by a number of glycopeptides and glycoproteins confirming the strong preference of this lectin for alpha GalNAc-Ser/Thr-bearing glycoproteins.

Analysis of glycosylation changes in IgG using lectins

A simple rapid assay based on the ability of lectins to bind carbohydrates has been developed to analyse changes in the oligosaccharide chains of IgG. Bandeiraea simplicifolia lectin and Ricinus communis agglutinin have been used to detect terminal N-acetylglucosamine and galactose moieties respectively in IgG using immunodot-blotting. IgG samples (approximately 1 micrograms) were dot-blotted onto nitrocellulose followed by boiling of the blots to expose the carbohydrate moieties. The blots were then treated with biotinylated lectins followed by either streptavidin-biotin-hydrogen peroxidase conjugate or 125I-labelled streptavidin. The colour was developed using chloronaphthol and the blots read on a densitometer. The labelled blots were cut and read on a gamma counter. The use of a monoclonal antibody to N-acetylglucosamine is also discussed. The results obtained using this method are comparable to those obtained by structural analysis.

Glycoconjugate histochemistry in the glycocalyx of guinea pig middle ear mucosa

An attempt was made to determine the composition of oligosaccharide side chains in the apical cell surface glycocalices of the middle ear epithelium. This glycoconjugate is located on the innermost luminal surface, but its function is still unknown. The lectins evaluated included Triticum vulgare, Canavalia ensiformis, Maclura pomifera, Arachis hypogaea, Ricinus communis I (RCA-I), and Limax flavus. The staining results obtained with the six different lectin probes in the Lowicryl K4M-embedded guinea pig middle ear mucosa suggest that the glycocalyx contains beta-D-N-acetylglucosamine, sialic acid, and beta-D-galactose in the major carbohydrate moiety. The present study also indicates that a polarity exists on the cell surfaces in the distribution pattern of the carbohydrate component, especially those of beta-galactosyl residues, as revealed by RCA-I binding. This may imply functional separation of the epithelial cells.

Molecular forms of human chorionic gonadotropin in choriocarcinoma serum and urine

The molecular forms of human chorionic gonadotropin (hCG) were assessed in parallel serum and urine samples from a choriocarcinoma patient by gel chromatography, isoelectric focusing, and Western blot analysis. There were significant qualitative differences in the molecular forms of hCG between the serum and the urine. The serum hCG had a greater molecular weight and a stronger acidic charge than the urinary hCG. These results may be attributed to differences of sialic acid contents. Affinity chromatography using Ricinus communis agglutinin-conjugated Sepharose showed that the serum hCG was completely sialylated, while the urinary hCG was partially desialylated. In addition to the complete hCG molecule, two kinds of hCGbeta-related fragments were detected in the urine of the patient, but not in the serum. In the Western blot using anti-hCGbeta or anti-hCGbeta-CTP under reducing conditions, the urine presented a new band (CTP') with Mr 23,000 in addition to the beta-subunit, while the serum revealed a single band of the beta-subunit with or without a reducing reagent. The present data revealed striking qualitative differences in the molecular forms of hCG between serum and urine of a patient with choriocarcinoma.

Incompletely processed LH molecules synthesized by rat gonadotrophs treated with inhibitors of oligosaccharide processing

Inhibitors of N-linked oligosaccharide processing are useful tools for studies on the biological function of the oligosaccharide structures in glycoprotein hormones. We have synthesized molecules of lutropin (LH) containing high-mannose- and hybrid-type oligosaccharides using rat gonadotroph-enriched primary cultures in the presence of castanospermine (a glucosidase I inhibitor) or swainsonine (a mannosidase II inhibitor), in order to compare the actions of these molecules with that of the hormone containing complex-type oligosaccharides in the activation of the receptor-adenylate cyclase system. Treatment of gonadotrophs with the above inhibitors caused an increase in the synthesis of highly basic LH molecules (pI 9.6-10.0), because addition of charged carbohydrate moieties to these molecules was prevented. Characterization of the oligosaccharide structure performed by enzymatic treatment (endoglycosidase H and neuraminidase) and the use of immobilized lectins (wheat germ agglutinin and Ricinus communis agglutinin-120) showed that these inhibitor-synthesized LH molecules contained high-mannose- and hybrid-type (asialo and sialylated) oligosaccharides. Their immunological properties were similar to that of complex-type oligosaccharide LH, but they had significantly higher receptor-binding ability in comparison with a sialylated complex-type oligosaccharide LH (about 12-fold) and an asialo complex-type oligosaccharide LH (about 3-fold). It was noted that the incompletely processed molecules were less potent than complex-type oligosaccharide LH in the activation of adenylate cyclase of Leydig cells, showing about 40-60% of the activity induced by the sialylated complex-type oligosaccharide molecule. The present data indicate that the inhibition of terminal processing of N-linked oligosaccharides by castanospermine and swainsonine impairs the full hormonal function of rat LH.

Lectinohistochemistry of human bladder cancer: loss of lectin binding structures in invasive carcinomas

With the purpose of studying changes in the expression of glycoconjugate structures in urothelium, nine different lectins (PNA, WGA, VFA, GSA II, STA, UEA I, LCA, DBA and HPA) with specificity for mono- or oligo-saccharides were used on formalin-fixed, paraffin-embedded tissue sections from 47 patients who had undergone surgical resection for bladder tumors and on normal urothelial biopsies from 10 patients. The tumors were graded and a lectinohistochemical method using biotinylated lectins and avidin-biotin-peroxidase complex was used to demonstrate the lectin binding. Positive staining reactions of cells in cytoplasm and on membranes were evaluated in the basal, the intermediate, and the luminal cell layers, respectively. In both normal and atypical urothelium lectin binding predominated in the luminal cell layer and decreased towards the basal cell layer. In normal urothelium all lectins stained greater than 66% of the cells in the luminal cell layer in cytoplasm and between 5 and 100% of the cells on membranes depending on the lectin used. A gradual loss of lectin-binding structures was seen with increasing grade of atypia. The range of this decrease varied considerably from one lectin to another, but it was consistently found that the percentage of cells stained in cytoplasm and on membranes decreased. A significantly lower percentage of cells stained in cytoplasm was found in invasive tumor cell-islands compared to normal urothelium. In invasive tumor cell-islands staining of cells on membranes was completely absent, except for HPA lectin that stained less than 10% of the cells. In conclusion, we demonstrate a dramatic decrease in lectin-binding carbohydrate structures associated with urothelial malignant progression.

Glycoproteins and glycolipids of rat small intestinal microvillus and basolateral membranes

Glycoprotein and glycolipid constituents were examined in purified microvillus and basolateral membranes isolated from rat small intestinal epithelial cells. SDS-polyacrylamide gel electrophoresis showed that the molecular weights of most of the major proteins from microvillus membranes were over 100 kD, whereas the majority of those from basolateral membranes tended to have lower molecular weights. Glycoprotein profiles were also examined using three labeling methods, and in each case marked differences were observed between microvillus and basolateral membranes. In both membranes, lectins with a specificity toward N-linked sugar chains bound to the majority of the glycoproteins, in contrast to those lectins which preferentially bind to O-linked sugar chains. Glycolipids were labeled in vivo and isolated from both membrane fractions. Some differences were observed in the fucolipids and neutral glycolipids suggesting a more complex pattern in microvillus membranes. These results indicate that there are differences in the glycoprotein and glycolipid compositions of microvillus and basolateral membranes that may reflect the functional polarity of intestinal epithelial cells.

Lutropin molecules synthesized by rat gonadotroph primary cultures in the presence of swainsonine: their oligosaccharides and biological potencies

The biosynthesis of lutropin (luteinizing hormone, LH) containing abnormally processed oligosaccharides has been studied in rat gonadotroph-enriched primary culture in the presence of swainsonine, an inhibitor of the N-linked oligosaccharide processing in the Golgi complex. The inhibitor led to time- and dose-dependent accumulation of highly alkaline LH molecules (pI 9.6, 10.0) with high binding affinity for concanavalin A (ConA), and concomitant decreases of less alkaline components (pI 8.0, 8.5, 8.8) with less affinity for the lectin. The accumulation of LH molecules was much amplified after gonadotrophin-releasing hormone (GnRH) stimulation. The characterization of the oligosaccharide structure performed by means of enzyme treatment and serial chromatography on immobilized ConA, Ricinin communis agglutinin-120 (RCA-120), and wheat germ agglutinin (WGA) showed that swainsonine-induced LH contained principally the hybrid-type oligosaccharide, which was processed by the addition of terminal sialic acid residues on one branch of each N-linked oligosaccharide in both subunits. Small amounts of LH molecules containing asialo or partially sialylated hybrid oligosaccharides were also synthesized. The data for in vitro steroidogenic activities of swainsonine-induced LH indicated that terminal sialic acid on one branch of the hybrid-type oligosaccharides decreased the full agonist activity by approximately 50%.

Immunochemical studies on the N-acetyllactosamine beta-(1----6)-linked trisaccharide specificity of Ricinus communis agglutinin

The combining site of Ricinus communis agglutinin (RCA1) was studied by quantitative precipitin and precipitin inhibition assays. Of 31 complex carbohydrates tested, all except active and inactive antifreeze glycoproteins, Streptococcus group C polysaccharide, and native rat salivary glycoprotein, reacted strongly, and 22 completely precipitated the lectin, indicating that RCA1 has both a broad range of affinity and a low solubility of its carbohydrate-bound complex. Of the monosaccharides and glycosides tested for inhibition of precipitation, p-nitrophenyl beta-D-galactopyranoside was the best. It was about 6.4 times better than methyl beta-D-galactopyranoside. The beta anomer of glycosides of D-galactose was much more potent than the corresponding alpha anomer. Among the oligosaccharides tested, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)-D-Gal was the best inhibitor, which was approximately 2/3 as active as p-nitrophenyl beta-D-galactopyranoside. It was approximately 1.4 times as active as beta-D-Gal-(1----4)-D-GlcNAc (N-acetyllactosamine), twice as active as beta-D-Gal-(1----3)-D-GlcNAc, and 4.5 times more active than lacto-N-tetraose. From the results, it can be concluded that; (a) hydrophobic interaction is important for binding; (b) the combining site of this lectin is at least as large as a trisaccharide; and (c) of the compounds studied, the trisaccharide beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)-D-Gal was the most complementary to the human blood group I Ma determinant beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)-D-Gal.

Carbohydrate-binding specificities of five lectins that bind to O-Glycosyl-linked carbohydrate chains. Quantitative analysis by frontal-affinity chromatography

The carbohydrate-binding specificities of lectins purified from Agaricus bisporus (ABA-I), Arachis hypogaea (PNA), Bauhinia purpurea (BPA), Glycine max (SBA), and Vicia villosa (VVA-B4) have been studied by affinity chromatography on columns of the immobilized lectins, and quantitatively analyzed by frontal affinity chromatography. These five lectins could be classified into two groups with respect to their reactivities with typical mucin-type glycopeptides, beta-D-Galp-(1----3)-alpha-D-GalpNAc-(1----3)-Ser/Thr (2) and alpha-D-GalpNAc-(1----3)-Ser/Thr (3). One group, which consists of ABA-I, PNA, and BPA, preferentially binds to 2, and the other, which consists of SBA and VVA-B4, shows higher affinity for 3 than for 2. Among the lectins tested, only ABA-I was found to bind to a sialylated glycopeptide, whic which was prepared from human erythrocyte glycophorin A and contains three three tetrasaccharide chains having the structure of alpha-NeuAc-(2----3)-beta-D-GAlp-(1----3)-NeuAC-(2----6)]-alpha-D-Galp NAc-(1----, with an association constant of 15 microM, whereas the association constants of the other four lectins for this sialylated glycopeptide were less than 3.5 mM. On the other hand, removal of the beta-D-galactopyranosyl group from a glycopeptide containing sequence 2 resulted in decreased association constants for the three lectins of the first group, especially ABA-I and PNA. The two lectins of the second group showed a high affinity for 3, but SBA preferentially interacted with oligosaccharides containing the alpha-D-GalpNAc-(1----3)-beta-D-Galp-(1----3)-D-GlapNAc sequence, prepared from a blood group A-active oligosaccharide.

Electrophoretic analysis of four high molecular weight sialoglycoproteins produced by metastatic human colon carcinoma cells

We have found that polyacrylamide gel electrophoresis in 3% gels in the presence of sodium dodecyl sulfate is suitable for the separation of cellular glycoproteins having molecular weights ranging from 200,000 to 1,000,000. The gels secured on a rigid support (Gelbond) allow blotting techniques with lectins and antibodies for the detection of glycoproteins. Using these methods we have separated lysates of HT-29 human colon carcinoma cells and detected at least four distinct high molecular weight sialoglycoproteins having molecular weights of 900,000, 740,000, 560,000, and 450,000. The expression of the 900,000 component, as revealed by wheat germ agglutinin binding, was much higher in a subline of HT-29 cells established from liver metastases in a nude mouse than it was in the parental cells. The relative intensity of wheat germ agglutinin binding to these four sialoglycoprotein components differs depending upon their growth phase in vitro. These glycoproteins were also detectable by the binding of peanut agglutinin, provided the glycoproteins were previously treated in the gels with mild acid to remove the sialic acid from their carbohydrate chains, suggesting that mucin-type carbohydrate chains are present on these glycoproteins. The same set of glycoproteins can be detected by metabolic labeling of the cells with [3H]glucosamine in tissue culture. Very similar glycoprotein profiles are revealed by metabolic labeling of fresh colon carcinoma tissues with [3H]glucosamine in vitro.

Biochemistry and lectin binding properties of mammalian salivary mucous glycoproteins

The molecules responsible for the highly viscous properties of mucus are secretory glycoproteins referred to as mucins. Salivary mucins are characterized by a high sugar to protein ratio and are of a broad range of molecular weight from 7 x 10(4) to millions. With a few exceptions, they contain up to 30% of hexosamine (galactosamine and glucosamine), 8-33% of sialic acid, trace to 15% of galactose or fucose and little or no mannose. The size of carbohydrate side chains of these glycoproteins ranges from one to about fifteen units of sugar. These carbohydrate side chains are usually O-glycosidically linked through N-acetylgalactosamine to a peptidyl serine or threonine. In some instances, ester sulfate groups, mainly on N-acetylglucosamine, are also a structural feature. In many of these glycoproteins, the saccharide sequence is the same as that which determines the specificity of blood groups. Carbohydrate sequence analysis shows that salivary mucins exhibit considerable polydispersity, great diversity and remarkable structural flexibility not only among animal species but also within the same mucin molecule. Based on their lectin-binding ability, they can be used for purification of lectins, and lectins coupled to resin may be useful for the isolation of mucin-type glycoproteins. The epithelial mucous secretions modulate oral microbial flora; many secretory components serve as lectin-receptors for the attachment of microbes. The judicious use of lectins with widely differing binding characteristics has already been valuable in the in situ localization of salivary glycoproteins, in elucidating structural details, recording sugar density within a given tissue section, and defining host-parasite interactions. It is hoped that their use, together with monoclonal antibody (158) and tissue culture techniques (159, 160) will further clarify the roles of individual secretory mucous glycoproteins in health and disease.

The separation of immunocyte subpopulations by use of various lectins

The use of lectins for the enrichment of various lymphocyte subpopulations was investigated. Bauhinia purpurea lectin (BPA) was found to be effective for the enrichment of B cells, and the B cells thus obtained were further fractionated with lentil lectin into subsets showing high and low responses to dextran sulfate. The ability of various lectins to selectively induce suppressor T cell activity or helper T cell activity was also examined. The suppressor T cells thus induced were enriched peanut lectin and, conversely, the helper T cells were enriched with Limulus polyhemus lectin. This method was applied to analysis of age-dependent changes in the levels of suppressor and helper T cells in autoimmune-prone mice. Cytotoxic T cells induced in an allogeneic mixed lymphocyte culture were enriched with Dolichos biflorus lectin (DBA). These cytotoxic T cells showed a specific killing effect in vitro. However, when spleen cells of tumor-bearing mice were fractionated by use of DBA, the DBA- cells mediated the regression of the tumors in vivo. BPA was also found to be effective for the enrichment of the interleukin-2-producing T cell subset and macrophage precursor cells. Using this technique, bone marrow cells of autoimmune-prone MRL/1 mice were found to be rich in macrophage precursor cells.

Characterization of the blood-brain barrier: glycoconjugate receptors of 14 lectins in canine brain, cultured endothelial cells, and blotted membrane proteins

The avidin-biotinylated peroxidase complex (ABC) method was used to detect binding of 14 lectins in tissue, cultured cells, and nitrocellulose blots. When applied to frozen sections of canine cerebral cortex and pituitary and evaluated by light microscopy, these lectins produced distinct staining patterns as determined by their individual carbohydrate specificities. Major saccharide residues detected in the endothelium of these cerebral tissues include alpha- and beta-galactose, alpha-mannose and/or alpha-glucose, and N-acetylglucosamine. Application to cells cultured from the canine cerebral endothelium gave staining results similar to those of microvessels in tissue. Thus, these characteristics of intact capillaries are retained in cultured cells and define fundamental properties of the blood-brain interface. Visual comparison of these staining patterns to those obtained for electrophoretic blots of solubilized membrane proteins identified multiple glycoprotein receptors and illustrated the vast quantity and variety of surface carbohydrate residues and the complexity of the cerebral endothelial cell glycocalyx. This carbohydrate-rich layer, which extends into the capillary lumen, may be of significant importance to the unique function of the blood-brain barrier.

Carbohydrate structures of bovine submaxillary mucin

The structures of carbohydrate chains derived from bovine submaxillary mucin (BSM) were investigated. Oligosaccharide-alditols released from BSM by alkaline borohydride treatment were separated into three acidic (A-1-A-3) and five neutral (N-1-N-5) oligosaccharide-alditol fractions by liquid chromatography on columns of an ion-exchange resin and Bio-Gel P-4. On the basis of the data obtained on compositional and methylation analyses, and digestion by exoglycosidase, the following structures were assigned to these oligosaccharide-alditols: A-1, alpha-NeuAc (or NeuGc)-(2----6)-GalNAc-ol; A-2, beta-Gal-(1----3)-[alpha-NeuAc-(2----6)]-GalNAc-ol; A-3, beta-GlcNAc-(1----3)-[alpha-NeuAc-(2----6)]-GalNAc-ol; N-1, GalNAc-ol; N-2, beta-Gal-(1----3)-GalNAc-ol; N-3, beta-GlcNAc-(1----3)-GalNAc-ol; N-4, beta-Gal-(1----3)-[beta-GlcNAc-(1----6)]-GalNAc-ol; and N-5, alpha-Fuc-(1----2)-beta-Gal-(1----3)-[beta-GlcNAc-(1----6)]-GalNAc-ol. These results showed the heterogeneous nature of the carbohydrate chains of BSM.

Sialoglycoproteins of murine RAW117 large cell lymphoma/lymphosarcoma sublines of various metastatic colonization properties

A metastatic model for large-cell lymphoma/lymphosarcoma has been developed by sequential selection in vivo of the murine RAW117 cell line for enhanced liver metastasis or in vitro for loss of lectin-binding properties. The metastatic variants obtained from such selections show alterations in cell surface lectin-binding components, such as the wheat germ agglutinin (WGA)-reactive sialoglycoproteins. Detergent lysates from RAW117 cells were analyzed by polyacrylamide gel electrophoresis (PAGE) followed by reaction with 125I-labeled WGA. The [125I]WGA became bound to a diffuse band of Mr 120 000-200 000 in the gels that overlapped with the major sialoglycoprotein band revealed by the periodate-sodium borotritide labeling. However, the [125I]WGA reactivity diminished when gels were pretreated with mild acid to remove sialic acid in situ. The binding of [125I]WGA to the glycoprotein(s) was greater in the high liver-colonizing RAW117-H10 subline than in the parental RAW117-P line. Another lectin with different saccharide specificity, Ricinus communis agglutinin I (RCAI), became bound to a similar class of sialoglycoproteins, as well as to glycoproteins of lower Mr, but only when the gels were pretreated with mild acid to remove sialic acid. These differences in the relative RCAI-binding intensities after chemical removal of sialic acid were similar to those seen with WGA and indicate that differences in WGA reactivity of this class of sialoglycoproteins were not due to increased sialylation of the carbohydrate chains. Sialic acid was removed from RAW117 cells by neuraminidase treatment, and lysates were analysed for [125I]RCAI reactivity after electrophoresis. The migration of the glycoproteins was not affected by neuraminidase, indicating that the diffuseness of the major sialoglycoprotein band was not due to differences in sialylation. [125I]WGA reactivity to the sialoglycoprotein components, before and after Smith degradation in situ, strongly suggests that the oligosaccharide back-bones are highly branched and asparagine-linked. Only the high Mr portion of the diffuse sialoglycoprotein band was stained with peanut agglutinin (PNA) after in situ removal of sialic acid. To determine whether the expression of the sialoglycoprotein was causally related to liver metastasis, the amounts of sialoglycoproteins in RAW117 cells obtained by in vitro selection for increased or decreased metastasis were examined. Binding of [125I]WGA to intact cells and affinity chromatography of vectorially radiolabeled cell surface proteins on WGA-agarose were performed, and the results indicated that the in vitro selected high liver-colonizing RAW117 variants possesses high WGA r

Cell surface carbohydrate involvement in controlling the adhesion and morphology of neural crest cells and melanophores of Xenopus laevis

Pieces of dorsal neural tube (stages 22-23) or late neural crest tissue (stages 24-26) of Xenopus laevis were cultured. Migratory cells moved out of explants to form an outgrowth of multipolar melanophores on the substratum. Treatment with beta-galactosidase (0.1-0.4 U/ml) to remove cell surface galactose was correlated with detachment of melanophores. In the presence of lower concentrations of this enzyme the shapes of these cells were converted to arborized, spidery morphologies and cell movement was inhibited. Unpigmented cells were affected more slowly. Neuraminidase treatment, to remove cell surface sialic acid and expose more galactose, only affected melanophores. These became increasingly spread on the substratum and cell overlap was observed. These results suggest that the relative amounts of galactose and sialic acid at the cell surface become increasingly important in controlling cell adhesion as X. laevis neural crest cells migrate and differentiate into melanophores.

Interaction between rabbit IgG immune complexes and Ricinus agglutinin

Ricinus communis agglutinin covalently bound to Sepharose 4B (RcA-Sepharose 4B) was able to selectively bind immune complexes consisting of antigen (bovine serum albumin) and rabbit IgG antibody which were rich in antibody (i.e., high molecular weight complexes of approximately 2000 000). No interaction was recorded between RcA-Sepharose 4B and immune complexes consisting of the antigen plus rabbit IgG antibody which were rich in antigen (i.e., complexes with a molecular weight of 300 000-500 000). These results indicate that binding to RcA is due to the increased density of galactose residues in the high molecular weight polymeric antibody component of the soluble immune complexes.

Ricin-resistant human T-cell hybridomas producing interferon gamma

Ricin-resistant variants of the SH9 T-cell line were selected after growth of this line in medium containing toxic amounts of ricin, a lectin derived from Ricinus communis. The ricin-resistant SH9 lines, SH9.R0 and SH9.R1, were demonstrated to be deficient in cell surface ricin-binding sites, but otherwise had the cellular phenotype of SH9 cells. Ricin-resistant T-cell hybridomas were prepared by fusion of SH9.R0 and SH9.R1 with activated T-lymphocytes. The presence of ricin in the selection medium rapidly killed unfused T-lymphocytes and prevented cell transformation by human T-cell leukaemia virus type 1 (HTLV-1) which is shed by the SH9.R0 and SH9.R1 cells. This ensured that the cells growing out were indeed hybridomas. Ricin-resistant T-cell hybridomas were characterised and also shown to lack cell surface receptors for ricin. Analysis of T-cell surface markers indicated that the T-cell hybridomas could be the result of fusions between SH9.R1 cells and T-helper lymphocytes or T-suppressor lymphocytes. All of the T-cell hybridomas prepared in this study spontaneously produced interferon gamma (IFN gamma).

Phosphorylated high mannose-type and hybrid-type oligosaccharide chains of human thyroglobulin isolated from malignant thyroid tissue

Structures of anionic oligosaccharides released by endo-beta-N-acetylglucosaminidase H from human thyroglobulin (19 S) purified from normal and malignant (papillary carcinoma) thyroid tissues were studied by sequential exoglycosidase digestion and lectin affinity chromatography. It was revealed that sialylated hybrid-type oligosaccharides were present in thyroglobulin from normal thyroid tissue, whereas, in the case of thyroglobulin from malignant thyroid tissue, phosphorylated high-mannose type and hybrid-type oligosaccharides each containing one phosphate group in a diester linkage were present instead of sialylated oligosaccharides. The possible meaning of the phosphorylated oligosaccharides was discussed in relation to the low thyroglobulin content in malignant thyroid tissue.

Correlation of interferon gamma inducing ability to sugar binding specificities of various lectins

Various lectins were examined to determine possible induction of gamma interferon (IFN-gamma) in human leukocytes. Among the seven positive lectins (Concanavalin A, pea lectin, lentil lectin, rice bran agglutinin, pokeweed mitogen, wheat germ agglutinin, phytohemagglutinin-P), six except rice bran agglutinin belonged to those which recognize carbohydrate chains connected to polypeptide through a glycosylamine linkage between N-acetylglucosamine (GlcNAc) and asparagine residues. The specificity of carbohydrate chain recognition of rice bran agglutinin, residual one positive lectin, has not been reported. Induction of IFN-gamma by wheat germ agglutinin, one of the positive lectins, was inhibited by the addition of GlcNAc during the induction, but not by the addition of glucose, galactose, alpha-methylmannose, N-acetylgalactosamine, N-acetylmannosamine, and lactose.

Differential binding characteristics and applications of DGal beta 1----3DGalNAc specific lectins

The binding properties of Arachis hypogaea (PNA), Bauhinia purpurea alba (BPL), Maclura pomifera ( MPL ) and Sophora japonica (SJL) lectins were studied by quantitative precipitin and precipitin inhibition assays, demonstrating them to be most specific for DGal beta 1---- 3DGalNAc residues. Additionally, each lectin had its own binding characteristic such as different binding activities to DGal beta 1---- 4DGlcNAc or DGal beta 1---- 3DGlcNAc beta 1----linked oligosaccharides, and/or DGalNAc alpha 1----linked to the Ser or Thr of the protein moiety. These differential binding characteristics can be used for investigating fine differences of the carbohydrate structure of the glycoconjugates, especially those having DGal beta 1---- 3DGalNAc residues as terminal non-reducing ends.

Binding characteristics of 3H-dihydroalprenolol to beta-adrenoceptors of rat heart treated with neuraminidase

Binding characteristics of the beta-blockers and beta-agonists with the beta-adrenoceptors were investigated in 3H-dihydroalprenolol (3H-DHA) binding to rat heart membranes treated with neuraminidase. When 60% of the total sialic acid content in the membranes was removed, reproducibility of the binding assay became much better than was attainable without neuraminidase treatment, and the maximum density of beta-adrenoceptors was increased. These data suggest that the binding of the test compounds with the beta-adrenergic receptors in cardiac muscle was under the influence of the sialic acid of the glycocalyx of the membrane. The 3H-DHA binding sites in membranes treated with neuraminidase showed a strict stereo-specificity when tested with propranolol. The ranking order of inhibition of beta-antagonists or agonists is: dl-propranolol greater than oxprenolol greater than alprenolol greater than pindolol greater than YM-09538 greater than labetalol greater than acebutolol greater than atenolol greater than metoprolol greater than sotalol greater than butoxamine greater than practolol as antagonists or l-isoproterenol greater than l-epinephrine greater than l-norepinephrine as agonists. A good correlation (r = 0.91, P less than 0.001) was observed between the Ki values observed by the present binding assay and the pA2 observed in the guinea-pig atria relative to the positive inotropic effect by Bieth et al. (Br. J. Pharmacol. 68, 563-569, 1980), indicating that the present method will be useful for screening new beta-adrenergic receptor antagonists or agonists.

Purification of peanut (Arachis hypogaea) agglutinin isolectins by chromatofocusing

This report describes the purification and isolation of the isolectins of peanut agglutinin (PNA). We find the affinity-purified PNA to have an amino acid composition similar to that reported by Lotan et al. (J. Biol. Chem. 250, 8518-8523 (1975)); however, our preparation contains three tryptophan residues per subunit rather than two as reported by Lotan et al. This higher tryptophan content is consistent with the extinction coefficient (E1 mg/ml 280) of 0.96 as previously reported (Fish et al., Arch. Biochem. Biophys. 190, 693-698 (1978)). The PNA, purified by affinity chromatography on lactosyl-Sepharose, contains six major and three minor components capable of agglutinating neuraminidase-treated erythrocytes. Seven of the isolectins were obtained in a highly purified form by chromatofocusing, a column chromatographic technique which separates proteins on the basis of their isoelectric points. Isoelectric focusing of the purified isolectins indicates that they have the following isoelectric points: A, 6.70; B, 6.55; C, 6.35; D, 6.25; E, 6.10; F, 5.90; and G, 5.70. Preliminary studies on the subunit composition of the isolectins are also presented.