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PubMed1992

Tumor progression in vivo: increased soybean agglutinin lectin binding, N-acetylgalactosamine-specific lectin expression, and liver metastasis potential.

Tumors which grew out from threshold s.c. inocula of L5178Y-F9 and SL2-5 murine T-cell lymphomas in syngeneic DBA/2 mice exhibited a unified natural defense-resistant phenotype including an increased tumorigenicity and correlating reductions in susceptibility to natural antibodies, natural killer cells, and activated macrophages in vitro. The metastatic potential and cell surface saccharide expression of these cells were determined to assess the impact of growth from a small tumor focus in vivo on subsequent metastatic ability and to determine whether there was any association with changes in cell surface carbohydrates, which have been implicated now for many years in tumor development. A significantly increased liver-colonizing ability was observed following i.v. injection. The most consistent change in cell surface saccharide expression detected in studies using five lectins was an increase in N-acetyl-D-galactosamine (D-GalNAc)-specific soybean agglutinin (SBA) binding. The log of experimental liver metastasis, SBA binding, and the percentage of hepatocyte rosetting of the parental and in vivo-selected cells exhibited significant direct correlations. While inhibition of rosetting with in vivo-selected lines by D-GalNAc and galactose was consistent with the involvement of the D-galactose/D-GalNAc-specific hepatocyte receptor, preincubation of the tumor cells but not hepatocytes with D-GalNAc inhibited hepatocyte rosetting and D-GalNAc inhibited homotypic tumor cell binding. These data suggest a role for a saccharide-specific, lectin-like receptor on tumor cells in both interactions and therefore in the increased experimental liver metastasis. Furthermore, the increased expression of D-GalNAc-inhibitable SBA binding sites on the in vivo-selected variants should increase the homotypic binding by the D-GalNAc-specific lectin-like receptors on the tumor cells providing a rationale for the direct relationship observed between increased SBA binding and i.v. metastatic potential.

Acetylgalactosamine↗

PubMed1990

X-ray structure of a (alpha-Man(1-3)beta-Man(1-4)GlcNAc)-lectin complex at 2.1-A resolution. The role of water in sugar-lectin interaction.

We describe herein the high resolution refined x-ray structure of a trisaccharide, which is a part of the N-acetyllactosamine type glycan found in the majority of the N-glycosyl-proteins, complexed to the isolectin I. According to the potentials used by Imberty et al. (Imburty, A., Gerber, S., Tran, V., and Pérez, S. (1990) Glycoconjugate J. 7, 27-54) the trisaccharide is in a low-energy state. Only one mannose moiety establishes direct hydrogen bonds with the lectin, as it is the case for monosaccharide-lectin complexes. The comparison of our trisaccharide with the one determined in solution by Warin et al. (Warin, V., Baert, F., Fouret, R., Strecker, G., Fournet, B., and Montreuil, J. (1979) Carbohydr. Res. 76, 11-22) shows that both adopt roughly the same conformation. The differences in these two sugar structures allow us to assign the role of water molecules present in the vicinity of our trisaccharide for the stabilization of this sugar-lectin complex.

Carbohydrate Sequence↗

PubMed1987

Identification of the post-translational modifications of the core-specific lectin. The core-specific lectin contains hydroxyproline, hydroxylysine, and glucosylgalactosylhydroxylysine residues.

The core-specific lectin (CSL) synthesized and secreted by rat hepatocytes and the rat hepatoma H-4-II-E shows affinity for mannose and N-acetylglucosamine residues in the "core" region of asparagine-linked oligosaccharides. The CSL undergoes two stages of post-translational modification which result in an increase in its Mr from 24,000 to 26,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We have determined that the lectin undergoes hydroxylation of proline and lysine and that the hydroxylysine is glycosylated to form glucosylgalactosylhydroxylysine (GlcGalHyLys). CSL metabolically labeled with [3H]lysine and [3H]proline contains hydroxylated forms of proline and lysine. The mature form of the lectin can also be metabolically labeled with [3H]galactose. alpha,alpha'-Dipyridyl, an inhibitor of collagen prolyl and lysyl hydroxylases, prevents the metabolic incorporation of [3H]galactose and the post-translational increases in the Mr of the CSL, indicating that both events are dependent upon hydroxylation of proline and lysine. Virtually all of the hydroxylysine present in the CSL is recovered as glucosylgalactosylhydroxylysine after alkaline hydrolysis. The post-translational modifications of the CSL place it in a select family of secreted proteins which contain collagen-like sequences, including the pulmonary surfactant proteins, complement component C1q, and the 18 S asymmetric form of acetylcholinesterase.

2,2'-Dipyridyl↗

PubMed1975

The use of flurorescein investigations with concanavalin A, Lens culinaris lectin and Ricinus communis lectin.

Investigations on methods for the utilization of fluorescein-isothiocyanate-labelled Concanavalin A, Lens culinaris lectin and Ricinus communis lectin for immunohistological demonstration as simple sugar moieties are reported. The stainings were carried out on rabbit erythrocytes. Ehrlich ascitee tumor cells and various mammalian tissues. Optimum results were obtained in living cells and native cryostate tissue sections. The influence of different fixing agents and conditions of fixation on the degree of tissue flurorescence were studied. Generally the fluorescense decreased by aldehyde fixation. Similar effect was observed following fixation by heat. Furthermore, changes in the pattern of fluorescence depending on the type of tissue and utilized lectin were observed after aldehyde fixation. The degree of tissue fluorescence was fairly independent of the pH value. The specificity of the particular reactions for saccharide demonstration was shown; glycerol is capable of a differently strong "hapten-like" action.

Animals↗

PubMed1978

Studies on lectins. XXXVIII. Isolation and characterization of the lectin from black locust bark (Robinia pseudacacia L.).

The lectin of black locust (Robinia pseudacacia) bark was isolated by specific adsorption on formaldehyde-fixed human erythrocytes and elution with a borate solution. The lectin is homogeneous on disc electrophoresis and ultracentrifugation (s20,w = 5.8 S) but yields three bands on isoelectric focusing. It has a molecular weight of approximately 110,000 and consists of two types of subunit (mol. wt 29,000 and 31,500). Its pI is approximately 5.9; it contains high amounts of aspartic acid, threonine and serine, no cysteine and very little methionine. Also 7.2% of covalently bound neutral sugar and 0.47% of glucosamine are present. The lectin is nonspecific in agglutination of human erythrocytes, it is inhibited by high concentrations of N-acetyl-D-galactosamine and is mitogenic in rabbit lymph node lymphocytes.

Amino Acids↗

PubMed1997

Investigation of Vicia graminea lectin- and Vicia unijuga lectin-binding glycoproteins as novel oncofetal antigens in cyst and ascitic fluids of human ovarian tumors in benign, dysplastic, and malignant stages.

Perchloric acid-soluble fractions (PASFs) were obtained from cyst fluids of human benign ovarian mucinous cystadenoma, benign dermoid cyst, "borderline" mucinous cystadenoma, and malignant ovarian clear cell carcinoma, and from fluids of malignant embryonal carcinoma and malignant serous cystadenocarcinoma. PASFs from benign lesions did not react with Arachis hypogaea lectin (PNA), Vicia graminea lectin (VGA), or Vicia unijuga lectin (VUA). PASFs from "borderline" lesions reacted with PNA but did not react with VGA and VUA. PASFs from malignant tumors reacted with PNA, VGA, and VUA. These PASFs did not react positively against anti-M or -N sera. These results show that VGA- and VUA-binding glycoprotein (Vgu glycoprotein) exist in PASFs from malignant ovarian tumors, and that PNA-binding glycoprotein was present in PASFs from malignant and "borderline" ovarian tumors. Furthermore, we found the existence of Vgu glycoprotein in PASFs from various human cancer cell lines; however, the antigens were not found in PASFs from benign human cell lines.

Antigens, Neoplasm↗

PubMedDate not supplied

[Purification of lectin from Paris quadrifolia L. and comparison of its carbohydrate-binding specificity with other lectins of the Liliaceae family].

Lectin from rhizomes of Paris quadrifolia I. was purified by affinity chromatography on cross-linked ovomucine with yield of 75 mg per 1 kg of fresh rhizomes. Purified lectin gave a single band on gel disk electrophoresis at pH 4.5 and two bands at pH 8.9. Electrophoresis in gradient 15-20% polyacrylamide gel in the presence of DS-Na at pH 8.9 has revealed two distinct bands with Mm 12.8 and 11.5 kDa. Gel chromatography on Sephadex G-200 has discovered two proteins with Mm 50 and 102 kDa. The agglutinating activity is inhibited by N-acetylneuraminic acid and several sialyl-glycoproteins. Lectins with such specificity were also discovered in grasses Scilla bifolia I, Gagea lutea I. and Polygonatum multiflorum (L) All.

Carbohydrate Metabolism↗

PubMed1977

Suppression of generation of human cytotoxic effectors by lectins or lectin-activated peripheral blood lymphocytes.

The lectins phytohemagglutinin, pokeweed mitogen and concanavalin A used at their optimal mitogenic concentration, or human lymphocytes activated by the same mitogens, were found to suppress the in vitro generation of cytotoxic effectors when added to a cell-mediated lympholysis (CML) mixture during the first 48 h of culture. The data suggest that the suppressive mechanism is mediated to a greater extent by an allogeneic interaction between lectin-activated cells and the allogeneic cells present in the CML mixture than by suppressor cells induced by the lectin. Since partial suppression was observed with supernatants of activated lymphocytes cultured for 18 h with allogeneic stimulating cells (but not activated lymphocytes alone), a soluble mediator may be involved in the suppressive mechanism. The mechanism of suppression therefore may be identical to the preemption phenomenon recently described in primary and secondary CML.

Antigens↗

PubMed1991

A mammalian sperm lectin related to rat hepatocyte lectin-2/3. Purification from rabbit testis and identification as a zona binding protein.

In rat liver the asialoglycoprotein receptor is composed of three polypeptides, RHL-1, RHL-2 and RHL-3. In rat testis and spermatozoa a galactosyl receptor (RTG-r) which is immunologically related to RHL-2/3 has been described. We now report that in addition to its presence in the rat, an antigenic species of 54 kDa related to RHL-2/3 is present on rabbit, human, pig and mouse spermatozoa. Purified rabbit testis galactosyl receptor (RbTG-r) consists of two major proteins of 54 and 49 kDa, while purified rabbit liver galactose lectin consists of two major proteins of 43 and 40 kDa. In an ELISA the purified rabbit testis galactosyl receptor was shown to bind biotinylated heat solubilized rabbit zonae, while the purified liver galactose lectin did not. We conclude that one of the mammalian sperm's zona binding proteins is a galactose lectin of 54 kDa related to rat liver RHL-2/3.

Animals↗

PubMed1984

Binding of fluorescein isothiocyanate conjugated lectins to rat spermatogenic cells in tissue sections. Enhancement of lectin fluorescence obtained by fixation in Bouin's fluid.

The testes from three months old Sprague-Dawley rats were fixed in Bouin's fluid or neutral buffered 10% formalin, embedded in paraffin, sectioned and after deparaffination stained with the following fluorescein isothiocyanate coupled lectins: PNA, WGA, Con A, RCA, SBA, DBA and UEA. The results show that there are considerable differences in the staining pattern of various spermatogenic cells between different lectins. The fixation in Bouin's fluid enhanced the staining of all the lectins compared to formalin fixation in which only a weak staining could be seen in the acrosomes of spermatids after WGA or PNA staining. PNA and WGA stained specifically the acrosome of the developing spermatids, which was seen from the beginning of the acrosome formation and lasted up to late spermiogenesis. However, the staining with PNA decreased in the late spermatids whereas the intensity of the staining remained unchanged with WGA. Con A did not stain the acrosome but stained unspecifically the cytoplasm of all spermatogenic cells. RCA stained faintly the acrosome throughout the spermatid differentiation. DBA and UEA stained specifically the chromosomes of B spermatogonia. DBA also faintly stained the cell membranes of early spermatids. SBA did not show any specific staining of the spermatogenic cells. Based on this it is suggested that the carbohydrates and glycoproteins which are known to be present in the acrosome are formed already in the beginning of the acrosome formation. The decrease in the PNA staining in late spermatids possibly reflects the fact that the receptor molecules are not synthesized in late spermatids but are formed in earlier developmental stages and are thereafter preserved in the acrosome.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Goat sperm membrane: lectin-binding sites of sperm surface and lectin affinity chromatography of the mature sperm membrane antigens.

The cell surface glycoproteins of goat epididymal maturing spermatozoa have been investigated using lectins as surface probes that interact with specific sugars with high affinity. Concanavalin A (ConA) and wheat-germ agglutinin (WGA) showed high affinity for mature cauda epididymal sperm agglutination, whereas RCA2, kidney beans lectin and peanut agglutinin caused much lower or little agglutination of the cells. The mature sperm exhibited markedly higher efficacy than the immature caput epididymal sperm for binding both ConA and WGA, as evidenced by sperm agglutination and the binding of the fluorescence isothiocyanate (FITC)-labelled lectins. FITC-ConA binds uniformly to the entire mature sperm surface whereas FITC-WGA binds to the acrosomal cap region of the head. The FITC-RCA2 mainly labelled the posterior head of mature cauda sperm. However, no WGA-specific glycoprotein receptors could be detected in sperm plasma membrane (PM) by WGA-Sepharose affinity chromatography. The data implied that the epididymal sperm maturation is associated with a marked increase in the ConA/WGA receptors and that WGA receptors may be glycolipids rather than glycoproteins. Analysis of the ConA receptors of cauda sperm PM identified by ConA-Sepharose affinity chromatography and subsequent resolution in SDS-PAGE demonstrated the presence of five glycopolypeptides of different concentrations (98, 96, 43, 27 and 17 kDa) of goat sperm membrane. The immunoblot of these ConA-specific glycopeptides with anti-sperm membrane antiserum showed that 98- and 96-kDa receptors are immunoresponsive.

Agglutination↗

PubMed1987

An enzyme-linked lectin-binding assay on cells (CELLBA) for the comparison of lectin receptor expression on cell surfaces.

Lectins can be used to specifically detect some cell surface glycans. Their expression on different cells or on cells of a given lineage throughout differentiation or following treatment with drugs can be compared using lectins labelled with radioactive, fluorescent or enzymatic probes. We describe a new method which, by analogy with CELISA (ELISA on cells), is called CELLBA (or ELLBA on cells) for cellular, enzyme-linked lectin-binding assay. It permits the comparison of the expression of specific glycans in a large number of different cell samples. As an example, it was able to detect alterations of cell surface glycan expression caused by inhibitors of N-linked oligosaccharide trimming.

Agglutination↗

PubMed1985

Horseshoe crab (Limulus polyphemus) lectin but not garden snail (Helix pomatia) lectin elicits insulin-like activities in vitro.

Lectins from the horseshoe crab (Limulus polyphemus) and the garden snail (Helix pomatia) were tested for insulinomimetic activities in isolated rat epididymal adipocytes. The sialic acid binding horseshoe crab lectin suppressed epinephrine-induced lipolysis and augmented lipogenesis from D-[3-3H]-glucose while the N-acetylgalactosamine binding snail lectin was inactive. The results suggest that the insulin receptor on rat adipocytes contains sialic acid in its carbohydrate moiety but does not possess non-reducing alpha-D-galactopyranosyl or 2-acetamido-2-deoxy-alpha-D-galactopyranosyl end groups.

Adipose Tissue↗

PubMed2004

The lectin-cell interaction and its implications to intestinal lectin-mediated drug delivery.

Based on the fact that oligosaccharides encode biological information, the biorecognition between lectinised drug delivery systems and glycosylated structures in the intestine can be exploited for improved peroral therapy. Basic research revealed that some lectins can mediate mucoadhesion, cytoadhesion, and cytoinvasion of drugs. Entering the vesicular pathway by receptor mediated endocytosis, part of the conjugated drug is accumulated within the lysosomes. Additionally, part of the drug is supposed to be transported across the epithelium. Moreover, factors probably adversely influencing feasibility of the concept such as toxicity, immunogenicity, and intestinal stability of plant lectins are discussed. As exemplified by lectin-grafted prodrug and carrier systems, this strategy is expected to improve absorption and probably bioavailability of poorly absorbable drugs, peptides and proteins as well as therapeutic DNA.

Animals↗

PubMed2006

Interplay between metal binding and cis/trans isomerization in legume lectins: structural and thermodynamic study of P. angolensis lectin.

The interplay between metal binding, carbohydrate binding activity, stability and structure of the lectin from Pterocarpus angolensis was investigated. Removal of the metals leads to a more flexible form of the protein with significantly less conformational stability. Crystal structures of this metal-free form show significant structural rearrangements, although some structural features that allow the binding of sugars are retained. We propose that substitution of an asparagine residue at the start of the C-terminal beta-strand of the legume lectin monomer hinders the trans-isomerization of the cis-peptide bond upon demetallization and constitutes an intramolecular switch governing the isomer state of the non-proline bond and ultimately the lectin phenotype.

Amino Acid Sequence↗

PubMed2006

Crystal structure of a lectin from Canavalia maritima (ConM) in complex with trehalose and maltose reveals relevant mutation in ConA-like lectins.

The crystal structure of Canavalia maritima lectin (ConM) complexed with trehalose and maltose revealed relevant point mutations in ConA-like lectins. ConM with the disaccharides and other ConA-like lectins complexed with carbohydrates demonstrated significant differences in the position of H-bonds. The main difference in the ConM structure is the replacement of Pro202 by Ser202, a residue that promotes the approximation of Tyr12 to the carbohydrate-binding site. The O-6' of the second glucose ring in maltose interacts with Tyr12, while in trehalose the interaction is established by the O-2' and Tyr12, explaining the higher affinity of ConM for disaccharides compared to monosaccharides.

Binding Sites↗

PubMed2001

Screening of a unique lectin from 16 cultivable mushrooms with hybrid glycoprotein and neoproteoglycan probes and purification of a novel N-acetylglucosamine-specific lectin from Oudemansiella platyphylla fruiting body.

Hybrid glycoprotein and neoproteoglycan probes were prepared by coupling various glycoproteins or polysaccharides to peroxidase or biotinyl bovine serum albumin, respectively. Lectins recognizable by the neoglycoconjugate probes were extracted from 16 cultivable mushrooms. Dot-blot assay revealed five extracts to be reactive with only hybrid glycoprotein probes, but others also reacted with neoproteoglycan probes. According to the reactivity pattern with probe screening, the one lectin from Oudemansiella platyphylla extract (OPL) bound best with asialotransferrin-- and asialoagalactotransferrin--peroxidase probes and was isolated using an asialotransferrin column, but it did not bind with other hybrid glycoprotein or neoproteoglycan probes. OPL, consisting of two polypeptides with high homology in the N-terminal amino acid sequences, exhibited weak hemagglutinating activity. Purified OPL specifically bound the beta-GlcNAc probe among various biotinylated polymeric sugar probes, while it exhibited essentially the same binding specificity toward neoglycoconjugate probes as that of the crude extract, showing a preference for the asialobiantennary complex type of N-linked glycans. These results indicate that the neoglycoconjugate probes are valuable in lectin screening.

Acetylglucosamine↗

PubMed2003

Altering the strength of lectin binding interactions and controlling the amount of lectin clustering using mannose/hydroxyl-functionalized dendrimers.

Protein-carbohydrate interactions play a critical role in many biological recognition events. Multivalent therapeutic agents that utilize protein-carbohydrate interactions have proven difficult to design, primarily because the fundamental requirements of protein-carbohydrate interactions are not well understood. Here, we report a systematic study of the effect on lectin binding of varying the loading of mannose surface residues on generations three through six PAMAM dendrimers. The degree of mannose functionalization was controlled by stoichiometric addition, and dendrimers were characterized using NMR and MALDI-TOF MS. Hemagglutination assays and quantitative precipitation assays were performed to determine the relative activity of the dendrimers. Using the mannose/hydroxyl-functionalized dendrimers reported here, we could systematically control both the degree of lectin clustering and the overall activity of the lectin with the dendrimer.

Concanavalin A↗