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PubMed2002

Lectin-mediated drug delivery: influence of mucin on cytoadhesion of plant lectins in vitro.

As the mucous layer represents the first barrier to peroral lectin-mediated drug delivery, the influence of mucin on the cytoadhesive properties of lectins was studied in vitro by establishing a rapid and simple microplate format assay using pig gastric mucin (PGM) for coating the wells. The lectin-binding capacity of mucin followed the order WGA>>UEA-I>>LCA=STL>PNA>DBA. The PGM-binding of wheat germ agglutinin (WGA) was strongly dependent on pH being highest at pH 5.0. In comparison, PGM-binding of WGA was about 15% at gastric pH and 60-70% at intestinal pH. This points to unimpeded gastric transit of WGA-grafted formulations and favorable conditions within the intestine for binding to mucus coated enterocytes. Moreover the WGA-PGM interaction was concentration-dependent, specific and fully reversible. According to a competitive assay in the presence of Caco-2 monolayers, the PGM-binding of WGA was saturated and influenced by the lectin-concentration yielding 28% Caco-2 bound WGA (125 ng WGA/0.29 cm(2) monolayer) and 68% Caco-2 bound WGA (4 microg WGA/0.29 cm(2) monolayer), respectively. Following on from these results, lectins are expected to suffer at least partially from premature inactivation by shed off mucus like bioadhesives of the first generation, however initial but reversible mucus-binding of lectins offers partititioning to the cell membrane followed by uptake into the enterocyte.

Adhesives↗

PubMed2003

Utilization of lectin-histochemistry in forensic neuropathology: lectin staining provides useful information for postmortem diagnosis in forensic neuropathology.

We have investigated the deposition of glycoconjugates in human brain tissue with or without brain disorders. In this review we describe the application of lectin-histochemistry techniques to forensic neuropathology. Lectin staining is able to reveal several kinds of carbohydrate-related depositions in addition to the conventional degenerative changes including senile plaques, neurofibrillary tangles and corpora amylacea. The senile plaques and neurofibrillary tangles were clearly stained by Con A, PSA and GSI lectins, the corpora amylacea which is relevant to repeated brain hypoxia and mitochondrial damage was also easily detected by these and many other kinds of lectins. Amorphous spaces were detected around blood vessels and independently from blood vessels by lectin staining in the white matter from patients with brain disorders or severe edema. The white matter lesions were not considered relevant for forensic pathology, until a large group of cerebral white matter lesions were detected in the elderly with increasing frequency by modern neuro-imaging methods. The spherical deposits were newly detected by lectin staining in the molecular layer of the dentate gyrus of the hippocampal formation chiefly from patients with schizophrenia or cognitive dysfunctions.

Alzheimer Disease↗

PubMed1988

Precipitation of galactose-specific lectins by complex-type oligosaccharides and glycopeptides: studies with lectins from Ricinus communis (agglutinin I), Erythrina indica, Erythrina arborescens, Abrus precatorius (agglutinin), and Glycine max (soybean).

We have recently demonstrated that certain oligomannose and bisected hybrid type glycopeptides and bisected complex type oligosaccharides are bivalent for binding to concanavalin A and can precipitate the lectin [Bhattacharyya, L., Ceccarini, C., Lorenzoni, P., & Brewer, C.F. (1987) J. Biol. Chem. 262, 1288-1293; Bhattacharyya, L., Haraldsson, M., & Brewer, C.F. (1987) J. Biol. Chem. 262, 1294-1299]. The present results show that tri- and tetraantennary complex type oligosaccharides containing nonreducing terminal galactose residues, and a related triantennary glycopeptide, precipitate the D-galactose-specific lectins from Ricinus communis (agglutinin I) (RCA-I), Erythrina indica (EIL), Erythrina arborescens (EAL), and Glycine max (soybean) (SBA). Nonbisected and bisected biantennary complex type oligosaccharides can precipitate SBA, which is a tetrameric lectin, but not RCA-I, EIL, or EAL, which are dimeric lectins. The relative affinities of the oligosaccharides and glycopeptide were determined by hemagglutination inhibition measurements and their valencies by quantitative precipitin analyses. The equivalence points of the precipitin curves indicate that the tri- and tetraantennary oligosaccharides are tri- and tetravalent, respectively, for EIL, EAL, and SBA binding. However, the oligosaccharides are all trivalent for RCA-I binding due apparently to the larger size of the monomeric subunit of the lectin. The triantennary glycopeptide was also trivalent for RCA-I and EIL binding. Biantennary oligosaccharides with adequate chain lengths were found to be bivalent for binding to SBA; those with shorter chains did not precipitate the lectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Conformation↗

PubMed1989

Binding characteristics of N-acetylglucosamine-specific lectin of the isolated chicken hepatocytes: similarities to mammalian hepatic galactose/N-acetylgalactosamine-specific lectin.

Binding characteristics of N-acetylglucosamine- (GlcNAc) specific lectin on the chicken hepatocyte surface were probed by an inhibition assay using various sugars and glycosides as inhibitors. Results indicated that the binding area of the lectin is small, interacting only with GlcNAc residues whose 3- and 4-OH's are open. The combining site is probably of trough-type, since substitution with as large a group as monosaccharide is permitted on the C-6 side of GlcNAc, and on the C-1 side, the aglycon of GlcNAc can be very large (e.g., a glycoprotein). These binding characteristics are shared with the homologous mammalian lectin specific for galactose/N-acetylgalactosamine, suggesting that tertiary structure of the combining area of these two lectins is similar. This is understandable, since there is approximately 40% amino acid sequence identity in the carbohydrate recognition domain of these two lectins [Drickamer, K., Mannon, J. F., Binns, G., & Leung, J. O. (1984) J. Biol. Chem. 259, 770-778]. A series of glycosides, each containing two GlcNAc residues separated by different distances (from 0.8 to 4.7 nm), were synthesized. Inhibition assay with these and other cluster glycosides indicated that clustering of two or more GlcNAc residues increased the affinity toward the chicken lectin tremendously. Among the ligands containing two GlcNAc residues, the structure which allows a maximal inter-GlcNAc distance of 3.3 nm had the strongest affinity, its affinity increase over GlcNAc (monosaccharide) amounting to 100-fold. Longer distances slightly diminished the affinity, while shortening the distance caused substantial decrease in the affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylgalactosamine↗

PubMed2006

Crystallization and preliminary characterization of a highly thermostable lectin from Trichosanthes dioica and comparison with other Trichosanthes lectins.

A lectin from Trichosanthes dioica seeds has been purified and crystallized using 25%(w/v) PEG 2K MME, 0.2 M ammonium acetate, 0.1 M Tris-HCl pH 8.5 and 50 microl 0.5%(w/v) n-octyl beta-D-glucopyranoside as thick needles belonging to hexagonal space group P6(4). Unit-cell parameters were a = b = 167.54, c = 77.42 A. The crystals diffracted to a Bragg spacing of 2.8 A. Both the structures of abrin-a and T. kirilowii lectin could be used as a model in structure determination using the molecular-replacement method; however, T. kirilowii lectin coordinates gave better values of reliability and correlation parameters. The thermal, chemical and pH stability of this lectin have also been studied. When heated, its haemagglutination activity remained unaffected up to 363 K. Other stability studies show that 4 M guanidinium hydrochloride (Gdn-HCl) initiates unfolding and that the protein is completely unfolded at 6 M Gdn-HCl. Treatment with urea resulted in a total loss of activity at higher concentrations of denaturant with no major structural changes. The protein remained stable over a wide pH range, from pH 6 to pH 12, except for partial unfolding at extremely alkaline pH. The role of disulfide bonds in the protein stability was found to be insignificant. Rayleigh light-scattering studies showed no molecular aggregation in any of the extreme treated conditions. The unusual stability of this lectin resembles that of type II ribosome-inactivating proteins (type II RIPs), which is also supported by structure determination. The structural features observed in a preliminary electron-density map were compared with the other two available Trichosanthes lectin structures.

Crystallization↗

PubMed1996

Molecular characterization of a saline-soluble lectin from a parasitic fungus. Extensive sequence similarities between fungal lectins.

It has been proposed that the interactions between several parasitic and pathogenic fungi and their hosts are mediated by soluble lectins present in the fungus. We have cloned and analyzed a gene encoding such a lectin (AOL) from the nematophagous fungus Arthrobotrys oligospora (deuteromycete). The deduced primary structure of the AOL gene displayed an extensive similarity (identity 46.3%) to that of a gene encoding a lectin (ABL) recently isolated from the mushroom Agaricus bisporus (basidiomycete), but not to any other fungal, microbial, plant or animal lectins. The similarities between AOL and ABL were further demonstrated by the observation that an antibody specific for AOL cross-reacted with ABL. Together with data showing that AOL has a binding specificity that is similar to that of ABL [Rosen, S., Bergström, J., Karlsson, K.-A. & Tunlid, A. (1996) Eur. J. Biochem. 238, 830-837], these results indicate that AOL and ABL are members of a novel family of saline soluble lectins present in fungi. Southern blots indicated that there is only one AOL gene in the genome encoding a subunit (monomer) of the lectin. The primary structure of AOL did not show the presence of a typical N-terminal signal sequence. Comparison of the deduced primary structure with the molecular mass of AOL as determined by electrospray mass spectrometry (16153 Da), indicated that AOL has an acetylated N-terminal but no other post-translational modifications, and that a minor isoform is formed by deamidation. Circular dichroism (CD) spectroscopy suggested that the secondary structure of AOL contains 34% beta-sheets, 21% alpha-helix, and 45% turns and coils.

Agaricus↗

PubMed1992

Interaction of lectins with human IgE: IgE-binding property and histamine-releasing activity of twelve plant lectins.

We examined the IgE-binding reaction and the histamine-releasing response of basophils to a panel of 12 lectins: concanavalin A (Con A), Lens culinaris hemagglutinin (LcH), Pisum sativum agglutinin (PSA), wheat germ agglutinin (WGA), soybean agglutinin (SBA), Bauhinia purpurea agglutinin (BPA), peanut agglutinin (PNA), Ricinus communis agglutinin I (RCA-I), Lotus tetragonolobus agglutinin (Lotus A), Ulex europeus agglutinin I (UEA-I), phytohemagglutinin E (PHA-E) and phytohemagglutinin L (PHA-L), IgE from allergic patients bound with high affinity to Con A, LcH, PSA, RCA-I and PHA-E, and with lower affinity to WGA, BPA, Lotus A and UEA-I, but they did not bind to SBA, PNA or PHA-L. There was no apparent individual difference in the reactivity of IgE to these lectins between 10 IgE preparations from allergic patients. The binding to these lectins, except Lotus A and UEA-I, were competitively inhibited by the lectin-specific sugars or glycopeptide. Upon stimulation by Con A, LcH, PSA, WGA, RCA-1 and PHA-E, leukocytes from allergic patients showed a significant release of histamine, but cells from IgE-deficient subjects did not respond to these lectins. The histamine-releasing responses by these lectins were also inhibited by specific sugars or glycopeptides.

Basophils↗

PubMed2000

Lectin binding patterns in rat nasal-associated lymphoid tissue (NALT) and the influence of various types of lectin on particle uptake in NALT.

We investigated the binding of four types of lectin to follicle-associated epithelium overlying the nasal-associated lymphoid tissue (NALT) of rats in order to identify M-cell specific surface markers and to determine the influence of lectin administration to NALT on the uptake of a particulate antigen. The NALT tissues were incubated with a panel of four types of lectin conjugated to horseradish peroxidase (HRP). Ulex europaeus-1 (UEA-1) and Dolichos biflorus (DBA) lectin stained the surface of M-cells and goblet cells. Uniform staining by Triticum vulgaris (WGA) was detected in the M-cells, ciliated cells and goblet cells. In contrast, staining of Griffonia simplicifolia I isolectin-B4 (GSI-B4) was almost exclusively M-cell specific. The administration of M-cell specific lectin (GS I-B4) to NALT suppressed the uptake of baker's yeast particles administered later, whereas the non-specific one (UEA-1) had no influence on the uptake. These results indicate that GS I-B4 is a useful marker for the identification of rat NALT M-cells and that such a specific expression of surface glycoconjugates by M-cells may permit the targeting of vaccines and drugs to the antigen sampling sites of the nose. It also appears possible to block the uptake of pathogens by an administration of M-cell specific lectin to NALT.

Animals↗

PubMed2001

Revisiting proteus: do minor changes in lectin structure matter in biological activity? Lessons from and potential biotechnological uses of the Diocleinae subtribe lectins.

Significant differences in function have been observed among lectins structurally similar to concanavalin A, but their high homology with this widely used lectin has kept them in obscurity. The observation of large differences in the potency of many of these Diocleinae lectins as stimulators of Interferon-g production by human peripheral blood mononuclear cells has lead to a major effort to unravel their chemical structure and biological activity. Modeling studies of some of these lectins reveal conformational changes in side chains of some residues involved in the carbohydrate-binding site, with possible effects on the ability of these proteins to recognize specific carbohydrate structures. Additionally, all them constitute in fact a mixture of isolectins, which in different proportions could lead to diverse effects. The present review of the biological actions of Diocleinae lectins includes several in vitro and in vivo immunological findings, as well as their effects on insect growth and reproduction. In these systems Diocleinae lectins proved to be quite diverse in their potency. Such diversity in the biological activity of highly related proteins recalls the origin of the name protein: like Proteus, the capability of assuming various forms is the essential feature of this class of molecules.

Amino Acid Sequence↗

PubMed1990

Endogenous lectins with specificity to beta-galactosides and alpha- or beta-N-acetyl-galactosaminides in human breast cancer. Their glycohistochemical detection in tissue sections by synthetically different types of neoglycoproteins, their quantitation on cultured cells by neoglycoenzymes and their usefulness as targets in lectin-mediated phototherapy in vitro.

Endogenous lectins may augment the panel of tumor markers. Specific protein-carbohydrate interactions especially involve carbohydrate moieties that are located at sequence termini, e.g. D-galactose and N-acetyl-D-galactosamine. Respective endogenous lectins can be detected by suitably constructed neoglycoproteins. In order to evaluate the influence of sugar and label density as well as coupling mode of the carbohydrate moiety to the carrier protein for lectin localization in histopathology, four different types of neoglycoproteins, carrying beta-galactosides or alpha- and beta-anomers of N-acetyl-D-galactosamine were employed to reveal the presence of specific receptors in invasive ductal mammary carcinomas with propensity for metastasis formation. Staining of tumor cells was more intense than staining of normal cell types. Coupling of the diazo derivatives of p-aminophenyl glycosides led in most cases to the relatively highest extent of staining in terms of number of stained cells and staining intensity. Classified next according to these categories attachment of sugars via p-isothiocyanato derivatives or via an aliphatic linker after his reaction with the C6-hydroxyl group of the sugar moiety was rather equally well effective, whereas reductive amination with concomitant ring opening at the reducing end of the disaccharide lactose resulted in neoglycoproteins, yielding the lowest extent of staining. The alpha-anomer is preferred as a ligand to endogenous lectins of tumor cells to the beta-anomer of N-acetyl-D-galactosamine. To reduce the number of steps in glycohistochemical processing, glycosylated enzymes were successfully employed. They also allowed to measure the lectin density on breast carcinoma cells, leading to rational selection for demonstrated lectin-mediated targeting of neoglycoprotein-hematoporphyrin conjugates. Immobilization of ligands as an approach to prepare histochemically valuable reagents to localize respective receptors is not confined to tumor lectinology, as emphasized by additional application of hormone-protein conjugates, termed neohormoproteins.

Acetylgalactosamine↗

PubMed1985

Galactoside-binding serum lectin of Xenopus laevis. Estrogen-dependent hepatocyte synthesis and relationship to oocyte lectin.

Xenopus laevis serum contains a lectin which binds alpha- and beta-galactosides. It was purified to homogeneity by affinity chromatography and consists of a single subunit with Mr approximately 69,000, associated in a multimer. The lectin is synthesized and secreted by hepatic parenchymal cells, and its synthesis is increased about 2-fold by estrogen treatment, both in vivo and in primary cell cultures. The serum lectin has the same carbohydrate binding properties as an oocyte lectin from X. laevis described previously, is immunologically cross-reactive, and shows similarities in its peptide map. However, marked differences in amino acid composition preclude the possibility that the serum lectin is a precursor of the oocyte lectin.

Amino Acids↗

PubMed1978

Regulation by antibody of lectin-induced lymphocyte proliferation: antibody inhibition of mitogenesis and release of lectin from cell surfaces.

Studies were conducted to determine the ways in which antibody regulates proliferation of lymphocytes stimulated by phytohemagglutinin (PHA) and concanavalin A (ConA). Equine lymphocytes were reacted with PHA or ConA for 1 to 10 hours, washed free of excess lectin, then cultured for 3 days and examined for proliferation and incorporation of [3H]thymidine. Both PHA and ConA induced lymphocytes to proliferate after short incubation periods. This response could be interrupted by the addition of antibody to the respective lectin. Total suppression of the proliferative response occurred if antibody was added within the first 2 hours after initial contact with PHA or ConA. Addition at times up to 48 hours produced either total or partial suppression. The removal of excess antibody 4 hours after addition to the culture did not reverse the suppression. Using radiolabeled ConA and PHA, it was observed that suppressive antibody inhibited the release of lectin from metabolically active lymphocytes and from surfaces where pinocytosis was not possible or was minimized. Antibody did not affect the rate of degradation of lectin by the cells. These results indicate that antibody attached to lectins, already bound to the lymphocyte surface, can terminate the lymphocyte response and retard the rate of release of lectin from the cell membrane.

Antibodies↗

PubMed1993

Characterization of a Lectin from Lactarius deterrimus (Research on the Possible Involvement of the Fungal Lectin in Recognition between Mushroom and Spruce during the Early Stages of Mycorrhizae Formation).

A lectin (LDetL) was isolated from carpophores of the mushroom Lactarius deterrimus, a specific symbiont of the spruce, by a combination of affinity, hydroxylapatite, and gel-filtration chromatography. Its molecular mass, as determined by gel filtration, is about 37,000 D, and its structure is dimeric, with two identical subunits assembled by noncovalent bonds. It appeared homogeneous on high-performance liquid chromatography gel filtration, but isoelectric focusing revealed microheterogeneity, with a main band in the pH zone near 6.5. Amino acid analysis showed that LDetL contains a large proportion of glycine and especially methionine. Hapten inhibition assay indicated that LDetL is most specific for [beta]-D-galactosyl(1->3)-D-N-acetyl galactosamine residues. The lectin was formed in the in vitro-cultivated mycelium, and anti-lectin antibodies revealed by indirect immunofluorescence the presence of lectin in the cell wall. Receptor sites for LDetL were found on the roots, especially on the root hairs, of axenically grown spruce seedlings. The lectin LDL previously isolated by us from the taxonomically related mushroom Lactarius deliciosus, a symbiont of the pine, does not bind to the spruce radicle. This suggests a role of the fungal lectin in recognition and specificity during the early stages of mycorrhizae formation.

Journal Article↗

PubMed1983

The intrathymic microenvironment: expression of lectin receptors and lectin-like molecules of differentiation antigens and MHC gene products.

The expression of MHC products, differentiation antigens and lectin receptors has been investigated in the various cell types populating different compartments of the thymus. The ultrastructural classification of suspended thymic epithelial cells was facilitated by using a technique that preserves cortical nursing cells or medullary epithelial cell clusters. A subset of peanut lectin positive lymphocytes could be distinguished by their ability to bind soybean lectin also. This subset corresponds to the large proliferating lymphocytes that populate the area between the thymic capsule and the cortex. Ia and H-2 D/K antigens could be detected on nearly all epithelial and lymphoid cells. Expression of H-2 antigens, however, is more pronounced on medullary epithelial cells. T-cell differentiation antigens such as Thy-1 and Lyt-1 could be demonstrated not only on lymphocytes, but, interestingly enough, on cortical epithelial cells as well. These latter cells, in addition, exhibit a cell membrane-bound lectin with a specificity for D-galactose which might well be the structure responsible for binding the galactosyl residues of the peanut lectin receptor of thymic lymphocytes. Binding sites for a large set of lectins could be demonstrated on both, thymic lymphocytes and epithelium. The intrathymic differentiation pathway of T-lineage cells is discussed with regard to those lymphocytic and epithelial cell surface structures considered to enable cellular interaction.

Animals↗

PubMed1993

Crystallization and preliminary X-ray diffraction studies of recombinant barley lectin and pro-barley lectin.

Barley lectin (BL) and its precursor form (proBL), synthesized and over-expressed in Escherichia coli, have been crystallized under conditions identical to those used for the closely related lectin wheat germ agglutinin. These lectins are members of the Gramineae family and possess a unique disulfide-rich domain structure. The pro-lectin polypeptides are extended by 15 amino acid residues at the carboxy terminus. This pro-peptide, which is proteolytically removed as the mature lectin is deposited in the vacuoles, is thought to function as a targeting signal for molecular sorting. Crystals of BL and proBL are well ordered and belong to space groups C222(1) and P2(1)2(1)2(1). The unit cell dimensions for BL and proBL are a = 51.9 A, b = 73.7 A, c = 89.3 A (one monomer per asymmetric unit), and a = 45.2 A, b = 70.5 A, c = 111.6 A (two monomers per asymmetric unit), respectively. Diffraction patterns on precession photographs of BL crystals are closely similar to those of mature wheat germ agglutinin crystals, suggesting similar crystal packing and correct conformation of this recombinant protein in terms of the four structural domains and 16 disulfide bridges.

Crystallization↗

PubMed1986

Lectin-resistant CHO cells: selection of four new pea lectin-resistant phenotypes.

The cytotoxic plant lectins from P. sativum have been used to select new lectin-resistant mutants from Chinese hamster ovary (CHO) cells. Two novel phenotypes that behave recessively but fall into the same complementation group have been termed Lec13 and Lec13A. Both of these mutant types are phenotypically reverted to pea lectin sensitivity following growth in L-fucose. In contrast, two other unique phenotypes behave dominantly in somatic cell hybrids and maintain their pea lectin-resistance in the presence of L-fucose. They have been termed LEC14 and LEC18, respectively. The lectin-resistance and complementation properties of the four new mutant types suggest that they define three different glycosylation genes of the CHO genome.

Animals↗

PubMed1998

Isolation and characterization of beta-galactoside specific lectin from Korean mistletoe (Viscum album var. coloratum) with lactose-BSA-sepharose 4B and changes of lectin conformation.

Lectins and its A- and B-chains from Korean mistletoe (Viscum album var. coloratum) were isolated by affinity chromatography on the Sepharose 4B modified by lactose-BSA conjugate synthesized by reductive amination of ligand (lactose) to epsilon-amino groups of lysine residues of spacer (BSA) after reduction by NaCNBH3. The lactose-BSA conjugate was coupled to Sepharose 4B activated by cyanogen bromide. The molecular weight determined by SDS-PAGE were a 31 kD of A-chain and a 35 kD of B-chain. Amino acid analysis and N-terminal sequencing were performed. The effects of pH, temperature and guanidine chloride on the conformation of the lectin were investigated by measuring its intrinsic fluorescence and compared with its hemagglutinating activities. Blue shift was detected on the acidic pH and there was a close relationship between activities and conformation of the lectin. Under denaturing conditions, the tryptophan emission profile of lectin showed typical denaturational red shift which also correspond to the conformations and activity of lectin.

Amino Acids↗

PubMed1981

Studies on lectins. LI. The role of Mn2+ in the activity of the soybean lectin.

In contradistinction to previous reports, the lectin of soybeans (Glycine soja) has been shown to retain its erythroagglutinating activity after complete removal of manganese from its molecule. The applied demetallization procedures (dialysis against 0.1 M HCl or 1M acetic acid and against 0.1 M EDTA following by dialysis against 1 M acetic acid) had no effect on the stability of the lectin subunit structure, as proved by ultracentrifugation analysis or thin-layer chromatography on Sephadex G-200 Superfine. Affinity electrophoresis on polyacrylamide gel containing immobilized alpha-D-galactosyl residues and affinity chromatography on alpha-D-galactosyl derivative of Separon have shown that the interaction of the demetallized lectin preparations does not differ from that of the native lectin in alkaline media but is decreased in acidic media. Demetallized preparations of soybean lectin can be fully reactivated by dialysis against solutions containing Mn2+, Zn2+ or Cd2+.

Animals↗