Purification and properties of the hemagglutinin from Maclura pomifera seeds

A Useful Guide to Lectin Binding: Machine-Learning Directed Annotation of 57 Unique Lectin Specificities

Glycans are critical to every facet of biology and medicine, from viral infections to embryogenesis. Tools to study glycans are rapidly evolving; however, the majority of our knowledge is deeply dependent on binding by glycan binding proteins (e.g., lectins). The specificities of lectins, which are often naturally isolated proteins, have not been well-defined, making it difficult to leverage their full potential for glycan analysis. Herein, we use a combination of machine learning algorithms and expert annotation to define lectin specificity for this important probe set. Our analysis uses comprehensive glycan microarray analysis of commercially available lectins we obtained using version 5.0 of the Consortium for Functional Glycomics glycan microarray (CFGv5). This data set was made public in 2011. We report the creation of this data set and its use in large-scale evaluation of lectin-glycan binding behaviors. Our motif analysis was performed by integrating 68 manually defined glycan features with systematic probing of computational rules for significant binding motifs using mono- and disaccharides and linkages. Combining machine learning with manual annotation, we create a detailed interpretation of glycan-binding specificity for 57 unique lectins, categorized by their major binding motifs: mannose, complex-type N-glycan, O-glycan, fucose, sialic acid and sulfate, GlcNAc and chitin, Gal and LacNAc, and GalNAc. Our work provides fresh insights into the complex binding features of commercially available lectins in current use, providing a critical guide to these important reagents.

Biochemical and functional properties of a lectin purified from the seeds of Cicer arietinum L

A 35 kDa rabbit erythrocyte agglutinating lectin from the seeds of Cicer arietinum was purified and designated as CAL. The lectin was inhibited by fetuin and N-acetyl-d-galactosamine at a concentration of 20 and 50 mM respectively, but not by simple mono or oligosaccharides. CAL is active between pH 5 and 10 presented thermo stability up to 50 °C and demonstrated DNA damage inhibition at 30 µg concentration. The lectin elicited maximum mitogenic activity towards mice splenocytes at 7.5 µg ml^- 1. CAL exerted an inhibitory activity on HIV-1 reverse transcriptase with IC₅₀ of 180 µM. CAL abilities in animal bioassay resulted decreased levels of total triglyceride and creatinine. In vitro and in vivo studies revealed that CAL may constitute an important role impending biomedical applications.

Two jacalin-related lectins from seeds of the African breadfruit (Treculia africana L.)

Two jacalin-related lectins (JRLs) were purified by mannose-agarose and melibiose-agarose from seeds of Treculia africana. One is galactose-recognizing JRL (gJRL), named T. africana agglutinin-G (TAA-G), and another one is mannose-recognizing JRL (mJRL), TAA-M. The yields of the two lectins from the seed flour were approximately 7.0 mg/g for gJRL and 7.2 mg/g for mJRL. The primary structure of TAA-G was determined by protein sequencing of lysyl endopeptic peptides and chymotryptic peptides. The sequence identity of TAA-G to other gJRLs was around 70%. Two-residue insertion was found around the sugar-binding sites, compared with the sequences of other gJRLs. Crystallographic studies on other gJRLs have shown that the primary sugar-binding site of gJRLs can accommodate Gal, GalNAc, and GalNAc residue of T-antigen (Galβ1-3GalNAcα-). However, hemagglutination inhibition and glycan array showed that TAA-G did not recognize GalNAc itself and T-antigen. TAA-G preferred melibiose and core 3 O-glycan.

Comprehensive list of lectins: origins, natures, and carbohydrate specificities

More than 100 years have passed since the first lectin ricin was discovered. Since then, a wide variety of lectins (lect means "select" in Latin) have been isolated from plants, animals, fungi, bacteria, as well as viruses, and their structures and properties have been characterized. At present, as many as 48 protein scaffolds have been identified as functional lectins from the viewpoint of three-dimensional structures as described in this chapter. In this chapter, representative 53 lectins are selected, and their major properties that include hemagglutinating activity, mitogen activity, blood group specificity, molecular weight, metal requirement, and sugar specificities are summarized as a comprehensive table. The list will provide a practically useful, comprehensive list for not only experienced lectin users but also many other non-expert researchers, who are not familiar to lectins and, therefore, have no access to advanced lectin biotechnologies described in other chapters.

The immunomodulatory effect of plant lectins: a review with emphasis on ArtinM properties

Advances in the glycobiology and immunology fields have provided many insights into the role of carbohydrate-protein interactions in the immune system. We aim to present a comprehensive review of the effects that some plant lectins exert as immunomodulatory agents, showing that they are able to positively modify the immune response to certain pathological conditions, such as cancer and infections. The present review comprises four main themes: (1) an overview of plant lectins that exert immunomodulatory effects and the mechanisms accounting for these activities; (2) general characteristics of the immunomodulatory lectin ArtinM from the seeds of Artocarpus heterophyllus; (3) activation of innate immunity cells by ArtinM and consequent induction of Th1 immunity; (4) resistance conferred by ArtinM administration in infections with intracellular pathogens, such as Leishmania (Leishmania) major, Leishmania (Leishmania) amazonensis, and Paracoccidioides brasiliensis. We believe that this review will be a valuable resource for more studies in this relatively neglected area of research, which has the potential to reveal carbohydrate targets for novel prophylactic and therapeutic strategies.

Recognition roles of the carbohydrate glycotopes of human and bovine lactoferrins in lectin-N-glycan interactions

BACKGROUND

Lactoferrin is an iron-binding protein belonging to the transferrin family. In addition to iron homeostasis, lactoferrin is also thought to have anti-microbial, anti-inflammatory, and anticancer activities. Previous studies showed that all lactoferrins are glycosylated in the human body, but the recognition roles of their carbohydrate glycotopes have not been well addressed.

METHODS

The roles of human and bovine lactoferrins involved in lectin-N-glycan recognition processes were analyzed by enzyme-linked lectinosorbent assay with a panel of applied and microbial lectins.

RESULTS AND CONCLUSIONS

Both native and asialo human/bovine lactoferrins reacted strongly with four Man-specific lectins - Concanavalia ensiformis agglutinin, Morniga M, Pisum sativum agglutinin, and Lens culinaris lectin. They also reacted well with PA-IIL, a LFuc>Man-specific lectin isolated from Pseudomonas aeruginosa. Both human and bovine lactoferrins also recognized a sialic acid specific lectin-Sambucus nigra agglutinin, but not their asialo products. Both native and asialo bovine lactoferrins, but not the human ones, exhibited strong binding with a GalNAc>Gal-specific lectin-Wisteria floribunda agglutinin. Human native lactoferrins and its asialo products bound well with four Gal>GalNAc-specific type-2 ribosome inactivating protein family lectins-ricin, abrin-a, Ricinus communis agglutinin 1, and Abrus precatorius agglutinin (APA), while the bovine ones reacted only with APA.

GENERAL SIGNIFICANCE

This study provides essential knowledge regarding the different roles of bioactive sites of lactoferrins in lectin-N-glycan recognition processes.

Molecular characterization of a wheat protein induced by vernalisation

Using a PCR strategy we isolated from winter wheat (Triticum aestivum L. cv. Bolero) the ver2 gene coding for a modular protein constituted by an N-terminal domain called "dirigent", found in several defence-related genes, and a C-terminal domain related to jacalin-related lectin (JRL). ver2 transcript as well as native Ver2 levels increased during vernalisation and upon methyl jasmonate treatment of young seedlings. ver2 transcript levels were kept constant either in infected tissues or in wounded samples indicating that Ver2 is not directly involved in plant defence mechanisms. The Ver2 protein was expressed in bacteria as a recombinant GST-Ver2 fusion protein. The purified recombinant protein was further characterized using an affinity chromatography approach based on its interaction with mannose-agarose beads. GST-Ver2 tightly bound to the matrix. Molecular modelling of the jacalin domain and mannose docking confirmed that Ver2 possesses D: -mannose binding capacity.

Polyvalent GalNAcalpha1-->Ser/Thr (Tn) and Galbeta1-->3GalNAcalpha1-->Ser/Thr (T alpha) as the most potent recognition factors involved in Maclura pomifera agglutinin-glycan interactions

The agglutinin isolated from the seeds of Maclura pomifera (MPA) recognizes a mucin-type disaccharide sequence, Galbeta1-->3GalNAc (T) on a human erythrocyte membrane. We have utilized the enzyme-linked lectinosorbent assay (ELLSA) and inhibition assay to more systematically analyze the carbohydrate specificity of MPA with glyco-recognition factors and mammalian Gal/GalNAc structural units in lectin-glycoform interactions. From the results, it is concluded that the high densities of polyvalent GalNAcalpha1-->Ser/Thr (Tn) and Galbeta1-->3GalNAcalpha1-->Ser/Thr (T(alpha)) glycotopes in macromolecules are the most critical factors for MPA binding, being on a nanogram basis 2.0 x 10(5), 4.6 x 10(4) and 3.9 x 10(4) more active than monovalent Gal, monomeric T and Tn glycotope, respectively. Other carbohydrate structural units in mammalian glycoconjugates, such as human blood group Sd (a+) related disaccharide (GalNAcbeta1-->4Gal) and Pk/P1 active disaccharide (Galalpha1-->4Gal) were inactive. These results demonstrate that the configurations of carbon-4 and carbon-2 are essential for MPA binding and establish the importance of affinity enhancement by high-density polyvalencies of Tn/T glycotopes in MPA-glycan interactions. The overall binding profile of MPA can be defined in decreasing order as high density of polyvalent Tn/T(alpha) (M.W. > 4.0 x 10(4)) >> Tn-containing glycopeptides (M.W. < 3.0 x 10(3)) > monomeric T/Tn and P (GalNAcbeta1-->3Gal) > GalNAc > Gal >> Man, L: ARA: , D: Fuc and Glc (inactive). Our findings should aid in the selection of this lectin for elucidating functions of carbohydrate chains in life processes and for applications in the biomedical sciences.

Structural analysis of the jacalin-related lectin MornigaM from the black mulberry (Morus nigra) in complex with mannose

The structures of MornigaM and the MornigaM-mannose complex have been determined at 1.8 A and 2.0 A resolution, respectively. Both structures adopt the typical beta-prism motif found in other jacalin-related lectins and their tetrameric assembly closely resembles that of jacalin. The carbohydrate-binding cavity of MornigaM readily binds mannose. No major structural rearrangements can be observed in MornigaM upon binding of mannose. These results allow corroboration of the structure-function relationships within the small group of Moraceae lectins.

Artocarpin is a polyspecific jacalin-related lectin with a monosaccharide preference for mannose

A reinvestigation of the carbohydrate-binding properties revealed that artocarpin, a previously described mannose-specific lectin from jackfruit (Artocarpus integrifolia) seeds, behaves as a polyspecific lectin. Surface plasmon resonance hapten inhibition experiments demonstrated that artocarpin readily interacted with a wide range of monosaccharides covering galactose, N-acetylgalactosamine, mannose, glucose, sialic acid and N-acetylmuramic acid. Molecular docking confirmed this unexpected ability of artocarpin to interact with structurally different sugars. The biological significance of the polyspecificity of the lectin is discussed in terms of the broadening of the range of potential target glycans present on the surface of plant phytopathogens or predators.

A structural basis for the difference in specificity between the two jacalin-related lectins from mulberry (Morus nigra) bark

The activity and specificity of a galactose-specific and a mannose-specific jacalin-related lectin from the bark of the black mulberry (Morus nigra) tree has been re-investigated using different experimental approaches. Both lectins definitely behave as polyspecific lectins recognizing galactose, mannose, and glucose even though MornigaG and MornigaM interact preferentially with galactose and mannose, respectively. The exceptionally extended size of the carbohydrate-binding site of both lectins apparently accounts for their polyspecific character. Parallel studies with other mannose-specific jacalin-related lectins confirmed that their exclusive specificity towards mannose/glucose relies on a reduced size of their carbohydrate-binding site.

The size, shape and specificity of the sugar-binding site of the jacalin-related lectins is profoundly affected by the proteolytic cleavage of the subunits

Mannose-specific lectins with high sequence similarity to jacalin and the Maclura pomifera agglutinin have been isolated from species belonging to the families Moraceae, Convolvulaceae, Brassicaceae, Asteraceae, Poaceae and Musaceae. Although these novel mannose-specific lectins are undoubtedly related to the galactose-specific Moraceae lectins there are several important differences. Apart from the obvious differences in specificity, the mannose- and galactose-specific jacalin-related lectins differ in what concerns their biosynthesis and processing, intracellular location and degree of oligomerization of the protomers. Taking into consideration that the mannose-specific lectins are widely distributed in higher plants, whereas their galactose-specific counterparts are confined to a subgroup of the Moraceae sp. one can reasonably assume that the galactose-specific Moraceae lectins are a small-side group of the main family. The major change that took place in the structure of the binding site of the diverging Moraceae lectins concerns a proteolytic cleavage close to the N-terminus of the protomer. To corroborate the impact of this change, the specificity of jacalin was re-investigated using surface plasmon resonance analysis. This approach revealed that in addition to galactose and N -acetylgalactosamine, the carbohydrate-binding specificity of jacalin extends to mannose, glucose, N -acetylmuramic acid and N -acetylneuraminic acid. Owing to this broad carbohydrate-binding specificity, jacalin is capable of recognizing complex glycans from plant pathogens or predators.

Two distinct jacalin-related lectins with a different specificity and subcellular location are major vegetative storage proteins in the bark of the black mulberry tree

Using a combination of protein isolation/characterization and molecular cloning, we have demonstrated that the bark of the black mulberry tree (Morus nigra) accumulates large quantities of a galactose-specific (MornigaG) and a mannose (Man)-specific (MornigaM) jacalin-related lectin. MornigaG resembles jacalin with respect to its molecular structure, specificity, and co- and posttranslational processing indicating that it follows the secretory pathway and eventually accumulates in the vacuolar compartment. In contrast, MornigaM represents a novel type of highly active Man-specific jacalin-related lectin that is synthesized without signal peptide or other vacuolar targeting sequences, and accordingly, accumulates in the cytoplasm. The isolation and cloning, and immunocytochemical localization of MornigaG and MornigaM not only demonstrates that jacalin-related lectins act as vegetative storage proteins in bark, but also allows a detailed comparison of a vacuolar galactose-specific and a cytoplasmic Man-specific jacalin-related lectin from a single species. Moreover, the identification of MornigaM provides the first evidence, to our knowledge, that bark cells accumulate large quantities of a cytoplasmic storage protein. In addition, due to its high activity, abundance, and ease of preparation, MornigaM is of great potential value for practical applications as a tool and bioactive protein in biological and biomedical research.

Classification of plant lectins in families of structurally and evolutionary related proteins

The majority of plant lectins can be classified in seven families of structurally and evolutionary related proteins. Within a given lectin family most but not necessarily all members are built up of protomers with a similar primary structure and overall 3-D fold. The overall structure of the native lectins is not only determined by the structure of the protomers but depends also on the degree of oligomerization and in some cases on the post-translational processing of the lectin precursors. In general, lectin families are fairly homogeneous for what concerns the overall specificity of the individual lectins, which illustrates that the 3-D structure of the binding site has been conserved during evolution. In the case of the jacalin-related lectins the occurrence of a mannose- and galactose-binding subfamily can be explained by the fact that a post-translational cleavage of the protomers (of the galactose-binding subfamily) yields a slightly altered binding site. Unlike the other families, the legume lectins display a wide range of specificites, which is clearly reflected in the occurrence of sugar-binding sites with a different 3-D structure.

Pigeon fanciers' lung: identification of disease-associated carbohydrate epitopes on pigeon intestinal mucin

Pigeon intestinal mucin, a complex high molecular weight glycoprotein, is a key antigen in the development of pigeon fanciers' lung (PFL). We have studied the specificity of antibodies to mucin in patients with PFL and asymptomatic antibody-positive individuals. Extensive papain digestion, which removes the non-glycosylated regions of the mucin leaving the heavily glycosylated 'bottle brush' regions, resulted in a 600-fold decrease in IgG3 antibody titres with little effect on IgG1 and IgG2 titres. This suggests that IgG1 and IgG2 are directed against the region rich in O-linked sugar chains whilst the majority of the IgG3 is directed against epitopes which are proteinase-sensitive. Lectin mapping of the carbohydrates present on pigeon intestinal mucin demonstrated high levels of exposed N-acetyl neuraminic acid, N-acetyl galactosamine and N-acetyl glucosamine, with lower levels of fucose and some galactose. Sera from pigeon fanciers inhibited binding of lectins specific for N-acetyl neuraminic acid, N-acetyl galactosamine, internal N-acetyl glucosamine and fucose. Sera from people with PFL, compared with sera from asymptomatic antibody-positive fanciers, had significantly higher titres of antibody that inhibited binding of four lectins specific for N-acetyl galactosamine and one fucose-specific lectin, suggesting that these sugars may play a dominant role in disease-associated epitopes. The results suggest that different IgG subclasses recognize different epitopes on mucin and that the epitopes recognized by the major subclasses are present on the O-linked oligosaccharides. Further, the carbohydrate-specific anti-mucin antibodies produced by PFL patients may differ in their specificity from those found in asymptomatic individuals.

The alpha-galactosyl specific lectin from Artocarpus integrifolia distinguishes between two lymphoma lines with different metastatic potential

A lectin purified from the seeds of the Vietnamese Artocarpus integrifolia distinguishes between the mouse T-cell lymphoma cell lines Eb and ESb, with low and high metastatic potential, respectively. It agglutinates Eb cells as well as human erythrocytes, but not ESb cells or the human colon carcinomas cells HT29. The haemagglutinin is specific for alpha-galactosyl residues and has a molecular mass of 62 kDa.

Ultrastructural lipid and glycoconjugate cytochemistry of membranous lipodystrophy (Nasu-Hakola disease)

In order to assess the lipid and glycoconjugate characteristics of membranous lipodystrophy, a 29-year-old male with this disease was studied using an ultrastructural cytochemical approach. The specific membranocystic lesions of the disease are composed of cystic spaces and the lining membranes. The membranes were observed to have a two-layered character: microtubular structures in the layer adjacent to the spaces and a central amorphous zone. Lipid staining and the lipase digestion test revealed triglycerides localized not only in the cystic spaces but also in the microtubular structures. Lectin histochemical examination of carbohydrate components demonstrated that Maclura pomifera agglutinin bound strongly to the membranes, while Griffonia simplicifolia I, G. simplicifolia II, Concanavalia ensiformis and Triticum vulgaris agglutinin reacted weakly. Our results indicate the presence of triglycerides and carbohydrates with mainly alpha-D-galactose residues in the distinctive membranocystic lesions, in particular in the microtubular structures.

Lectin binding sites in normal, scarred, and lattice dystrophy corneas

Normal, scarred, and dystrophic corneas were histochemically probed with a panel of 16 lectins by means of an avidin-biotin revealing system. Normal corneal epithelial cells, keratocytes, and endothelial cells expressed at least two distinct N-linked oligosaccharide subsets, of the non-bisected, biantennary and bisected, bi-/triantennary types. Corneal scars stained variably with the lectin subsets described above, and with Maclura pomifera agglutinin. Lattice dystrophy corneas showed a loss of the oligosaccharide expression observed on the plasma membranes of normal epithelial cells, and there was concurrent deposition of extracellular glycoprotein within the corneal stroma, which was of the same oligosaccharide subsets as were lost from the epithelial cell plasma membranes. This extracellular stromal glycoprotein was far more widely deposited than the amyloid and extended well beyond the stromal scarring. We propose that these observations are related and that in lattice corneal dystrophy a glycoprotein(s) is shed from the plasma membranes of epithelial cells and sequestrated within the corneal stroma, where it subsequently stimulates amyloid deposition.

Crystallization and preliminary X-ray diffraction studies of the complex of Maclura pomifera agglutinin with the disaccharide Gal beta 1-3GalNAc

Single crystals of Maclura pomifera agglutinin, a seed lectin from the Moraceae family, complexed with the disaccharide Gal beta 1-3GalNAc have been obtained by the method of vapor diffusion with Li2SO4 as precipitant at pH 4.5. The crystals belong to the trigonal space group P3(1)21 or P3(2)21, with a = b = 67.4 A, c = 149.3 A. They contain two subunits per asymmetric unit and diffract beyond 2.7 A. This and other evidence indicate that both this lectin and the Artocarpus integrifolia lectin, jacalin, have dimeric structures rather than the tetrameric structures previously proposed.

Human salivary gland glycoconjugates: a lectin histochemical study

The glycoconjugate content of normal salivary glands has been extensively investigated in humans by biochemical means and in non-human mammals by histochemical methods. However, there have been few histochemical studies of human tissues. This paper describes the findings obtained in parotid, submandibular and minor salivary glands by applying a panel of 13 biotinylated lectins, directed against a range of N-linked, fucosylated and galactosylated sequences, using an avidin-peroxidase technique, with appropriate enzymatic and inhibitory sugar controls. The results were generally in accord with those observed in biochemical assays but the use of lectin histochemistry permitted the localization in situ of small amounts of oligosaccharide and, therefore, allowed the recognition of subtle tissue differences. This study expands the current knowledge on the glycoconjugate composition of salivary glands and their lectin histochemistry and serves as a baseline for further studies, particularly in the field of neoplasia.

Homology of the D-galactose-specific lectins from Artocarpus integrifolia and Maclura pomifera and the role of an unusual small polypeptide subunit

The Maclura pomifera agglutinin (MPA) was purified by affinity chromatography from a seed extract and its properties were compared with those of the Artocarpus integrifolia lectin, jacalin. Reverse-phase high-performance liquid chromatography showed both proteins had multiple forms of a small approximately 20-residue polypeptide chain in addition to the major 12,000 Mr subunit. The amino acid sequences of the small chains and the N-terminal sequences of the large subunits showed considerable similarity between the two proteins, approximately 60% identical residues. The homology of the proteins was confirmed by the similarity of their circular dichroism and fluorescence emission spectra. MPA showed much greater spectral changes upon binding methyl alpha-D-galactoside, suggesting it has complete activity rather than the partial activity found for jacalin. The binding of methyl alpha-D-galactoside by MPA was measured by fluorescence titration; the KA was 1.9 X 10(4) M-1 compared to 3.4 X 10(4) M-1 for jacalin. MPA also precipitated human IgA1 in the same manner as jacalin. The spectra indicate the involvement of tryptophan and tyrosine residues in the binding site of these lectins. Since a tryptophan residue is conserved in all the small subunits, they may form part of the binding site.

Differential expression of galactose and N-acetylgalactosamine residues during fetal development and postnatal maturation of rat glomeruli as revealed with lectin conjugates

A battery of fluorochrome- or peroxidase-coupled lectins, reacting with alpha- or beta-galactose (Gal), terminal N-acetylgalactosamine (GalNAc), or Gal-(beta 1-3)-GalNAc residues, was used to study the emergence and distribution of cellular glycoconjugates in developing and adult rat glomeruli. Neuraminidase pretreatment of the specimens was applied to monitor the maturation of the glomerular sialoglycoprotein coat. In the adult glomeruli, the lectin conjugates applied reacted sparsely or not at all, but most of them showed an increased reactivity with podocytes and/or the glomerular basement membrane after neuraminidase treatment. In the embryonic glomeruli, lectins reacting with beta-Gal residues prominently bound to the basement membranes, as revealed in double-staining with laminin antibodies. This reactivity decreased first during late postnatal development. Some terminal Gal-(beta 1-3)-GalNAc residues were noted in the earliest podocytes, but obviously soon became covered by sialylation. Furthermore, the developing podocytes prominently displayed alpha-Gal residues, as marked by Maclura pomifera (MPA) and Jacalin reactivities but not by the GSA-I conjugates. During postnatal maturation these reactivities also decreased. The GalNAc-specific Helix pomatia (HPA) and Helix aspersa (HAA) agglutinins bound to basement membranes of evolving podocytes but later revealed in the podocytes only a Golgi-like cytoplasmic reactivity. These two lectins showed a marked difference in their binding to tubular basement membranes. In lectin blotting experiments of electrophoretically separated polypeptides transferred onto nitrocellulose, the peanut agglutinin (PNA) and MPA conjugates revealed upon neuraminidase treatment a broad Mr 140,000 polypeptide, compatible with podocalyxin, both in isolated developing and adult glomeruli. The MPA conjugate revealed a similar polypeptide in developing glomeruli, even without neuraminidase treatment. Similar experiments with the HPA and HAA conjugates revealed different polypeptides in both adult and developing glomeruli. Obviously, in the rat kidney the maturation of the podocyte sialoglycoprotein coat and the glomerular basement membranes are multiphasic processes that continue even during late postnatal development.

The binding of peroxidase-labelled lectins to human endometrium in normal cyclical endometrium and endometrial adenocarcinoma

The nature of endometrial glycoconjugates throughout the menstrual cycle was investigated using a panel of lectins directed against specific sugar groups. This approach was also applied to a series of endometrial adenocarcinomas the findings for which were compared with those of normal controls. A change in the expression of glycosubstances was found in relation to the phase of the menstrual cycle; that there was increasing sialylation of terminal galactose groups during the secretory phase. This change may be influenced by progesterone. One group of endometrial adenocarcinomas exhibited binding patterns similar to those seen in secretory endometrium and this may be related to progesterone receptor state. Expression of fucose containing glycosubstances was identified in half of the carcinomas but not in the normal control tissue, thus indicating that a change in fucosylation occurs with endometrial neoplasia. None of the lectin binding patterns, however, correlated with variables in the patients themselves or within the tumours.

Ultrastructural demonstration of Maclura pomifera agglutinin binding sites in the membranocystic lesions of membranous lipodystrophy (Nasu-Hakola disease)

This paper reports three cases of membranous lipodystrophy (Nasu-Hakola disease) in two families and studies the carbohydrate components of membranocystic lesions in all three cases, using twelve kinds of lectins labelled by horseradish peroxidase (HRP). Maclura pomifera agglutinin (MPA), which specifically binds alpha-D-galactose residues, strongly stained typical membranocystic lesions, whereas the other lectins did not. However, Helix pomatia agglutinin (HPA), which specifically binds to N-acetyl-D-galactosamine (GalNAc), stained the membranes of degenerated adipose cells. These were thought to appear during the initial or early stage of the membranocystic lesions. This suggests that a change of carbohydrate residues occurs during the formation of the membranocystic lesions. We also investigated the lectin binding sites at the ultrastructural level using MPA-HRP colloidal gold (CG) conjugate. In the well developed membrane, CG particles were arranged regularly along the minute tubular structures. On the other hand, there were a few irregularly spaced CG particles on the thinner membranes and also on the membranes of the degenerating adipose cells. No CG particles labelled the cell membranes of normal adipose cells. The presence of alpha-D-galactose residues in the membranocystic lesions is demonstrated for the first time at the electron microscopic level.

A lectin, peanut agglutinin, as a probe for the extracellular matrix in living neuromuscular junctions

The extracellular matrix plays important roles in the differentiation of synapses. To identify molecules concentrated specifically in the synaptic extracellular matrix, fluorescently-labelled lectins were applied to neuromuscular junctions. A lectin, peanut agglutinin (PNA), stains the neuromuscular region selectively and irreversibly (up to at least 3 weeks in situ), outlining the periphery of the nerve terminal arborization in the frog. Snake neuromuscular junctions also stain intensely with fluorescent PNA, while mouse diaphragm staining is faint. At the electron microscopic level, the reaction products of horseradish peroxidase-conjugated PNA are found primarily in the extracellular matrix flanking Schwann cells in the frog endplate regions. Fluorescently labelled PNA does not affect synaptic potentials and can serve as a simple stain for correlating functional studies of living neuromuscular junctions. Moreover, it can be combined with a presynaptic dye to observe nerve terminals and synaptic extracellular matrix in the same junctions in situ. This report reveals the existence of synapse-specific carbohydrates associated with Schwann cell extracellular matrix in the frog neuromuscular junction. The specific binding and its physiological compatibility make PNA a useful probe for further investigation of synaptic differentiation, plasticity and maintenance.

Griffonia simplicifolia lectins bind specifically to endothelial cells and some epithelial cells in mouse tissues

The binding of Griffonia simplicifolia agglutinin-I (GSA-I) and the isolectins GSA-I-AB3 and GSA-I-B4, having affinity for some alpha-D-galactosyl and N-acetyl galactosaminyl residues was studied in different mouse tissues. In brain, cardiac muscle and skeletal muscle, the GSA-I-lectin conjugates showed prominent binding only to blood vessel endothelia. Similarly, in the liver and kidney cortex the GSA-I-conjugates selectively reacted with endothelial cells of the sinusoids and with intertubular and glomerular capillaries, respectively. However, a strong reactivity with the GSA-I-conjugates was additionally seen in the acinar cells of the pancreas, in the stratified squamous epithelia of skin and tongue, and in transitional epithelium. SDS-PAGE electrophoresis combined with the lectin-blotting technique indicated that a similar set of glycoproteins are responsible for the GSA-I binding, even in different tissues. Another lectin with specificity for alpha-D-galactose, the Maclura pomifera agglutinin, displayed a distinctly different distribution of binding sites, mainly in the basement membranes, of all mouse tissues studied. The results suggest that some alpha-D-galactosyl residues, recognized by the binding of GSA-I lectins, are preferentially expressed in endothelial cells of mouse tissues, and also provide further evidence that endothelial cells can present a highly specific surface glycosylation pattern.

Lactosaminoglycans are involved in uterine epithelial cell adhesion in vitro

The cell type specificity of glycoconjugate synthesis between the epithelial and stromal cells of the uterus is described. Lactosaminoglycans (LAGs) constituted a major fraction of the cell-associated glycoconjugates synthesized by epithelial, but not stromal, cells. Furthermore, LAGs comprised the bulk (greater than 90%) of glycoconjugates that could be released from epithelial cell surfaces by proteases. Several lines of evidence indicate that the epithelial cell-specific lactosaminoglycans appear to interact directly with a cell surface galactosyltransferase (GalTase). This includes the observation that agents that perturb galactosyltransferase function also interrupt epithelial cell adhesion and cause LAG release from the cell layer. In addition, LAGs are galactosylated when UDP-[3H]galactose is added to intact epithelial cell layers. Interference with cell surface GalTase activity with alpha-lactalbumin or UDP-galactose, but not other agents, specifically interrupted epithelial cell adhesion; however, the same agents had absolutely no effect on stromal cells. Collectively, these studies describe the novel occurrence of lactosaminoglycans on cell surfaces in an adult tissue other than hematopoietic cells and provide evidence for cell type-specific involvement of lactosaminoglycans in uterine cell adhesion processes.

The separation of lymphocyte subpopulations with lectins

Wistaria floribunda agglutinin (WFA), Sophora japonica agglutinin (SJA) and Maclura pomifera lectin (MPL) were employed as immunofluorescent and leucoagglutinating reagents to study murine lymphocytes. WFA, which labels 90% of thymocytes, binds to only 57% of the splenocyte population. The latter subset corresponds to surface immunoglobulin bearing cells. Differential agglutination of splenocytes with this lectin results in the isolation of a WFA negative population which exhibits T-lymphocyte surface markers. The agglutinable splenocytes bind only 2.5 times more WFA than non-agglutinable cells suggesting that the preferential agglutination of B-splenocytes is due to a combination of reduced cell surface negative charge and increased number of lectin binding sites on these cells as compared to T-lymphocytes. Forty percent of splenocytes are positive for SJA and differential agglutination of splenocytes yields a population of SJA non-agglutinable cells that are not labeled by this lectin. The two populations fractionated by SJA are unrelated to T- and B-lymphocyte subsets. Differential agglutination of thymocytes by SJA yields a non-agglutinable group representing 42% of total thymocytes. Although the nature of the two thymocyte subsets discriminated by SJA remains unknown, this lectin appears useful in identifying and separating unique thymocyte and splenocyte populations.

Analysis of N-linked oligosaccharide chains of glycoproteins on nitrocellulose sheets using lectin-peroxidase reagents

A rapid and convenient method was established for analysis of the N-linked carbohydrate chains of glycoproteins on nitrocellulose sheets. Proteins were separated by polyacrylamide gel electrophoresis, transferred to nitrocellulose sheets, reacted with peroxidase-coupled lectins, and detected by color development of the enzyme reaction. Four glycoproteins having N-linked oligosaccharide chains were used as test materials: Taka-amylase A (which has a high-mannose-type chain), ovalbumin (high-mannose-type chains and hybrid-type chains), transferrin (biantennary chains of complex type), and fetuin (triantennary chains of complex type and O-linked-type chains). Concanavalin A interacted with Taka-amylase A, transferrin, and ovalbumin but barely interacted with fetuin. After treatment of the glycoproteins on a nitrocellulose sheet with endo-beta-N-acetylglucosaminidase H, transferrin reacted with concanavalin A but Taka-amylase A and ovalbumin did not. Wheat germ agglutinin interacted with Taka-amylase A but not ovalbumin; therefore, they were distinguishable from each other. Fetuin and transferrin were detected by Ricinus communis agglutinin or peanut agglutinin after removal of sialic acid by treatment with neuraminidase or by weak-acid hydrolysis. Erythroagglutinating Phaseolus vulgaris agglutinin detected fetuin and transferrin. Thus, the combined use of these procedures distinguished the four different types of N-linked glycoproteins. This method was also applied to the analysis of membrane glycoproteins from sheep red blood cells. The terminally positioned sugars of sialic acid, alpha-fucose, alpha-galactose, and alpha-N-acetylgalactosamine were also detected with lectins from Limulus polyphemus, Lotus tetragonolobus, Maclura pomifera, and Dolichos biflorus, respectively.

The large sialoglycoprotein of human lymphocytes. II. Biochemical features

Large sialoglycoprotein of human lymphocytes (L-LSGP) from thymocytes and from peripheral blood lymphocytes (PBL) of normal donor and of B chronic lymphocytic leukemia (CLL) patients was purified by affinity chromatography to Maclura pomifera agglutinin (MPA)-Sepharose followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). L-LSGP from the three different sources was very similar in amino acid composition. It contained a high proportion of acidic and hydroxy amino acids and also significant amounts of cysteine. No reduction in mobility in SDS-PAGE was noted for unreduced L-LSGP. The molecule may already in its native form have an extended conformation containing either free sulfhydryl groups or small S-S loops not affecting mobility in SDS-PAGE. L-LSGP was found to be highly glycosylated, the thymocyte glycoprotein containing somewhat less carbohydrate by weight (44%) than that of PBL (normal PBL 53% and B CLL 52%). This was due primarily to a lower content of sialic acid. The molecules contained mannose, galactose, N-acetyl galactosamine, N-acetylglucosamine and sialic acid in molar ratios 1.0:3.0:1.1:1.2:1.3 (thymocyte L-LSGP), 1.0:3.8:1.2:1.0:1.7 (PBL L-LSGP) and 1.0:3.5:2.2:1.3:2.8 (B CLL L-LSGP). The weak interaction of L-LSGP with lentil lectin, concanavalin A (Con A) and leucoagglutinin (La), its unchanged mobility in SDS-PAGE after tunicamycin treatment and its high amount of hydroxy amino acids suggest that most carbohydrate chains are O-glycosidically linked to the peptide chain. Native as well as Nase-treated L-LSGP show size microheterogeneity. This is probably due to small chemical differences in the L-LSGP molecules from different lymphocyte subsets.

A sperm-agglutinating lectin from seeds of Jack fruit (Artocarpus heterophyllus)

A lectin specific for N-acetylgalactosamine was isolated from seed extract of Jack fruit (Artocarpus heterophyllus) by ammonium sulfate precipitation, followed by affinity chromatography on a Affigel-galactosamine-agarose column. The lectin possessed agglutinating activities for human and rat sperm as well as human red blood cells. It was found to have Mr = 62,000 consisting of two dissimilar subunits of Mr = 18,000 and 13,000. It also cross-reacted with an antibody against the lectin of Osage Orange (Maclura pomifera).

Interaction of Salmonella telaviv with Maclura pomifera lectin

Salmonella telaviv, Salmonella tranoroa, and Salmonella illinois were examined for their ability to interact with 15 purified lectins of known sugar specificity. The only interaction observed was between the lectin of Maclura pomifera and S. telaviv. M. pomifera lectin specifically agglutinated suspensions of S. telaviv and precipitated with its purified lipopolysaccharide and isolated lipid A free O polysaccharide. Quantitative inhibition assays showing methyl-alpha-D-galactopyranoside and N-acetyl-D-galactosamine to be potent inhibitors of Maclura lectin precipitation by S. telaviv O polysaccharide suggest that the interaction is mediated by D-galactose or N-acetyl-D-galactosamine units of bacterial polysaccharide structure, or both.

Uptake of lectins by pulmonary alveolar type II cells: subsequent deposition into lamellar bodies

Type II cells of the alveolar epithelium of adult rats have been shown to internalize the ferritin-labeled lectin from Maclura pomifera (MPA-F). This alpha-galactose-binding molecule binds specifically to the apical plasma membrane of the cells. Once within the cell the lectin is cycled from pinocytic vesicles, to multivesicular bodies of two types, and finally to lamellar bodies, the storage granules of surfactant. Those multivesicular bodies that first contain MPA-F lack detectable lysosomal enzymes, while those labeled later are reactive. For 30-60 min, uptake of MPA-F is blocked by adding methyl alpha-D-galactoside to the instillate. Lectins that have no or limited binding to type II cells are taken up in amounts similar to fluid phase markers. These observations indicate that type II cells can take up substances from alveoli by the process of adsorptive endocytosis and deposit the ingested material into lamellar bodies.

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.

Isolation of the Maclura pomifera hemagglutinin on a deoxymelibiotol affinity support and preliminary characterization by buffer electrofocusing and high-performance liquid chromatography

Maclurin, the potent non-specific blood-group hemagglutinin present in extracts of Maclura pomifera, has been purified by a new biospecific affinity-chromatographic procedure. Additional studies have indicated that this hemagglutinin occurs as five closely related tetrameric protein isoforms derived from two non-covalently-linked polypeptide chains, mol. wts. ca. 10,000 and 13,000 respectively. Buffer electrofocusing fractionated the lectin into 12 components; the major isolectin exhibited an isoelectric point at pH 4.8.

Separation of isolated hamster intestinal epithelial cells by velocity sedimentation on Ficoll Gradients

Isolated hamster intestinal epithelial cells can be separated by velocity sedimentationion on 2-10% Ficoll gradients into three subpopulations of cells which differ in morphology, biochemistry, physiology, and membrane components. These subpopulations are not pure but are enriched in a single cell type to the extent that differences in cell function can be observed. The proliferative crypt cells are separated from the digestive-absorptive villus cells. A third subpopulation with a distinctive morphology is also obtained. Quantitation of DNA recoveries from the gradients indicates that this population constitutes approximately one-third of the epithelial cell population. These carrot-shaped cells are found adjacent to the digestive-absorptive columnar epithelial cells on the villus. The two types of villus cells differ in glycolipid or glycoprotein components of the brush border as shown by lectin binding experiments with the isolated cells. The gradient data also suggest that only one-third of the intestinal epithelial cell population is responsible for most monosaccharide absorption in hamster small intestine.