Tissue Lectins Research Articles

Correlation of expression of nuclear proteins pKi67 and p63 with lectin histochemical features in head and neck squamous cell cancer

This study represents a combined lectin and immuno-histochemical analysis of normal, dysplastic and malignant squamous epithelia of the upper aerodigestive tract with emphasis on the relation between lectin reactivity and the cells' proliferative/anti-apoptotic potential. Staining by double-labeling to detect pKi67, DeltaNp63alpha, alpha2,3/6-linked sialic acid (NeuNAc) and galectin-3-reactive epitopes was performed on specimens of 8 normal cases, 27 primary tumours and 15 regional lymph node metastases. Normal epithelia expressed alpha2,6-linked NeuNAc in the basal layer, while alpha2,3-linked NeuNAc was observed in suprabasal layers. In normal epithelium pKi67 and DeltaNp63alpha positivity was seen in the basal layer and galectin-3-reactive sites in suprabasal layers. The studied squamous cell carcinomas and their metastases showed a tendency for stratification but with markedly altered architecture. The expression of the studied markers was heterogeneous between the different cancer cases but comparable between the corresponding primary and secondary lesions. Glycophenotypic properties were correlated with the level of differentiation. Tumour cell populations were characterized by occurrence of the p63+/pKi67+ alpha2,3-NeuNAc+ alpha2,6-NeuNAc+ phenotype. Analysis of the expression patterns of pKi67, p63 and galectin-3-reactive epitopes (Gal-3-RE) delineated statistically significant interrelationships (Gal-3-RE vs. p63: r = -0.709; Gal-3-RE vs. pKi67: r = -0.623; pKi67 vs. p63: r = 0.895). Of the studied markers only Gal-3-RE expression was correlated to the differentiation-dependent grading (G1 vs. G2: p = 0.007, G2 vs. G3: p = 0.006, G1 vs. G3: p = 0.002). DeltaNp63alpha expression was statistically different only between G1 and G3 (p = 0.03). No statistically significant differences were detected between the primary tumours and the corresponding regional lymph node metastases. Based on the concept of the sugar code further analysis of cell characteristics such as proliferation together with lectin histochemical features, especially using tissue lectins as probes, is thus warranted.

Toward functional glycomics by localization of tissue lectins: immunohistochemical galectin fingerprinting during diethylstilbestrol-induced kidney tumorigenesis in male Syrian hamster

The current study focused on galectins (-1, -3, -4, -7, and -8) and deliberately performed immunohistochemical fingerprinting to explore their complexity in a context of experimental renal carcinogenesis. The diethylstilbestrol (DES)-induced renal tumors in male Syrian hamster kidney (SHKT) represent a unique animal model for the study of estrogen-dependent renal malignancies. Kidney sections of DES-treated hamsters (3 days to 11 months of DES exposure) were analyzed by immunohistochemistry using a panel of non-crossreactive antibodies raised against galectins-1, -3, -4, -7, and -8. Levels of expression were quantitatively determined by using computer-assisted microscopy on immunostained tissue sections. Except for galectin-4, all above mentioned galectins were expressed in kidney tumors. Small clusters of galectin-1-positive, most likely preneoplastic cells at the corticomedullary junction were already evident 1 week after DES administration. Galectin-1 and -3 expression was apparently associated with the first steps of the neoplastic transformation, because small tumorous buds were found to be positive after 1 month of treatment. In contrast, galectins-7 and -8 were detected in large tumors and medium-sized tumors, respectively, thereby indicating an involvement in later stages of DES-induced SHKT. Galectins-1, -3, -7, and -8 were also detected by immunofluorescence staining in the HKT-1097 cell line established from SHKT, thus illustrating the stability of galectin expression in tumor cells. Our data document the presence and differential regulation of galectins in the course of renal tumorigenesis in the model of DES-induced SHKT.

Decrease of Nuclear Reactivity to Growth‐regulatory Galectin‐1 in Senescent Human Keratinocytes and Detection of Non‐uniform Staining Profile Alterations upon Prolonged Culture for Galectin‐1 and ‐3

Summary Multipotent stem cells (source for interfollicular epidermis, hairs and sebaceous glands) are localized in the bulge region of the outer root sheath of hair follicles, while stem cells giving rise to interfollicular epidermis reside in its basal. Using the multifunctional lectin galectin-1 as a marker to localize accessible binding sites in situ as a step to figure out galectin functionality in stem cells, we studied hair follicle-derived keratinocytes. Specific nuclear binding of galectin-1 associated with expression of DeltaNp63alpha, a potential marker of epidermal stem cells, was detected. Binding of chimera-type galectin-3 to a nuclear site was not found in parallel assays. During the process of ageing in culture when cells acquire properties of senescence, disappearance of the nuclear signal for galectin-1 binding was accompanied by a similar decrease of nuclear DeltaNp63alpha expression and increased binding of galectin-3 to the cell membrane, namely in regions of intercellular contacts. Expression of cytokeratin 10, a marker of the terminal differentiation was seen only in a small fraction of the cell population. These data extend the evidence for nuclear sites with galectin-1 reactivity in squamous epithelial cells, the expression of which is modulated upon senescence. Moreover, the results document the divergence of galectin-1 and -3 on the level of ligand selection in this cell type, underscoring the importance of the technical aspect to employ tissue lectins as probe and to perform a fingerprinting with several markers of the galectin family in parallel.

Galectin-3 – an emerging prognostic indicator in advanced head and neck carcinoma

Galectin-3, is a multifunctional effector. It is the only chimera-type member of the galectin family of endogenous lectins, which share specificity with β-galactosides and have a jelly-roll-like folding pattern. It’s activity profile includes modulation of cell–cell and cell–extracellular matrix interactions and the regulation of proliferation and apoptosis/anoikis. While lectin histochemistry with plant/invertebrate proteins is routine practice and immunohistochemical analysis of endogenous lectins has been thoroughly examined, the application of an endogenous lectin as a marker is presently primarily a promising concept. The aims of our study were to test galectin-3 as a technical probe and to correlate staining by the tissue lectin, localising accessible ligands in situ, to clinicopathological characteristics and the prognosis of patients (relapse-free and overall survival) in advanced head and neck squamous cell cancer. We measured galectin-3-dependent staining in 53 surgically resected oropharyngeal and laryngeal cancer specimens (stage III or IV). Patients were divided into two groups based on a threshold of 5% positivity in the tumour cell population. The patient’s degree of positivity was significantly correlated with their level of differentiation and keratinisation and lack of lymph node involvement ( P = 0.0001, P = 0.0007 and P = 0.0224, respectively). Periods of relapse-free and overall survival were significantly shortened when the tumour population failed to meet the positivity criterion, i.e. to harbour ligands for the endogenous lectin ( P = 0.0039 and P = 0.0259, respectively). We conclude that (a) studies with an endogenous lectin as a marker are technically feasible and (b) detection of accessible galectin-3-specific ligands is an independent prognostic marker in advanced head and neck squamous cell cancer with therapeutic potential. Of note, histochemical application of an endogenous effector after its purification and labelling may bear relevance beyond the galectins.

Chemical biology of the sugar code.

A high-density coding system is essential to allow cells to communicate efficiently and swiftly through complex surface interactions. All the structural requirements for forming a wide array of signals with a system of minimal size are met by oligomers of carbohydrates. These molecules surpass amino acids and nucleotides by far in information-storing capacity and serve as ligands in biorecognition processes for the transfer of information. The results of work aiming to reveal the intricate ways in which oligosaccharide determinants of cellular glycoconjugates interact with tissue lectins and thereby trigger multifarious cellular responses (e.g. in adhesion or growth regulation) are teaching amazing lessons about the range of finely tuned activities involved. The ability of enzymes to generate an enormous diversity of biochemical signals is matched by receptor proteins (lectins), which are equally elaborate. The multiformity of lectins ensures accurate signal decoding and transmission. The exquisite refinement of both sides of the protein-carbohydrate recognition system turns the structural complexity of glycans--a demanding but essentially mastered problem for analytical chemistry--into a biochemical virtue. The emerging medical importance of protein-carbohydrate recognition, for example in combating infection and the spread of tumors or in targeting drugs, also explains why this interaction system is no longer below industrial radarscopes. Our review sketches the concept of the sugar code, with a solid description of the historical background. We also place emphasis on a distinctive feature of the code, that is, the potential of a carbohydrate ligand to adopt various defined shapes, each with its own particular ligand properties (differential conformer selection). Proper consideration of the structure and shape of the ligand enables us to envision the chemical design of potent binding partners for a target (in lectin-mediated drug delivery) or ways to block lectins of medical importance (in infection, tumor spread, or inflammation).

Defining the glycophenotype of squamous epithelia using plant and mammalian lectins. Differentiation-dependent expression of alpha2,6- and alpha2,3-linked N-acetylneuraminic acid in squamous epithelia and carcinomas, and its differential effect on binding of the endogenous lectins galectins-1 and -3.

A thorough characterization of the properties of squamous epithelial cells is necessary in order to improve our understanding of the functional aspects of normal development and malignant aberrations. Up to now, studies have focused almost exclusively on monitoring distinct protein markers. With our growing awareness of the coding function of glycan chains of cellular glycoconjugates and their interaction with receptors (lectins) in situ, defining the glycophenotype of these cells has become an important issue. Whereas the commonly applied plant lectins are tools used to map the presence and localization of biochemically defined saccharide epitopes, the introduction of endogenous (mammalian) lectins to this analysis enables us to take the step from monitoring the presence of glycan to understanding the functional implications by revealing ligand properties of the detected epitope for tissue lectin. Thus, in this study we investigated a distinct aspect of glycosylation using plant and mammalian lectins, i.e. the linkage type of sialylation. We first mapped the expression profile of the type of sialylation (alpha2,3- or alpha2,6-linked) by plant lectins. Based on the hypothesis that this factor regulates accessibility of ligands for endogenous lectins we introduced two labeled galectins to this study. Galectin-3 (but not galectin-1) binding was related to cell differentiation in normal adult and developing epithelia, cultured epidermal cells, and carcinomas derived from these epithelia. The presented data suggest that alpha2,6-linked N-acetyl-D-neuraminic acid moieties could serve to mask galectin-3-reactive glycoepitopes. As a consequence, monitoring of the linkage type of sialic acid in glycans by plant lectins therefore has implications for the extent of glycan reactivity with endogenous lectins, pointing to a potential function of changes in sialylation type beyond these cell and lectin systems.

Glycohistochemistry: the why and how of detection and localization of endogenous lectins.

The central dogma of molecular biology limits the downstream flow of genetic information to proteins. Progress from the last two decades of research on cellular glycoconjugates justifies adding the enzymatic production of glycan antennae with information-bearing determinants to this famous and basic pathway. An impressive variety of regulatory processes including cell growth and apoptosis, folding and routing of glycoproteins and cell adhesion/migration have been unravelled and found to be mediated or modulated by specific protein (lectin)-carbohydrate interactions. The conclusion has emerged that it would have meant missing manifold opportunities not to recruit the sugar code to cellular information transfer. Currently, the potential for medical applications in anti-adhesion therapy or drug targeting is one of the major driving forces fuelling progress in glycosciences. In histochemistry, this concept has prompted the introduction of carrier-immobilized carbohydrate ligands (neoglycoconjugates) to visualize the cells' capacity to be engaged in oligosaccharide recognition. After their isolation these tissue lectins will be tested for ligand analysis. Since fine specificities of different lectins can differ despite identical monosaccharide binding, the tissue lectins will eventually replace plant agglutinins to move from glycan profiling and localization to functional considerations. Namely, these two marker types, i.e. neoglycoconjugates and tissue lectins, track down accessible binding sites with relevance for involvement in interactions in situ. The documented interplay of synthetic organic chemistry and biochemistry with cyto- and histochemistry nourishes the optimism that the application of this set of innovative custom-prepared tools will provide important insights into the ways in which glycans can act as hardware in transmitting information during normal tissue development and pathological situations.

Sialomucin complex (rat Muc4) transmembrane subunit binds the differentiation marker peanut lectin in the normal rat mammary gland.

Sialomucin complex (SMC, rat Muc4) is a heterodimeric glycoprotein composed of two subunits, the mucin component ASGP-1 and the transmembrane subunit ASGP-2. SMC/Muc4 is highly expressed on the surface of 13762 rat mammary adenocarcinoma cells at approximately 100 times the level found in the lactating mammary gland. Immunocytochemical staining of SMC/Muc4 in the developing rat mammary gland is localized to the apical membrane of the ductal epithelium. This staining pattern is similar to that for peanut lectin, a differentiation marker, which binds to cells expressing the disaccharide Thomsen-Friedenreich or TF antigen. Blotting of glycoproteins expressing the TF antigen from mammary tissues with peanut lectin detects a protein matching the migration of ASGP-2. Analysis of immunoprecipitated SMC/Muc4 by peanut lectin blotting shows that the TF antigen is abundantly present on the ASGP-2 subunit, hence the similarity of staining pattern with SMC/Muc4 antisera and peroxidase-conjugated lectin in mammary tissues. The TF antigen is also present on ASGP-2 of SMC/Muc4 produced by confluent cultures of Rama 37 rat mammary epithelial stem cells after their induction to an alveolar-like phenotype with prolactin. These results indicate that the TF antigen is present on the ASGP-2 transmembrane subunit of SMC/Muc4 from phenotypically normal tissues and cells, in contrast to malignant cells whose peanut lectin-binding disaccharide is located on ASGP-1.

Lectin histochemistry as a predictor of dysplasia grade in colorectal adenomas.

Lectins are sugar-binding proteins that bind to specific cellular carbohydrates, commonly affecting cellular physiology. Phaseolus vulgaris leucoagglutinin (PHA), ulex europaeus isoagglutinin-I (UEA-I), wheat germ agglutinin (WGA) and peanut agglutinin (PNA) are among the most well studied lectins in various tissues. The purpose of this study was to detect the above lectins binding sites and so examine alterations in glycoconjugate expression in neoplastic cells of 52 colorectal adenomas with various clinicopathologic characteristics and proliferation rates. Lectin histochemistry was performed in paraffin sections with and without neuraminidase treatment. Proliferative fraction was determined by immunolabelling for Proliferating Cell Nuclear Antigen. PHA was the more frequently positive lectin in the examined specimens; however, it was simultaneously detected in normal colonic mucosa and so was WGA. The frequency of high grade dysplasia was significantly greater in older patients and in samples with UEA-I positivity without neuraminidase pretreatment. UEA-I-reactive adenomas were generally characterized by high cell proliferation rates. A statistical model based on patients age and UEA-I binding without neuraminidase treatment can generally predict grade of dysplasia in 83% of adenomas and particularly high grade dysplasia in up to 93% of adenomas; so, such a model may be potentially useful for the early detection of neoplasia, for instance in exfoliative cells from the large intestine.

Endogenous lectins as targets for drug delivery

To minimize side effects of drugs it would be ideal to target them exclusively to those cell types which require treatment. As a means to this end prototypical cellular recognition systems pique our interest to devise biomimetic strategies. Since oligosaccharides of glycoconjugates outmatch other information-carrying biomolecules (proteins, nucleic acids) in theoretical storage capacity by far, work on the sugar code can spark off development of effective targeting devices. Conjugation of custom-made glycan epitopes to proteins or biocompatible non-immunogenic polymeric scaffolds produces neoglycoconjugates with purpose-adaptable properties. In the interplay with endogenous receptors such as lectins, suitable oligosaccharides such as histo-blood group trisaccharides as parts of neoglycoconjugates have already proven their practical applications in histopathology. Elucidation of the structure of cell lectins with currently five main families aids to tailor ligand characteristics rationally. They include the types of functional groups and their topological presentation to optimize the bimolecular binding as well as the optimal spatial clustering and spacer characteristics to exploit cooperativity. Indeed, the potent trivalent cluster glycosides designed for the C-type asialoglycoprotein receptors furnish an instructive example how to turn the theoretical guideline on ligand modification into nM-affinity. By placing emphasis on tissue lectins as targets of neoglycoconjugate-mediated drug delivery, the long-term perspective is opened to likewise test members of these families themselves for routing of therapeutic payloads, aiming at cell addressins. This review illustrates the conceivable potential which work on the sugar code with custom-made neoglycoconjugates and tissue lectins can have in store for drug delivery.

Endogenous lectins (galectins-1 and -3) as probes to detect differentiation-dependent alterations in human squamous cell carcinomas of the oropharynx and larynx.

Expression of glycan determinants for in situ binding is the prerequisite for a productive protein (lectin)-carbohydrate recognition. Labeled tissue lectins as tools are preferable to plant lectins to assess this parameter, because plant and animal lectins with identical saccharide specification can well differ in their profiles of oligosaccharide binding pattern. Due to their relevance in growth control and matrix adhesion the family of galectins (galactoside-binding metal ion independent animal lectins) is receiving increasing utilization in human biology. Employing biotinylated galectin-1 and galectin-3 we studied the expression of binding sites for these galectins in normal human squamous epithelium and human carcinomas from the oropharyngeal region and larynx in relation to the expression of LP-34+ cytokeratins by the procedure of double labeling. Tissue sites accessible for galectin-1 were located in all layers of normal epithelium and in tumor cells. In contrast, galectin-3 binding was suprabasal in the normal epithelium and in tumor cells exhibiting signs of keratinization. These results reveal differences in the localization of accessible sites for the two galectins. Relating to cell development galectin-3 appeared to display affinity to areas with increased extent of differentiation.

Fusion of macrophages on an implant surface is associated with down-regulated expression of ligands for galectin-1 and -3 in the rat

Galectins have a wide range of biological activities which are elicited by binding to appropriate glycoligands. Besides regulation of the expression of the galectins the extent of the presence of suitable binding sites will be relevant to infer the cellular responsiveness to this class of sugar receptors. Thus ligand presentation requires monitoring by the tissue lectin. We demonstrate the expression of galectin-3 by macrophages and foreign-body giant multinucleate cells colonizing a cellophane implant in the rat by the A1D6 monoclonal antibody. The extents of ligand presence are visualized in the same cells by biotinylated galectin-3 and also by galectin-1 which is produced by diverse mammalian cell types and widely distributed. Labeled mistletoe (VAA) and tomato (LEA) lectins are used as tools to assess the degree of similarity of the binding profile between endogenous and exogenous proteins. The presentation of α-galactosides is monitored with a natural immunoglobulin G subfraction obtained by two consecutive affinity chromatography steps. The binding of labeled galectins and plant lectins was significantly lower to foreign-body giant multinucleate cells than to mononuclear macrophages. The application of the α-galactoside-specific probe yielded no significant staining. The potential problem of epitope accessibility could be excluded by the concomitant positivity obtained with an IgG subfraction with selectivity to β-galactosides also obtained by affinity chromatography. These results provide no evidence for a role of α-galactosides for the binding of galectins in the rat macrophages colonizing the implant. The reduced level of expression of glycoligands for galectin-1 and -3 in foreign-body giant multinucleate cells in contrast with the mononuclear macrophages suggests an inhibitory influence of macrophage fusion on the expression of galectin-reactive molecules.

Histochemical Analysis Using Lectin in the Mouse Uterine Tissues with Experimentally-Induced Adenomyosis.

Transplantation of a single anterior pituitary into the uterine lumen is known to induce the development of adenomyosis in mice associated with hyperprolactinemia. The uterine tissues of experimentally-induced adenomyosis were investigated histochemically with 21 kinds of biotinylated lectins and compared to control tissues of both intact mice and mice one day after parturition. Glandular and luminal epithelial cells and lymphocytes showed different lectin staining patterns between adenomyotic uteri and intact ones, whereas endometrial stromal cells and myometrial cells showed no differences. Even uteri at a very early stage of the pathological disorder already had changes in their lectin binding pattern. Some lectin groups had a different staining pattern between adenomyotic uteri and intact ones. Among them, some showed a similar pattern between adenomyotic uteri and uteri after delivery, and the others showed a different pattern between them. The former groups were closely related to an elevated level of circulating prolactin, and the latter to a pathological change in adenomyosis. This is the first evidence which shows that experimentally-induced adenomyosis involves substantial changes even at a very early stage of the pathogenesis.

Estimation of functional carbohydrate-binding lectin in peanut tissues by enzyme-linked immunoassay

A glycoprotein antibody sandwich enzyme-linked immunoassay (GAS ELISA) was used for the detection of functional galactose- and mannose-binding lectins (GL and ML, respectively) in the tissues of peanut ( Arachis hypogaea L.) as an alternative to haemagglutination assay (HA). Selection of an appropriate glycoprotein receptor for each lectin was essential as nodule GL and seed GL differed in their respective GAS ELISA reactions with asialothyroglobulin. Their reaction with blood group substance A + H (BGS) was identical, however. Nodule ML and cotyledon ML did not differ in their ability to bind to either ovalbumin or transferin. Use of the glycoproteins BGS and ovalbumin for the assay of GL and ML, respectively, allowed the detection of each lectin down to 30–80 ng/ml. This was less sensitive than the double antibody sandwich (DAS) ELISA (2 ng/ml) but more sensitive than HA (400 μg/ml). Estimates of GL and ML in peanut tissues by GAS ELISA were comparable to those obtained by DAS ELISA but HA appeared to overestimate ML concentrations.

Heparin binding lectin of human placenta as a tool for histochemical ligand localization and isolation.

Biotinylated heparin has been used to detect the presence of specific binding sites in sections of human placenta, which has prompted demonstration of expression of lectin activity for this proteoglycan. Purification of this lectin from full-term placenta facilitates the synthesis of its biotinylated derivative, using biotin-amidocaproyl hydrazide, without affecting its activity. It also enables immunization to obtain antibodies. The labeled lectin is shown to bind specifically to nuclear and cytoplasmic locations in various cell types of human placenta, nuclear expression of lectin binding sites being more pronounced at the full-term stage than after 8 weeks of development. The structurally related histone H2B exhibits obvious differences in its binding pattern. The presence of ligands accessible to the lectin whose binding activity can be inhibited by addition of an excess of heparin correlates in most instances with the level of lectin expression detected immunohistochemically. Biochemical information on the nature of the glycohistochemically inferred lectin-specific ligand(s) is obtained by affinity chromatography on resin-immobilized lectin. It leads to isolation of a proteoglycan with similar electrophoretic mobility in agarose-polyacrylamide gel electrophoresis relative to the independently purified heparan sulfate-containing fibronectin binding proteoglycan from human placenta. Both fractions inhibit binding of heparin to the lectin and contain immunologically detected co-purified lectin, emphasizing their ligand properties. Application of labeled tissue lectins in conjunction with lectin-specific antibodies is proposed to obtain valuable insights into the expression of the receptor as well as the ligand part of protein-carbohydrate recognition.

Binding of hydroxylysine-linked saccharides by galaptin, a galactoside-binding animal tissue lectin

Binding of hydroxylysine-linked saccharides by galaptin, a galactoside-binding animal tissue lectin

Evidence of differences between mannose-binding lectins from nodules and cotyledons of peanut

The mannose/glucose-binding lectin (ML) from the nodules of peanut ( Arachis hypogaea L.) was found to be antigenically identical to ML from hypocotyls, stems, leaves and roots but cotyledon ML was antigenically different. The different tissue lectins had relative molecular weights similar to nodule ML and were each composed of two identical or nearly identical subunits. There were no differences between the set of multiple bands that each lectin formed during isoelectric focusing. The antigenically different cotyledon ML and nodule ML had similar carbohydrate specificities but differed in their sensitivity to haemagglutination inhibition by sugars and certain glycoproteins. In contrast, the antigenically identical leaf ML was identical to nodule ML in its reaction with sugars and glycoproteins. Nodule and cotyledon ML both contained mannose, galactose, fucose, xylose and acetylglucosamine although the proportions and content of sugars differed. The amino acid composition of nodule and cotyledon ML was similar but slight differences in their amino-terminal amino acid sequences suggested that they are produced by alleles of the same gene.

Localization of Endogenous β-Galactoside-Binding Lectin in Human Cells and Tissues

A rabbit antiserum raised against the 14.5-kilodalton (kDa) subunit of human splenic galaptin was used to probe protein blots of several tissue extracts. For all tissues examined, the only immunoreactive species detected was a 14.5-kDa polypeptide. This antiserum and a rabbit antiserum raised against native lung galaptin were used in immunohistochemical assays to determine the localization of galaptin in selected tissues and cells. In normal colon, galaptin was found prominently in the basement membrane and in the stroma. The cytoplasm of epithelial cells stained lightly for galaptin whereas mucous granules and secreted mucin were uniformly negative for galaptin. Hemagglutination inhibition assays also failed to demonstrate an interaction between galaptin and mucin. Macrophages stained conspicuously for galaptin in colonic and cutaneous tissue as did some capillary walls. In cutaneous tissue, the extracellular matrix and hair follicle cells contained abundant galaptin. Galaptin was absent in basal cell carcinoma and associated stroma. Galaptin was found throughout the cytoplasm of carcinoma cells of gynecologic origin present in effusions. Protein blot analysis of extracts of extracellular matrix synthesized in vitro by endothelial cells confirmed the presence of galaptin in matrix. The results show that: (1) galaptin is variably expressed by different cells and tissues; (2) its cellular location is not restricted to the cell surface; (3) galaptin is not associated with normal mucin; (4) the extracellular matrix is a major site of galaptin deposition, and (5) some malignant tissue may be characterized by a deficiency of galaptin.

Developmental changes and tissue distribution of lectin inGalanthus nivalis L. andNarcissus cv. Carlton

A sensitive immunosorbent assay was developed to quantify the lectin in different tissues ofGalanthus nivalis (snowdrop) andNarcissus cv. Carlton (daffodil) and follow the distribution of the lectin during the life cycle of the plants. The lectin in snowdrops and daffodils occurs in almost all plant tissues. Moreover, in many tissues the lectin is the most prominent protein. High lectin concentrations are found in the bulb where the lectin accounts for up to 15% of the total protein during the resting period. However, as the shoot grows and the plant turns on to flowering the lectin content rapidly decreases. Soon after flowering the lectin accumulates in the new bulb units. Whereas in daffodil the lectin concentration in the aerial plant parts is about one order of magnitude lower than in the bulb, lectin concentrations in the upper parts of snowdrop are similar to those in the bulb. The lectin in the former tissues is already present before the sprout emerges. As the shoot starts to grow lectin concentrations in leaves, stems and flower parts gradually decrease so that at flowering time virtually all lectin has disappeared from the aerial parts. The highest lectin concentrations are found in the ovary and increase, initially, as the sprout emerges from the bulb.

Differences in the distribution of mannose- and galactose-binding lectins in peanut tissues

A mannose/glucose-binding lectin (ML), previously purified from peanut ( Arachis hypogaea L.) nodules, was detected in other tissues using an enzyme-linked immunoassay system and its distribution in nodulated and non-nodulated plants compared with that of the galactose-binding lectin (GL) of peanut. Unlike GL, ML was not detection seed but was present in cotyledons and roots of 5-day-old seedlings at planting and in all tissues throughout growth of plants receiving fixed or inorganic N. Concentrations of ML declined to base levels only in tissues of plants deprived of N whereas GL declined from high levels in seed to less than 0.2 μg/g in all plant tissues irrespective of conditions of N-supply. Levels of GL rose slightly after 6 weeks but remained below 1 μg/g except in pods where levels reached 3–6 μg/g at 10 weeks. Both lectins were detected in Bradyrhizobium-incited nodules at 2 weeks and their pattern of synthesis was similar in this tissue although levels of ML were higher than those of GL. Appropriate sugar haemagglutination inhibition tests confirmed the presence of each lectin in tissue extracts. Neither purified nodule lectin reacted with cells or bacteroids of symbiotic peanut rhizobia.