The identification of membrane glycoconjugates in Leishmania species

The membrane glycoconjugates of 8 different species of Leishmania were compared by lectin blotting. Five different lectins with various sugar specificities were examined: concanavalin A, Lens culinaris, Ricinus communis, soybean agglutinin, and peanut agglutinin. Concanavalin A and Lens culinaris reacted with every Leishmania tested. The patterns observed for these 2 lectins, as well as the various species of parasites, were different. However, a common 41,000-52,000 and a 160,000-185,000 Mr component was present in almost all the parasite isolates examined. Ricinus communis only recognized a nondiscrete galactose-containing glycoconjugate similar to Leishmania-excreted factor. Soybean and peanut agglutinins reacted with a few low molecular weight parasite components. Soybean agglutinin reacted with all the Leishmania species tested, whereas peanut lectin only recognized 3 isolates. The latter lectin bound to discrete components migrating with the dye front and with Mr's of 35,000 and 52,000. Increased glycosylation was noted on avirulent L. major promastigotes and was associated with the appearance of several new peanut agglutinin-binding glycoproteins.     

Hepatocyte cell surface polarity as demonstrated by lectin binding

We performed an investigation at the ultrastructural level of the differential distribution of lectin-binding sites among sinusoidal, lateral, and bile canalicular domains of adult rat hepatocytes. Lectin binding to hepatocyte glycocalices was studied in situ or after cellular dissociation by enzymatic (collagenase), chemical (EDTA), and mechanical methods, as well as during cell culture. Using thirteen biotinylated lectins and an avidin-biotin-peroxidase complex (ABC), we have identified lectin-binding sites that are predominantly localized in the bile canalicular [Ricinus communis agglutinin (RCA)] or sinusoidal [Phaseolus vulgaris (PHA)] domains in situ and in mechanically dissociated cells. Lens culinaris (LCA) staining was prominent on sinusoidal surfaces, slight along lateral surfaces, and completely absent in the bile canalicular domain. Concanavalin A (ConA) was unique in binding equally to all domains. Triticum vulgaris [wheat germ agglutinin (WGA)] was also bound to all domains, but most intensely to the bile canalicular region. Cells dissociated via collagenase or EDTA treatment exhibited a spherical morphology characterized by many surface microvilli and absence of morphological domains. Lectin binding to dissociated cells was uniformly distributed over the entire cell surface, suggesting a redistribution of lectin receptors that was independent of the separation procedure. Hepatocytes in culture exhibited a partial restoration of morphological domains, but lectin binding polarity was not re-established.     

Lectin-Reactive Components in White Matter Membranes from Normal and Multiple Sclerosis Brains

Abstract: Polypeptides derived from human white matter membranes reacted with the radioiodinated lectins concanavalin A, Lens culinaris phytohemagglutinin, Ricinus communis agglutinin and wheat germ agglutinin after electrophoresis in polyacrylamide pore gradient gels. The molecular weights of these lectin-reactive bands were estimated by comparison with radioiodinated protein standards by using the linear relationship between log of the molecular weight and log of the gel concentration reached by the protein after electrophoresis in a polyacrylamide gradient gel. The molecular weight estimates for components reactive with concanavalin A were 176,800, 141,200, 72,800, 52,800, 44,700, 40,000, 24,800 and 23,900. The molecular weights of the bands reactive with both wheat germ agglutinin and Lens culinaris phytohemagglutinin were 138,000, 113,500, 92,100, 52,800, 44,700, 24,800 and 23,900. Wheat germ agglutinin was bound also to a band with a molecular weight of 72,800. Ricinus communis agglutinin bound to bands with estimated molecular weights of 138,000, 72,800, 52,800, 44,700, 24,800 and 23,900. The electrophoretic pattern of lectin-reactive polypeptides derived from normal-appearing white matter of multiple sclerosis brains was not qualitatively different from the lectin-binding pattern of control brain membrane polypeptides.     

Detection of anomalies in cell-surface carbohydrates on thrombasthenic platelets using 125I-labeled lectins

The composition of carbohydrates on the surface of platelets from a patient with Glanzmann's thrombasthenia and from seven normal donors were determined and compared. To this end, binding studies were performed using nine different purified 125I-labeled lectins; Concanavalin A, P-Phytohaemagglutinin, Wheat Germ Agglutinin, Dolichos biflorus, Pisum sativum, Ricinus communis II Agglutinin, Tetragonolobus purpureus, Lens culinaris and Soybean Agglutinin. These studies show that thrombasthenic platelets bear significantly decreased numbers of receptors for Concanavalin A and Lens culinaris, both with a specificity for D-mannose, and Ricinus communis II, with specificity for D-galactose. There were no detectable differences in the numbers of other lectin receptors. These results provide further evidence of molecular defects in thrombasthenic platelets. Moreover, the use of 125I-labeled lectins, as shown here, provides a fast and reliable technique for identifying abnormalities in the carbohydrate composition on the surface of platelets in various thrombopathies.     

Adhesive specificity of developing cerebellar cells on lectin substrata

Ten lectins, each with a different carbohydrate-binding specificity, have been coupled to tissue culture substrata with carbodiimide [1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide-metho-p-toluene sulfonate] and assayed for their efficacy as substrates for the carbohydrate-specific adhesion of cells dissociated from mouse cerebellum at embryonic Day 13 and postnatal Days 0 and 7. On surfaces treated with concanavalin A, succinyl-concanavalin A, Lens culinaris agglutinin, and wheat germ agglutinin, both embryonic and early postnatal cerebellar cells formed a monolayer. On surfaces coupled with Ricinus communis_I agglutinin (120,000 daltons) both embryonic and postnatal cells formed cellular aggregates with extensive fiber outgrowth. On surfaces treated with peanut agglutinin, Dolichos bifloris agglutinin, Wistaria floribunda agglutinin, soybean agglutinin, or Ulex europaeus_I agglutinin, embryonic cerebellar cells formed cellular aggregates with a cell viability of 25–35% and little or no fiber outgrowth. Postnatal cerebellar cells, in contrast, formed cellular aggregates with a cell viability of 60–70% and extensive fiber outgrowth. On surfaces treated with Ulex europaeus_I agglutinin, cells from postnatal Day 7 formed limited areas of monolayer in addition to cellular aggregates. After 12 hr in vitro the specific attachment of cerebellar cells to lectin-derivatized substrata was inhibited 60–80% by the inclusion of free hapten carbohydrate (50–100 mM) in the growth medium. The addition of soluble concanavalin A or Ricinus communis_I agglutinin (100 μg/ml) was toxic. These studies suggest the presence of glycoconjugate-binding sites for concanavalin A, Lens culinaris agglutinin, and wheat germ agglutinin which promote cerebellar cellular adhesion.     

Expression of lectin-binding surface glycoproteins during the development of Schistosoma mansoni schistosomula

Tegumental glycoproteins of Schistosoma mansoni cercariae, mechanically produced 24-hr and 48-hr schistosomula, and adult worms were radioiodinated with the Bolton-Hunter reagent, then isolated by lectin affinity chromatography. SDS-PAGE revealed Con A binding glycoproteins with apparent molecular weights of 180,000, 150,000, 43,000, and 30,000 in detergent extracts of the tegument of cercariae. These glycoproteins are retained by 24-hr mechanically produced, cultured schistosomula and are accompanied by the appearance of 2 additional labeled glycoproteins, mol. wt. 66,000 and 57,000. In 48-hr schistosomula, there is a marked increase in the relative size of the 66,000 mol. wt. peak. In contrast, the 57,000 mol. wt. glycoprotein is the major radiolabeled Con A binding component of the adult tegument; the other peaks are either reduced or absent in adults. Similar findings were obtained following affinity chromatography using immobilized Lens culinaris lectin or Ricinus communis agglutinin, and following metabolic labeling of glycoproteins with tritiated galactose.     

The binding of lectins to components of plasma membranes from porcine submaxillary lymph node lymphocytes

By sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis the plasma membranes from porcine lymphocytes contain at least 30--35 glycopolypeptides and one or more glycolipids to which one or more of 12 purified lectins bind. The specificities of binding generally followed the same pattern as those of the reaction of the lectin with intact pig lymphocytes. Some lectins (e.g., the isolectin pair, Agaricus bisporus lectins A and B and a group consisting of the Lens culinaris A and B isolectins and the closely related Pisum sativum lectins) bind to almost identical populations of plasma membrane components and compete with each other for all their binding sites. Others (e.g., Concanavalin A and the Lens culinaris-Pisum sativum group and a group consisting of phytohemagglutinin-L, Ricinus communis lectin-60 and Ricinus communis lectin-120 bind in a cross reactive manner to some common binding moieties but, in addition, to certain nonshared ones. Still others (e.g., soybean agglutinin, peanut agglutinin and wheat germ agglutinin) do not share any common binding moieties with the other lectins. The amount of lectin binding and the number of membrane components to which a lectin binds is directly related to the Ka of binding of the lectin to the intact lymphocyte. Those with high Ka (Cocanavalin A Lens culinaris lectins, Pisum sativum lectins, phytohemagglutinin-L), bind to 20-30 different components giving very complex binding patterns while those with lower Ka (Agaricus bisporus lectins, wheat germ agglutinin, peanut agglutinin, and soybean agglutinin) bind to 8--13 components with easily distinguishable patterns. Soybean agglutinin binds almost exclusively to a glycolipid fraction while for the others one or more glycopolypeptides served as the major lectin-binding molecule. The Ricinus lectins, two lymphocyte toxins, bind to essentially every plasma membrane component to which the mitogen phytohemagglutinin-L binds, in fact competing for most of those plasma membrane moieties which bind phytohemagglutinin-L.     

Synergistic effects of lectins in the interaction of thrombin with human platelets

Several lectins have been studied for their effects on the interaction of thrombin with human platelets. Wheat germ agglutinin, concanavalin A and Ricinus communis lectin increased the number of high affinity sites for diisopropylphosphothrombin on washed platelets from 3000 to about 12 000 but the binding affinities were unchanged (Kd approx 4 nM). Two other lectins, Lens culinaris and Bandieria simplicifolia, were without effect. (2) Using formalinized platelets to avoid possible complications of the platelet release reaction, wheat germ agglutinin showed a marked increase (5-fold) in the binding of active thrombin, peanut agglutinin had no effect while Ricinus communis and :Bandieria simplicifolia showed marginal increases (2-fold). Thrombin binding was decreased to about one quarter with Lens culinaris, Phaseolus vulgaris and concanavalin A. (3) Wheat germ agglutinin caused a synergistic increase of platelet aggregation at low concentrations of thrombin (12.5 mU/ml) and ADP (1 microM), both in the absence and presence of added fibrinogen, but had no effect on ristocetin-induced aggregation.     

Lectin binding to cystic stages of Taenia taeniaeformis

Studies of membrane glycoconjugates of Taenia taeniaeformis were initiated by assays of the lectin binding characteristics of 35-day-old cysticerci. Parasites fixed in glutaraldehyde were incubated with one of the following FITC-labelled lectins: Concanavalin A (Con A), Lens culinaris agglutinin (LCA), Ricinus communis agglutinin (RCA), peanut agglutinin (PNA), fucose binding protein (FBP) and wheat germ agglutinin (WGA) and either their specific or a nonspecific sugar. Ultraviolet microscopy revealed that only Con A and LCA bound in large amounts to the surface of cysticerci. This binding was partly inhibited by the specific sugar, but the nonspecific sugar had little effect. The lectin not removed by either of the sugars may have been bound nonspecifically to the charged glycocalyx. Lectins were primarily bound on the anterior third of the parasite around the scolex invagination. Kinetic studies of lectin interactions were carried out with LCA and RCA by spectrophotofluorometric analysis of the amount bound specifically or nonspecifically over a range of lectin concentrations. Lens culinaris lectin binding was found to be specific and involve 2 receptors which showed large differences in their affinity for lectin and prevalence on the surface. Ricinus communis lectin did not bind specifically but nonspecific interactions were observed. Adherence of small numbers of host cells was shown to have no measurable effect on the lectin binding characteristics. The results suggest that the major surface carbohydrates exposed are D-mannose and/or D-glucose residues with the other sugar groups poorly represented. This relatively homogeneous surface may have implications for the antigenicity of the parasite in its host.     

Cell type-specific binding of Ricinus lectin to murine cerebellar cell surfaces in vitro

Summary The binding of several plant lectins, Concanavalin A (ConA), Lens culinarisA (LCA), wheat germ agglutinin (WGA), and Ricinus communis agglutinin 120 (RCA120) to cell surfaces of developing mouse cerebellar cells was assayed by the use of fluorescein isothiocyanate (FITC)-conjugated compounds. Freshly dissociated, live single-cell suspensions from 6-day-old mouse cerebellum contain 93% ConA, 99% LCA, 98% WGA, and 59% RCA 120-positive cells with ring fluorescence. Of the RCA 120-positive cells, 4% express a high and 55% a lower or very low number of lectin receptors. Flow cytometric analysis of fluorescent lectin binding yields results qualitatively similar to those obtained by scoring positive and negative cells in the fluorescence microscope.In monolayer cultures of 6-day-old mouse cerebellum practically all cells express receptors for ConA, LCA, and WGA, whereas RCA 120 binding sites are absent from neurons with small cell bodies (granule, basket and stellate cells) and present in large number on neurons with large cell bodies (Purkinje and possibly Golgi Type-II cells) and fibroblasts. RCA 120 receptors are weakly expressed on astro-and oligodendroglia. Cell type-specific expression of RCA 120 receptors is constant throughout all ages studied (embryonic day 13 to postnatal day 9). At early embryonic ages the proportion of highly fluorescent neurons with large cell bodies is significantly increased.     

The surface membrane of Leishmania. I. The effects of lectins on different stages of Leishmania braziliensis.

The infective stages of Leishmania braziliensis, amastigotes and promastigotes subcultured a limited number of times, were agglutinated by Ricinus communis agglutinin and Concanavalin A. These results suggest that terminal ligands similar or identical with alpha-D mannose, alpha-D glucose (specific receptors for Con A), and alpha-D galactose (specific receptor for RCA) are present in the surface membrane of L. braziliensis. Noninfective promastigotes from the same stock, but subcultured approximately 500 times, were not agglutinated by RCA suggesting either the absence of the alpha-D galactose groups in the surface membrane or their presence in a very reduced number. Agglutination with soybean agglutinin, wheat germ agglutinin, or phytohemagglutinin P was not observed in any of the L. braziliensis forms tested. The difference in polysaccharide residues on the surface membrane of L. braziliensis may be related to the different pathogenic properties of the cell.     

Cell reassociation behavior and lectin-induced agglutination of embryonic mouse cells from different brain regions

Cells from dissociated embryonic mouse cerebellum, when plated at high cell density in a 10 μl microwell, assembled into a reproducible three-dimensional pattern of reaggregates containing 2–10000 cells each and interconnecting cables of processes. The details of this pattern were modifiable by coating the culture substratum with poly-d-lysine and by the use of different types of serum in the growth medium. Formation of interconnecting cables was inhibited reversibly by the dimeric lectin Succinyl Concanavalin A (Succ-ConA). Cells from cerebellum, midbrain, medulla and cerebral cortex, cultured separately in microwells, formed distinguishable patterns that appeared to be more region-specific than developmental stage-specific.With lectins as probes of carbohydrate-containing surface macromolecules, cells harvested from different tissue regions had different cell surface properties. In addition the concentration of concanavalin A (ConA) or wheat germ agglutinin (WGA) required for half maximal agglutination was greatly increased for cerebellar cells harvested later than embryonic day 16. These observations suggest both regional and age-specific alterations in cell surface elements required for lectin-induced agglutination during mouse brain development.     

Molecular characterization of the human red cell Rho(D) antigen

Human red cells of Rh blood groups -D-/-D- ('super-D'), -/- (Rhnull) and normal Rho(D)+ cells were radioactively surface-labeled using the lactoperoxidase 125I method. Polyacrylamide gel electrophoresis in the presence of SDS followed by fluorography showed a strong enrichment of a polypeptide with an apparent mol. wt. of 28,0000-33,000 in the 125I-labeled -D-/-D- membranes. This polypeptide was specifically immune precipitated with anti-Rho(D) antiserum. Treatment of intact cells with trypsin or Pronase did not digest the protein. The Rho polypeptide migrated identically on polyacrylamide gel electrophoresis under reducing and non-reducing conditions. It was not phosphorylated after in vitro incubation of red cells with 32P. When whole labeled membranes were solubilized in neutral detergent and applied to lectin-Sepharose columns the Rho(D) polypeptide adsorbed to Ricinus communis lectin but not to wheat germ lectin or Lens culinaris lectin. The purified molecule did not adsorb to R. communis lectin-Sepharose. Treatment of the Rho(D) antigen with endo-N-acetyl glucosaminidase H, endo-beta-galactosidase or mild alkali did not lower its apparent mol. wt.     

Differential lectin-mediated agglutinabilities of the embryonic and the first extraembryonic cell line of the early chick embryo

Summary The lectin-mediated agglutinability of cells dissociated from different areas of the gastrulating chick embryo was investigated. Differences in agglutinability were quantified by using a Coulter counter. Cells from the area pellucida (AP) and those from the endoderm of the area opaca (AOEn) are agglutinated by Concanavalin A (Con A), wheat germ agglutinin (WGA) andRicinus communis agglutinin (RCA). In cells from both areas the greatest agglutination response is obtained with RCA. Trypsinization of AOEn cells enhances their agglutinability with Con A, WGA and RCA. The lectin-induced agglutinability of cells from the area pellucida is similar in EDTA-dissociated and trypsinized cells.Cells from the AP are significantly more agglutinable with Con A than those of the AOEn regardless whether the former are obtained by trypsinization or dissociation with EDTA. The higher agglutinability of cells of the area pellucida with Con A, as well as the differential enhancement by trypsin of the agglutinability of AOEn cells with Con A, WGA, and RCA may reflect a difference in the cell surface glycoreceptors between the cells of the are pellucida (predominantly embryonic) and the first extraembryonic (AOEn) cell line. These cells have been shown to sort out from each other at the earliest stages of development.     

A quantitative assay for concanavalin A- and Ricinus communis agglutinin-mediated agglutinations of rat ascites hepatoma cells. Relationship between concanavalin A binding and cell agglutination.

A simple quantitative assay method was developed for the agglutination of rat ascites hepatoma cells mediated by Concanavalin A or Ricinus communis agglutinin. This method was based on the principle that the turbidity of a cell suspension is proportional to the sum of the cross-sectional area of cells and aggregatesmas predicted by the theoretical consideration, the turbidity decreased when cells were aggregated and the decrease was a function of the average number of the cells in aggregates. The agglutinability of the cells, judged by this method, showed a maximum value at a certain concentration of the agglutinin. By further addition of the agglutinin, the agglutinability slightly decreased from the maximum. These phenomena were observed both for Concanavalin A and Ricinus communis agglutinin. The binding and the agglutination experiments using [3-H]concanavalin A revealed that the binding to approx;0% of the total receptors caused a maximal agglutination. This suggested that the receptors responsible for the agglutination constitute only a small part of the total receptors on the surface.     

Glycoprotein changes in the rat sperm plasma membrane during maturation in the epididymis.

To investigate surface glycoprotein changes during post-testicular maturation, plasma membranes were isolated from proximal caput, distal caput, and cauda epididymal rat spermatozoa. Membrane glycoproteins were identified on Western blots of SDS-PAGE fractionated samples using biotinylated lectins and Vecta-stain reagents; these were compared to glycoproteins present in cauda epididymal luminal fluid. Lens culinaris agglutinin, Pisum sativum agglutinin, peanut agglutinin, wheat germ agglutinin, Ricinus communis agglutinin, Ulaex europaeus agglutinin, and Dolichol biflorus agglutinin each bound a specific subset of the polypeptides present. Several types of glycoprotein changes were noted including their appearance, loss, alteration of staining intensity, and alteration of electrophoretic mobility. Some maturation-dependent sperm surface glycoproteins co-migrated with glycoproteins present in epididymal fluid. This approach of direct analysis of the glycoproteins in purified plasma membranes identifies a broader spectrum of maturation-related surface changes occurring within the epididymis than are noted with surface labeling procedures.     

Changes in the glycosylation pattern during embryonic development of mouse kidney as revealed with lectin conjugates

Distribution of lectin-binding sites in adult and developing mouse kidney was studied with fluorochrome- and peroxidase-coupled lectins. Effects of fixation methods on lectin-binding patterns were also compared. Un-induced mesenchymal cells and ureter bud of the early metanephros reacted with Concanavalin A, Lens culinaris, Ricinus communis I, and wheat germ agglutinins, whereas binding sites for both soybean and peanut (PNA) agglutinins were seen only in ureter bud tissue. On induction, PNA positivity rapidly appeared in the induced, condensed areas of the metanephrogenic mesenchyme. Early glomeruli expressed heterogeneously terminal galactosyl and N-acetylgalactosaminyl moieties in the podocytes. Later, these sites disappeared and were apparently covered by sialic acids. Endothelia also displayed a comparable sialylation of terminal saccharide moieties during maturation. Binding sites for many of the above lectins were also found in the developing proximal and distal tubules. Terminal fucosyl residues, characteristic of mature proximal tubules, appeared during day 13 of development. Dolichos biflorus agglutinin reactivity, typically seen in the collecting ducts, appeared by day 13. Griffonia simplicifolia-I-B4 isolectin reactivity was exclusively localized to endothelial in adult kidney cortex, but in embryonic kidneys reactivity with collecting duct and podocytes was also seen. These results suggest that the compartmentalized expression of cell glycoconjugates in adult mouse kidney is acquired in a sequential manner during development. Such sequential appearance of the mature glycosylation pattern probably reflects functional maturation of the nephron.     

Fluorochrome-coupled lectins reveal distinct cellular domains in human epidermis

The distribution of saccharide moieties in human interfollicular epidermis was studied with fluorochrome-coupled lectins. In frozen sections Concanavalin A (Con A), Lens culinaris agglutinin (LCA), Ricinus communis agglutinin I (RCAI), and wheat germ agglutinin (WGA) stained intensively both dermis and viable epidermal cell layers, whereas peanut agglutinin (PNA) bound only to living epidermal cell layers. Ulex europaeus agglutinin I (UEAI) bound to dermal endothelial cells and upper cell layers of the epidermis but left the basal cell layer unstained. Dolichos biflorus agglutinin (DBA) bound only to basal epidermal cells, whereas both soybean agglutinin (SBA) and Helix pomatia agglutinin (HPA) showed strong binding to the spinous and granular cell layers. On routinely processed paraffin sections, a distinctly different staining pattern was seen with many lectins, and to reveal the binding of some lectins a pretreatment with protease was required. All keratin-positive cells in human epidermal cell suspensions, obtained with the suction blister method, bound PNA, whereas only a fraction of the keratinocytes bound either DBA or UEAI. Such a difference in lectin binding pattern was also seen in epidermal cell cultures both immediately after attachment and in organized cell colonies. This suggests that in addition to basal cells, more differentiated epidermal cells from the spinous cell layer are also able to adhere and spread in culture conditions. Gel electrophoretic analysis of the lectin-binding glycoproteins in detergent extracts of metabolically labeled primary keratinocyte cultures revealed that the lectins recognized both distinct and shared glycoproteins. A much different lectin binding pattern was seen in embryonic human skin: fetal epidermis did not show any binding of DBA, whereas UEAI showed diffuse binding to all cell layers but gave a bright staining of dermal endothelial cells. This was in contrast to staining results obtained with a monoclonal cytokeratin antibody, which showed the presence of a distinct basal cell layer in fetal epidermis also. The results indicate that expression of saccharide moieties in human epidermal keratinocytes is related to the stage of cellular differentiation, different cell layers expressing different terminal saccharide moieties. The results also suggest that the emergence of a mature cell surface glycoconjugate pattern in human epidermis is preceded by the acquisition of cell layer-specific, differential keratin expression.     

Lectin-binding patterns on the plasma membranes of dissociated rat liver cells

Carbohydrate moieties on the surface of dissociated rat liver cells were examined electron microscopically using ferritin- or horseradish peroxidase (HRP)-conjugated lectins as probes. Rat liver was fixed by perfusion with 0.7% glutaraldehyde via the portal vein and dissociated into single cells with gentle homogenization. Concanavalin A (Con A), Ricinus communis agglutinin (RCA), and wheat germ agglutinin (WGA) bound almost evenly to the entire cell surface of hepatocytes as well as of endothelial cells. Ulex europaeus agglutinin I (UEA-I) and peanut agglutinin (PNA) revealed no binding to any region. Dolichos biflorus agglutinin (DBA) was found to bind exclusively to the sinusoidal surface of hepatocytes and to endothelial cell surfaces. Soybean agglutinin (SBA)-binding was restricted to the endothelial cell surfaces and part of the sinusoidal microvilli of hepatocytes. Regional differences in lectin-binding pattern were visualized between the sinusoidal and the lateral or bile-canalicular surfaces of the hepatocytes. A polarity may exist on the hepatocyte cell surfaces in terms of the distribution pattern of the carbohydrate moieties, especially those of N-acetylgalactosamine.     

Enhanced glycosylation of a melanoma cell surface glycoprotein by retinoic acid: carbohydrate chain analysis by lectin binding

Retinoic acid (RA) inhibits the growth of mouse S91-C2 melanoma cells and enhances the glycosylation of a cell surface sialoglycoprotein (gp160). The present study analyzed the binding of 125I-labeled lectins to gp160 within polyacrylamide slab gels after electrophoretic separation of cellular macromolecules. Wheat germ agglutinin (WGA) and concanavalin A (Con A) bound to gp160 of RA-treated cells (RA-gp160) more extensively than to gp160 of control cells (C-gp160). Lens culinaris hemagglutinin (LCH), pokeweed mitogen (PWM), Ricinus communis agglutinin I (RCAI), and peanut agglutinin (PNA) failed to bind to either C-gp160 or to RA-gp160. The binding of WGA was greatly diminished after sialic acid removal. In contrast, desialylation made possible the binding of RCAI to RA-gp160. LCH, PWM and PNA did not bind to gp160 even after desialylation. Smith degradation exposed WGA-binding sites on RA-gp 160. These results suggest that gp 160 contains one or more highly branched, sialylated, N-linked complex-type side chains and lacks O-linked oligosaccharides and poly N-acetyllactosamine side chains.