Localization of the binding sites for the Ricinus communis, Agaricus bisporus and wheat germ lectins on human erythrocyte membranes.

Freeze-etch electron microscopy has been utilized to localize the binding sites for the Ricinus communis, Agaricus bisporus and wheat germ lectins on human erythrocyte membranes and to determine the relation of these different glycoprotein receptors to the intramembranous particles. A. bisporus lectin, which could be visualized directly on the surface of erythrocyte membranes, and ferritin conjugates of wheat germ agglutinin showed a distribution that correlates exactly with the intramembranous particles at all lectin concentrations tested. The binding sites for both of these lectins are located on the major sialoglycoprotein of the membrane. The R. communis agglutinin-ferritin conjugate which binds to receptors on membrane glycoproteins that are distinct from the major sialoglycoprotein showed a close correlation with the intramembranous particles at low lectin concentrations and a poor correlation at high lectin concentrations. High concentrations resulted in virtually complete coating of the surface of trypsinized ghosts which displayed marked aggregation of the intramembranous particles. We conclude that the intramembranous particles of erythrocyte membranes contain at least two glycoproteins and that some membrane lectin receptors are not associated with the intramembranous particles.     

Lectin labeling of sprouting neurons. I. Regional distribution of surface glycoconjugates

Well-defined ferritin-conjugated lectins were used to map glycoconjugates on the surface of sprouting neurons from rat superior cervical ganglion (SCG) and spinal cord (SC). The cultured neurons were exposed to the markers and processed for electron microscopy, and the number of ferritin particles per unit area of plasmalemma was measured in three different regions: perikaryon, neuritic shaft, and growth cone. Three different binding patterns are observed for different lectin: equal receptor density throughout the plasmalemma of the growing neuron (e.g., Ricinus communis agglutinin I in SCG neurons), gradual decrease (e.g., wheat-germ agglutinin in SCG and SC neurons) and gradual increase (e.g., Ricinus communis agglutinin II in SC neurons) in the density of lectin receptors as one moves from the perikaryon to the growth cone. Furthermore, lectin receptor densities differ in the two types of neurons analyzed. We can conclude that the plasmalemma of the growth cone has biochemical properties different from those of the perikaryon, and that the neuron's structural polarity is expressed in its surface glycoconjugates. This phenomenon may be related to the growth cone's special functional properties and to the process of expansion of the plasma membrane.     

Regulated plasmalemmal expansion in nerve growth cones

To study the mechanisms underlying plasmalemmal expansion in the nerve growth cone, a cell-free assay was developed to quantify membrane addition, using ligand binding and sealed growth cone particles isolated by subcellular fractionation from fetal rat brain. Exposed versus total binding sites of 125I-wheat germ agglutinin were measured in the absence or presence of saponin, respectively, after incubation with various agents. Ca2(+)-ionophore A23187 in the presence of Ca2+ increases the number of binding sites (Bmax) but does not change their affinity (KD), indicating that new receptors appear on the plasma membrane. Similarly, membrane depolarization by high K+ or veratridine significantly induces, in a Ca2(+)-dependent manner, the externalization of lectin binding sites from an internal pool. Morphometric analysis of isolated growth cones indicates that A23187 and high K+ treatment cause a significant reduction in a specific cytoplasmic membrane compartment, thus confirming the lectin labeling results and identifying the plasmalemmal precursor. The isolated growth cones take up gamma-amino-butyric acid and serotonin, but show no evidence for Ca2(+)-dependent transmitter release so that transmitter exocytosis is dissociated from plasmalemmal expansion. The data demonstrate that plasmalemmal expansion in the growth cone is a regulated process and identify an internal pool of precursor membrane.     

Localization of the binding sites for the Ricinus communis, Agaricus bisporus and wheat germ lectins on human erythrocyte membranes

Freeze-etch electron microscopy has been utilized to localize the binding sites for the Ricinus communis, Agaricus bisporus and wheat germ lectins on human erythrocyte membranes and to determine the relation of these different glycoprotein receptors to the intramembranous particles. A. bisporus lectin, which could be visualized directly on the surface of erythrocyte membranes, and ferritin conjugates of wheat germ agglutinin showed a distribution that correlates exactly with the intramembranous particles at all lectin concentrations tested. The binding sites for both of these lectins are located on the major sialoglycoprotein of the membrane. The R. communis agglutinin-ferritin conjugate which binds to receptors on membrane glycoproteins that are distinct from the major sialoglycoprotein showed a close correlation with the intramembranous particles at low lectin concentrations and a poor correlation at high lectin concentrations. High concentrations resulted in virtually complete coating of the surface of trypsinized ghosts which displayed marked aggregation of the intramembranous particles. We conclude that the intramembranous particles of erythrocyte membranes contain at least two glycoproteins and that some membrane lectin receptors are not associated with the intramembranous particles.     

Distribution of ferritin-conjugated lectins on sialidase-treated membranes of human erythrocytes.

The labeling of sialidase-treated, human erythrocyte membranes with ferritin-conjugates of four plant lectins, concanavalin A, Ricinus communis hemagglutinin, Bauhinia purpurea hemagglutinin and Arachis hypogoea hemagglutinin, is reported. Among these ferritin-conjugated lectins, ferritin-conjugated concanavalin A and ferritin-conjugated R. communis hemagglutinin were found in clusters on the sialidase-treated membranes, whereas ferritin-conjugated B. purpurea hemagglutinin and ferritin-conjugated A. hypogoea hemagglutinin were found in a random distribution on the membranes. Furthermore, when the membranes were labeled with a mixutre of concanavalin A and ferritin-conjugated B. purpurea hemagglutinin, ferritin particles were found in clusters, indicating that the membrane receptors for B. purpurea hemagglutinin were forced to more together with those for concanavalin A. A method for the quantitative estimation of the clustering of ferritin particles on the membranes was also devised and applied to the labeling of sialidase-treated, human erythrocyte membranes with the above four ferritin-conjugated lectins.     

Differentiated microdomains on the luminal surface of capillary endothelium: distribution of lectin receptors

Lectins conjugated with either peroxidase or ferritin were used to detect specific monosaccharide residues on the luminal front of he fenestrated endothelium in the capillaries of murine pancreas and intestinal mucosa. The lectins tested recognize, if accessible, the following residues: alpha-N-acetylgalactosaminyl (soybean lectin), beta- D-galactosyl (peanut agglutinin [PA] and Ricinus communis agglutinin- 120 [RCA]), beta-N-acetylglucosaminyl and sialyl residues (wheat germ agglutinin [WGA]), alpha-L-fucosyl (lotus tetragonolobus lectin), and alpha-D-glucosyl and beta-D-mannosyl (concanavalin A [ConA]). Thi labeled lectins were introduced by perfusion in situ after thoroughly flushing with phosphate-buffered saline the microvascular beds under investigation. Specimens were fixed by perfusion, and subsequently processed for peroxidase detection and electron microscopy. Control experiments included perfusion with: (a) unlabeled lectin before lectin conjugate; (b) labeled lectin together with the cognate hapten sugar, and (c) horseradish peroxidase or ferritin alone. Binding sites were found to be relatively homogeneously distributed on the plasmalemma proper, except for Lotus tetragonolobus lectin and Con A, which frequently bound in patches. Plasmalemmal vesicles, transendothelial channels, and their associated diaphragms were particularly rich in residues recognized by RCA and PA (beta-D-galactosyl residues) and by WGA (beta-N-acetylglucosaminyl residues). Receptors for all lectins tested appeared to be absent or considerably less concentrated on fenestral diaphragms. The results reported here extend and complement previous findings on the existence of microdomains generated by the preferential distribution of chemically different anionic sites (Simionescu et al., 1981, J. Cell Biol., 9:605-613 and 614-621).     

A method for the fine-structural demonstration of lectin receptors

A new two-step method using an Fc-fragment/ferritin conjugate as a marker for the visualization of lectin-binding sites on neuronal and other cell membranes is described. In this study of rat synaptosomes, three lectins were tested: concanavalin A, mistletoe lectin I and wheat germ agglutinin. The specificity of the method was proved by control experiments.     

Lectin-binding sites on the plasma membranes of rabbit spermatozoa: Changes in surface receptors during epididymal maturation and after ejaculation

Modifications in rabbit sperm plasma membranes during epididymal passage and after ejaculation were investigated by used of three lectins: concanavalin A (Con A); Ricinus communis I (RCA(I)); and wheat germ agglutinin (WGA). During sperm passage from caput to cauda epididymis, agglutination by WGA drastically decreased, and agglutination by RCA(I) slightly decreased, although agglutination by Con A remained approximately unchanged. After ejaculation, spermatozoa were agglutinated to a similar degree or slightly less by Con A, WGA, and RCA(I), compared to cauda epididymal spermatozoa. Ultrastructural examination of sperm lectin-binding sites with ferritin- lectin conjugates revealed differences in the densities of lectin receptors in various sperm regions, and changes in the same regions during epididymal passage and after ejaculation. Ferritin-RCA(I) showed abrupt changes in lectin site densities between acrosomal and postacrosomal regions of sperm heads. The relative amounts of ferritin-RCA(I) bound to heads of caput epididymal or ejaculated spermatozoa. Tail regions were labeled by ferritin RCA(I) almost equally on caput and cauda epididymal spermatozoa, but the middle-piece region of ejaculated spermatozoa was slightly more densely labeled than the principal-piece region, and these two regions on ejaculated spermatozoa were labeled less than on caput and cuada epididymal spermatozoa. Ferritin-WGA densely labeled the acrosomal region of caput epididymal spermatozoa, although labeling of cauda epidiymal spermatozoa was relatively sparse except in the apical area of the acrosomal region. Ejaculated spermatozoa bound only a few molecules of ferritin-WGA, even at the highest conjugate concentrations used. Caput epididymal, but not cauda epididymal or ejaculated spermatozoa, bound ferritin-WGA in the tail regions. Dramatic differences in labeling densities during epididymal passage and after ejaculation were not found with ferritin-Con A.     

Distribution of ferritin-conjugated lectins on sialidase-treated membranes of human erythrocytes

The labeling of sialidase-treated, human erythrocyte membranes with ferritin-conjugates of four plant lectinss, concanavalin A, Ricinus communis hemagglutinin, Bauhinia purpurea hemagglutinin and Arachis hypogoea hemagglutinin, is reported. Among these ferritin-conjugated lectins, ferritin-conjugated concanavalin A and ferritin-conjugated R. communis hemagglutinin were found in clusters on the sialidase-treated membranes, whereas ferritin-conjugated B. pupurea hemagglutinin and ferritin-conjugated A. hypogoea hemagglutinin were found in a random distribution on the membranes. Furthermore, when the membranes were labeled with a mixture of concanavalin A and ferritin-conjugated B. purpurea hemagglutinin, ferritin particles were found in clusters, indicating that the membrane receptors for B. purpurea hemagglutinin were forced to move together with those for concanavalin A. A method for thentitative estimation of the clustering of ferritin particles on the membranes was also devised and applied to the labeling of sialidase-treated, human erythrocyte membranes with the above four ferritin-conjugated lectins.     

Ultrastructural localization of lectin receptors on the surface of the rat retinal pigment epithelium. Decreased sensitivity of the avidin-biotin method due to cell surface charge

Monosaccharides on the apical processes of the retinal pigment epithelium were examined using lectin-affinity cytochemical methods. Lectin receptor sugars were localized with lectin-horseradish peroxidase (HRP) and lectin-ferritin conjugates as well as with biotinylated lectins, avidin, and biotinylated HRP. In contrast, only wheat germ agglutinin (WGA) receptors were identified with biotinylated WGA followed by avidin-ferritin or free avidin and biotinylated ferritin. Labeling with avidin-ferritin subsequent to biotinylated lectin treatment was dependent upon the source and lot of the reagent. These findings are similar to those reported for the endothelium of bone marrow sinusoids (Pino RM: Am J Anat, 169:259, 1984). Since both the retinal pigment epithelial and bone marrow sinusoidal surfaces are highly anionic (negative), we investigated the possibility that the charge of the lectin reagents and cell surfaces might affect the localization of monosaccharides on cell surfaces. Analytical isoelectric focusing revealed that biotinylated ferritin and some avidin-ferritins are highly anionic, while the other lectin reagents have more cationic (positive) components. Based on this information, a less charged biotinylated ferritin marker was made that made it possible to localize biotinylated lectins bound to the cell surface.     

Binding of purified lectins to guinea pig lymphocytes. Studies of the number, binding constant, and distribution of lens culinaris lectin A and Agaricus bisporus lectin molecules on lymphocyte surfaces

The surface membrane of guinea pig lymphocytes contains discrete receptors for several different homogeneous lectins. Two very similar lectins from the lentil, LcL-A and LcL-B, bind to the same receptor. Three other lectins, AbL, WGA, and Con A, do not bind detectably to the LcL receptor. AbL binds to another discrete receptor to which none of the other lectin molecules bind. The LcL and AbL receptors are contained on different units, each of which is capable of independent movement on the cell surface. The normal distribution of LcL molecules on the surface is different than the distribution of AbL molecules. However, when lymphocytes are simultaneously incubated with LcL and AbL, the distribution of bound LcL molecules on the cell surface parallels the normal distribution of AbL molecules, which indicates that the movement of AbL molecules and AbL receptors on the surface can strongly influence the movement of LcL and LcL receptors. When lymphocytes are held in close contact by LcL or AbL, the lectin molecules and receptors appear to concentrate at the area of contact between two cells. A model is presented which suggests that the migration of lectins and lectin receptors can occur by a multicellular process.     

A novel approach to the identification of surface receptors. The use of photosensitive hetero-bifunctional cross-linking reagent.

Methyl 4-azidobenzoimidate, a photosensitive hetero-bifunctional cross-linking reagent, was synthesized and characterized. This reagent has an imidoester at one end, which reacts spontaneously with primary amines, and an arylazide at the other end, which reacts with a variety of chemical groups upon photolysis by ultraviolet radiation. The reagent molecules were attached to concanavalin A by reactions between imidoester groups of the reagents and free amino groups of the lectin. These activated lectins were purified on a Sephadex G-25 column and showed the binding affinity to an affinity column, glucosylated Sepharose, and to the human erythrocyte ghost membrane. The activated lectins were incubated with the membranes and then unbound lectins were removed by washing. The lectins bound to receptors in the membranes were irradiated with a shortwave ultraviolet lamp to photolyze arylazides attached to the lectins, thus cross-linking the lectins and receptors together. Then the membranes were solubilized and electrophoresed. On gels, the intensity of the lectin receptor band diminished slightly and concomitantly a new band of a higher molecular weight appeared. When 125I-labeled concanavalin A was used, the new band contained the radioactivity. The extent of the appearance of the new band and the decrease of the receptor band were reduced significantly when the ultraviolet irradiation was omitted or the activated lectins were incubated with the membranes in the presence of the lectin inhibitor, alpha-methylmannoside. The irradiation of nonactivated, receptor-bound concanavalin A did not cause those changes. When the activated lectins alone were irradiated with ultraviolet, the band of the lectin dimer appeared whereas nonirradiated lectins appeared mostly as monomers. It is concluded that a small fraction of the activated lectins were cross-linked to receptors in the membrane upon photolysis. In this study, only 8 reagent molecules were attached to a tetramer of the lectin, compared with the presence of approximately 40 available free amino groups. The efficiency of such cross-links of ligands to receptors may be increased by employing longer versions of the hetero-bifunctional cross-linking reagents and also by attaching more of the reagent molecule to ligands.     

Interactions of lectins with plasma membrane glycoproteins of the Ehrlich ascites carcinoma cell.

Several aspects of the interaction of various lectins with the surface of Ehrlich ascites carcinoma cells are described. The order of agglutinating activity for various lectins is Ricinus communis greater than wheat germ greater than or equal to concanavalin A greater than or equal to soybean greater than Limulus polyphemus. No agglutination was noted for Ulex europaeus. Using 125I-labeled lectins it was determined that there are 1.6 and 7 times as many Ricinus communis lectin binding sites for concanavalin A and soybean lectins. Sodium deoxycholate-solubilized plasma membrane material was subjected to lectin affinity chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The lectin receptors of the plasma membrane appeared to be heterogeneous and some qualitative differences could be discerned among the electrophoretically analyzed material, which bound to and was specifically eluted from the various lectin affinity columns. The characteristics of elution of bound material from individual lectin columns indicated secondary hydrophobic interactions between concanavalin A or wheat germ agglutinin and their respective lectin receptor molecules.     

Surface changes at fertilization: integration of sea urchin (Arbacia punctulata) sperm and oocyte plasma membranes

To examine the integration and fate of the sperm plasma membrane following its incorporation into the oocyte plasma membrane, we have fertilized sea urchin (Arbacia punctulata) gametes reciprocally labeled with cationized ferritin. When unlabeled oocytes were inseminated with labeled sperm, cationized ferritin acceptors moved laterally from the sperm plasma membrane into the fertilization cone and surrounding microvilli, mixing with components of the oocyte plasmalemma. Labeled oocytes inseminated with unlabeled sperm produced extremely large fertilization cones, completely devoid of cationized ferritin, while the remainder of the oocyte surface remained heavily labeled. Surface area measurements indicated that if all the sperm plasmalemma were utilized to delimit a fertilization cone it would provide less than 10% of the total surface membrane. Evidence is presented indicating that a principal source of membrane to the expanding fertilization cone of inseminated oocytes is from microvilli, i.e., microvilli are retracted to accommodate fertilization cone formation. Membrane delimiting the fertilization cone has a much lower affinity for agents (cationized ferritin and concanavalin A) that stain negatively charged and carbohydrate moieties compared to other regions of the oocyte surface. These ultrastructural observations indicate that significant rearrangements occur in the oocyte and sperm plasma membranes following gamete fusion which give rise to asymmetries in membrane topography; components of both membranes are redistributed within the bilayer adjacent to and delimiting the fertilization cone.     

Distribution of cell surface saccharides on pancreatic cells. II. Lectin-labeling patterns on mature guinea pig and rat pancreatic cells

The surface saccharide composition of collagenase-dispersed pancreatic cells from adult guinea pig and rat glands was examined by using eight lectins and their ferritin conjugates: Concanavalin A (ConA); Lens culinaris (LCL); Lotus tetragonolobus (LTL); Ricinus communis agglutinins I and II (RCA I, RCA II); Soybean agglutinin (SBA); Ulex europeus lectin (UEL); and wheat germ agglutinin (WGA). Binding studies of iodinated lectins and lectin-ferritin conjugates both revealed one population of saturable, high-affinity receptor sites on the total cell population (approximately 95% acinar cells). Electron microscopy, however, revealed differences in lectin-ferritin binding to the plasmalemma of acinar, centroacinar, and endocrine cells. Whereas acinar cells bound heavily all lectin conjugates, endocrine and centroacinar cells were densely labeled only by ConA, LCL, WGA, and RCA I, and possessed few receptors for LTL, UEL, and SBA. Endocrine and centroacinar cells could be differentiated from each other by using RCA II, which binds to centroacinar cells but not to endocrine cells. Some RCA II receptors appeared to be glycolipids because they were extracted by ethanol and chloroform-methanol in contrast to WGA receptors which resisted solvent treatment but were partly removed by papain digestion. RCA I receptors were affected by neither treatment. The apparent absence of receptors for SBA on endocrine and centroacinar cells, and for RCA II on endocrine cells, was reversed by neuraminidase digestion, which suggested masking of lectin receptors by sialic acid. The absence of LTL and UEL receptors on endocrine and centroacinar cells was not reversed by neuraminidase. We suggest that the differential lectin-binding patterns observed on acinar, centroacinar, and endocrine cells from the adult pancreas surface-carbohydrate-developmental programs expressed during morphogenesis and cytodifferentiation of the gland.     

Direct visualization of the binding and internalization of a ferritin conjugate of epidermal growth factor in human carcinoma cells A-431

We have prepared a conjugate of epidermal growth factor (EGF) and ferritin that retains substantial binding affinity for cell receptors and is biologically active. Glutaraldehyde-activated EGF was covalently linked to ferritin to produce a conjugate that contained EGF and ferritin in a 1:1 molar ratio. The conjugate was separated from free ferritin by affinity chromatography using antibodies to EGF. Monolayers of human epithelioid carcinoma cells (A-431) were incubated with EGF:ferritin at 4 degrees C and processed for transmission electron microscopy. Under these conditions, approximately 6 X 10(5) molecules of EGF:ferritin bound to the plasma membrane of each cell. In the presence of excess native EGF, the number of bound ferritin particles was reduced by 99%, indicating that EGF:ferritin binds specifically to cellular EGF receptors. At 37 degrees C, cell-bound EGF:ferritin rapidly redistributed in the plane of the plasma membrane to form small groups that were subsequently internalized into pinocytic vesicles. By 2.5 min at 37 degrees C, 32% of the cell-bound EGF:ferritin was localized in vesicles. After 2.5 min, there was a decrease in the proportion of conjugate in vesicles with a concomitant accumulation of EGF:ferritin in multivesicular bodies. By 30 min, 84% of the conjugate was located in structures morphologically identified as multivesicular bodies or lysosomes. These results are consistent with other morphological and biochemical studies utilizing 125I-EGF and fluorescein-conjugated EGF.     

Quantum-dye labeled proteins for glycobiology: a viable nonradioactive alternative tracer

Quantum dye (QD), a macrocyclic europium-chelate, developed as a cytological marker, has never been used for quantitative applications. It would be ideal, however, if the same tracer can be used for both qualitative and quantitative purposes. We have labeled some lectins and neoglycoproteins with QD for the purpose of quantitative analyses in glycobiology, and tested its suitability in three different areas in glycobiology: (1) glycosyltransferase, (2) an animal lectin - mannose- binding protein, and (3) the Gal/GalNAc receptor of rat liver membrane. Usefulness of QD-labeled lectins was amply demonstrated by the quantification of galactosyltransferase activity using QD-soybean agglutinin and QD-RCA120 ( Ricinus communis agglutinin). We also showed that QD-labeled neoglycoproteins, QD-Man-BSA and QD-Gal-BSA, can replace radioiodinated counterparts in the binding assays of animal lectins (serum mannose binding protein and hepatic Gal/GalNAc receptor.) The advantage of QD and other europium labels is that it does not decay as radioiodides do. The long shelf-life results in more consistent results from repeated experiments.      

Plasminogen activator: Morphological evidence of binding, internalization and delivery to lysosomes in 3T3 mouse fibroblasts

Summary Using a direct conjugate of urokinase and ferritin, the binding has been followed at the plasma membrane and the internalization of urokinase into BALB/C-3T3 fibroblasts, cultured in plasminogen-free conditions. At 0° C, the conjugate was observed bound on both coated and uncoated cell surface regions as singlets, and small and large clusters. No binding was observed in the presence of excess native urokinase. The binding was impaired by preincubation of the conjugate with a competitive inhibitor of the catalytic site, suggesting an interaction between the receptor and the catalytic site of the enzyme.Within 1 min at 37° C, urokinase clustered on coated regions of the plasma membrane. At 5 min after warming, ferritin was found on deeply indented coated pits and in both coated and uncoated vesicles close to the cell surface. By 10 min at 37° C, ferritin particles were present in uncoated endosomes and in multivesicular bodies in the Golgi area. Within 10 min, the receptors on the surface strongly decreased. New receptors were observed on the membrane after 20 min at 37° C. At this time, ferritin was observed both in endosomes or multivesicular bodies and in vesicles close to the plasma membrane.     

Differential effects of protease digestion on photoreceptor lectin binding sites

The use of lectin cytochemistry together with proteolytic digestion techniques to partially characterize lectin binding sites of several intracellular compartments in frog photoreceptors was studied. Uniform access of reagents to all intracellular compartments was obtained by performing the experiments directly on semithin sections of retinal tissue embedded in a hydrophilic plastic resin. Protease pretreatment of sections of Xenopus laevis eyecup leads to a loss of wheat germ agglutinin (WGA) binding sites from most of the rod outer segment. Under experimental conditions used here, cone outer segment WGA binding sites are resistant to proteolytic digestion. Another major difference between rod and cone under segments is that rod outer segments are heavily labeled with succinylated WGA, whereas cone outer segments are barely labeled except for a region of intense staining thought to be at the connecting cilium. WGA binding sites in the shed outer segment tip (phagosome) are also relatively resistant to proteolytic digestion, as is the tip region of a few rod outer segments. This difference in lectin binding properties between the bulk of the outer segment membrane and the shed outer segment membrane is the only distinction we have observed between the two compartments in terms of their glycoconjugates. These results may be useful in terms of designing experiments to isolate cone and rod outer segments separately. They indicate that a change in outer segment glycoconjugates may accompany the shedding and phagocytosis events, as previously suggested, but this change does not necessarily involve the addition of saccharides to outer segment glycoproteins.     

Lectins implicate specific carbohydrate domains in electric field stimulated nerve growth and guidance

Both endogenous lectins and DC electric fields may control aspects of early nerve growth and nerve guidance. To test whether such endogenous cues interact, lectins of varying sugar affinity and valency were studied for effects on electric field induced growth and reorientation of cultured Xenopus neurites. Concanavalin A (Con A), succinylated concanavalin A (S-Con A), and wheat germ agglutinin all completely inhibited field-induced cathodal reorientation. Lentil and pea lectins, which share the same sugar affinity as Con A/S-Con A, were only partially effective in inhibiting reorientation. Because S-Con A does not alter lateral mobility of membrane receptors, the previously accepted notion that Con A inhibited field-induced reorientation by preventing receptors from translocating and becoming redistributed asymmetrically in the membrane may be oversimplified. There are likely to be additional steric interactions that Con A and S-Con A share that inactive asymmetrically redistributed receptors and prevent reorientation. Additionally, nerves growing in an applied field branch more commonly toward the cathode. Con A and S-Con A alone prevented this development of asymmetric branching. All the lectins tested prevented the normal field-induced increase in nerve growth rate, while all, except peanut agglutinin, prevented the usual faster growth cathodally than anodally. We suggest that lectin interactions with electric field effects in vitro may involve modulation of neuronal nicotinic acetylcholine receptors, neurotrophin receptors, or voltage-dependent calcium channels. Similar interactions between endogenous lectins and endogenous electric fields are to be expected. © 1996 John Wiley & Sons, Inc.