Two-dimensional gel electrophoretic analysis of lectin receptors in the bovine interphotoreceptor matrix

Proteins and glycoproteins of the bovine interphotoreceptor matrix (IPM) with or without neuraminidase treatment was analysed by two-dimensional gel electrophoresis combined with Western blotting and staining with seven horseradish peroxidase-labeled lectins. More than 80 spots of proteins and glycoproteins were revealed on the gel. Nineteen spots (or groups of spots) were revealed by staining with five lectins [concanavalin A, wheat germ agglutinin (WGA), peanut agglutinin (PNA), Ricinus communis agglutinin-1 (RCA-1) and soybean agglutinin (SBA)]; some of those spots were specific for one lectin and others reacted with several lectins. We could not detect distinct spots reacting with Dolichos biflorus agglutinin or Ulex europaeus agglutinin-1. Neuraminidase digestions of the IPM increased and unmasked the binding spots for PNA, RCA-1 and SBA. The spots of WGA-receptors without neuraminidase treatment were mostly identical to the receptors for PNA, RCA-1 and SBA, which became prominent after the digestion. Spots reacting with RCA-1 were mostly identical to the spots of SBA-receptors. The spots reacting with PNA coincided only partially with the spots reacting with RCA-1 and SBA.

Application of lectins for detection of goblet cell carbohydrates of the human conjunctiva

Paraffin-embedded and frozen biopsies from the human conjunctival epithelium were examined by fluorescence microscopy after labeling with eight fluorescein-conjugated lectins: wheat germ agglutinin; soybean agglutinin; peanut agglutinin; Ricinus communis agglutinin-1; Limulus polyphemus agglutinin; Ulex europaeus agglutinin-1; Dolichos biflorus agglutinin; concanavalin A. The lectins were used as specific molecular probes to detect carbohydrate composition of glycoproteins secreted from the conjunctival goblet cells. The labeling pattern of goblet cells and conjunctival epithelial surfaces with various lectins suggested that N-acetyl-glucosamine, galactose, N-acetyl-galactosamine and sialic acid are contained in goblet cells and contribute to the formation of tear mucus glycoprotein. Fucose and mannose, which are present in the tear mucus, were not detectable in goblet cells.

Localization of fluorescence-labeled lectin binding sites on photoreceptor cells of the monkey retina

The binding of eight fluorescence-labeled lectins to the photoreceptors of the monkey retina was investigated using a post-embedding staining method. Concanavalin A (specific for mannosyl and glucosyl residues) bound to the outer and inner segments of both rods and cones, while the degree of staining was more intense in the rods. The rod outer segments showed patchy fluorescence and the proximal portions of the inner segments were diffusely stained. Wheat germ agglutinin (specific for sialyl and N-acetylglucosaminyl residues) bound preferentially to the surface of the outer and inner segments of both rods and cones. Ricinum communis agglutinin-1 (specific for galactosyl residues) stained the rod outer segments in patches, particularly strongly in the region dividing the outer and inner segments. The cones were also stained, although faintly, in the same pattern as the rods. The distal halves of the rods and cones showed diffuse weak staining and their proximal halves stained spotty. Peanut agglutinin (specific for Gal beta 1 leads to 3GalNAc sequence) bound preferentially to the cones and only scarcely to the rods. The external surface of both outer and inner segments of cones were uniformly stained; the interior of the cone outer segments was also stained, while the interior of the inner segments was not. Two lectins specific for fucosyl residues, namely, Ulexeuropaeus agglutinin-1 and Lotustetragonolobus agglutinin, bound diffusely to the distal halves of the inner segments of both rods and cones. Lectins reacting with N-acetyl-galactosamine residue, i.e. Dolichos biflorus agglutinin and soybean agglutinin, bound weakly to the distal portions of rods and cones.