Imaging with Lectin Fluorescent Conjugates

Lectins are carbohydrate binding proteins that are highly specific to oligosaccharides, or sugar groups attached to other molecules. They can cause agglutination of specific cells or precipitation of glycoconjugates. Lectins are involved in regulation of cell adhesion, glycoprotein synthesis, and blood protein levels along with playing a role in the immune system.

Oligosaccharides are found throughout the cell surface but can also be found attached within the cell. Specific oligosaccharides and their distribution can vary among cell type and organelle. Lectins, because of their specificity to their target, can serve to identify cell types or cellular components when used in conjunction with various labeling approaches. Fluorescent derivatives, or conjugated lectins, have been used to localize and detect cell-surface or intracellular glycoconjugates, making them versatile primary detection reagents for microscopy or with flow cytometry. Additionally, cellular differentiation of cancerous cell types are often identified by the makeup of their surface glycoproteins, making lectins useful markers in detecting those distinct cellular phenotypes.

Concanavalin A (Con A), a widely used fluorescent lectin marker in cell biology, selectively binds to α‑mannopyranosyl and α‑glucopyranosyl residues (Figure 1). There are several fluorescent markers of Con A and they are useful for various applications including localization of oncogene products, intracellular enzymes, viral proteins, and cytoskeletal components.

Wheat germ agglutinin (WGA), another widely used fluorescent lectin marker in cell biology, selectively binds to N‑acetylglucosamine and N‑acetylneuraminic acid (sialic acid) residues (Figure 2). Similar to Concanavalin A, WGA is useful for localization of oncogene products, specific intracellular enzymes, viral proteins, and cytoskeletal components.

WGA conjugates can also be used as a lectin marker for bacterial cell wall peptidoglycans, chitin, and cartilage glycosaminoglycans. WGA conjugates have been shown to stain gram-positive but not gram-negative bacteria.

Arachis hypogaea lectin (PNA), isolated from peanuts, specifically binds terminal β-galactose residues of glycoproteins (Figure 3). After neuraminidase treatment, PNA has been shown to bind human erythrocytes. Since PNA-binding sites are widespread in human tissues, the staining patterns will vary by tissue type.

Learn more about fluorescent lectin conjugates