Wheat germ agglutinin binds to the epidermal growth factor receptor of artificial Caco-2 membranes as detected by silver nanoparticle enhanced fluorescence.

Abstract

The purpose of this study was to identify one of the ligands that mediate carbohydrate-specific cytoadhesion and cytoinvasion of wheat germ agglutinin (WGA)-containing drug delivery systems. The receptor-ligand studies were performed with isolated epidermal growth factor (EGF) receptors as well as biomimetic membranes prepared from Caco-2 and A-431 cells. The binding of fluorescent labeled WGA was detected by the silver nanoparticle enhanced fluorescence technique. The binding of WGA to isolated EGF receptors is saturable and the equilibrium is reached within 1 min. The interaction between WGA and isolated EGF receptors is fully inhibited by the complementary carbohydrate and at least 85% of WGA binding to artificial Caco-2 membranes is caused by protein-carbohydrate interactions involving the tetrasialo-binding motif. The integrity and the presence of EGF-receptors in artificial Caco-2 membranes as well as their WGA-binding capacity were confirmed by immunoblot detection. The glycosylated extracellular domain III of the EGF receptor is involved in the WGA-Caco-2 cell interaction. Accordingly, receptor mediated endocytosis is the basic mechanism for internalization of WGA. As the EGF receptor is overexpressed in a high number of tumors but also occurs in non-malignant tissue at considerable density, WGA-mediated drug delivery opens exciting possibilities for specific binding and uptake of poorly absorbable drugs.