Lactose-containing starburst dendrimers: influence of dendrimer generation and binding-site orientation of receptors (plant/animal lectins and immunoglobulins) on binding properties.
Starburst glycodendrimers offer the potential to serve as high-affinity ligands for clinically relevant sugar receptors. In order to define areas of application, their binding behavior towards sugar receptors with differential binding-site orientation but identical monosaccharide specificity must be evaluated. Using poly(amidoamine) starburst dendrimers of five generations, which contain the p-isothiocyanato derivative of p-aminophenyl-beta-D-lactoside as ligand group, four different types of galactoside-binding proteins were chosen for this purpose, i.e., the (AB)(2)-toxic agglutinin from mistletoe, a human immunoglobulin G fraction, the homodimeric galectin-1 with its two binding sites at opposite ends of the jelly-roll-motif-harboring protein and monomeric galectin-3. Direct solid-phase assays with surface-immobilized glycodendrimers resulted in obvious affinity enhancements by progressive core branching for the plant agglutinin and less pronounced for the antibody and galectin-1. High density of binding of galectin-3 with modest affinity increases only from the level of the 32-mer onwards points to favorable protein-protein interactions of the monomeric lectin and a spherical display of the end groups without a major share of backfolding. When the inhibitory potency of these probes was evaluated as competitor of receptor binding to an immobilized neoglycoprotein or to asialofetuin, a marked selectivity was detected. The 32- and 64-mers were second to none as inhibitors for the plant agglutinin against both ligand-exposing matrices and for galectin-1 on the matrix with a heterogeneous array of interglycoside distances even on the per-sugar basis. In contrast, a neoglycoprotein with the same end group was superior in the case of the antibody and, less pronounced, monomeric galectin-3. Intimate details of topological binding-site presentation and the ligand display on different generations of core assembly are major operative factors which determine the potential of dendrimers for applications as lectin-targeting device, as attested by these observations.
André
S
S
Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstrasse 13, D-80539 Munich, Germany.
Ortega
P J
PJ
Perez
M A
MA
Roy
R
R
Gabius
H J
HJ
D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D001665:Binding Sites; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002417:Cattle; D037502:Galectin 3; D006001:Glycoconjugates / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006027:Glycosides / Q000378:metabolism; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D007785:Lactose / Q000737:chemistry*; D037102:Lectins / Q000378:metabolism*; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D028321:Plant Preparations; D010940:Plant Proteins; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism*; D054790:Ribosome Inactivating Proteins, Type 2; D013816:Thermodynamics; D014118:Toxins, Biological / Q000378:metabolism
D000943:Antigens, Differentiation; D037502:Galectin 3; D006001:Glycoconjugates; D006027:Glycosides; D007074:Immunoglobulin G; D037102:Lectins; D008024:Ligands; D028321:Plant Preparations; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C009674:ribosome inactivating protein, Viscum; C029976:4-aminophenyl beta-lactoside; D007785:Lactose