ABSTRACT
The tetrasaccharide 1, a substructure of ganglioside GQ1b alpha, shows a remarkable affinity for the myelin-associated glycoprotein (MAG) and was therefore selected as starting point for a lead optimization program. In our search for structurally simplified and pharmacokinetically improved mimics of 1, modifications of the core disaccharide, the alpha(2-->3)- and the alpha(2-->6)-linked sialic acid were synthesized. Biphenylmethyl and (S)-lactate were identified as suitable replacements for the alpha(2-->6)-linked sialic acid. Combined with a core modification and the earlier found aryl amide substituent in the 9-position of the alpha(2-->3)-linked sialic acid, high affinity MAG antagonists were identified. All mimics were tested in a competitive target-based binding assay, providing relative inhibitory potencies (rIP). Compared to the reference tetrasaccharide 1, the rIPs of the most potent antagonists 59 and 60 are enhanced nearly 400-fold. Their K(D)s determined in surface plasmon resonance experiments are in the low micromolar range. These results are in semiquantitative agreement with molecular modeling studies. This new class of glycomimetics will allow to validate the role of MAG in the axon regeneration process.
Subject(s)
Gangliosides/metabolism , Myelin-Associated Glycoprotein/metabolism , N-Acetylneuraminic Acid/metabolism , Animals , Axons/physiology , CHO Cells , Cricetinae , Cricetulus , Molecular Mimicry , Myelin-Associated Glycoprotein/antagonists & inhibitors , Nerve Regeneration , Protein BindingSubject(s)
Gangliosides/chemistry , Myelin-Associated Glycoprotein/chemistry , Binding Sites , Carbohydrate Conformation , Epitopes/metabolism , Gangliosides/pharmacology , Myelin-Associated Glycoprotein/antagonists & inhibitors , Myelin-Associated Glycoprotein/metabolism , Nuclear Magnetic Resonance, BiomolecularSubject(s)
Epitopes/chemistry , Gangliosides/chemistry , Lectins/chemistry , Myelin-Associated Glycoprotein/antagonists & inhibitors , Myelin-Associated Glycoprotein/chemistry , Carbohydrate Conformation , Computer Simulation , E-Selectin/chemistry , E-Selectin/pharmacology , Epitopes/metabolism , Gangliosides/pharmacology , Myelin-Associated Glycoprotein/metabolism , Nuclear Magnetic Resonance, Biomolecular , Sialic Acid Binding Immunoglobulin-like Lectins , Stereoisomerism , Structure-Activity RelationshipABSTRACT
The trisaccharide substructure 13 of the ganglioside GQ1balpha shows a remarkable affinity for the myelin-associated glycoprotein (MAG). In the search for structurally simplified and pharmacokinetically improved mimics of 13, sialosides with modifications at the reducing and non-reducing end were synthesized. The biological evaluation of mimics 12a-o was performed in a competitive target-based assay. It was found that the relative inhibitory potency (rIP) of antagonist 12h was enhanced by more than 1000-fold in comparison to the reference trisaccharide 13, despite the former having a much simpler structure. In addition, the sialic acid derivatives, for example, 12h, have clearly improved pharmacokinetic properties due to the presence of aromatic moieties, a lower molecular weight, and a reduced number of polar hydroxy functions compared to the reference compound 13.
