Probing the Binding Specificity of C-Type Lectins in Vivo

Abstract

An approach has been developed to use N -glycans to probe the specificity of animal lectins in vivo . Tyrosinamide- N -glycans seem well suited because of their ease of separation and radioiodination. Analysis of ASGP-R ligands established a strong correlation between in vitro -binding affinity and in vivo -targeting efficiency to the liver. Pharmacokinetic analysis also provides clues as to the binding specificity of N -glycans for lectins. Using this approach, a biantennary ligand possessing terminal sialyl Lewis x was discovered as a putative ligand for E-selectin. These studies represent the first of a series aimed at analyzing the biodistribution of N -glycans in the hope of discovering new mammalian lectins. With careful deduction, it is possible to decipher the specificity of mammalian lectins in their native environment. This chapter describes the design and utilization of tyrosinamide- N -glycans as radioiodinated ligand probes to study lectins in mice. The binding specificity of lectins is studied in their native state and in the presence of physiological concentrations of competing ligands. The experimental results allow estimation of the affinity and capacity of endogenous lectins and are thereby directly applicable to the design of targeted -drug delivery systems.