Substitutions in the N-glycan core as regulators of biorecognition: the case of core-fucose and bisecting GlcNAc moieties

Biochemistry. 2007 Jun 12;46(23):6984-95. doi: 10.1021/bi7000467. Epub 2007 May 12.

Abstract

Core fucosylation and the bisecting N-acetylglucosamine residue are prominent natural substitutions of the N-glycan core. To address the issue of whether these two substituents can modulate ligand properties of complex-type biantennary N-glycans, we performed chemoenzymatic synthesis of the respective galactosylated and alpha2,3/6-sialylated N-glycans. Neoglycoproteins were then produced to determine these glycans' reactivities with sugar receptors in solid-phase assays and with tumor cells in vitro as well as their in vivo biodistribution profiles in mice. Slight protein-type-dependent changes were noted in lectin binding, including adhesion/growth-regulatory galectins as study objects, when the data were related to properties of N-glycans without or with only one core substituent. Monitoring binding in vitro revealed cell-type-dependent changes. They delimited the ligand activity of this glycan type from that of chains with un- and monosubstituted cores. A markedly prolonged serum half-life was conferred to the neoglycoprotein by the galactose-terminated N-glycan, which together with increased organ retention of all three neoglycoproteins underscores the conspicuous relevance for glycoengineering of pharmaproteins. The predominant presentation of the two branches in the disubstituted N-glycan as extended (alpha1,3-antenna) and backfolded (alpha1,6-antenna) forms, revealed by molecular dynamics simulations, can underlie the measured characteristics. These results obtained by a combined strategy further support the concept of viewing N-glycan core substitutions as non-random additions which exert a modulatory role on ligand properties. Moreover, our data inspire us to devise new, non-natural modifications to realize the full potential of glycoengineering for diagnostic and therapeutic purposes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylglucosamine*
  • Binding Sites
  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • Fucose*
  • Ligands
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • Polysaccharides / chemistry*
  • Sialic Acids*

Substances

  • Ligands
  • Polysaccharides
  • Sialic Acids
  • Fucose
  • Acetylglucosamine