Kevin G. Rice

Receptor Mediated Glycotargeting

Glycotargeting relies on carrier molecules possessing carbohydrates that are recognized and internalized by cell surface mammalian lectins. Numerous types of glycotargeting vehicles have been designed based on the covalent attachment of saccharides to proteins, polymers and other aglycones. These carriers have found their major applications in antiviral therapy, immunoactivation, enzyme replacement therapy and gene therapy. This review compared different types of glycotargeting agents and the lectins which have been successfully targeted to treat both model and human diseases. It may be concluded that the discovery of new mammalian lectins which endocytose their ligands will lead to the rapid development of new glycotargeting agents founded on the principles of carbohydrate-protein interactions.

Experimental determination of oligosaccharide three-dimensional structure

Abstract The three-dimensional structures of oligosaccharides and their complexes with proteins determined by X-ray crystallography, NMR spectroscopy, and optical techniques during the past year are surveyed. The receptor-bound conformation of oligosaccharides often deviates from the lowest energy solution conformation, suggesting a functional role for oligosaccharide flexibility in carbohydrate-protein interactions.

Preparative purification of tyrosinamide N-linked oligosaccharides

N-linked oligosaccharides from glycoproteins can be either analyzed on a sub-nanomole scale or preparatively purified on a multi-micromole scale. Each goal necessitates a unique analytical strategy often involving oligosaccharide derivatization to enhance separation and detection. Tyrosinamide-oligosaccharides were developed to facilitate the preparative purification of N-linked oligosaccharides. These have found many uses in oligosaccharide remodeling, in the preparation of neoglycoconjugates, in developing receptor probes, and even as analytical standards in chromatography. This review discusses progress in the preparation of tyrosinamide-oligosaccharides from different glycoproteins and their utility in glycobiology research.

In Vivo Targeting Function of N-Linked Oligosaccharides

In plants and animals carbohydrate/protein interactions are fundamental to biological function. This form of biomolecular recognition usually involves binding of a carbohydrate ligand to a lectin receptor [1]. One of the well known and thoroughly studied lectin systems in mammals is the asialoglycoprotein receptor (ASGP-R) found on hepatocytes [2–5]. This receptor binds ligands with terminal galactose or N-acetylgalactosamine and routes these to lysosomes before recycling to the cell surface [6]. The natural ligands for the ASGP-R are believed to be serum glycoproteins which lose their terminal sialic acid during circulation exposing clusters of subterminal galactose residues on their N-linked oligosaccharides. Thereby, the ASGP-R is believed to be primarily involved in maintaining the serum concentration of structurally diverse glycoproteins.

S8.13 Pharmacokinetic and biodistribution analysis of N-linked oligosaccharides

Although NK cells and their activated forms represent one of the most important components of cellular immunity, the nature of their cell surface receptors remains controversial. Recently, several members of the evolutionary group V of C-type lectin family (1) emerged as strong candidates for this function (2,3). We have expressed extracellular soluble portions of rat NKR-P1 and human NKG2 proteins in bacterial expression vectors pMALc/p2 and pIN-III-ompA2. Purified proteins containing coiled-coil regions and extracellular carbohydrate-recognition (lectin) domains have been used to probe possible physiological (endogenous) ligands for these molecules. The ability to recognize both carbohydrate and peptide determinants as a part of complex target structure seems to be characteristic for these C-type lectins. Two glycoproteins (Mr 42 and 130 kDa) and several oligosaccharide components of glycoproteins and glycolipids have been identified as possible ligands; L-fucose and acidic sugars seem to constitute determinants important for recognition. Transfection of genetic deletion mutants of NK cell lectin receptors into eukaryotic cell lines in combination with cellular plate adhesion assays and biochemical activation assays have been also employed to assess the role of these molecules during individual stages of NK cell cytolysis. (1) Weis, W. et al. (1993) Cold Spring Harbor Syrup. Quant. Biol., in press (2) Giorda, R. et al. (1990) Science, 249, 12981300 (3) Hofer, E. et al. (1992) Immunol. Today, 13, 429-430