Glycosylation Modifiers and the First Cellular Migrations/Inductions in Early Chick Embryo

Abstract

Glycoproteins are integral components of membranes and of the extra-cellular matrix (ECM) and are involved in several aspects of cellular behaviour such as cellular migration, recognition, adhesion and differentiation (Manasek, 1975; Sanders, 1983;Edelman, 1984,1986,1988; Thiery, 1984; Liotta et al., 1986; West, 1986; Ruoslahti and Pierschbacher, 1987). The oligosaccharide chains of glycoproteins can be classified into oligosaccharides attached to the polypeptide by an O-glycosidic linkage from N-acetylgalactosamine to serine or threonine and oligosaccharides linked-N glycosidically from N-acetylglucosamine to the amide nitrogen of asparagine. There are two types of N-linked glycans referred to as high-mannose and complex type. Biosynthesis of N-linked glycans of the complex type proceeds via a high-mannose intermediate. Oligosaccharides of the complex type are diverse differing mainly in the number of terminal branches and in the pattern of addition of sialic acid and fucose residues. Cellular behaviour may be modulated by variations in glycosylation of glycoproteins and/or glycolipids. The availability of specific inhibitors acting it different stages in the glycosylation process has permitted the synthesis of protein without oligosaccharide moieties or protein with altered oligosaccharide structures (Fuhrmann et al., 1985; Elbein, 1987).