Developmental changes in the oligosaccharide composition of synaptic junctional glycoproteins

Synaptic junctions (SJs) were isolated from the forebrains of rats ranging in postnatal age from 10 days to greater than 1 year. SJ glycoproteins that react with Concanavalin A (Con A) were isolated by chromatography on Con A-agarose and separated by gel electrophoresis. The concentrations of the major SJ Con A binding (Con A+) glycoproteins (apparent Mr 180,000, 130,000, and 110,000) increased between 10 and 28 days, with GP180 and GP110 showing greater relative increases than GP130. Con A binding oligosaccharides associated with 10-day SJs were sensitive to digestion with endoglycosidase C11 and alpha-mannosidase, indicating that they were of the high-mannose type, as previously shown for 28-day SJs. Con A+ oligosaccharides from rats of increasing postnatal age were analyzed by chromatography on Biogel P-4. Two major oligosaccharides, containing five and eight mannose residues, were present in SJs of all ages examined. During development the ratio of man5 to man8 oligosaccharides increased, so that man5 constituted the predominant species in 28-day and adult SJs. Peptide mapping experiments showed that GP180, GP130, and GP110 were each associated with a unique polypeptide composition. Little or no change in peptide composition of the major SJ glycoproteins occurred during development.