Abstract
The glycoproteins responsible for calcium-dependent oligodendrocyte aggregation were purified and characterized. Using detergent extraction, lentil-lectin-Sepharose 4B affinity chromatography, and preparative gel electrophoresis, 3 proteins were purified to apparent homogeneity, with relative Mrs of 120,000, 140,000, and 180,000. The aggregation assay showed that all 3 proteins had the ability to block antibody-mediated inhibition of oligodendrocyte aggregation. The 120,000 protein was the most active of the three. Antisera were raised in rabbits to these 3 individual proteins. Western blot analyses showed that all three antisera recognized 120,000, 140,000, and 180,000 proteins, which indicated that the proteins were related. Western-blot analyses of cultured oligodendrocytes and purified rat myelin showed only the 120,000 protein. Immunoprecipitation of iodinated membrane proteins of cultured oligodendrocytes also indicated the presence of only the 120,000 Mr protein. Deglycosylation of the 120,000 protein by N-glycanase resulted in a 110,000 protein. The immunoblot pattern suggested some similarities between oligodendrocyte adhesion molecules and the neural cell adhesion molecule (N-CAM). Therefore, the 120,000, 140,000, and 180,000 Mr proteins were compared to N-CAM by Western-blot analysis, immunofluorescence staining, and by immunoprecipitation. The results suggest that oligodendrocytes contain a 120,000 membrane glycoprotein that is related to N-CAM.