CARBOHYDRATE MOIETIES OF MYELIN-ASSOCIATED GLYCOPROTEIN, MAJOR GLYCOPROTEIN OF THE PERIPHERAL NERVOUS-SYSTEM MYELIN AND OTHER MYELIN GLYCOPROTEINS POTENTIALLY INVOLVED IN CELL-ADHESION

The myelin-associated glycoprotein (MAG) and the major glycoprotein of the peripheral nervous system myelin (PO) are two members of the fami ly of cell adhesion molecules (CAMs). A role in cell adhesion of the c arbohydrate moiety of these molecules has been attributed to the prese nce of N-glycans bearing the HNK-1 carbohydrate epitope. On the other hand, it has been suggested that these glycoproteins could be ligands of an endogenous mannose-binding lectin present in myelin, the cerebel lar soluble lectin (CSL). In order to further document the heterogenei ty of the glycans of these two CAMs, we have used several probes: an a nti-carbohydrate antibody of the HNK-1 type, called Elec-39, the plant lectin concanavalin A (ConA), and the endogenous lectin CSL involved in myelin compaction. This study shows that CSL binds to a small propo rtion of the polypeptide chains of MAG found in adult CNS of rats and man and the polypeptide chains of PO molecules from adult human and ra t sciatic nerve. For MAG from adult rat brain, the binding of CSL is r estricted to glycans of polypeptide chains which could be separated fr om the others according to their solubility properties. These MAG mole cular entities react also with the Elec-39 antibody and with ConA. The se results confirm that PO and MAG are heterogeneous in their carbohyd rate moieties. They show that, in the CNS of adult rats, the MAG molec ules potentially involved in cell adhesion as ligands of the endogenou s lectin CSL possess polypeptide chains physicochemically different fr om the others, but endowed with similar porperties to those of other C SL ligands, unrelated to MAG, present in myelin preparations.