The novel carbohydrate epitope L3 is shared by some neural cell adhesion molecules

The monoclonal L3 antibody reacts with an N-glycosidically linked carbohydrate structure on at least nine glycoproteins of adult mouse brain. Three out of the L3 epitope-carrying glycoproteins could be identified as the neural cell adhesion molecules L1 and myelin-associated glycoprotein, and the novel adhesion molecule on glia. Expression of the L3 carbohydrate epitope is regulated independently of the protein back-bone of these glycoproteins. Based on the observation that out of three functionally characterized L3 epitope-carrying glycoproteins three fulfill the operational definition of an adhesion molecule, we would like to suggest that they form a new family of adhesion molecules that is distinct from the L2/HNK-1 carbohydrate epitope family of neural cell adhesion molecules. Interestingly, some members in each family appear to be unique to one family while other members belong to the two families.