Monoclonal antibody detects carbohydrate microheterogeneity on the murine cell adhesion molecule L1

The cell surface glycoprotein L1 is involved in neural cell interactions and shares with other adhesion molecules, i.e. the neural cell adhesion molecule N-CAM, the myelin-associated glycoprotein MAG and the J1 glycoproteins, an unusual carbohydrate structure designated L2/HNK-1. Recent evidence suggests that the L2/HNK-1 carbohydrate participates in adhesion. Since indirect evidence indicated that the L2/HNK-1 carbohydrate is not present on all molecules within a particular species of glycoproteins, it seemed pertinent to investigate this more directly by sequential immunoprecipitations. Here we show that the L2/HNK-1 epitope appears to be present on 35% of the L1 glycoproteins isolated from mouse brain. The epitope is restricted to the proteolytic fragment of L1 at the aminoterminal, extracellular domain in that it is detectable on L1-200 and L1-140, but absent from L1-80 and L1-50.