Johnson_2001_Int.J.Dev.Neurosci_19_439

The HNK-1 carbohydrate epitope is expressed in neural and natural killer cells and is a mediator of cell adhesion. It is well documented that acetylcholinesterase has a secondary function in cell adhesion and differentiation. The presence of HNK-1 on isoforms of Torpedo and Electrophorus acetylcholinesterase, as well as isoforms from the bovine central nervous system has been described. In this paper, we have investigated the association of the epitope with acetylcholinesterase from human neuroblastoma cells. Acetylcholinesterase was extracted, with or without detergent, purified on immunoaffinity columns and the isoforms separated by sucrose density gradient sedimentation. Secreted acetylcholinesterase, from spent serum-free culture medium, was similarly treated. The presence of the HNK-1 epitope was determined by ELISA using the anti-HNK-1 and Elec 39 monoclonal antibodies. The epitope was found to be associated with the detergent-soluble G4 isoform, but not with the hydrophilic G1 nor the secreted hydrophilic G4 isoforms. Likewise, no HNK-1 was observed associated with human erythrocyte acetylcholinesterase. These results indicate that acetylcholinesterase-G4, anchored in the extracellular membrane, is capable of mediating cell-substrate adhesion through HNK-1.