Nectadrin, the
cell surface glycoprotein recognized by the novel mAb 79, was found to be immunologically identical to the heat-stable
antigen (HSA). It is a
glycoprotein with a
polypeptide core of only 30
amino acids and a very high
carbohydrate content (Wenger, R. H., M. Ayane, R. Bose, G. Köhler, and P. J. Nielsen. 1991. Eur. J. Immunol. 21:1039-1046). Immunocytological studies using cultured splenic B-lymphocytes,
neuroblastoma cells, and cerebellar cells indicated that
nectadrin is preferentially expressed at sites of cell-cell contact. Purified
nectadrin and monoclonal
nectadrin antibody 79, but not other monoclonal
nectadrin antibodies, inhibited the aggregation of B-lymphocytes by 70%, suggesting that
nectadrin may act as a
cell adhesion molecule.
Nectadrin was purified from a mouse
lymphoma cell line in two forms of 40-60 and 23-30 kD. The lower molecular weight form appears to be generated from the higher molecular weight form by degradative removal of saccharide residues characteristic of complex type
oligosaccharide side chains.
Latex beads coated with purified
nectadrin aggregated and the rate of their aggregation depended on the molecular form of
nectadrin, with the larger form being more potent than the smaller one in mediating bead aggregation.
Nectadrin thus appears to be a self-binding
cell adhesion molecule of a structurally novel type in that its extensive
glycan structures may be implicated in mediating cell adhesion.