Adult and embryonic mouse neural cell adhesion molecules have different binding properties

Abstract

Interactions between neural cell surfaces seem to be of prime importance during neuroontogenesis, and responsible for the guidance of migrating neuroblasts and growing axons and for the formation of synapses. Little is known about the underlying molecular mechanisms, but most hypotheses imply the existence of cell-surface molecules that mediate the formation of transient or permanent bonds between neural cells. Recently, a membrane glycoprotein called neural cell adhesion molecule (N-CAM) has been characterized in chick^1,2 and rodent³ nervous tissue that appears to act as a ligand in adhesion among neural cell bodies^4,5 or neurites⁶. We have identified a mouse neural surface glycoprotein, named BSP-2 (ref. 7), which by criteria of electrophoretic migration^7–9, developmental changes^8,9, amino acid¹⁰ and sugar¹¹ composition seems to be closely related or identical to N-CAM. Both BSP-2 (refs 8,9) and N-CAM^2,12 undergo conversion from an embryonic to an adult form during brain development and it has been suggested that this transition changes the adhesive properties¹² or the binding specificity⁸ of the molecule. Using a neuroblastoma line to study functional differences between embryonic and adult BSP-2/N-CAM molecules, we show here that liposomes bearing adult BSP-2 but not those bearing the embryonic form adhere to neuroblastoma cells, demonstrating that the two forms do indeed possess different binding properties.