Effect of cellular desialylation on choline high affinity uptake and ecto-acetylcholinesterase activity of cholinergic neuroblasts.

It is not definitely established whether choline can be synthesized by nerve tissue (1,2). Its uptake by the neuronal membrane may be an important regulator of neuronal phosphatidylcholine and acetylcholine metabolism. An energy-dependent component of the choline uptake system has recently been found in neuroblastoma cell cultures (3). Choline uptake in cholinergic neuroblasts is markedly reduced by inhibition of cholinesterase activity (4). Further information about the system for choline transport still is lacking.To gain insight into the biochemical mechanism(s) at the cell surface which are involved in choline uptake by nerve cells, cultured cholinergic neuroblasts in the present study were subjected to gentle sialidase treatment, and choline uptake and acetylcholinesterase activities (AChE, EC 3.1.1.7) were determined in parallel. Removal of a portion of the cell surface sialic acid markedly reduced choline uptake and concurrently enhanced AChE activity. These findings suggest an interrelatedness of choline uptake and acetylcholinesterase activity mediated by sialic acid components in the outer surface of the cell.