There is accumulating evidence that
acetylcholinesterase has secondary noncholinergic functions, related to adhesion, differentiation, and the deposition of
beta-amyloid in
Alzheimer's disease. We have observed that the specific
acetylcholinesterase peripheral anionic site inhibitors,
BW284c51 and
propidium iodide, abrogated cell-substrate adhesion in three human
neuroblastoma cell lines. The active-site inhibitors,
eserine and
edrophonium, in contrast, had no effect. Certain anti-AChE
antibodies were also shown to inhibit adhesion. Of these, the most effective were a monoclonal (E8) and a polyclonal having
cholinesterase-like catalytic activity. These were raised against an
acetylcholinesterase-inhibitor complex, implying that the
epitope is associated with active-site structures. Two other
monoclonal antibodies (E62A1 and E65E8) partially inhibited adhesion. The
epitopes of these
antibodies have been shown to overlap the peripheral anionic site of
acetylcholinesterase. Competition ELISA between the
monoclonal antibodies and inhibitors indicated competition between E8, E62A1, and E65E8 and the peripheral-site inhibitors
BW284c51 and
propidium, but not with the active-site inhibitors
eserine and
edrophonium. Fluorescence titration between
antibodies and
propidium confirmed these results. We conclude that the adhesion function of
acetylcholinesterase is located at the peripheral anionic site. This has implications, not only for our understanding of neural development and its disorders, but also for the treatment of
neuroblastoma, the
leukemias, and
Alzheimer's disease.