Overexpression of Alternative Human Acetylcholinesterase Forms Modulates Process Extensions in Cultured Glioma Cells

Abstract: In addition to its well‐known synaptic function, acetylcholinesterase was recently shown to stimulate neurite outgrowth from cultured chick neurons in a manner unrelated to its catalytic activity. It remained unclear, however, whether each of the variant acetylcholinesterase enzyme forms can promote such process extension and whether this effect of acetylcholinesterase was limited to neurite outgrowth. Using DNA microinjections and stable transfections of cultured glioma cells, we explored the possibility that specific acetylcholinesterase isoforms affect cellular development and morphology of CNS astrocytes. Cells microinjected with human ACHEDNA constructs that differ in their exon‐intron composition displayed rapid yet stable induction of cell body enlargement and process extensions. Cells transfected with ACHEDNA carrying the neuronal‐characteristic 3′‐E6 domain also displayed stable process extensions. However, stable transfections with ACHEDNAs including the 3′‐alternative I4/E5 region induced the appearance of small, round cells in a dominant manner. This was associated with expression of I4/E5‐ACHEmRNA transcripts and the production of soluble acetylcholinesterase monomers that were catalytically indistinguishable from the 3′‐E6 enzyme but displayed higher electrophoretic mobility than that of the 3′‐E6 form. Thus, variable expression levels and alternative splicing modes of the ACHE gene correlated in these experiments with glial development in a manner that was apparently unrelated to catalysis.