Characterization of Acetylcholinesterase Secretion in Neuronal Cultures and Regulation by High K+ and Soluble Factors from Target Cells

Abstract

We have observed that cultured neurons from chick spinal cord and the neuroblastoma hybrid line 108CC15 released lower amounts of acetylcholinesterase (AChE) when compared with the parental line, N18TG2. AChE activity extracted by hypotonic buffer, which can be regarded as the source of the released enzyme, was considerably higher in the parental than in the hybrid 108CC15 (respectively, approximately 80% and approximately 40% of cellular activity). On the other hand, evaluation of ectocellular, with respect to total, AChE activity showed that in N18TG2 cells only 7% of AChE was localized on the plasmalemma, whereas in the hybrid line the percentage of ectocellular activity was 3.7 times higher than in the parental line. We have also examined the effect of cytochalasin B and nocodazole. In the N18TG2 line, the former did not affect AChE release, which was significantly reduced by the latter. High K+ level in the culture medium, of both N18TG2 and hybrid 108CC15 cultures, induced an increase in AChE secretion; Ca2+ presence was required for high K(+)-induced release. Muscle extracts increased AChE secretion in both the hybrid 108CC15 and the spinal cord neurons. The present data suggest that AChE secretion during neuronal development is modulated by depolarizing stimuli and by soluble factors produced by target cells and may be involved in the control of neuronal differentiation.