A EWINGS-SARCOMA CELL-LINE SHOWING SOME, BUT NOT ALL, OF THE TRAITS OF A CHOLINERGIC NEURON

The Ewing's sarcoma cell line ICB 112 was examined in detail for a cho linergic phenotype. Choline acetyltransferase activity (12.3 +/- 2.9 n mol/h/mg of protein) was associated with the presence of multiple mRNA species labeled with a human choline acetyltransferase riboprobe. Cho line was taken up by the cells by a high-affinity, hemicholinium-3-sen sitive transporter that was partially inhibited when lithium replaced sodium in the incubation medium; the choline taken up was quickly inco rporated into both acetylcholine and phosphorylcholine. High-affinity binding sites for vesamicol, an inhibitor of vesicular acetylcholine t ransport, were also present. The mRNAs for synaptotagmin (p65) and the 15-kDa proteolipid were readily detected and were identical in size t o those observed in cholinergic regions of the human brain. Cumulative acetylcholine efflux was increased by raising the extracellular potas sium level or the addition of a calcium ionophore, but the time course of stimulated efflux was slow and persistent. These results show that this morphologically undifferentiated cell line is capable of acetylc holine synthesis and expresses markers for synaptic vesicles as well a s proteins implicated in calcium-dependent release but lacks an organi zed release mechanism.