DIFFERENTIAL REGULATION OF PHENOTYPIC-EXPRESSION IN A PLURIPOTENTIAL NEUROBLASTOMA CELL-LINE

Our laboratory has recently been involved in investigating factors whi ch influence plasticity of neurotransmitter phenotypic expression both in vivo and in culture. Our previous studies have shown that precurso r neuroblasts are pluripotential with respect to neurotransmitter phen otype and respond differentially to microenvironmental signals. In the present study, we examined phenotypic expression in neuroblastoma cel ls, P-2 clone, using the activities of choline acetyltransferase (ChAT ) and tyrosine hydroxylase (TH) as neuronal markers for the cholinergi c and catecholaminergic phenotypes, respectively. Cells were plated an d grown for 4 days in culture, harvested and frozen for assay of ChAT and TH. Basal activity of ChAT was 2.47 +/- 0.22 nmoles Ach formed/h/m g protein and that of TH was 5.23 +/- 0.41 pmoles CO2 formed/h/mg prot ein in control cultures. When intracellular cAMP levels were increased by addition to the growth medium of 10 mu g/ml prostaglandin E(1) (PG E(1); a receptor-mediated enhancer of adenylate cyclase activity) or 2 00 mu g/ml RO20-1724 (an inhibitor of cyclic nucleotide phosphodiester ase) the activity of TH was increased 340- and 423-fold, respectively. In marked contrast, the activity of ChAT was not affected by either a gent. Double staining immunocytochemical examination demonstrated that both ChAT and TH were colocalized in the same cell. The molecular mec hanism whereby catecholaminergic expression exclusively is affected in this cell model is currently under investigation. We conclude that (1 ) P-2 neuroblastoma is a pluripotential cell line, (2) phenotypic expr ession in a homogenous cell population, such as P-2 neuroblastoma, is differentially regulated. Moreover, this cell line is a unique model f or studying the molecular mechanisms of phenotypic expression and neur onal plasticity.