Neuron specific protein (NSP) in neuroblastoma cells: relation to differentiation.

The spectrum of enolase enzyme forms has been examined in several lines of neuroblastoma cells and compared to those present in whole brain. The neuron specific enolase (NSP) is greatly decreased in the cultured cells as judged by activity profiles and radioimmunoassay. The synthesis of neuronal enolase appears to be extensively depressed in these cells while the total enolase activity is not affected. The non-neuron form of enolase (NNE) apparently compensates for the lack of the neuronal forms in the cultured cells. The preponderance of NNE in cultured neurons suggests that this enzyme is present in immature neurons, and that neuroblastoma cells are not fully differentiated with respect to the enolase function. Dibutyryl cyclic adenosine monophosphate treatment does increase NSP levels in mouse neuroblastoma cells, but not to the levels expected for fully differentiated neurons. The results indicate that NSP is a molecular correlate of fully differentiated neurons.