Changes in the expression of the alpha alpha form of enolase during neuroblastoma differentiation.

The relative amounts of the different enolase isozymes present in neuroblastoma cells change during differentiation. When differentiation is induced by low serum in the presence of DMSO (dimethyl sulfoxide), there is a 50% decrease in the concentration of enolase activity associated with the form alpha alpha, and an increase in the activity associated with the gamma-containing isozymes (alpha gamma plus gamma gamma); in the absence of DMSO, there is no decrease in alpha alpha or in total enolase activity. In order to study the mechanism of the changes in alpha alpha, cells differentiated with low serum with and without DMSO were compared. Measurements of the concentration of the alpha antigen by microcomplement fixation and by immunotitration demonstrate that the decreased enolase activity in DMSO cells is due to a decreased concentration of the alpha antigen. Measurements of the relative rate of synthesis of the antigen show that the decreased concentration of the alpha antigen is due to a decreased rate of synthesis. Enolase in differentiated cells is sufficiently stable (t1/2 greater than 100 h) that a comparison of the relative rates of degradation has not been possible. The decreased synthesis of the alpha subunit of enolase that occurs under these conditions appears to be a useful model system for studying the de-expression of the alpha gene that occurs in vivo during neuronal differentiation.