Induction of the proto-oncogene fos by nerve growth factor.

Nerve growth factor (NGF) causes the differentiation of PC12 cells to sympathetic neuron-like cells and also induces a rapid but transient expression of fos mRNA and protein. fos mRNA transcripts can be detected 5 min after the addition of NGF, are maximally abundant after 30 min, and then their levels decrease. fos protein synthesis parallels the expression of fos mRNA, and the induced fos proteins are located in the nucleus. cAMP, epidermal growth factor, the phorbol ester phorbol 12-myristate 13-acetate, and K+ depolarization also induce the fos gene. Growth of PC12 cells in the presence of dexamethasone, which induces differentiation into chromaffin-like cells, is not accompanied by fos expression. We propose that while fos gene induction is associated with the differentiation of PC12 cells to sympathetic nerve, its enhanced expression is primarily involved in the anabolic responses induced by NGF and many growth factors.