INDUCTION OF A NERVE GROWTH FACTOR-SENSITIVE KINASE THAT PHOSPHORYLATES THE DNA-BINDING DOMAIN OF THE ORPHAN NUCLEAR RECEPTOR NGFI-B

Nerve growth factor (NGF) induces the synthesis and the phosphorylatio n of the orphan nuclear receptor NGFI-B in PC12 cells. Previous work h as shown that phosphorylation, by protein kinase A, of a specific seri ne in the DNA-binding domain inhibits its binding to the NGFI-B respon se element. Also, cytoplasmic extracts from PC12 cells phosphorylate t his serine, and phosphorylation is greater in extracts from cells trea ted with NGF. The present work describes the induction, identification , and partial purification of a kinase (termed NGFI-B kinase I) from P C12 cell extracts that catalyzes this phosphorylation. Phosphorylation of the DNA-binding domain with this purified preparation inhibits its binding to the NGFI-B response element, The kinase is rapidly activat ed by treatment of the cells with NGF, and the activation lasts for at least several hours. It also is activated by fibroblast growth factor and epidermal growth factor (EGF), but the activation by EGF is quite transient. The kinase requires Mg2+ but will use Mn2+. The molecular mass of the kinase is 95-100 kDa, and it is different from protein kin ase A, Fos kinase, or pp90(rsk). Comparison with a partially purified preparation of cyclic AMP response element-binding protein kinase, how ever, indicates that the two are either Very similar or identical.