K-252a, a kinase inhibitor isolated from the culture broth of Nocardiopsis sp., selectively inhibits the actions of nerve growth factor (NGF) on PC 12 cells. At a concentration of 200 nM, K-252a prevents neurite generation initiated by NGF, but not neurite generation produced by fibroblast growth factor or outgrowth produced by dibutyryl cAMP. K-252a also inhibits the induction of ornithine decarboxylase by NGF, but stimulates ornithine decarboxylase induction by epidermal growth factor. Stimulation of phosphatidylinositol breakdown by NGF was similarly inhibited by K-252a, while stimulation by epidermal growth factor was enhanced. The NGF-induced decrease in the phosphorylation of a soluble protein, Nsp 100, was prevented by K- 252a. K-252a blocks the NGF-induced heterodown-regulation of the epidermal growth factor receptor, but not the epidermal growth factor- induced homodown-regulation of the epidermal growth factor receptor. K- 252a, then, provides a new tool for the dissection and study of NGF- requiring processes.

No abstract

The treatment of PC12 cells with either nerve growth factor or phorbol 12-myristate 13-acetate caused a decrease in the phosphorylation of a soluble 100-kDa protein (NsplOO). After treatment with nerve growth factor, the activity of Ca2+/phospholipid-dependent protein kinase (protein kinase C) in the cytosol was increased. When the cytosol from untreated PC12 cells was preincubated with purified protein kinase C and its cofactors, the phosphorylation of NsplOO was decreased. The preincubation of cytosol from nerve growth factor-treated PC12 cells with protein kinase C did not decrease NsplOO phosphorylation further. Moreover, preincubation of partially purified NsplOO kinase with protein kinase C decreased its ability to phosphorylate NsplOO. These results suggest that the binding of nerve growth factor to its receptor on PC12 cells causes an increase in the activity of protein kinase C in the cytosol and phosphorylation of NsplOO kinase, which in turn lowers its ability to phosphorylate NsplOO.

No abstract

No abstract