STAUROSPORINE INDUCES THE OUTGROWTH OF NEURITES FROM THE DORSAL-ROOT GANGLION OF THE CHICK-EMBRYO AND PC12D CELLS

Staurosporine, a potent inhibitor of protein kinases, caused the rapid outgrowth of neurites from cultured dorsal root ganglia of chick embr yos and from PC12D cells, a subline of PC12 cells. Treatment of dorsal root ganglia with 1 to 20 nM staurosporine resulted in the extensive outgrowth of neurites that were indistinguishable from those induced b y NGF, as assessed by phase-contrast microscopy, electron microscopy a nd cytochemical staining of actin and tubulin. However, neurites gener ated from the ganglia in response to the higher concentrations of stau rosporine (40-100 nM) seemed to have different characteristics, possib ly as a result of the inhibition of cell migration from ganglia. The s equential changes in morphology of PC12D cells in response to staurosp orine and to NGF were revealed by staining of actin. Ruffling membrane s emerged at the margins of PC12D cells within 4 min after the additio n of staurosporine or of NGF. From 10 min to 24 h after the addition o f either compound, the ruffles were transformed into several projectio ns that became growing neurites. The formation of ruffles and the outg rowth of neurites were both apparent at a concentration of staurospori ne of 10 nM. The neurites that emerged from PC12D cells in response to staurosporine and in response to NGF were indistinguishable under the phase-contrast microscope and after staining of actin and tubulin. Ho wever, staurosporine never promoted survival of PC12D cells in serum-f ree conditions as that promoted by NGF. The observations indicate that staurosporine at nanomolar concentrations may reproduce the neurogeni c changes that induced by NGF in primed neuronal cells, although it ca n not mimic the action of NGF that supports survival of neurons.