Divergence in the anti-apoptotic signalling pathways used by nerve growth factor and basic fibroblast growth factor (bFGF) in PC12 cells: rescue by bFGF involves protein kinase C delta

The mechanisms whereby nerve growth factor (NGF) and basic fibroblast growt h factor (bFGF) block apoptosis in serum-deprived PC12 cells were investiga ted. NGF, but not bFGF, strongly activated Akt/protein kinase B, a downstre am effector of phosphoinositide (phosphatidylinositol) 3-kinase CPI 3kinase ), In addition, inhibition of PI 3-kinase by LY294002 partially blocked inh ibition of apoptosis by NGF, but not that by bFGF, suggesting divergence in NGF and bFGF antiapoptotic signalling pathways. Both growth factors strong ly activated mitogen-activated protein (MAP) kinases, but blockade of signa lling through this pathway, either by the expression of dominant-negative R as or by treatment with the MAP kinase/ERK kinase (MEK) inhibitor U0126, pa rtially inhibited only bFGF, but not NGF, anti-apoptotic signalling, Use of isoform-specific protein kinase C (PKC) inhibitors such as bisindoylmaleim ide-1 and Go 6983 suggested that PKC delta is a likely component of bFGF tr ophic signalling. A role for PKC delta was confirmed in PC12 cells expressi ng a dominant-negative PKC delta fragment, in which reversal of apoptosis b y bFGF was partially blocked. The PKC delta signal was not mediated by the MAP kinase cascade, as bFGF activation of this pathway was not affected in cells expressing the dominant-negative PKC delta fragment. Full inhibition of bFGF anti-apoptotic signalling occurred when both the PKC delta and Ras/ MAP kinase pathways were inhibited. Together, these data demonstrate that i nhibition of apoptosis by bFGF in PC12 cells operates differently from that mediated by NGF, requiring the addition of signals from both the Ras/MAP k inase and PKC signalling pathways.