The common neurotrophin receptor p75NTR enhances the ability of PC12 cells to resist oxidative stress by a trkA-dependent mechanism.

Functional role(s) for the common neurotrophin receptor p75NTR in nerve growth factor (NGF) signaling have yet to be fully elucidated. Many studies have demonstrated that p75NTR can enhance nerve growth factor-induced survival mediated via the trkA receptor. In addition, newly identified pathways for p75NTR signaling have included distinct p75NTR-specific and trk-independent effects which generally appear to be pro-apoptotic. In the present study, we have examined the influence of p75NTR on NGF-mediated protective effects from hydrogen peroxide (H2O2)-induced apoptotic cell death of PC12 cells. Exposure of PC12 cells to H2O2 resulted in Caspase-3 activation and apoptosis. NGF protected PC12 cells against H2O2-mediated apoptosis in a dose-dependent manner and inhibited Caspase-3 activation. These effects of NGF required activation of both PI 3-kinase and MAP kinase signal pathways. When NGF binding to p75NTR was blocked by treating cells with either BDNF or PD90780, and where p75NTR expression was reduced by treating cells with antisense oligonucleotide to p75NTR, the protective effects of NGF were attenuated. Further, NGF had no effect on cell viability in PC12nn5 cells, which express only p75NTR. When trk-mediated signal transduction was blocked, leaving p75NTR signaling activated, PC12 cells were not more vulnerable to H2O2. These data suggest that p75NTR enhances the ability of PC12 cells to resist oxidative stress by a trkA-dependent mechanism, potentially by allosteric mechanisms. Further, potential trkA-independent and pro-apoptotic signaling of p75NTR does not contribute to apoptotic cell death of PC12 cells in a setting of oxidative insult.