Nerve Growth Factor Promotes the Survival of Sympathetic Neurons through the Cooperative Function of the Protein Kinase C and Phosphatidylinositol 3-Kinase Pathways

Brian A Pierchala,Rebecca C Ahrens,Andrew J Paden,Eugene M Johnson

doi:10.1074/jbc.m312237200

Brian A Pierchala, Rebecca C Ahrens + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m312237200

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Abstract

The signaling pathways activated by nerve growth factor (NGF) that account for its ability to promote the survival of neurons are not completely understood. Phosphatidylinositol 3-kinase (PI3K) is critical for the survival of several cell types, including neurons. To determine whether additional signaling pathways cooperate with PI3K to promote survival, we examined other pathways known to be activated by NGF. NGF activated protein kinases C (PKCs) in sympathetic neurons, and pharmacologic PKC activation rescued neurons from apoptosis induced by the withdrawal of NGF. Inhibition of PKCs did not inhibit the survival of NGF-maintained neurons. Similarly, inhibition of PI3K caused only a modest attrition of neurons in the presence of NGF. In contrast, the simultaneous inhibition of both PKCs and PI3K induced the apoptotic death of NGF-maintained sympathetic neurons. Inhibition of both PI3K and PKCs promoted the expression and phosphorylation of the proapoptotic transcription factor c-Jun, indicating that these pathways inhibit programmed cell death at the stage of proapoptotic gene expression. In culture conditions under which PI3K inhibition alone kills NGF-maintained neurons, PKC inhibition also led to a significant loss of viability, indicating that both pathways are required. Therefore, PKC and PI3K, regardless of the culture conditions, cooperate to promote the NGF-dependent survival of sympathetic neurons.

Highlights

Nerve growth factor (NGF)1 can maintain the survival of sympathetic neurons in vitro and is required for their targetdependent survival in vivo [1, 2]
To determine the extent to which activators of protein kinase C (PKC) can promote the phosphorylation of these proteins, sympathetic neurons that were briefly deprived of nerve growth factor (NGF) were treated with either PMA or bryostatin 1, another potent PKC activator, for various times
These results further confirm that the proteins that are phosphorylated by NGF treatment (Fig. 1A) are, downstream substrates of phorbol ester-sensitive PKCs

Summary

Introduction

Nerve growth factor (NGF)1 can maintain the survival of sympathetic neurons in vitro and is required for their targetdependent survival in vivo [1, 2]. Stimulation of serum-maintained sympathetic neurons with NGF induced PKC activity as indicated by enhanced phosphorylation of several proteins on PKC consensus sites (Fig. 5A).

Results

Conclusion