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Nerve growth factor induces survival and differentiation through two distinct signaling cascades in PC12 cells
L J Klesse1, K A Meyers, C J Marshall
1Center for Developmental Biology, University of Texas, Southwestern Medical Center, Dallas 75235-9133, USA.
Abstract:
Nerve growth factor induces differentiation and survival of rat PC12 pheochromocytoma cells. The activation of the erk cascade has been implicated in transducing the multitude of signals induced by NGF. In order to explore the role of this signaling cascade in NGF mediated survival, differentiation and proliferation, we generated recombinant adenoviruses which express the intermediates of the erk cascade in their wild type, dominant negative and constitutively activated forms. We show that differentiation of PC12 cells requires activity of the ras/erk pathway, whereas inhibition of this pathway had no effect on survival or proliferation. Constitutively active forms of ras, raf and mek induced PC12 cell differentiation, while dominant interfering forms inhibited differentiation. Survival of PC12 cells in serum-free medium did not require activity of the ras/erk pathway. Instead, PI3 Kinase signaling was necessary for PC12 cell survival. Interestingly, constitutively activated versions of raf and mek were able to promote survival, but again this was dependent on activation of PI3 Kinase. Therefore, at least two distinct signaling pathways are required in PC12 cells for mediation of NGF functions.
Insights
Nerve growth factor (NGF) triggers PC12 cell differentiation via the ras/ERK pathway, but not survival. Phosphoinositide 3-kinase (PI3K) signaling is crucial for NGF-induced cell survival.
Area of Science:
- Molecular Biology
- Cell Signaling
- Neuroscience
Background:
- Nerve growth factor (NGF) is known to induce differentiation and survival in rat PC12 pheochromocytoma cells.
- The extracellular signal-regulated kinase (ERK) cascade is a key signaling pathway implicated in mediating NGF's effects.
Purpose of the Study:
- To investigate the specific roles of the ras/ERK pathway in NGF-mediated PC12 cell differentiation, survival, and proliferation.
- To elucidate the signaling mechanisms underlying NGF's functions in PC12 cells.
Main Methods:
- Generation of recombinant adenoviruses to express wild-type, dominant-negative, and constitutively active forms of ras/ERK pathway intermediates.
- Utilized PC12 cell cultures treated with NGF and manipulated signaling pathways.
- Assessed cell differentiation, survival, and proliferation in response to genetic and chemical modulations.
Main Results:
- PC12 cell differentiation induced by NGF requires the activity of the ras/ERK pathway.
- Inhibition of the ras/ERK pathway did not affect PC12 cell survival or proliferation.
- Phosphoinositide 3-kinase (PI3K) signaling, not ras/ERK, is essential for PC12 cell survival in serum-free conditions.
- Constitutively active raf and MEK could promote survival, but only through PI3K activation.
Conclusions:
- NGF utilizes distinct signaling pathways to mediate its diverse functions in PC12 cells.
- The ras/ERK pathway is critical for NGF-induced differentiation, while PI3K signaling is necessary for survival.
- Cross-talk between ERK and PI3K pathways may exist, particularly in promoting cell survival.