Hedgehog and PI-3 kinase signaling converge on Nmyc1 to promote cell cycle progression in cerebellar neuronal precursors.
Neuronal precursor cells in the developing cerebellum require activity of the sonic hedgehog (Shh) and phosphoinositide-3-kinase ( PI3K) pathways for growth and survival. Synergy between the Shh and PI3K signaling pathways are implicated in the cerebellar tumor medulloblastoma. Here, we describe a mechanism through which these disparate signaling pathways cooperate to promote proliferation of cerebellar granule neuron precursors. Shh signaling drives expression of mRNA encoding the Nmyc1 oncoprotein (previously N-myc), which is essential for expansion of cerebellar granule neuron precursors. The PI3K pathway stabilizes Nmyc1 protein via inhibition of GSK3-dependent Nmyc1 phosphorylation and degradation. The effects of PI3K activity on Nmyc1 stabilization are mimicked by insulin-like growth factor, a PI3K agonist with roles in central nervous system precursor growth and tumorigenesis. These findings indicate that Shh and PI3K signaling pathways converge on N-Myc to regulate neuronal precursor cell cycle progression. Furthermore, they provide a rationale for therapeutic targeting of PI3K signaling in medulloblastoma.[1]References
- Hedgehog and PI-3 kinase signaling converge on Nmyc1 to promote cell cycle progression in cerebellar neuronal precursors. Kenney, A.M., Widlund, H.R., Rowitch, D.H. Development (2004) [Pubmed]
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