Evidence for involvement of ERK, PI3K, and RSK in induction of Bcl-2 by valproate

J Mol Neurosci. 2009 Feb;37(2):123-34. doi: 10.1007/s12031-008-9122-2. Epub 2008 Aug 3.

Abstract

Valproate, an anticonvulsant and mood stabilizer, up-regulates Bcl-2, a neurotrophic/neuroprotective protein. In this study, we investigated the molecular mechanism through which Bcl-2 is up-regulated by valproate using cultured human neuron-like cells. Valproate, within therapeutically relevant ranges, induced time- and concentration-dependent up-regulations of both Bcl-2 messenger RNA and protein implicating an underlying gene transcriptional-mediated mechanism. Bcl-2 up-regulations were associated with ERK1/2 and PI3K pathway activations and elevated levels of activated phospho-RSK and phospho-CREB, convergent targets of the ERK1/2 and PI3K pathways. Valproate increased transcriptional activity of a human bcl-2 promoter-reporter gene construct. This effect was attenuated, but not blocked, by mutation of a CREB DNA binding site, a CRE site in the human bcl-2 promoter sequence. ERK and/or PI3K pathway inhibitors and RSK1 small hairpin RNA knockdown reduced, but did not abolish, baseline and valproate-induced promoter activities and lowered Bcl-2 protein levels. These data collectively suggest that valproate induces Bcl-2 regulation partially through activations of the ERK and PI3K cascades and their convergent kinase, RSK, although other unknown mechanism(s) are likely involved. Given the known roles of Bcl-2 in the central nervous system, the current findings offer a partial yet complex molecular mechanistic explanation for the known neurobiological effects of valproate including neurite growth, neuronal survival, and neurogenesis.

Publication types

  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anticonvulsants / pharmacology*
  • Cell Line, Tumor
  • Dose-Response Relationship, Drug
  • Genes, Reporter
  • Humans
  • MAP Kinase Signaling System / drug effects*
  • MAP Kinase Signaling System / physiology*
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Neuroblastoma
  • Neurons / drug effects
  • Neurons / enzymology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins c-bcl-2 / genetics*
  • Ribosomal Protein S6 Kinases, 90-kDa / metabolism
  • Valproic Acid / pharmacology*

Substances

  • Anticonvulsants
  • Proto-Oncogene Proteins c-bcl-2
  • Valproic Acid
  • Phosphatidylinositol 3-Kinases
  • RPS6KA1 protein, human
  • Ribosomal Protein S6 Kinases, 90-kDa
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3