Brain-derived neurotrophic factor causes cAMP response element-binding protein phosphorylation in absence of calcium increases in slices and cultured neurons from rat visual cortex

J Neurosci. 2000 Apr 15;20(8):2809-16. doi: 10.1523/JNEUROSCI.20-08-02809.2000.

Abstract

Neurotrophins play a crucial role in the developmental plasticity of the visual cortex, but very little is known about the cellular mechanisms involved in their action. In many models of synaptic plasticity, increases in cytosolic calcium concentration and activation of the transcription factor cAMP response element-binding protein (CREB) are crucial factors for the induction and maintenance of long-lasting changes of synaptic efficacy. Whether BDNF modulates intracellular calcium levels in visual cortical neurons and the significance of this action for BDNF signal transduction is still controversial. We investigated whether CREB phosphorylation and calcium changes are elicited by acute BDNF presentation in postnatal visual cortical slices and cultures. We found that BDNF did not cause any calcium increase, but it induced robust CREB phosphorylation in neurons from both preparations. We further analyzed signal transduction and its dependency on calcium changes in cultured neurons. CREB phosphorylation required trkB activation because treatment with the trk inhibitor k252a completely blocked CREB phosphorylation. In agreement with the imaging experiments, we verified that calcium changes were not necessary for CREB activation because preincubation with BAPTA-AM did not diminish the level of CREB phosphorylation induced by BDNF stimulation. CREB phosphorylation was accompanied by gene expression, because we observed the upregulation of c-fos expression, which was also not affected by preincubation with BAPTA-AM. Finally, BDNF caused phosphorylation of mitogen-activated protein kinase (MAPK), and because the treatment with the MAPK inhibitor U0126 completely abolished CREB activation and c-fos upregulation, it is likely that both processes depend mainly on the MAP kinase pathway. These results indicate that MAPK and CREB, but not intracellular calcium, are important mediators of neurotrophin actions in the visual cortex.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activating Transcription Factor 2
  • Animals
  • Brain-Derived Neurotrophic Factor / pharmacology*
  • Calcium / metabolism*
  • Cells, Cultured
  • Cyclic AMP Response Element-Binding Protein / drug effects*
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • Genes, fos / drug effects
  • Genes, fos / physiology
  • Mitogen-Activated Protein Kinases / drug effects*
  • Mitogen-Activated Protein Kinases / metabolism
  • Neuronal Plasticity / drug effects
  • Neuronal Plasticity / physiology
  • Neurons / drug effects*
  • Neurons / metabolism
  • Phosphorylation / drug effects
  • Rats
  • Rats, Long-Evans
  • Transcription Factors / drug effects*
  • Transcription Factors / metabolism
  • Visual Cortex / drug effects*
  • Visual Cortex / metabolism

Substances

  • Activating Transcription Factor 2
  • Brain-Derived Neurotrophic Factor
  • Cyclic AMP Response Element-Binding Protein
  • Transcription Factors
  • Mitogen-Activated Protein Kinases
  • Calcium

Grants and funding