5-HT stimulates eEF2 dephosphorylation in a rapamycin-sensitive manner in Aplysia neurites

J Neurochem. 2004 Sep;90(6):1464-76. doi: 10.1111/j.1471-4159.2004.02634.x.

Abstract

In Aplysia, serotonin mediates behavioral sensitization by increasing the strength of the synapse between sensory and motor neurons, a process known as facilitation. The retention of long-term facilitation is blocked by rapamycin, an inhibitor of a specific translational pathway. One possible rapamycin-sensitive target is the increased translation of 5'-terminal oligopyrimidine mRNAs. These transcripts encode components of the translational machinery and have been proposed to be important for retention of long-term facilitation. We have cloned the 5'-terminal oligopyrimidine mRNA encoding eukaryotic elongation factor 2 and shown that serotonin increased its translation in synaptosomes. Another possible rapamycin-sensitive target is the inactivation of eukaryotic elongation factor 2 kinase. Eukaryotic elongation factor 2 kinase phosphorylates and inactivates eukaryotic elongation factor 2, blocking translational elongation. Serotonin application decreased eukaryotic elongation factor 2 phosphorylation in synaptosomes and in isolated neurites, and this was blocked by rapamycin. We propose a role for the rapamycin-sensitive pathway in neurons. Stimulation blocks translation by inducing calcium entry and phosphorylation of eukaryotic elongation factor 2. This block is reversed through activation of the rapamycin-sensitive system and dephosphorylation of eukaryotic elongation factor 2.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Aplysia
  • Axotomy / methods
  • Base Sequence
  • Blotting, Western / methods
  • Cells, Cultured
  • Cloning, Molecular / methods
  • Drug Interactions
  • Enzyme Inhibitors / pharmacology
  • Fluorescence Recovery After Photobleaching / methods
  • Gene Expression Regulation / drug effects
  • Immunohistochemistry / methods
  • Models, Neurological
  • Neurites / drug effects*
  • Neurons / cytology*
  • Peptide Elongation Factor 2 / genetics
  • Peptide Elongation Factor 2 / metabolism*
  • Phosphorylation / drug effects
  • Potassium Chloride / pharmacology
  • Serotonin / pharmacology*
  • Sirolimus / pharmacology*
  • Synaptosomes / drug effects
  • Synaptosomes / metabolism
  • Tacrolimus Binding Protein 1A / metabolism
  • Threonine / metabolism
  • Time Factors

Substances

  • Enzyme Inhibitors
  • Peptide Elongation Factor 2
  • Threonine
  • Serotonin
  • Potassium Chloride
  • Tacrolimus Binding Protein 1A
  • Sirolimus