5-HT stimulates eEF2 dephosphorylation in a rapamycin-sensitive manner in Aplysia neurites.
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.
Carroll
Matthew
M
Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
Warren
Otis
O
Fan
Xiaotang
X
Sossin
Wayne S
WS
D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia; D019771:Axotomy / Q000379:methods; D001483:Base Sequence; D015153:Blotting, Western / Q000379:methods; D002478:Cells, Cultured; D003001:Cloning, Molecular / Q000379:methods; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D036681:Fluorescence Recovery After Photobleaching / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry / Q000379:methods; D008959:Models, Neurological; D016501:Neurites / Q000187:drug effects*; D009474:Neurons / Q000166:cytology*; D020652:Peptide Elongation Factor 2 / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D012701:Serotonin / Q000494:pharmacology*; D020123:Sirolimus / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D022061:Tacrolimus Binding Protein 1A / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D013997:Time Factors
D004791:Enzyme Inhibitors; D020652:Peptide Elongation Factor 2; D013912:Threonine; D012701:Serotonin; D011189:Potassium Chloride; D022061:Tacrolimus Binding Protein 1A; D020123:Sirolimus