Glutamate-dependent phosphorylation of elongation factor-2 and inhibition of protein synthesis in neurons.
Postischemic delayed neuronal death is attributed to excitotoxic activation of glutamate receptors. It is preceded by a persistent inhibition of protein synthesis, the molecular basis of which is not known. Here we have examined in cortical neurons in culture the regulation by glutamate of phosphorylation of eukaryotic elongation factor-2 (eEF-2) by eEF-2 kinase, a Ca2+/calmodulin-dependent enzyme. Using a phosphorylation state-specific antibody, we show that glutamate, which triggers a large influx of Ca2+, enhances dramatically the phosphorylation of eEF-2. On the basis of kinetic and pharmacological analysis, we demonstrate a close correlation among the increase in cytosolic Ca2+ concentration, the degree of eEF-2 phosphorylation, and the inhibition of protein synthesis. A 30 min treatment with NMDA induced a transient phosphorylation of eEF-2 and delayed neuronal death. However, pharmacological inhibition of protein translation was not neurotoxic by itself and protected neurons against the toxicity evoked by low concentrations of NMDA. Thus, phosphorylation of eEF-2 and the resulting depression of protein translation may have protective effects against excitotoxicity and open new perspectives for understanding long-term effects of glutamate.
Marin
P
P
Chaire de Neuropharmacologie, Institut National de la Santé et de la Recherche Médicale U114, Collège de France, 75231 Paris Cedex 05, France.
Nastiuk
K L
KL
Daniel
N
N
Girault
J A
JA
Czernik
A J
AJ
Glowinski
J
J
Nairn
A C
AC
Prémont
J
J
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D000918:Antibody Specificity; D002118:Calcium / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D009498:Neurotoxins / Q000494:pharmacology; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000276:immunology / Q000378:metabolism*; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D018091:Receptors, AMPA / Q000819:agonists / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D011500:Protein Synthesis Inhibitors; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D002118:Calcium