Ischaemia induces changes in the association of the binding protein 4E-BP1 and eukaryotic initiation factor (eIF) 4G to eIF4E in differentiated PC12 cells.
Ischaemia was obtained in vitro by subjecting nerve-growth-factor-differentiated PC12 cells to glucose deprivation plus anoxia. During ischaemia the rate of protein synthesis was significantly inhibited, and eIF4E-binding protein (4E-BP1) and eukaryotic initiation factor 4E (eIF4E) were significantly dephosphorylated in parallel. In addition, ischaemia induced an enhancement of the association of 4E-BP1 to eIF4E, which in turn decreased eIF4F formation, whereas no degradation of initiation factor 4G was observed. The treatment of PC12 cells with the specific p38 mitogen-activated protein kinase inhibitor SB203580 induced eIF4E dephosphorylation but did not cause any effect on protein synthesis rate. Rapamycin, the inhibitor of mammalian target of rapamycin ('mTOR'), but not PD98059, the inhibitor of extracellular signal-regulated protein kinases ('ERK1/2'), induced similar effects on 4E-BP1 phosphorylation to ischaemia; nevertheless, 4E-BP1-eIF4E complex levels were higher in ischaemia than in rapamycin-treated cells. In addition, both protein synthesis rate and eIF4F formation were lower in ischaemic cells than in rapamycin-treated cells.
Martín
M E
ME
Departmento de Bioquímica y Biología Molecular, Universidad de Alcalá, Alcalá de Henares, 28871 Madrid, Spain.
Muñoz
F M
FM
Salinas
M
M
Fando
J L
JL
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D002352:Carrier Proteins; D002470:Cell Survival; D004791:Enzyme Inhibitors / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D005419:Flavonoids / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D000860:Hypoxia; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D007511:Ischemia; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D016716:PC12 Cells; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D020123:Sirolimus / Q000494:pharmacology; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases
D000903:Antibiotics, Antineoplastic; D002352:Carrier Proteins; C499526:Eif4ebp1 protein, rat; D004791:Enzyme Inhibitors; D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D005419:Flavonoids; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011500:Protein Synthesis Inhibitors; D011725:Pyridines; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D005947:Glucose; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D020123:Sirolimus