Translational control of programmed cell death: eukaryotic translation initiation factor 4E blocks apoptosis in growth-factor-restricted fibroblasts with physiologically expressed or deregulated Myc.
There is increasing evidence that cell cycle transit is potentially lethal, with survival depending on the activation of metabolic pathways which block apoptosis. However, the identities of those pathways coupling cell cycle transit to survival remain undefined. Here we show that the eukaryotic translation initiation factor 4E (eIF4E) can mediate both proliferative and survival signaling. Overexpression of eIF4E completely substituted for serum or individual growth factors in preserving the viability of established NIH 3T3 fibroblasts. An eIF4E mutant (Ser-53 changed to Ala) defective in mediating its growth-factor-regulated functions was also defective in its survival signaling. Survival signaling by enforced expression of eIF4E did not result from autocrine release of survival factors, nor did it lead to increased expression of the apoptosis antagonists Bcl-2 and Bcl-XL. In addition, the execution apparatus of the apoptotic response in eIF4E-overexpressing cells was found to be intact. Increased expression of eIF4E was sufficient to inhibit apoptosis in serum-restricted primary fibroblasts with enforced expression of Myc. In contrast, activation of Ha-Ras, which is required for eIF4E proliferative signaling, did not suppress Myc-induced apoptosis. These data suggest that the eIF4E-activated pathways leading to survival and cell cycle progression are distinct. This dual signaling of proliferation and survival might be the basis for the potency of eIF4E as an inducer of neoplastic transformation.
Pulmonary and Critical Care Division, Department of Medicine, University of Minnesota Medical School, Minneapolis 55455, USA.
V A
VA
Polunovsky
I B
IB
Rosenwald
A T
AT
Tan
J
J
White
L
L
Chiang
N
N
Sonenberg
P B
PB
Bitterman
D016475:3T3 Cells; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D000077214:Becaplermin; D015415:Biomarkers; D002453:Cell Cycle; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D039561:Eukaryotic Initiation Factor-4E; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006133:Growth Substances / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008168:Lung; D051379:Mice; D008807:Mice, Inbred BALB C; D010448:Peptide Initiation Factors / Q000096:biosynthesis / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D014176:Protein Biosynthesis; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis / Q000502:physiology*; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D051020:bcl-X Protein
C494812:Bcl2l1 protein, mouse; D015415:Biomarkers; D039561:Eukaryotic Initiation Factor-4E; D006133:Growth Substances; D010448:Peptide Initiation Factors; D010982:Platelet-Derived Growth Factor; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D051020:bcl-X Protein; D000077214:Becaplermin; D007334:Insulin-Like Growth Factor I