Abstract
Phosphorylation of the eukaryotic translation initiation factor eIF4E is associated with malignant progression and poor cancer prognosis. Accordingly, here we have analyzed the association between eIF4E phosphorylation and cellular resistance to oxidative stress, starvation, and DNA-damaging agents in vitro. Using immortalized and cancer cell lines, retroviral expression of a phosphomimetic (S209D) form of eIF4E, but not phospho-dead (S209A) eIF4E or GFP control, significantly increased cellular resistance to stress induced by DNA-damaging agents (cisplatin), starvation (glucose+glutamine withdrawal), and oxidative stress (arsenite). De novo accumulation of eIF4E-containing cytoplasmic bodies colocalizing with the eIF4E-binding protein 4E-T was observed after expression of phosphomimetic S209D, but not S209A or wild-type eIF4E. Increased resistance to cellular stress induced by eIF4E-S209D was lost upon knockdown of endogenous 4E-T or use of an eIF4E-W73A-S209D mutant unable to bind 4E-T. Cancer cells treated with the Mnk1/2 inhibitor CGP57380 to prevent eIF4E phosphorylation and mouse embryonic fibroblasts derived from Mnk1/2 knockout mice were also more sensitive to arsenite and cisplatin treatment. Polysome analysis revealed an 80S peak 2 hours after arsenite treatment in cells overexpressing phosphomimetic eIF4E, indicating translational stalling. Nonetheless, a selective increase was observed in the synthesis of some proteins (cyclin D1, HuR, and Mcl-1). We conclude that phosphorylation of eIF4E confers resistance to various cell stressors and that a direct interaction or regulation of 4E-T by eIF4E is required. Further delineation of this process may identify novel therapeutic avenues for cancer treatment, and these results support the use of modern Mnk1/2 inhibitors in conjunction with standard therapy.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Aniline Compounds / pharmacology
-
Animals
-
Arsenites / toxicity
-
Cell Line
-
Cell Proliferation / drug effects
-
Cisplatin / toxicity*
-
Cyclin D1 / metabolism
-
DNA / chemistry
-
DNA / metabolism
-
DNA Damage / drug effects*
-
ELAV-Like Protein 1 / metabolism
-
Eukaryotic Initiation Factor-4E / genetics
-
Eukaryotic Initiation Factor-4E / metabolism*
-
HeLa Cells
-
Humans
-
Mice
-
Mice, Knockout
-
Mutagenesis, Site-Directed
-
Myeloid Cell Leukemia Sequence 1 Protein / metabolism
-
Nucleocytoplasmic Transport Proteins / antagonists & inhibitors
-
Nucleocytoplasmic Transport Proteins / genetics
-
Nucleocytoplasmic Transport Proteins / metabolism*
-
Oxidative Stress / drug effects*
-
Phosphorylation / drug effects
-
Protein Binding
-
Protein Biosynthesis / drug effects
-
Protein Serine-Threonine Kinases / deficiency
-
Protein Serine-Threonine Kinases / genetics
-
Protein Serine-Threonine Kinases / metabolism
-
Purines / pharmacology
Substances
-
Aniline Compounds
-
Arsenites
-
CGP 57380
-
EIF4ENIF1 protein, human
-
ELAV-Like Protein 1
-
Elavl1 protein, mouse
-
Eukaryotic Initiation Factor-4E
-
Mcl1 protein, mouse
-
Myeloid Cell Leukemia Sequence 1 Protein
-
Nucleocytoplasmic Transport Proteins
-
Purines
-
Cyclin D1
-
DNA
-
Mknk1 protein, mouse
-
Mknk2 protein, mouse
-
Protein Serine-Threonine Kinases
-
arsenite
-
Cisplatin
Grants and funding
SRC is funded by the following grants: Fondo de Investigaciones Sanitarias (PI 11/00185, RD09/0076/00066), Mutua Madrileña (FMMA/2011/11), Redes Temáticas de Investigación Cooperativa en Salud (Ref. RD06/0020/0104), and Generalitat de Catalunya (Ref. 2009SGR756). TA is funded by Instituto de Salud Carlos III, grant CP10/00624 and grant PI13/00763 co-financed by the European Regional Development Fund (ERDF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.