Cellular stresses profoundly inhibit protein synthesis and modulate the states of phosphorylation of multiple translation factors.
We have examined the effects of widely used stress-inducing agents on protein synthesis and on regulatory components of the translational machinery. The three stresses chosen, arsenite, hydrogen peroxide and sorbitol, exert their effects in quite different ways. Nonetheless, all three rapidly ( approximately 30 min) caused a profound inhibition of protein synthesis. In each case this was accompanied by dephosphorylation of the eukaryotic initiation factor (eIF) 4E-binding protein 1 (4E-BP1) and increased binding of this repressor protein to eIF4E. Binding of 4E-BP1 to eIF4E correlated with loss of eIF4F complexes. Sorbitol and hydrogen peroxide each caused inhibition of the 70-kDa ribosomal protein S6 kinase, while arsenite activated it. The effects of stresses on the phosphorylation of eukaryotic elongation factor 2 also differed: oxidative stress elicited a marked increase in eEF2 phosphorylation, which is expected to contribute to inhibition of translation, while the other stresses did not have this effect. Although all three proteins (4E-BP1, p70 S6 kinase and eEF2) can be regulated through the mammalian target of rapamycin (mTOR), our data imply that stresses do not interfere with mTOR function but act in different ways on these three proteins. All three stresses activate the p38 MAP kinase pathway but we were able to exclude a role for this in their effects on 4E-BP1. Our data reveal that these stress-inducing agents, which are widely used to study stress-signalling in mammalian cells, exert multiple and complex inhibitory effects on the translational machinery.
Patel
Jashmin
J
Department of Biosciences, University of Kent at Canterbury, Canterbury, UK.
McLeod
Laura E
LE
Vries
Robert G J
RG
Flynn
Andrea
A
Wang
Xuemin
X
Proud
Christopher G
CG
D000818:Animals; D018053:Arsenites / Q000494:pharmacology*; D016466:CHO Cells / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D006224:Cricetinae; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009994:Osmolar Concentration; D020652:Peptide Elongation Factor 2 / Q000378:metabolism*; D010448:Peptide Initiation Factors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D014176:Protein Biosynthesis / Q000187:drug effects*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases / Q000187:drug effects / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D018053:Arsenites; D002352:Carrier Proteins; D020652:Peptide Elongation Factor 2; D010448:Peptide Initiation Factors; D010750:Phosphoproteins; D011500:Protein Synthesis Inhibitors; D006861:Hydrogen Peroxide; D019893:Ribosomal Protein S6 Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C015001:arsenite