Translation regulation after taxol treatment in NIH3T3 cells involves the elongation factor (eEF)2.
Changes to the translational machinery that occur during apoptosis have been described in the last few years. The two principal ways in which translational factors are modified during apoptosis are: (i) changes in protein phosphorylation and (ii) specific proteolytic cleavages. Taxol, a member of a new class of anti-tubulin drugs, is currently used in chemotherapeutic treatments of different types of cancers. We have previously demonstrated that taxol induces calpain-mediated apoptosis in NIH3T3 cells [Piñeiro et al., Exp. Cell Res., 2007, 313:369-379]. In this study we found that translation was significantly inhibited during taxol-induced apoptosis in these cells. We have studied the phosphorylation status and expression levels of eIF2a, eIF4E, eIF4G and the regulatory protein 4E-BP1, all of which are implicated in translation regulation. We found that taxol treatment did not induce changes in eIF2alpha phosphorylation, but strongly decreased eIF4G, eIF4E and 4E-BP1 expression levels. MDL28170, a specific inhibitor of calpain, prevented reduction of eIF4G, but not of eIF4E or 4E-BP1 levels. Moreover, the calpain inhibitor did not block taxol-induced translation inhibition. All together these findings demonstrated that none of these factors are responsible for the taxol-induced protein synthesis inhibition. On the contrary, taxol treatment increased elongation factor eEF2 phosphorylation in a calpain-independent manner, supporting a role for eEF2 in taxol-induced translation inhibition.
Piñeiro
David
D
Departamento de Bioquímica-Investigación, Hospital Ramón y Cajal, 28034 Madrid, Spain.
González
Víctor M
VM
Hernández-Jiménez
Macarena
M
Salinas
Matilde
M
Martín
M Elena
ME
D048868:Adaptor Proteins, Signal Transducing; D000255:Adenosine Triphosphate / Q000172:deficiency; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis; D002154:Calpain / Q000037:antagonists & inhibitors; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D053148:Caspase 3 / Q000235:genetics; D061945:Caspase Inhibitors; D018797:Cell Cycle Proteins; D039561:Eukaryotic Initiation Factor-4E / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D039642:Eukaryotic Initiation Factors; D051379:Mice; D041681:NIH 3T3 Cells; D017239:Paclitaxel / Q000494:pharmacology*; D020652:Peptide Elongation Factor 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000187:drug effects*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism