Alcohol regulates eukaryotic elongation factor 2 phosphorylation via an AMP-activated protein kinase-dependent mechanism in C2C12 skeletal myocytes.
Ethanol decreases protein synthesis in cells, although the underlying regulatory mechanisms of this process are not fully established. In the present study incubation of C2C12 myocytes with 100 mm EtOH decreased protein synthesis while markedly increasing the phosphorylation of eukaryotic elongation factor 2 (eEF2), a key component of the translation machinery. Both mTOR and MEK pathways were found to play a role in regulating the effect of EtOH on eEF2 phosphorylation. Rapamycin, an inhibitor of mammalian target of rapamycin, and the MEK inhibitor PD98059 blocked the EtOH-induced phosphorylation of eEF2, whereas the p38 MAPK inhibitor SB202190 had no effect. Unexpectedly, EtOH decreased the phosphorylation and activity of the eEF2 upstream regulator eEF2 kinase. Likewise, treatment of cells with the inhibitor rottlerin did not block the stimulatory effect of EtOH on eEF2, suggesting that eEF2 kinase (eEF2K) does not play a role in regulating eEF2. In contrast, increased eEF2 phosphorylation was correlated with an increase in AMP-activated protein kinase (AMPK) phosphorylation and activity. Compound C, an inhibitor of AMPK, suppressed the effects of EtOH on eEF2 phosphorylation but had no effect on eEF2K, indicating that AMPK regulates eEF2 independent of eEF2K. Finally, EtOH decreased protein phosphatase 2A activity when either eEF2 or AMPK was used as the substrate. Thus, this later action may partially account for the increased phosphorylation of eEF2 in response to EtOH and the observed sensitivity of AMPK to rapamycin and PD98059 treatments. Collectively, the induction of eEF2 phosphorylation by EtOH is controlled by an increase in AMPK and a decrease in protein phosphatase 2A activity.
Hong-Brown
Ly Q
LQ
Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA. lqh10@psu.edu
Brown
C Randell
CR
Huber
Danuta S
DS
Lang
Charles H
CH
D055372:AMP-Activated Protein Kinases; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D054736:Elongation Factor 2 Kinase; D000431:Ethanol / Q000737:chemistry / Q000494:pharmacology*; D051379:Mice; D009097:Multienzyme Complexes / Q000502:physiology*; D032342:Muscle Cells / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000737:chemistry / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D009097:Multienzyme Complexes; D011500:Protein Synthesis Inhibitors; D000431:Ethanol; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517690:Eef2k protein, mouse; D054736:Elongation Factor 2 Kinase; D055372:AMP-Activated Protein Kinases