| First Author | Demeulder B | Year | 2013 |
| Journal | Biochim Biophys Acta | Volume | 1832 |
| Issue | 6 | Pages | 780-90 |
| PubMed ID | 23466593 | Mgi Jnum | J:202427 |
| Mgi Id | MGI:5519012 | Doi | 10.1016/j.bbadis.2013.02.015 |
| Citation | Demeulder B, et al. (2013) Differential regulation of eEF2 and p70S6K by AMPKalpha2 in heart. Biochim Biophys Acta 1832(6):780-90 |
| abstractText | Eukaryotic elongation factor 2 (eEF-2) and mammalian target of rapamycin (mTOR)-p70 ribosomal protein S6 kinase (p70S6K) signaling pathways control protein synthesis and are inhibited during myocardial ischemia. Intracellular acidosis and AMP-activated protein kinase (AMPK) activation, both occurring during ischemia, have been proposed to participate in this inhibition. We evaluated the contribution of AMPKalpha2, the main cardiac AMPK catalytic subunit isoform, in eEF2 and mTOR-p70S6K regulation using AMPKalpha2 KO mice. Hearts were perfused ex vivo with or without insulin, and then submitted or not to ischemia. Insulin pre-incubation was necessary to activate mTOR-p70S6K and evaluate their subsequent inhibition by ischemia. Ischemia decreased insulin-induced mTOR-p70S6K phosphorylation in WT and AMPKalpha2 KO mice to a similar extent. This AMPKalpha2-independent p70S6K inhibition correlated well with the inhibition of PKB/Akt, located upstream of mTOR-p70S6K and can be mimicked in cardiomyocytes by decreasing pH. By contrast, ischemia-induced inhibitory phosphorylation of eEF-2 was drastically reduced in AMPKalpha2 KO mice. Interestingly, AMPKalpha2 also played a role under normoxia. Its deletion increased the insulin-induced p70S6K stimulation. This p70S6K over-stimulation was associated with a decrease in inhibitory phosphorylation of Raptor, an mTOR partner identified as an AMPK target. In conclusion, AMPKalpha2 controls cardiac p70S6K under normoxia and regulates eEF-2 but not the mTOR-p70S6K pathway during ischemia. This challenges the accepted notion that mTOR-p70S6K is inhibited by myocardial ischemia mainly via an AMPK-dependent mechanism. |
