Abstract 10070: Sestrin2 Mediates the LKB1-AMPK Signaling Cascade in the Ischemic Heart
Background: AMP-activated Protein Kinase (AMPK) has recently emerged as a pertinent stress-activated kinase shown to have substantial cardioprotective capabilities against myocardial ischemia/reperfusion (I/R) injury. The regulation and activation of AMPK in the ischemic and reperfused heart still remains largely elusive and is critical to the development of new therapeutic strategies. In this study, we hypothesized that a novel stress-inducible protein, sestrin2, mediates AMPK activation in the ischemic heart.
Methods and Results: C57BL/6 mice were subjected to left anterior descending coronary artery occlusion for different time points of ischemia and I/R in order to detect the signaling activity in the left ventricle. The kinetics of AMPK phosphorylation at Thr172 of the α catalytic subunit appears brief and bell-shaped, peaking between 10 and 15 min (3.6-fold vs. sham, p<0.01), decreasing with prolonged ischemia (30 min, 2-fold vs. sham, p<0.05), and leveling off to basal levels upon reperfusion. Intriguingly, at 10 min of ischemia, there was also a robust increase in p53 accumulation compared to basal conditions (8.2-fold vs. sham, p<0.05). Consequently, sestrin2 a p53-inducible protein, accumulates at the peak of ischemic AMPK activation (10 min, 2.5-fold vs. sham, p<0.05). Respective left ventricle lysates were immunoprecipitated with sestrin2 and the immunoblots revealed that sestrin2 interacts and forms a complex with AMPK during I/R, moreover, AMPKα2 is the predominant isoform that interact with sestrin2 as compared to AMPKα1 isoform during I/R. Interestingly, LKB1, an upstream AMPK kinase becomes significantly associated with sestrin2 (5 min, 11.8-fold vs. sham, p<0.01), while there is a dramatic interaction between sestrin2 and p-AMPK (Thr172) (10 min, 4.5-fold vs. sham, p<0.01), suggesting the interaction of LKB1 with sestrin2 initiates the phosphorylation of AMPK in this complex.
Conclusions: Here we show for the first time evidence of a unique mechanism that suggests sestrin2 is a stress-induced scaffold protein that mediates the activation of AMPK in the ischemic myocardium via a time-dependent interaction with LKB1. These acute signaling events appear to be largely mediated by p53.
- © 2011 by American Heart Association, Inc.