Abstract 12324: Sestrin2 is an Essential Regulator of Cardiac AMPK Signaling During Ischemia
Background: A novel stress-inducible protein, sestrin2, has emerged as a mediator of AMP-activated Protein Kinase (AMPK) signaling pathway. AMPK is a pertinent stress-activated kinase shown to have substantial cardioprotective capabilities against myocardial ischemia/reperfusion (I/R) injury. The regulation of AMPK in the ischemic heart remains elusive and is critical to the development of new therapeutic strategies. We hypothesized that sestrin2 mediating cardiac AMPK activation and protecting heart from ischemic damage.
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, sestrin2 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. Intriguingly, sestrin2 knock out hearts did demonstrate impaired ischemic AMPK activation and more sensitive to I/R-induced injury as compared to wild type hearts (p≤0.01).
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.
- © 2013 by American Heart Association, Inc.