Abstract 15799: Snf1-Related Kinase Enhances Cardiomyocyte Metabolism and Increases Mitochondrial Membrane Potential and Glycolysis Through Tribbles Homolog 3 Downregulation
Introduction: Snf1-related Kinase (SNRK) is a serine/threonine kinase with sequence similarity to AMP-activated kinase, but its function and substrates are unknown. We have found that SNRK is upregulated in hearts from patients with ischemic cardiomyopathy, and our previous gene array data indicates that SNRK alters metabolic gene expression. Here, we assessed the hypothesis that SNRK regulates cardiomyocyte metabolism.
Results: SNRK downregulation reduced ATP by 23.34±4.86% in neonatal rat cardiomyocytes (NRCM) compared to nonsilencing siRNA, and SNRK adenovirus increased ATP by 20.67±2.37% compared to GFP control. SNRK knockdown reduced the oxygen consumption rate both at baseline and with the mitochondrial uncoupler carbonyl cyanide 3-chlorophenylhydrazone, while SNRK overexpression increased oxygen consumption. Mitochondrial content was unchanged, however, tetramethylrhodamine ethyl ester (TMRE) staining was increased, suggesting that SNRK maintains mitochondrial membrane potential. Furthermore, the extracellular acidification rate was reduced 19.47±1.36% with SNRK knockdown and increased 12.57±1.10% with overexpression, signifying that SNRK enhances glycolytic flux. This was supported by findings that SNRK also increased lactate, hexokinase I and II mRNA, glucose uptake, and glucose transporter GLUT1 and 4 mRNA. Additionally, palmitate oxidation was reduced 69.39±6.81% with SNRK downregulation and increased 96.47±9.69% with overexpression, and phosphorylation of acetyl-coA carboxylase (ACC) was increased by SNRK. To find a mechanism for these effects, we conducted a yeast two hybrid screen with SNRK bait. Tribbles homolog 3 (TRIB3), an inhibitor of Akt activation, was identified as a SNRK-interacting protein through prototrophic and LacZ+ screening. In NRCM, SNRK decreased TRIB3 protein levels. Additionally, TRIB3 knockdown rescued the effects of SNRK knockdown on mitochondrial membrane potential and glycolytic rate, suggesting that SNRK regulates metabolism through TRIB3.
Conclusions: Our results demonstrate that SNRK augments mitochondrial membrane potential, glucose utilization, and fatty acid oxidation, and that SNRK downregulates TRIB3 to enhance cardiomyocyte metabolic flux.
- © 2011 by American Heart Association, Inc.