Abstract 16240: Tristetraprolin (TTP) is a Novel Regulator of Branched-chain Amino Acid (BCAA) Catabolism in the Heart

Abstract

Introduction: Heart failure (HF) is associated with the accumulation of branched-chain amino acids (BCAAs) in heart and plasma. Besides, BCAAs are essential for normal cell growth and function. Therefore, tight regulation of BCAA metabolism is crucial to maintain normal cellular homeostasis. Tristetraprolin (TTP), an mRNA binding protein that promotes the degradation of its targets and regulates a number of biological processes including cellular metabolism. In in silico analyses, we identified the E2 subunit of branched-chain α-ketoacid dehydrogenase complex (BCKDC), the rate-limiting enzyme complex in BCAA catabolism, as a potential target of TTP. Here we assess the hypothesis that TTP plays a regulatory role in BCAA catabolism through regulating BCKDC-E2 in the heart. We also investigate TTP’s contribution in the pathogenesis of HF by modulating BCAA catabolism. Results: We observed a significant increase in TTP levels in cardiac tissue of human HF and mouse myocardial infarct induced HF samples. We also showed that deletion of TTP significantly decreases BCAA levels in vitro. As BCAA accumulation in the heart is associated with the pathogenesis of HF, we investigated whether TTP can regulate cardiac BCAA catabolism. Computational analysis of mRNAs of enzymes, which are involved in BCAA catabolism, revealed highly conserved TTP binding sites in BCKDC-E2 mRNA, suggesting that it is a potential target of TTP. BCKDC-E2 mRNA levels were significantly higher in the heart of TTP knock-out mice and TTP siRNA treated cardiomyocytes. Additionally, the mRNA stability of BCKDC-E2 was higher in cardiomyocytes with TTP downregulation, further confirming that TTP regulates the stability of this mRNA. Moreover, RNA co-immunoprecipitation studies demonstrated that TTP physically interacts with the BCKDC-E2 mRNA. Finally, we showed that BCKDC-E2 mRNA levels were significantly decreased in human HF samples. Conclusion: Our data indicate that TTP levels are increased in HF samples and TTP regulates BCAA catabolism in the heart by binding to and degrading BCKDC-E2 mRNA. These findings suggest that alterations in TTP expression may play a role in the development of HF based on its effect upon BCKDC-E2 and BCAA catabolism.