S-nitrosylation of transglutaminase 2 impairs fatty acid-stimulated contraction in hypertensive cardiomyocytes.

The myocardium in hypertensive heart exhibits decreased fatty acid utilization and contractile dysfunction, leading to cardiac failure. However, the causal relationship between metabolic remodeling and cardiomyocyte contractility remains unestablished. Transglutaminase 2 (TG2) has been known to promote ATP production through the regulation of mitochondrial function. In this study, we investigated the involvement of TG2 in cardiomyocyte contraction under fatty acid supplementation. Using TG2 inhibitor and TG2-deficient mice, we demonstrated that fatty acid supplementation activated TG2 and increased ATP level and contractility of cardiac myocyte from the normal heart. By contrast, in cardiac myocytes from angiotensin-II-treated rats and mice, the effects of fatty acid supplementation on TG2 activity, ATP level, and myocyte contraction were abolished. We found that TG2 was inhibited by S-nitrosylation and its level increased in hypertensive myocytes. Treatment with inhibitor for neuronal NOS restored fatty acid-induced increase of TG2 activity and myocyte contraction. Moreover, intracellular Ca2+ levels were increased by fatty acid supplementation in both normal and hypertensive myocytes, showing that S-nitrosylation of TG2 but not alteration of intracellular Ca2+ levels is responsible for contractile dysfunction. These results indicate that TG2 plays a critical role in the regulation of myocyte contractility by promoting fatty acid metabolism and provide a novel target for preventing contractile dysfunction in heart with high workload.

Genetic Code Expansion by Degeneracy Reprogramming of Arginyl Codons.

The genetic code in most organisms codes for 20 proteinogenic amino acids or translation stop. In order to encode more than 20 amino acids in the coding system, one of stop codons is usually reprogrammed to encode a non-proteinogenic amino acid. Although this approach works, usually only one amino acid is added to the amino acid repertoire. In this study, we incorporated non-proteinogenic amino acids into a protein by using a sense codon. As all the codons are allocated in the universal genetic code, we destroyed all the tRNA(Arg) in a cell-free protein synthesis system by using a tRNA(Arg) -specific tRNase, colicin D. Then by supplementing the system with tRNACCU , the translation system was partially restored. Through this creative destruction, reprogrammable codons were successfully created in the system to encode modified lysines along with the 20 proteinogenic amino acids.