Abstract 9466: Recombinant Mitochondrial Transcriptional Factor A Protein Attenuates Pathological Remodeling in Cardiac Myocytes
Introduction: Mitochondrial transcriptional factor A (TFAM), a nucleoid protein of mitochondrial DNA (mtDNA), is essential not only for transcription and replication but also maintenance of mtDNA. We have previously reported that, in failing myocardium, TFAM expression and the myocardial mtDNA copy number were decreased. Moreover, in myocardial infarction, overexpression of TFAM attenuated the decrease in the mtDNA copy number, ameliorated cardiac remodeling, and markedly improved survival. Since exogenously-administrated recombinant TFAM protein has been shown to enter mitochondria in cultured cells, we examined our hypothesis that recombinant TFAM protein administration attenuates pathological remodeling in cardiac myocytes.
Methods and Results: We prepared recombinant human TFAM including mitochondrial targeting signal by glutathione s-transferase fusion protein purification protocol. Recombinant TFAM was successfully recruited into mitochondria of rat neonatal cardiac myocytes, whereas TFAM without mitochondrial targeting signal was observed in nucleus. Treatment with TFAM increased the mtDNA copy number dose-dependently (100 nM: 1.8±0.1-folds), whereas it did not change morphology or population of mitochondria (electron microscopy). To elucidate the mechanism of TFAM on signaling pathways in cardiac hypertrophy, we investigated the effects of TFAM on the nuclear factor of activated T cell (NFAT) signaling, which is a major transcriptional factor regulating pathological hypertrophy and remodeling. TFAM totally abolished NFAT nuclear translocation induced by both angiotensin II (41±3% to 2±1%, p<0.01) and endothelin-1 (43±3% to 3±1%, p<0.01), suppressing respective NFAT transcriptional activity and NFAT-dependent gene expression. TFAM inhibited subsequent morphological hypertrophy of cardiac myocytes (angiotensin II: 1686±37 to 1167±20 μ m2, p<0.01, and endothelin-1: 1759±44 to 1206±21 μ m2, p<0.01).
Conclusion: Recombinant TFAM increases the mtDNA copy number, and attenuates angiotensin II and endothelin-1-induced hypertrophy via inhibiting NFAT signaling. Recombinant TFAM would be an attractive, novel therapeutic strategy for cardiac hypertrophy and remodeling.
- © 2011 by American Heart Association, Inc.