Suppression of interferon signaling via small-molecule modulation of TFAM.

Abstract

The mitochondrial transcription factor A (TFAM) is essential for mitochondrial genome maintenance. It binds to mitochondrial DNA (mtDNA) and determines the abundance, packaging, and stability of the mitochondrial genome. Because its function is tightly associated with mtDNA, TFAM has a protective role in mitochondrial diseases, and supportive studies demonstrate reversal of disease phenotypes by TFAM overexpression. In addition, TFAM deficiency has been shown to cause release of mtDNA into the cytosol and activation of the cGAS/STING innate immune response pathway. As such, TFAM presents as a unique target for therapeutic intervention, but limited efforts for activators have been reported. Herein, we disclose novel TFAM small-molecule modulators with sub-micromolar activity. Our results demonstrate that these compounds result in an increase of TFAM protein levels and mtDNA copy number. This results in inhibition of a mtDNA stress-mediated inflammatory response by preventing mtDNA escape into the cytosol. Furthermore, we see beneficial effects in cellular disease models in which boosting TFAM activity has been advanced as a disease-modifying strategy including improved energetics in MELAS cybrid cells and a decrease of fibrotic markers in systemic sclerosis fibroblasts. These results highlight the therapeutic potential of using small-molecule TFAM activators in indications characterized by mitochondrial dysfunction.