TFAM is an autophagy receptor that limits inflammation by binding to cytoplasmic mitochondrial DNA

Abstract

When cells are stressed, DNA from energy-producing mitochondria can leak out and drive inflammatory immune responses if not cleared. Cells employ a quality control system called autophagy to specifically degrade damaged components. We discovered that mitochondrial transcription factor A (TFAM)—a protein that binds mitochondrial DNA (mtDNA)—helps to eliminate leaked mtDNA by interacting with the autophagy protein LC3 through an autolysosomal pathway (we term this nucleoid-phagy). TFAM contains a molecular zip code called the LC3 interacting region (LIR) motif that enables this binding. Although mutating TFAM’s LIR motif did not affect its normal mitochondrial functions, more mtDNA accumulated in the cell cytoplasm, activating inflammatory signalling pathways. Thus, TFAM mediates autophagic removal of leaked mtDNA to restrict inflammation. Identifying this mechanism advances understanding of how cells exploit autophagy machinery to selectively target and degrade inflammatory mtDNA. These findings could inform research on diseases involving mitochondrial damage and inflammation. Liu, Zhen, Xie, Luo, Zeng, Zhao et al. show that the major nucleoid protein TFAM interacts with cytoplasmic LC3B during oxidative or inflammatory stress to attenuate mitochondrial DNA-induced inflammation via the cGAS–STING pathway.