ATM is activated by ATP depletion and modulates mitochondrial function through NRF1
We have uncovered new insights into the symptoms of ataxia-telangiectasia (A-T). Neurons with high physiological activity, particularly cerebellar Purkinje cells, have large and dynamic ATP demands. Depletion of ATP generates reactive oxygen species that activate ATM (the A-T Mutated gene product). Activated in this way, but not by DNA damage, ATM phosphorylates nuclear respiratory factor-1 (NRF1). This leads to NRF1 dimerization, nuclear translocation and the upregulation of nuclear-encoded mitochondrial genes, thus enhancing the capacity of the electron transport chain (ETC) and restoring mitochondrial function. In cells with ATM deficiency, resting ATP levels are normal, but cells replenish ATP poorly following surges in energy demand and chronic ATP insufficiency endangers cell survival. This is a particular problem for energy-intensive cells such as Purkinje cells, which degenerate in A-T. Our findings thus identify ATM as a guardian of mitochondrial output as well as genomic integrity, and suggest that alternate fuel sources may ameliorate A-T disease symptoms.\n\nSummaryOxidative stress, resulting from neuronal activity and depleted ATP levels, activates ATM, which phosphorylates NRF1, causing nuclear translocation and upregulation of mitochondrial gene expression. In ATM deficiency, ATP levels recover more slowly, particularly in active neurons with high energy demands.