Highlights d Impairment of most, but not all, mitochondrial processes causes UPR mt d Conditions inducing UPR mt lead to a decrease in mitochondrial membrane potential d Decrease in mitochondrial membrane potential acts as a signal that triggers UPR mt d The MTS of ATFS-1 acts as a sensor for decreased mitochondrial membrane potential

Graphical AbstractHighlights d Impairment of most, but not all, mitochondrial processes causes UPR mt d Conditions inducing UPR mt lead to a decrease in mitochondrial membrane potential d Decrease in mitochondrial membrane potential acts as a signal that triggers UPR mt d The MTS of ATFS-1 acts as a sensor for decreased mitochondrial membrane potential