Abstract
Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein occasionally involved in cell death that primarily regulates mitochondrial energy metabolism under normal cellular conditions. AIF catalyzes the oxidation of NADH in vitro, yet the significance of this redox activity in cells remains unclear. Here, we show that through its enzymatic activity AIF is a critical factor for oxidative stress-induced activation of the mitogen-activated protein kinases JNK1 (c-Jun N-terminal kinase), p38, and ERK (extracellular signal-regulated kinase). AIF-dependent JNK1 signaling culminates in the cadherin switch, and genetic reversal of this switch leads to apoptosis when AIF is suppressed. Notably, this widespread ability of AIF to promote JNK signaling can be uncoupled from its more limited role in respiratory chain stabilization. Thus, AIF is a transmitter of extra-mitochondrial signaling cues with important implications for human development and disease.