Keap1 controls protein S-nitrosation and apoptosis-senescence switch in endothelial cells

Abstract Premature senescence, a death escaping pathway for cells experiencing stress, is conducive to aging and cardiovascular diseases. The molecular switchbetween senescentand apoptotic fate remains, however, poorly recognized. Nrf2 is an important transcription factor orchestrating adaptive responseto cellular stress. Here, we show that both human primary endothelial cells (ECs) and murine aortas lacking Nrf2 signaling are senescentbut unexpectedly do not encounter damaging oxidative stress. Instead, they exhibit markedly increased S- nitrosationof proteins. A functional role of S- nitrosationis protection of ECs from death by inhibition of NOX4-mediated oxidative damage and redirection of ECs to premature senescence. S- nitrosationand senescenceare mediated by Keap1, a direct binding partner of Nrf2, which colocalizes and precipitates with nitric oxide synthase (NOS) and transnitrosating protein GAPDH in ECs devoid of Nrf2. We conclude that the overabundance of this “unrestrained” Keap1determines the fate of ECs by regulation of S- nitrosationand propose that Keap1/GAPDH/NOS complex may serve as an enzymatic machinery for S- nitrosationin mammalian cells.