Mitochondrial active Ras2 protein promotes apoptosis and regulated cell death in a cAMP/PKA pathway-dependent manner in budding yeast

In previous papers, using the eGFP-RBD3 probe, which binds Ras-GTP with high affinity, we showed that activated Ras proteins are localized to the plasma membrane and in the nucleus in wild-type Saccharomyces cerevisiae cells growing exponentially on glucose, while an aberrant accumulation of activated Ras in mitochondria correlates to mitochondrial dysfunction, accumulation of ROS and an increase of apoptosis. In this paper, we show that lack of TPS1 , which is known to trigger apoptosis in S. cerevisiae , induces localization of active Ras proteins in mitochondria, confirming the above-mentioned correlation. Next, by characterizing the ras1 Δ and ras2 Δ mutants concerning localization of active Ras proteins and propensity to undergo cell death, we show that active Ras2 proteins, which accumulate in the mitochondria following addition of acetic acid, a well-known pro-apoptotic stimulus, might be the GTPases involved in regulated cell death, while active Ras1 proteins, constitutively localized in mitochondria, might be involved in a pro-survival molecular machinery. Finally, by characterizing the gpa2 Δ and cyr1 Δ mutants concerning the propensity to undergo cell death, we show that active mitochondrial Ras proteins promote apoptosis through the cAMP/PKA pathway.