Background: Oma1 is a conserved membrane-bound protease that forms a high molecular mass complex. Results: Oma1 activity is induced by stress stimuli and required for survival. The activation is linked to changes in Oma1 oligomer stability and involves its C-terminal region. Conclusion: Oma1 function is activated by mitochondrial stress and is important for stress tolerance. Significance: Novel insights into Oma1 function and a potential stress activation mechanism are provided.

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Mitochondrial functions are critical for cellular physiology; therefore, several conserved mechanisms are in place to maintain the functional integrity of mitochondria. However, many of the molecular details and components involved in ensuring mitochondrial fidelity remain obscure. Here, we identify a novel role for the conserved mitochondrial AAA ATPase Afg1 in mediating mitochondrial protein homeostasis during aging and in response to various cellular challenges. Saccharomyces cerevisiae cells lacking functional Afg1 are hypersensitive to oxidative insults, unable to tolerate protein misfolding in the matrix compartment and exhibit progressive mitochondrial failure as they age. Loss of the Afg1 ortholog LACE-1 in Caenorhabditis elegans is associated with reduced lifespan, impeded oxidative stress tolerance, impaired mitochondrial proteostasis in the motor neuron circuitry and altered behavioral plasticity. Our results indicate that Afg1 is a novel protein quality control factor, which plays an important evolutionarily conserved role in mitochondrial surveillance, and cellular and organismal health.

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