isolation-specific-neuron-populations-from-roundworm-caenorhabditis

Isolation of Specific Neuron Populations from Roundworm <em>Caenorhabditis elegans</em>

During the aging process, many cells accumulate high levels of damage leading to cellular dysfunction, which underlies many geriatric and pathological ...

University of Nebraska

Functional integrity of mitochondria is critical for optimal cellular physiology. A suite of conserved mitochondrial proteases known as intramitochondrial quality control represents one of the mechanisms assuring normal mitochondrial function. We previously demonstrated that ATP-independent metalloprotease Oma1 mediates degradation of hypohemylated Cox1 subunit of cytochrome c oxidase and is active in cytochrome c oxidase-deficient mitochondria. Here we show that Oma1 is important for adaptive responses to various homeostatic insults and preservation of normal mitochondrial function under damage-eliciting conditions. Changes in membrane potential, oxidative stress, or chronic hyperpolarization lead to increased Oma1-mediated proteolysis. The stress-triggered induction of Oma1 proteolytic activity appears to be associated with conformational changes within the Oma1 homo-oligomeric complex, and these alterations likely involve C-terminal residues of the protease. Substitutions in the conserved C-terminal region of Oma1 impair its ability to form a labile proteolytically active complex in response to stress stimuli. We demonstrate that Oma1 genetically interacts with other inner membrane-bound quality control proteases. These findings indicate that yeast Oma1 is an important player in IM protein homeostasis and integrity by acting in concert with other intramitochondrial quality control components. 

Stress-triggered activation of the metalloprotease Oma1 involves its C-terminal region and is important for mitochondrial stress protection in yeast.

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.  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  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.

The AAA ATPase Afg1 preserves mitochondrial fidelity and cellular health by maintaining mitochondrial matrix proteostasis.

 Normal mitochondrial function and integrity are crucial for cellular physiology. Given the paramount role of mitochondrial quality control proteases in these processes, our study focused on investigating mechanisms by which the activity of a key quality control protease Oma1 is regulated under normal conditions and in response to homeostatic insults.  Oma1 was found to be a redox-dependent protein that exists in a semi-oxidized state in yeast and mammalian mitochondria. Biochemical and genetic analyses provide evidence that activity and stability of the Oma1 oligomeric complex can be dynamically tuned in a reduction/oxidation-sensitive manner. Mechanistically, these features appear to be mediated by two intermembrane space (IMS)-exposed highly conserved cysteine residues, Cys and Cys. These residues form a disulfide bond, which likely plays a structural role and influences conformational stability and activity of the Oma1 high-mass complex. Finally, in line with these findings, engineered Oma1 substrate is shown to engage with the protease in a redox-sensitive manner.  This study provides new insights into the function of the Oma1 protease, a central controller of mitochondrial membrane homeostasis and dynamics, and reveals the novel conserved mechanism of the redox-dependent regulation of Oma1.  Disulfide bonds formed by IMS-exposed residues Cys and Cys play an important evolutionarily conserved role in the regulation of Oma1 function. We propose that the redox status of these cysteines may act as a redox-tunable switch to optimize Oma1 proteolytic function for specific cellular conditions or homeostatic challenges.

Article	Year
Stress-triggered activation of the metalloprotease Oma1 involves its C-terminal region and is important for mitochondrial stress protection in yeast. The Journal of biological chemistry\| PubMed ID: 24648523	2014
The AAA ATPase Afg1 preserves mitochondrial fidelity and cellular health by maintaining mitochondrial matrix proteostasis. Journal of cell science\| PubMed ID: 30301782	2018
Redox Regulation of the Mitochondrial Quality Control Protease Oma1. Antioxidants & redox signaling\| PubMed ID: 31044600	2019

Nataliya Zahayko

Biography

JoVE Journal Publications

Other Publications