The Role of Conserved Uncharacterized Proteins in Mitochondrial Health and Protein Homeostasis

Establishing and maintaining proper mitochondrial functions are critical for cellular wellbeing. To maintain this homeostasis, several conserved mechanisms are tasked to survey and protect the mitochondria against damage. This system is known as mitochondrial quality control (MQC). Malfunctioning MQC can lead to an accumulation of damaged or misfolded proteins, leading to a multitude of diseases and general degeneration while aging. Although paramount to overall mitochondrial health, few mechanistic details are known about the molecular functions and the proteins involved with the MQC. With a goal in mind to elucidate functions of highly conserved mitochondrial proteins of unknown functions, our lab identified Afg1, a conserved mitochondrial AAA+ ATPase (LACE-1 or AFG1L in higher eukaryotes), in a genetic knockout screen as a potential member of the MQC. Specifically, expression of Afg1 in Saccharomyces cerevisiae model lacking the mitochondrial proteases Oma1 and the m-AAA protease mitigated survival defect of this mutant. By applying mechanistic biochemistry and genetic approaches, we further discovered a novel role of Afg1 in mediating mitochondrial matrix proteostasis, in particular through aging and at times of cellular oxidative stress. Finally, we determined an evolutionarily conserved physiological role of the Afg1 ortholog, LACE-1, in the metazoan model Caenorhabditis elegans. Animals deficient in LACE-1 display a reduced lifespan and impaired oxidative stress tolerance. In particular, we found that loss of LACE-1 lead to impaired mitochondrial proteostasis in motor neuron circuitry and abnormal behavioral plasticity. Taken together, these results demonstrate that Afg1/LACE-1 is a bona fide member of the MQC and establish its conserved role in mediating mitochondrial proteostasis. The molecular function Afg1/LACE-1 performs has a profound effect on both physiological and behavioral aspects in higher eukaryotes