Presentation description

It has been characterized that mitochondria perform an essential role in numerous metabolic pathways and that defects in mitochondrial function are associated with the progression of several age-related neurodegenerative diseases. Our lab recently discovered a mitochondrial degradation pathway, called mitochondrial-derived-compartments (MDCs) that is induced in response to several cellular stressors, as well as in old-aged cells. We have shown that MDCs selectively remove a subset of membrane proteins from the outer mitochondrial membrane and failure to form these structures exacerbates mitochondrial dysfunction, suggesting that the MDC pathway protects mitochondria in times of stress. Formation of MDCs requires the conserved import receptor Tom70, an outer mitochondrial membrane protein that facilitates the import of hydrophobic proteins into the mitochondria and acts as a cochaperone that assists in reducing the proteotoxicity of aggregation-prone proteins. Currently, the role that Tom70 plays in MDC formation is unknown. To analyze the function of Tom70 in MDC formation, we used the budding yeast, Saccharomyces cerevisiae, to create genetically mutated strains that expressed either truncated versions of the Tom70 protein, which systematically removed functional domains, or expressed Tom70 mutations that removed binding to cytosolic chaperones. Assessment of MDC formation was done via MDC formation assays, and growth was analyzed by temperature sensitivity assays. Preliminary results determined that the majority of Tom70 mutations analyzed were unable to rescue the temperature sensitivity of a tom70Δ strain and were also unable to support MDC formation. These results indicate that many of the Tom70 mutations analyzed strongly disrupted Tom70 function and suggest that even minor alterations to Tom70 structure impair multiple functions of this protein. In total, the results from this study will contribute to our understanding of the MDC pathway as it provides an important first step in elucidating key features of Tom70 that are required for MDC formation.