BIOGENESIS OF THE MITOCHONDRIAL INNER MEMBRANE

SUMMARY Mitochondrial dysfunction is a common contributing factor to degenerative diseases, including the neural and muscular systems; yet mechanistic studies in mammals are limited because adequate tools and approaches are lacking. Moreover, a greater understanding of the protein translocation mechanisms in model organisms such as S. cerevisiae and zebrafish is needed, because protein translocation is linked to metabolism, signaling, and mitochondrial quality control and stress pathways such as mitophagy. Long-term, modulating mitochondrial protein import pathways therefore is a potential target for treating diseases. The overall goals of this proposal are (1) to increase our mechanistic understanding of protein import pathways into mitochondria in both yeast and mammalian cells and (2) to understand how defects in protein translocation contribute to disease. Attenuating protein translocation pathways can alter the location of mitochondrial proteins that are dual-localized (located to mitochondria and another compartment), change mitochondrial stress pathways, and induce selective turnover of mitochondria via mitophagy. However, there is a critical gap in developing small molecule probes with specificity for modulating mitochondrial protein import specifically in mammalian cells while minimizing off-target effects. Three specific study aims are proposed to accomplish these goals. In Aim 1, a new cell based screen in mammalian cells to identify modulators for all mitochondrial protein import pathways and specific cargo will be implemented. In Aim 2, a series of experimental approaches will be used to characterize specificity of the probes, to minimize off-target effects in mammalian cells and yeast, with the goal of developing specific probes. In Aim 3, existing and new small molecules will be characterized in mechanistic studies, particularly focusing on how defects in protein import alter mitochondrial stress pathways in mitophagy. In addition to increasing fundamental knowledge about the mechanisms of protein translocation in mitochondria, this application may have a broad impact on public health because our approach will provide new tools that will provide a strategy for developing therapeutics for diseases that can be modified by attenuating protein translocation.