Josh Elias (Chemical & Systems Biology)
Richard Zare (Chemistry)

Mitochondria are more than the “powerhouses” of cells; they lie at the nexus of many signaling networks, and influence diverse disease processes, including aging, cancer, heart disease, and metabolic disorders. Recent research has suggested that mitochondrial enzymes, just like many proteins in the rest of the cell, may be regulated not just by mass action, but also by protein post-translational modifications (PTMs). These dynamic modifications may explain how mitochondrial enzymes both contribute to a cell’s energy state, and shunt important metabolites towards the biosynthesis of molecules that are required for the specialized functions of the body’s diverse cell types.

One such PTM, acetylation of lysines, has been shown to decrease the activity of many energy-related enzymes inside mitochondria. Although acetylation is best understood in the context of regulating gene expression in the nucleus, it has recently been shown to be a crucial component of mitochondrial regulation. In the nucleus, acetylation, is regulated by enzymes that add this PTM to proteins (acetyltransferases) and enzymes that remove it (deacetylases). In mitochondria, only deacetylase activity has been documented however. Our proposal explores possible mechanisms that acetylation is added to lysines. Our hypothesis is that acetylation is influenced by the concentration of the metabolite acetyl coenzyme A. This could cause a negative feedback loop that regulates energy and metabolite flux through mitochondria. We propose a cross-disciplinary, collaborative set of experiments that test this hypothesis using a proteomic and metabolomic view of cellular metabolism (Elias Lab) and a novel use of Desorption Electrospray Ionization (DESI) to definitively and simultaneously measure rates of protein acetylation, and consequent changes in enzyme activity at millisecond time scales (Zare lab). This proof-of-concept proposal represents the beginning for this new technology; measurement of the precise effect PTMs have on intact enzyme complexes could fundamentally change the way we study enzyme pathways.