Subcellular analysis of the disulfide proteome in mammlian cells

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Cells in our bodies are continually exposed to potentially harmful molecules called reactive oxygen species (ROS) as a result of normal cellular metabolism and exposure to inflammatory factors called cytokines. It is essential for cells to detect ROS levels and respond in an appropriate manner. Recent studies in yeast and bacteria have shown that certain proteins within the cell can "sense" ROS by virtue of sulfur containing amino acids which can be directly oxidized by ROS and undergo a chemical linkage called a disulfide bond. The formation of disulfide bonds leads to activation of key proteins which can then function to increase expression of genes that either participate in a protective anti-oxidant response or, if the levels of ROS are high, initiate cell death. Emerging evidence indicates that a similar disulfide-bond controlled activation system may also occur in mammalian cells as well. ROS, produced at the cell membrane and in specialized organelles called mitochondria, can trigger signaling events leading to altered gene expression in the nucleus. The exact type of proteins within mitochondria and nuclei that undergo disulfide bonding in response to elevated ROS is poorly understood. Using mouse cell culture models that mimic physiological conditions, combined with a novel protein separation technique, we will determine the spectrum of disulfide linked proteins in mitochondria and nuclei that are affected by increased ROS levels. Initial studies have revealed that a major anti-oxidant protein can interact, via disulfide bonding, with nuclear proteins involved in development and DNA repair. Identification and analysis of ROS sensing proteins will provide insight into how oxidative cellular conditions influence both normal and disease-associated signaling processes.