Does H202 Regulate the Ubiquitination of System Xc-
Dr. Leah Chase
The cystine/glutamate exchanger, System xc-, plays a critical role in maintaining oxidative balance and regulating extracellular glutamate levels in the brain. Dysregulation of the transporter can be disastrous, leading to excitotoxic cell death or the development of oxidative stress, processes which are the hallmark of most neurodegenerative diseases. Unfortunately, little is known about the factors which acutely regulate System xc- activity. We recently demonstrated that oxidants acutely upregulate System xc- activity by triggering the rapid redistribution of the transporter from intracellular compartments to the cell surface. Our current work suggests that the trafficking of the transporter may be regulated by ubiquitination and that oxidant exposure directly influences the ubiquitination of the transporter. Specifically, we hypothesize that oxidant exposure leads to a reduction in ubiquitination of the transporter, slowing the internalization of the transporter from the plasma membrane. Therefore, we are testing this hypothesis directly by transfecting Cos-7 cells with a myc-tagged xCT (the primary component of the System xc- transporter) and histidine-tagged ubiquitin. These cells are then exposed to oxidants or vehicle. Ubiquitinated proteins are purified on a nickle-column and the presence of xCT is detected by western blot analysis. When completed, this project will allow us to better understand the role that ubiquitination plays in the trafficking of System xc-.
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