Chase-Wallar Research Group

Regulation of Cystine/Glutamate Exchange by System x_c^-

The loss of dopaminergic neurons in the substantia nigra, a specific region of the brain that is involved in modulating motor activity, is a hallmark of Parkinson's disease. Numerous studies have implicated reactive oxygen species, such as H₂O₂, as a contributing factor in the death of these cells. Specifically, the build up of H₂O₂ and other reactive oxygen species is proposed to lead to oxidative stress-mediated neuronal death and the loss of motor control. Since the metabolism of dopamine by monoamine oxidase results in the production of H₂O₂, dopaminergic neurons are particularly susceptible to such damage.

System x_c^- is a Na⁺-independent anionic amino acid transport system that mediates the direct exchange of extracellular cystine for intracellular glutamate across the plasma membrane of neurons and glia. One of the primary physiological roles of this transporter is to provide cystine for cells for the synthesis of the free radical scavenger, glutathione, and protect cells from oxidative stress. Thus, inhibition of this transporter leads directly to oxidative-stress and ultimately apoptotic cell death in many cell types.

In the Chase lab, we are very interested how the activity of System x_c^- is acutely regulated by reactive oxygen species to combat oxidative stress. We are interested in the specific effects peroxide has on intrinsic transporter activity and the trafficking of the transporter to the plasma membrane. Students working on this project will examine the regulation of System x_c^- by intracellularly produced H₂O₂ in a dopaminergic cell line. In order to do this, students will learn to grow mammalian cells in culture, examine System x_c^- expression by immunocytochemical and western blot analysis, and perform a variety of enzymatic assays to measure glutathione and peroxide levels in cultured cells. Thus, students working on this project will have the opportunity to identify a portion of the project most interesting to them and focus their energies on their individual subproject.