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CARYN E. OUTTEN , PhD
Assistant Professor, USC College of Arts and Sciences, Chemistry and Biochemistry
DEGREES
B.S., 1995, College of William and Mary
Ph.D., 2001, Northwestern University
Postdoctoral Fellow, 2001-2005, Johns Hopkins University
RESEARCH INTERESTS
Cellular and molecular mechanisms of redox homeostasis; mitochondrial and cytosolic anti-oxidant defense systems; intracellular sulfur chemistry; molecular genetic and biochemical studies of oxidative stress resistance in yeast.
 Oxidative stress presents a serious danger to the cell in the form of reactive oxygen species (ROS), such as H2O2, •O2-, and •OH, which can damage cellular components. Reduced cysteine and methionine residues in proteins are particularly susceptible to damage, and upon oxidation form disulfide bonds or methionine sulfoxides, respectively, which can lead to enzyme inactivation (Fig. 1). Most of the ROS in the eukaryotic cell are generated as by-products of respiration in the mitochondrion, an essential organelle involved in many diverse cellular functions. Exogenous ROS-producing stresses such as hyperoxia, radiation, heavy metals, and redox-active chemicals also pose a significant threat to the cell. Mitochondria have been implicated in the dangerous nature of some of these environmental insults as well. Given its vital role in the cell, along with its potential to generate damaging molecules, it is not surprising that mitochondrial defects are associated with a variety of neurodegenerative diseases, aging, and cancer, presumably via the accumulation of ROS-induced damage. However, the mechanisms for combating oxidative damage in this organelle are poorly understood.
 Research in my lab is focused on identifying and characterizing mitochondrial vs. cytosolic factors that guard against oxidative stress and uncovering the mechanisms for maintaining mitochondrial redox balance using Saccharomyces cerevisiae, or bakers’ yeast, as a model system. This simple eukaryote is easy to maintain and genetically manipulate in the lab, yet expresses many of the same anti-oxidant factors as mammalian cells. Taking advantage of the power of yeast genetics and cell biology, we have previously identified and localized anti-oxidant factors in the cell, including the mitochondrial NADH kinase (POS5) and glutathione reductase (GLR1), which is partitioned between both the mitochondria and cytosol. POS5 supplies the critical reductant NADPH for the mitochondria by phosphorylating NADH. NADPH, in turn, is required for maintenance of the reduced forms of glutathione (GSH) and thioredoxin (TRX), via the NADPH-dependent TRX reductase (TRR) and GSH reductase (GLR1). The reduced forms of GSH (a thiol-containing tripeptide) and TRX (a small protein with at least two redox-active cysteines) can serve as anti-oxidants themselves or as co-factors for specific anti-oxidant enzymes such as glutaredoxin (GRX) and methionine sulfoxide reductase (MSR) (Fig. 2).
Current research in my lab is aimed at understanding 1) how anti-oxidant defense systems are targeted to the mitochondria vs. the cytosol and 2) how these systems work together to maintain redox homeostasis within the compartmentalized environment of the cell. A variety of biochemical, genetic, and molecular and cell biology techniques are used to address these issues, including recombinant protein purification and characterization, in vitro enzyme activity assays, growth assays, gene deletion experiments, site-directed mutagenesis, subcellular fractionation, metal analysis, immunodetection, and fluorescence microscopy. Together, this information will shed light on the cellular and molecular mechanisms involved in protecting the cell from oxidative stress and repairing oxidative damage, which may be extrapolated to mammalian systems.
CONTACT INFORMATION
University of South Carolina
Department of Chemistry and Biochemistry
631 Sumter Street, GSRC 510
Columbia, SC 29208
E-mail
Office: 803 . 777 . 8783 | Fax: 803 . 777 . 9521
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