Discipline: Biological Sciences
Subcategory: Biochemistry (not Cell and Molecular Biology and Genetics)
Alexander Best - Tuskegee University
Co-Author(s): Peter Dornbos and John J. LaPres, Michigan State University, East Lansing, MI
The Aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that is responsible for mediating most, if not all, of the toxic effects of a class of planar aromatic hydrocarbon, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Exposure to TCDD leads to a variety of toxic endpoints, including chloracne, immune suppression, and metabolic dysfunction. Over the last several years research has shown that TCDD, via the activation of the AHR, can negatively impact the mitochondria. This negative impact includes alterations in electron transport chain (ETC) function, reactive oxygen species generation and perturbation of the nuclear-to-mitochondrial stress-signaling axis. In the absence of ligand, the AHR is primarily thought to be located within the cytosol; however, recently, we have shown that a portion of the AHR is found within the intermembrane space of the mitochondria. In addition, we have shown that short-term treatment of cells with TCDD disrupts mitochondrial function at the level of membrane potential. The goal of this project is to determine if the pool of mitochondrial AhR influences the ETC directly.
To test this hypothesis, we will use a human B lymphoblastoid cell line that was transformed with EBV, called SKW6.4 cells. Interestingly, the parental SKW6.4 cells do not express the AHR endogenously. We will use this parental cell line and SKW6.4 that have been engineered to expressing a wild type version of the AHR. We will use these cells to determine if TCDD exposure impacts mitochondrial function in an AHR-dependent manner. To measure mitochondrial function, we will use a Seahorse XF24 Extracellular Flux Analyzer. This machine measures the oxygen consumption rate of cells in culture. Since the mitochondria consume 95% of cellular oxygen, this is an excellent measure of the organelle’s function. In addition, the XF24 also measures the extracellular acidification rate, a measure of glycolytic flux. We hope to determine the impact of long and short-term TCDD exposure has on these to measure the cellular metabolic activity and determine if the AHR plays a role in modulating the observed impact of TCDD. In the future, the lab hopes to Manipulate the protein sequence of the AHR to determine the motifs with the receptor that are important for its import into the mitochondria and its function within the intermembrane space.
Funder Acknowledgement(s): Michigan State University CVM Summer Research Scholars Program R25 Grant: NIH R25 HL103156
Faculty Advisor: Richard Whittington,