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Past Research of Dr. Russell DeBose-Boyd lab
Dr. DeBose-Boyd received his graduate training in the laboratory of Dr. Richard D. Cummings at the University of Oklahoma Health Sciences Center in Oklahoma City, OK. After defending a thesis entitled "Identification, characterization, and molecular cloning of a1,3 fucosyltransferases in helminthes, he joined the laboratory of Drs. Michael S. Brown and Joseph L. Goldstein at the University of Texas Southwestern Medical Center in Dallas, TX. The overall research goal of Dr. DeBose-Boyd's post-doctoral studies was to better understand the molecular basis of lipid homeostasis in animal cells, which is mediated by membrane-bound transcription factors termed sterol regulatory element-binding proteins (SREBPs). Specifically, he sought to determine how the protein SCAP (SREBP cleavage-activating protein) facilitates the release of active SREBP fragments from membranes when cells are deprived of cholesterol. Dr. DeBose-Boyd began his work by characterizing a mutant cell line in which the SCAP gene was inactivated. Initially, he demonstrated that SCAP is absolutely required for SREBP activation and was restored in mutant cells upon introduction of SCAP by transfection. The availability of the SCAP-deficient cells allowed Dr. DeBose-Boyd to further investigate the function of SCAP. He demonstrated that treatment of cells with brefeldin A, a drug that causes redistribution of Golgi proteins to the ER, caused SREBP proteases to translocate to the ER and abrogated the need for transport of SREBP to the Golgi. In addition, brefeldin A restored SREBP processing in SCAP-deficient cells. The results of these studies led to a model in which SCAP escorts SREBPs from the ER to the Golgi apparatus in sterol-deprived cells and recycles back to the ER following SREBP release by Golgi-localized proteases. Sterols block SREBP processing by preventing the transport of the SCAP-SREBP complex to the Golgi. These studies have had profound effects on the understanding of lipid homeostasis in animal cells. On the cellular level, the demonstration that SCAP functions to transport SREBPs from the ER to the Golgi represents a novel means of transcriptional factor activation. Transport-dependent proteolysis of SREBPs explains how signals generated in distinct cellular compartments can be relayed to the nucleus, thus laying the groundwork for the study of other membrane-bound transcription factors.
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