The long-term objective is to investigate the enzymes and signal transduction processes of steroid hormone biosynthesis. The current emphasis is on the mechanism by which the peptide hormone ACTH (adrenocorticotropic hormone) regulates the rate-limiting side-chain cleavage of cholesterol, an inner mitochondrial membrane reaction which is catalyzed by cytochrome P-450scc and associated enzymes. We will emphasize during the current grant period the regulation by ACTH and cAMP of cholesterol trafficking within the adrenal cell, and the regulation of this process by putative regulatory factors including Steroidogenesis Activator Polypeptide, Sterol Carrier Protein-2, nucleotide triphosphates, and cholesterol sulfate. Experimental systems to be used include the Y-1 adrenal and MA-10 Leydig cell lines. Methods to be used include cell permeabilization with Streptolysin O and generation of """"""""semi-intact"""""""" cells. In addition, recombinant methodology and cell transfection will be used to express putative protein and peptide regulators in Y-1 cells. Subfractionation studies will also be used to localize functional cholesterol pools which are involved in moving cholesterol to its inner mitochondrial membrane metabolic site. Emphasis will be placed on a putative cholesterol-rich vesicle and inner-outer mitochondrial membrane contact junctions.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
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Physical Biochemistry Study Section (PB)
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Emory University
Schools of Medicine
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Stevens, V L; Xu, T; Lambeth, J D (1993) Cholesterol trafficking in steroidogenic cells. Reversible cycloheximide-dependent accumulation of cholesterol in a pre-steroidogenic pool. Eur J Biochem 216:557-63
Stevens, V L; Xu, T; Lambeth, J D (1992) Cholesterol pools in rat adrenal mitochondria: use of cholesterol oxidase to infer a complex pool structure. Endocrinology 130:1557-63
Xu, T S; Bowman, E P; Glass, D B et al. (1991) Stimulation of adrenal mitochondrial cholesterol side-chain cleavage by GTP, steroidogenesis activator polypeptide (SAP), and sterol carrier protein2. GTP and SAP act synergistically. J Biol Chem 266:6801-7
Glass, D B; Robertson, D G; Xu, T S et al. (1991) Chemical synthesis, initial conformational studies, and activity of rat steroidogenesis activator peptide and a truncated analog. Endocr Res 17:307-26
Robertson, D G; Perry, D; Lambeth, J D (1991) Inhibition of mitochondrial cholesterol side-chain cleavage by structural analogs of cholesterol sulfate. Endocr Res 17:297-306
Lambeth, J D; Xu, X X (1989) Cholesterol sulfate: a naturally-occurring inhibitor of cholesterol side-chain cleavage which functions at the level of intramitochondrial cholesterol translocation. Endocr Res 15:85-99
Xu, X S; Xu, T S; Robertson, D G et al. (1989) GTP stimulates pregnenolone generation in isolated rat adrenal mitochondria. J Biol Chem 264:17674-80
Xu, X X; Lambeth, J D (1989) Cholesterol sulfate is a naturally occurring inhibitor of steroidogenesis in isolated rat adrenal mitochondria. J Biol Chem 264:7222-7