title: ATP and a mitochondrial electrochemical gradient are required for functional activity of the steroidogenic acute regulatory (StAR) protein in isolated mitochondria.
abstract: The Steroidogenic Acute Regulatory (StAR) protein has been put forth as the rapidly synthesized, cycloheximide-sensitive protein that is required for the transport of cholesterol to the inner mitochondrial membrane and the P450scc enzyme and thereby acutely regulates steroidogenesis in steroidogenic tissues. In this study, several of the factors that may be required for StAR activity were examined using an in vitro system. Lysates from StAR-transfected COS-1 cells were added to mitochondria isolated from MA-10 Leydig tumor cells. Results obtained demonstrated that StAR-containing cell lysate increased steroidogenesis in isolated mitochondria, but failed to do so in the presence of m-CCCP, apyrase, or AMP-PNP, suggesting that StAR function requires ATP hydrolysis as well as an electrochemical gradient for maximal steroidogenic activity.
authors.affiliation: Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock 79430, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: King
authors.forename: D M
authors.initials: DM
authors.lastname: Stocco
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D019556:COS Cells; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D004563:Electrochemistry; D007984:Leydig Cell Tumor / Q000648:ultrastructure; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011374:Progesterone / Q000096:biosynthesis; D013736:Testicular Neoplasms / Q000648:ultrastructure; D014162:Transfection; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D010750:Phosphoproteins; D000098682:Steroidogenic Acute Regulatory Protein; D011374:Progesterone; D000255:Adenosine Triphosphate; D002786:Cholesterol Side-Chain Cleavage Enzyme