The purification, cloning, and expression of a novel luteinizing hormone-induced mitochondrial protein in MA-10 mouse Leydig tumor cells. Characterization of the steroidogenic acute regulatory protein (StAR).
The acute response of steroidogenic cells to trophic hormone stimulation is the mobilization of cholesterol from cellular stores to the mitochondrial outer membrane and the transfer of this cholesterol to the mitochondrial inner membrane where the first enzymatic step in steroidogenesis occurs. The transfer of cholesterol across the mitochondrial membranes is dependent upon de novo protein synthesis, and this is the regulated step in the process. Although the newly synthesized regulatory protein(s) have yet to be identified, we previously have proposed a candidate protein which we identified in MA-10 cells that is synthesized in response to luteinizing hormone stimulation and that is localized to the mitochondria. In the present study, we report the isolation of a cDNA that encodes this luteinizing hormone-induced protein. Analysis of the cDNA and protein sequences reveals this is a novel protein. Importantly, we demonstrate for the first time that expression of the protein in MA-10 cells in the absence of hormone stimulation is sufficient to induce steroid production. We conclude that this protein is required in the acute regulation of steroidogenesis and propose to call this protein the Steroidogenic Acute Regulatory protein (StAR).
Department of Biochemistry and Molecular Biology, Texas Tech University Health Sciences Center, Lubbock 79430.
B J
BJ
Clark
J
J
Wells
S R
SR
King
D M
DM
Stocco
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002522:Chlorocebus aethiops; D002793:Cholic Acids; D003001:Cloning, Molecular; D003902:Detergents; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression; D007984:Leydig Cell Tumor / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000494:pharmacology*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010750:Phosphoproteins; D014176:Protein Biosynthesis; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D015183:Restriction Mapping; D014162:Transfection; D014407:Tumor Cells, Cultured; D000098682:Steroidogenic Acute Regulatory Protein
D002793:Cholic Acids; D003902:Detergents; D009363:Neoplasm Proteins; D009838:Oligodeoxyribonucleotides; D010446:Peptide Fragments; D010750:Phosphoproteins; D011994:Recombinant Proteins; D000098682:Steroidogenic Acute Regulatory Protein; D007986:Luteinizing Hormone; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate