title: Luteinizing hormone/human chorionic gonadotropin-mediated activation of mTORC1 signaling is required for androgen synthesis by theca-interstitial cells.
abstract: LH triggers the biosynthesis of androgens in the theca-interstitial (T-I) cells of ovary through the activation of a cAMP-dependent pathway. We have previously shown that LH/human chorionic gonadotropin (hCG) activates mammalian target of rapamycin complex 1 (mTORC1) signaling network, leading to cell proliferation. In the present study, we provide evidence that the LH/hCG-mediated activation of the mTORC1 signaling cascade is involved in the regulation of steroidogenic enzymes in androgen biosynthesis. Treatment with LH/hCG increased the expression of downstream targets of mTORC1, ribosomal protein S6 kinase 1, and eukaryotic initiation factor 4E as well as steroidogenic enzymes. LH/hCG-mediated stimulation of the steroidogenic enzyme mRNA was blocked by the mTORC1 inhibitor, rapamycin. This inhibitory effect was selective because rapamycin failed to block hCG-mediated increase in the expression of Star mRNA levels. Furthermore, pharmacological targeting of mTORC1 with rapamycin also blocked LH/hCG- or forskolin-induced expression of cAMP response element-binding protein (CREB) and steroidogenic enzymes (P450 side-chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase type 1, and 17α-hydroxylase/17,20 lyase) but produced no effect on steroidogenic acute regulatory protein levels. These results were further confirmed by demonstrating that the knockdown of mTOR using small interfering RNA selectively abrogated the LH/hCG-induced increase in steroidogenic enzyme expression, without affecting steroidogenic acute regulatory protein expression. LH/hCG-stimulated androgen production was also blocked by rapamycin. Furthermore, the pharmacological inhibition of mTORC1 or ribosomal protein S6 kinase 1 signaling prevented the LH/hCG-induced phosphorylation of CREB. Chromatin immunoprecipitation assays revealed the association of CREB with the proximal promoter of the Cyp17a1 gene in response to hCG, and this association was reduced by rapamycin treatment. Taken together, our findings show for the first time that LH/hCG-mediated activation of androgen biosynthesis is regulated by the mTORC1 signaling pathway in T-I cells.
authors: Departments of Obstetrics and Gynecology and Biological Chemistry, University of Michigan MedicalSchool, Ann Arbor, Michigan 48109, USA.
authors: Murugesan
authors: M
authors: Palaniappan
authors: K M J
authors: KM
authors: Menon
mesh_terms: D000728:Androgens / Q000096:biosynthesis*; D000735:Androstenedione / Q000096:biosynthesis; D000818:Animals; D002478:Cells, Cultured; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000235:genetics / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000494:pharmacology / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004790:Enzyme Induction; D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism; D005260:Female; D055785:Gene Knockdown Techniques; D007986:Luteinizing Hormone / Q000494:pharmacology / Q000502:physiology*; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D013799:Theca Cells / Q000378:metabolism*; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D000728:Androgens; D006063:Chorionic Gonadotropin; D017362:Cyclic AMP Response Element-Binding Protein; D039561:Eukaryotic Initiation Factor-4E; D046912:Multiprotein Complexes; D010750:Phosphoproteins; D011506:Proteins; D000098682:Steroidogenic Acute Regulatory Protein; D005576:Colforsin; D000735:Androstenedione; D007986:Luteinizing Hormone; D013254:Steroid 17-alpha-Hydroxylase; D002786:Cholesterol Side-Chain Cleavage Enzyme; C546845:mTOR protein, rat; D000076222:Mechanistic Target of Rapamycin Complex 1; D019893:Ribosomal Protein S6 Kinases; C526901:Rps6kb1 protein, rat; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus