title: Regulation of Leydig cell steroidogenesis by extracellular signal-regulated kinase 1/2: role of protein kinase A and protein kinase C signaling.
abstract: The steroidogenic acute regulatory (StAR) protein plays a central role in the regulation of steroid biosynthesis. While steroidogenesis is influenced by many processes, their modes of actions, in a few cases, remain obscure. In this study, we explored the mechanism of action of one such signaling pathway, the extracellular signal-regulated kinase 1/2 (ERK1/2), in regulating StAR expression and steroidogenesis in conjunction with the protein kinase A (PKA) and protein kinase C (PKC) pathways. Using MA-10 mouse Leydig tumor cells, we demonstrate that the activation of PKC and PKA signaling, by phorbol-12-myristate-13-acetate (PMA) and dibutyryl cAMP (dbcAMP)/human chorionic gonadotropin (hCG) respectively, was able to phosphorylate ERK1/2, an event markedly decreased by an upstream kinase inhibitor, U0126. Treatment with PMA enhanced StAR protein expression (associated with a slight increase in progesterone synthesis) but not its phosphorylation (P-StAR), which, in contrast, coordinately increased in response to dbcAMP/hCG. Inhibition of ERK1/2 activity by U0126 decreased PMA-treated StAR expression but increased dbcAMP/hCG-mediated StAR and P-StAR; however, progesterone levels were attenuated. U0126 was found to affect StAR expression and steroidogenesis both at the transcriptional and translational levels. Further studies demonstrated that the effect of U0126 on PMA- and dbcAMP/hCG-mediated StAR expression and steroid synthesis was tightly correlated with the expression of dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene 1 (DAX-1) and scavenger receptor class B type 1 (SR-B1). In fact, both DAX-1 and SR-B1 appear to play important roles in hormone-regulated steroidogenesis. These findings clearly demonstrate that the ERK1/2 signaling cascade involved in regulating StAR expression and steroid synthesis is mediated by multiple factors and pathways and is stimulus specific in mouse Leydig cells.
authors.affiliation: Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA.
authors.forename: Pulak R
authors.initials: PR
authors.lastname: Manna
authors.forename: Youngah
authors.initials: Y
authors.lastname: Jo
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Stocco
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D003994:Bucladesine / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D045744:Cell Line, Tumor; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins / Q000494:pharmacology; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D007546:Isoquinolines / Q000494:pharmacology; D007985:Leydig Cells / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D009570:Nitriles / Q000494:pharmacology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011374:Progesterone / Q000096:biosynthesis*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051122:Scavenger Receptors, Class B / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D002070:Butadienes; D006063:Chorionic Gonadotropin; D057137:DAX-1 Orphan Nuclear Receptor; D004268:DNA-Binding Proteins; D007546:Isoquinolines; C539965:NR0B1 protein, human; D009570:Nitriles; C539966:Nr0b1 protein, mouse; D010750:Phosphoproteins; D018168:Receptors, Retinoic Acid; D012097:Repressor Proteins; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D013449:Sulfonamides; C113580:U 0126; D000098682:Steroidogenic Acute Regulatory Protein; D011374:Progesterone; D003994:Bucladesine; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D013755:Tetradecanoylphorbol Acetate