KMT Set7/9 is a new regulator of Sam68 STAR-protein

Abstract Although the precise mechanism whereby cholesterol is transported across the outer mitochondrial membrane is uncertain, a multimeric receptor complex termed the peripheral-type benzodiazepine receptor (PBR) appears essential for this process. We therefore predicted that adrenal cells at different developmental stages would express PBR coincidentally with the advent of steroidogenesis. Adrenals of neonatal rats demonstrate greatly reduced sensitivity to ACTH that gradually increases after the first 2 weeks of life. Thus, neonates have lower circulating corticosterone levels following exposure to stress. We examined mitochondrial PBR ligand binding activity, immunoreactive (ir) PBR content, and adrenal sensitivity to ACTH in vivo and in vitro. Ontogeny of both mitochondrial PBR ligand binding capacity and irPBR directly paralleled that of ACTH-inducible steroidogenesis in isolated rat adrenal cells and in rats injected with ACTH. In addition, neonatal PBR had approximately 2-fold higher affinity for PK11195, a synthetic ligand that binds with high affinity to PBR. No correlation was observed during neonatal life between ir-steroidogenic acute regulatory (StAR) protein content and steroidogenesis. These results are consistent with the hypothesis that PBR is an absolute prerequisite for adrenocortical steroidogenesis, and suggest that the stress hyporesponsive period of neonatal rats may result from decreased PBR expression. In addition, the higher affinity of neonatal PBR and the relatively high basal expression of StAR protein in neonatal adrenals may partly explain the high constitutive steroidogenesis characteristic of neonatal rat adrenal cells.

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CREM confers cAMP responsiveness in human steroidogenic acute regulatory protein expression in NCI-H295R cells rather than SF-1/Ad4BP

Journal of Endocrinology ◽

10.1677/joe.1.06601 ◽

2006 ◽

Vol 191 (1) ◽

pp. 327-337 ◽

Cited By ~ 26

Author(s):

Teruo Sugawara ◽

Noriaki Sakuragi ◽

Hisanori Minakami

Keyword(s):

Promoter Activity ◽

Activity Level ◽

Expression Vectors ◽

Camp Response Element ◽

Star Protein ◽

Protein Levels ◽

Sirna Treatment ◽

H295r Cells ◽

Steroidogenic Acute Regulatory ◽

Camp Induction

Steroidogenic acute regulatory (StAR) protein plays a critical role in steroid hormone synthesis. Tropic hormones induce human StAR gene expression by a cAMP-dependent pathway. Steroidogenic factor-1/adrenal-4-binding protein (SF-1/Ad4BP) plays an important role in the expression of human StAR gene. We investigated the mechanism of cAMP responsiveness in human StAR gene expression in NCI-H295R cells. The StAR promoter activity and protein levels in cells subjected to various treatments were examined. Anti-SF-1/Ad4BP IgG transfection treatment resulted in decreases in the basal StAR promoter activity and StAR protein levels, but did not affect cAMP-stimulated promoter activity and protein levels. The basal and cAMP-stimulated StAR promoter activity levels were reduced in SF-1/Ad4BP mutant (G35E)-transfected cells, but the cAMP induction of StAR promoter activity in response to 1 mM 8-Br-cAMP was not inhibited when G35E SF-1/Ad4BP mutant expression vectors were co-transfected with cAMP-response element-binding (CREB) expression vectors. Although the basal StAR mRNA expression and protein levels were decreased by SF-1/Ad4BP-siRNA treatment, the cAMP-stimulated StAR mRNA expression and protein levels did not change. The basal StAR promoter activity level was not decreased by cAMP-response element modulator (CREM)-siRNA treatment, but the cAMP-stimulated StAR promoter activity level, the magnitude of cAMP induction of StAR promoter, and the cAMP-stimulated StAR protein level were decreased. The cAMP induction of StAR promoter activity in cells was inhibited when S117ACREM mutant expressionvectors were transfected. We conclude that inhibition of the function of SF-1/Ad4BP does not reduce the cAMP induction of StAR promoter activity and protein level. CREM is needed to confer cAMP responsiveness in human StAR protein expression.

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Inhibition of Cyclooxygenase-2 Activity Enhances Steroidogenesis and Steroidogenic Acute Regulatory Gene Expression in MA-10 Mouse Leydig Cells

Endocrinology ◽

10.1210/en.2002-0081 ◽

2003 ◽

Vol 144 (8) ◽

pp. 3368-3375 ◽

Cited By ~ 45

Author(s):

XingJia Wang ◽

Matthew T. Dyson ◽

Youngah Jo ◽

Douglas M. Stocco

Keyword(s):

Gene Expression ◽

Protein Expression ◽

Leydig Cells ◽

Promoter Activity ◽

Regulatory Gene ◽

Steroid Production ◽

Star Protein ◽

Cox Inhibitor ◽

Steroidogenic Acute Regulatory ◽

Star Gene

Abstract To study the mechanism for the regulatory effect of arachidonic acid (AA) on steroidogenesis, the role of cyclooxygenase (COX) in steroid production and steroidogenic acute regulatory (StAR) gene expression was investigated. Although stimulation with 0.05 mm dibutyryl cAMP (Bt2cAMP) did not increase StAR protein or progesterone in MA-10 mouse Leydig cells, the addition of 1 μm of the COX inhibitor indomethacin increased StAR protein expression and progesterone production by 5.7-fold and 34.3-fold, respectively. In the presence of indomethacin, the level of Bt2cAMP required for maximal steroidogenesis was reduced from 1.0 mm to 0.25 mm. Similar results were obtained in studies on StAR promoter activity and in Northern blot analyses of StAR mRNA expression, suggesting that inhibition of COX activity enhanced StAR gene transcription. COX2 (an inducible isoform of COX) was constitutively detected in MA-10 cells. Although SC560, a selective COX1 inhibitor, did not affect steroidogenesis, the COX2 inhibitor NS398 significantly enhanced Bt2cAMP-stimulated StAR protein expression and steroid production. Overexpression of the COX2 gene in COS-1 cells significantly inhibited StAR promoter activity. The results of the present study suggest that inhibition of COX2 activity increases the sensitivity of steroidogenesis to cAMP stimulation in MA-10 Leydig cells.

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46, XY Female with Congenital Lipoid Adrenal Hyperplasia: Atypical Presentation and Novel StAR Protein Gene Mutation.

10.1210/endo-meetings.2010.part1.p13.p1-637 ◽

2010 ◽

pp. P1-637-P1-637

Author(s):

O Lekarev ◽

Y Morel ◽

MI New

Keyword(s):

Gene Mutation ◽

Protein Gene ◽

Atypical Presentation ◽

Adrenal Hyperplasia ◽

Star Protein ◽

Congenital Lipoid Adrenal Hyperplasia ◽

Xy Female

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Role of Dosage-Sensitive Sex Reversal, Adrenal Hypoplasia Congenita, Critical Region on the X Chromosome, Gene 1 in Protein Kinase A- and Protein Kinase C-Mediated Regulation of the Steroidogenic Acute Regulatory Protein Expression in Mouse Leydig Tumor Cells: Mechanism of Action

Endocrinology ◽

10.1210/en.2008-0368 ◽

2008 ◽

Vol 150 (1) ◽

pp. 187-199 ◽

Cited By ~ 38

Author(s):

Pulak R. Manna ◽

Matthew T. Dyson ◽

Youngah Jo ◽

Douglas M. Stocco

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Protein Kinase A ◽

Tumor Cells ◽

Orphan Nuclear Receptor ◽

Star Protein ◽

Kinase C ◽

Leydig Tumor Cells ◽

Steroidogenic Acute Regulatory ◽

Kinase A

Dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene 1 (DAX-1) is an orphan nuclear receptor that has been demonstrated to be instrumental to the expression of the steroidogenic acute regulatory (StAR) protein that regulates steroid biosynthesis in steroidogenic cells. However, its mechanism of action remains obscure. The present investigation was aimed at exploring the molecular involvement of DAX-1 in protein kinase A (PKA)- and protein kinase C (PKC)-mediated regulation of StAR expression and its concomitant impact on steroid synthesis using MA-10 mouse Leydig tumor cells. We demonstrate that activation of the PKA and PKC pathways, by a cAMP analog dibutyryl (Bu)2cAMP [(Bu)2cAMP] and phorbol 12-myristate 13-acetate (PMA), respectively, markedly decreased DAX-1 expression, an event that was inversely correlated with StAR protein, StAR mRNA, and progesterone levels. Notably, the suppression of DAX-1 requires de novo transcription and translation, suggesting that the effect of DAX-1 in regulating StAR expression is dynamic. Chromatin immunoprecipitation studies revealed the association of DAX-1 with the proximal but not the distal region of the StAR promoter, and both (Bu)2cAMP and PMA decreased in vivo DAX-1-DNA interactions. EMSA and reporter gene analyses demonstrated the functional integrity of this interaction by showing that DAX-1 binds to a DNA hairpin at position −44/−20 bp of the mouse StAR promoter and that the binding of DAX-1 to this region decreases progesterone synthesis by impairing transcription of the StAR gene. In support of this, targeted silencing of endogenous DAX-1 elevated basal, (Bu)2cAMP-, and PMA-stimulated StAR expression and progesterone synthesis. Transrepression of the StAR gene by DAX-1 was tightly associated with expression of the nuclear receptors Nur77 and steroidogenic factor-1, demonstrating these factors negatively modulate the steroidogenic response. These findings provide insight into the molecular events by which DAX-1 influences the PKA and PKC signaling pathways involved in the regulation of the StAR protein and steroidogenesis in mouse Leydig tumor cells. The characterization of protein kinase A- and protein kinase C-mediated steroidogenic acute regulatory (StAR) expression and steroidogenesis suggests that the orphan nuclear receptor DAX-1 is an important regulator of the steroidogenic response in Leydig cells.

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Involvement of the Thromboxane A2 Receptor in the Regulation of Steroidogenic Acute Regulatory Gene Expression in Murine Leydig Cells

Endocrinology ◽

10.1210/en.2008-1425 ◽

2009 ◽

Vol 150 (7) ◽

pp. 3267-3273 ◽

Cited By ~ 3

Author(s):

Akhilesh K. Pandey ◽

Xiangling Yin ◽

Randolph B. Schiffer ◽

James C. Hutson ◽

Douglas M. Stocco ◽

...

Keyword(s):

Gene Expression ◽

Leydig Cells ◽

Regulatory Gene ◽

Thromboxane A2 ◽

Cyclooxygenase 2 ◽

Thromboxane A2 Receptor ◽

Star Protein ◽

Dependent Inhibition ◽

Steroidogenic Acute Regulatory ◽

Star Gene

Recent studies suggested an involvement of thromboxane A2 in cyclooxygenase-2-dependent inhibition of steroidogenic acute regulatory (StAR) gene expression. The present study further investigated the role of thromboxane A2 receptor in StAR gene expression and steroidogenesis in testicular Leydig cells. The thromboxane A2 receptor was detected in several Leydig cell lines. Blocking thromboxane A2 binding to the receptor using specific antagonist SQ29548 or BM567 resulted in dose-dependent increases in StAR protein and steroid production in MA-10 mouse Leydig cells. The results were confirmed with Leydig cells isolated from rats. StAR promoter activity and StAR mRNA level in the cells were also increased after the treatments, suggesting an involvement of the thromboxane A2 receptor in StAR gene transcription. Furthermore study indicated that blocking the thromboxane A2 receptor reduced dosage sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene 1 protein, a transcriptional repressor of StAR gene expression. Specific binding of the antagonists to the receptors on cellular membrane was demonstrated by binding assays using 3H-SQ29548 and binding competition between 3H-SQ29548 and BM567. Whereas SQ29548 enhanced cAMP-induced StAR gene expression, in the absence of cAMP, it was unable to increase StAR protein and steroidogenesis. However, when the receptor was blocked by the antagonist, subthreshold levels of cAMP were able to induce maximal levels of StAR protein expression, suggesting that blocking the thromboxane A2 receptor increase sensitivity of MA-10 cells to cAMP stimulation. Taken together, the results from the present and previous studies suggest an autocrine loop, involving cyclooxygenase-2, thromboxane A synthase, and thromboxane A2 and its receptor, in cyclooxygenase-2-dependent inhibition of StAR gene expression.

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Mechanism of mRNA-STAR domain interaction: Molecular dynamics simulations of Mammalian Quaking STAR protein

Scientific Reports ◽

10.1038/s41598-017-12930-2 ◽

2017 ◽

Vol 7 (1) ◽

Cited By ~ 5

Author(s):

Monika Sharma ◽

C. R. Anirudh

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Domain Interaction ◽

Star Protein ◽

Dynamics Simulations

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The potential function of steroid sulphatase activity in steroid production and steroidogenic acute regulatory protein expression

Biochemical Journal ◽

10.1042/bj20031379 ◽

2004 ◽

Vol 380 (1) ◽

pp. 153-160 ◽

Cited By ~ 10

Author(s):

Teruo SUGAWARA ◽

Seiichiro FUJIMOTO

Keyword(s):

Western Blot ◽

Blot Analysis ◽

Expression Vector ◽

Regulatory Protein ◽

Steroidogenic Acute Regulatory Protein ◽

Steroid Production ◽

Star Protein ◽

Protein Levels ◽

Steroid Sulphatase ◽

Steroidogenic Acute Regulatory

The first step in the biosynthesis of steroid hormones is conversion of cholesterol into pregnenolone. StAR (steroidogenic acute regulatory) protein plays a crucial role in the intra-mitochondrial movement of cholesterol. STS (steroid sulphatase), which is present ubiquitously in mammalian tissues, including the placenta, adrenal gland, testis and ovary, desulphates a number of 3β-hydroxysteroid sulphates, including cholesterol sulphate. The present study was designed to examine the effect of STS on StAR protein synthesis and steroidogenesis in cells. Steroidogenic activities of COS-1 cells that had been co-transfected with a vector for the cholesterol P450scc (cytochrome P450 side-chain-cleavage enzyme) system, named F2, a StAR expression vector (pStAR), and an STS expression vector (pSTS) were assayed. Whole-cell extracts were subjected to SDS/PAGE and then to Western blot analysis. pSTS co-expressed in COS-1 cells with F2 and pStAR increased pregnenolone synthesis 2-fold compared with that of co-expression with F2 and pStAR. Western blot analysis using COS-1 cells that had been co-transfected with pSTS, F2 and pStAR revealed that StAR protein levels increased, whereas STS and P450scc protein levels did not change. The amount of StAR protein translation products increased when pSTS was added to an in vitro transcription–translation reaction mixture. Pulse–chase experiments demonstrated that the 37 kDa StAR pre-protein disappeared significantly (P<0.01) more slowly in COS-1 cells that had been transfected with pSTS than in COS-1 cells that had not been transfected with pSTS. The increase in StAR protein level is not a result of an increase in StAR gene expression, but is a result of both an increase in translation and a longer half-life of the 37 kDa pre-StAR protein. In conclusion, STS increases StAR protein expression level and stimulates steroid production.

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