CREM confers cAMP responsiveness in human steroidogenic acute regulatory protein expression in NCI-H295R cells rather than SF-1/Ad4BP.
CREM confers cAMP responsiveness in human steroidogenic acute regulatory protein expression in NCI-H295R cells rather than SF-1/Ad4BP.
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DOI：
10.1677/joe.1.06601
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发表时间：
2006-10
期刊：
影响因子：
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通讯作者：
T. Sugawara;N. Sakuragi;H. Minakami
中科院分区：
文献类型：
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作者：
T. Sugawara;N. Sakuragi;H. Minakami
类固醇合成急性调节蛋白(STAR)在类固醇激素合成中起着关键作用。热带激素通过cAMP依赖的途径诱导人类STAR基因的表达。类固醇生成因子-1/肾上腺-4结合蛋白(SF-1/Ad4BP)在人类STAR基因的表达中起重要作用。我们研究了人STAR基因在NCI-H295R细胞中表达的cAMP反应机制。检测不同处理条件下细胞中STAR启动子的活性和蛋白水平。反义SF-1/Ad4BP免疫球蛋白转染组STAR启动子活性和蛋白水平下降，但不影响cAMP刺激的启动子活性和蛋白水平。在SF-1/Ad4BP突变体(G35E)转染的细胞中，STAR启动子的基础活性和cAMP刺激的活性水平降低，但当G35E突变体表达载体与cAMP反应元件结合(CREB)表达载体共转染时，对1 mM 8-BR-cAMP诱导的STAR启动子活性的cAMP诱导不受抑制。经SF-1/Ad4BP-siRNA处理后，星形胶质细胞的基础STAR基因表达和蛋白水平均降低，但cAMP刺激后的STAR基因表达和蛋白水平无明显变化。CAMP反应元件调节剂(CREM)-siRNA处理并未降低STAR启动子的基础活性水平，但降低了cAMP刺激的STAR启动子活性水平、cAMP诱导的STAR启动子活性的幅度和cAMP刺激的STAR蛋白水平。S117ACREM突变型表达载体可抑制cAMP对细胞内STAR启动子活性的诱导。我们的结论是，抑制SF-1/Ad4BP的功能不会降低cAMP对STAR启动子活性和蛋白水平的诱导。在人类STAR蛋白的表达中，需要CREM来赋予cAMP反应性。
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.