Reinikainen P, Palvimo J J, Jänne O A
Department of Physiology, University of Helsinki, Finland.
Endocrinology. 1996 Oct;137(10):4351-7. doi: 10.1210/endo.137.10.8828495.
The effects of mitogens and agents affecting tyrosine phosphorylation signaling on androgen-regulated transcription were investigated. CV-1 and HeLa cells were cotransfected with an androgen receptor (AR) expression vector and an androgen-responsive chloramphenicol acetyltransferase (CAT) reporter gene driven by the mouse mammary tumor virus promoter. Growth factors [epidermal growth factor (EGF) and insulin-like growth factor I] that activate receptor tyrosine kinases, an inhibitor of phosphotyrosine phosphatases (vanadate), or an inhibitor of tyrosine kinases (genistein) did not influence basal promoter activity or that of unliganded AR. However, EGF, insulin-like growth factor I, and vanadate enhanced AR-dependent transactivation by 1.5- to 2.5-fold, and genistein diminished it by two thirds in the presence of androgen. None of the treatments affected pRSV-CAT or pSV-beta-galactosidase expression, suggesting that gross activation of the transcription machinery was not involved. A reporter with two androgen response elements (AREs) in front of the thymidine kinase promoter (p delta ARE2tk-CAT) was used to examine promoter specificity. EGF activated this reporter even in the absence of androgen. However, when EGF was used concomitantly with testosterone, it augmented the action of androgen. Vanadate enhanced androgen-induced transactivation 2-fold without altering basal promoter activity. Neither EGF nor vanadate altered immunoreactive AR content or elicited changes in the receptor's DNA-binding properties. The intracellular content of hormone-binding AR was not influenced by EGF, but was decreased by vanadate and increased by genistein, as judged by [3H]mibolerone binding assays. An AR form lacking the hormone-binding domain (delta 641-902 mutant) transactivated p delta ARE2tk-CAT reporter similar to or better than the wild-type receptor in the presence of androgen. The transactivation by the delta 641-902 mutant was augmented by EGF and vanadate, but was attenuated by genistein, implying that the steroid-binding region is not critical for regulatory events initiated by tyrosine phosphorylation. Collectively, these data indicate that there is cross-talk between androgen-mediated signaling systems and growth factor/receptor tyrosine kinase pathways.
研究了丝裂原和影响酪氨酸磷酸化信号传导的试剂对雄激素调节转录的作用。将CV - 1和HeLa细胞与雄激素受体（AR）表达载体以及由小鼠乳腺肿瘤病毒启动子驱动的雄激素反应性氯霉素乙酰转移酶（CAT）报告基因共转染。激活受体酪氨酸激酶的生长因子[表皮生长因子（EGF）和胰岛素样生长因子I]、磷酸酪氨酸磷酸酶抑制剂（钒酸盐）或酪氨酸激酶抑制剂（染料木黄酮）均不影响基础启动子活性或未结合配体的AR的活性。然而，在雄激素存在的情况下，EGF、胰岛素样生长因子I和钒酸盐使AR依赖性反式激活增强了1.5至2.5倍，而染料木黄酮使其降低了三分之二。所有处理均不影响pRSV - CAT或pSV-β-半乳糖苷酶的表达，这表明转录机制的总体激活未参与其中。使用在胸苷激酶启动子（pδARE2tk - CAT）前带有两个雄激素反应元件（ARE）的报告基因来检测启动子特异性。即使在没有雄激素的情况下，EGF也能激活该报告基因。然而，当EGF与睾酮同时使用时，它会增强雄激素的作用。钒酸盐使雄激素诱导的反式激活增强2倍，而不改变基础启动子活性。EGF和钒酸盐均未改变免疫反应性AR的含量，也未引起受体DNA结合特性的变化。通过[³H]米勃龙结合试验判断，激素结合性AR的细胞内含量不受EGF影响，但受钒酸盐降低，受染料木黄酮增加。在雄激素存在的情况下，缺乏激素结合结构域的AR形式（δ641 - 902突变体）对pδARE2tk - CAT报告基因的反式激活与野生型受体相似或更好。δ641 - 902突变体的反式激活被EGF和钒酸盐增强，但被染料木黄酮减弱，这意味着类固醇结合区域对于由酪氨酸磷酸化引发的调节事件并不关键。总体而言，这些数据表明雄激素介导的信号系统与生长因子/受体酪氨酸激酶途径之间存在相互作用。
