ACTIONS OF ESTROGEN IN MATURING GRAAFIAN FOLLICLES

描述（由申请人提供）：目前的竞争性更新扩展了我们早期的主题，即卵巢细胞中关键固醇代谢基因的营养激素控制的生殖机制。颗粒细胞在占优势的Graafian卵泡进行进行性类固醇细胞分化，准备黄体期生产孕酮。同时，卵泡膜细胞提供限制雄激素底物芳构化雌激素。雌激素和孕激素协同作用，使子宫内膜成熟，以便胚泡着床，并为排卵前促性腺激素高峰计时。这两种性类固醇来源于胆固醇在固醇摄取和限速递送到线粒体酶后转化为双烯醇酮。我们最近的研究记录了LH和有效的胰岛素样生长因子IGF-1在（猪）颗粒细胞和卵泡膜细胞的体外原代培养物中对低密度脂蛋白受体（LDL-R）和类固醇生成急性调节蛋白（星星）基因表达的协同驱动。事实上，这两个基因都受到强大的转录控制。它们的产物对于指导固醇底物的细胞摄取及其向线粒体内小叶的限速递送是关键的。与此同时，我们可以证明体内颗粒黄体细胞中LDL-R基因和卵泡膜细胞中星星基因的主要表达。因此，我们提供了它们的5 '上游调控区，并通过启动子缺失分析，已经开始绘制介导LH和IGF-1的超加和效应的顺式作用DNA区域。基于这个平台，我们提出了以下新的假说来解释颗粒黄体和卵泡膜细胞中固醇调节基因表达的双激素控制：假说（1）。LH和IGF-1通过间接放大远端效应器信号传导途径的选定方面实现协同作用。假设（2）。LH和IGF-1通过离散的顺式作用DNA区域和相应的核反式激活蛋白超加性地上调颗粒黄体细胞中的LDL-R基因表达。假设（3）。LH和IGF-I通过刺激不同的顺式作用DNA元件和相关的反式作用核因子协同驱动卵泡膜细胞中星星基因的表达。总之，上述论文的类固醇代谢基因表达的双激素控制的颗粒黄体和卵泡膜细胞应该提供新的见解垂体促性腺激素，LH，和本地产生的生长因子，IGF-1，如何收敛地采取行动，以管理（a）细胞内信号和（B）基因表达在卵巢细胞。了解这些基本的相互作用是很重要的替代策略的合理设计，以中断正常和救援受损的类固醇激素在成熟的Graafian卵泡和黄体。

DESCRIPTION (provided by applicant): The present competitive renewal extends our earlier theme of speafic mechanisms of trophic hormone control of key sterol-metabolizing genes in ovarian cells. Granulosa cells in the dominant Graafian follide undergo progressive steroidogenic cytodifferentiation in preparation for the luteal-phase production of progesterone. Concomitantly, theca cells provide limiting androgen substrate required for aromatization to estrogen. Estrogen and progesterone act coordinately to mature the endometrium for implantation of the blastocyst and time the preovulatory gonadotropin surge. Both sex steroids originate from cholesterol's conversion to pregnenolone after sterol uptake and rate-limiting delivery to mitochondnal enzymes. Our recent studies document synergistic drive by LH and the potent insulin-like growth factor, IGF-l, of expression of the low-density lipoprotein-receptor (LDL-R) and steroidogenic acute regulatory protein (StAR) genes in vitro primary cultures of (swine) granulosa and theca cells. Indeed, both genes are under strong transcriptional control. Their products are pivotal to direct the cellular uptake of sterol substrate and its rate-limiting delivery to the inner mitochrondial leaflet. Concomitantly, we could demonstrate predominant expression of the LDL-R gene in granulosa-luteal cells and of the StAR gene in theca cells in vivo Accordingly, we doned their 5'-upstream regulatory regions, and, by promoter deletional analyses, have begun to map cis-acting DNA regions mediating the supraadditive effects of LH and IGF-l. Based on this platform, we propose the following new hypotheses to explicate bihormonal control of sterol-regulatory gene expression in the granulosa-luteal and theca cell: Hypothesis (1). LH and IGF-l achieve synergism by reciprocally amplifying selected facets of distal effector-signaling pathways. Hypothesis (2). LH and IGF-l upregulate LDL-R gene expression supraadditively in the granulosa-luteal cell by way of discrete cis-acting DNA regions and corresponding nuclear transactivating proteins. Hypothesis (3). LH and IGF-I drive StAR gene expression synergistically in theca cells by stimulating distinct cis-acting DNA elements and associated transacting nuclear factors. In ensemble, the foregoing thesis of bihormonal control of sterol-metabolizing gene expression in the granulosa-luteal and theca cell should provide novel insights into how the pituitary gonadotropin, LH, and the locally produced growth factor, IGF-l, act convergently to govern (a) intracellular signaling and (b) gene expression in ovarian cells. Understanding such fundamental interactions is important to the rational design of alternative strategies to interrupt normal and rescue impaired steroidogenesis in the maturing Graafian follicle and corpus luteum.