FSH-Stimulated Signals that Regulate Follicular Maturation

描述(由申请人提供)：女性生育需要卵母细胞、支持颗粒细胞(GC)和组成卵泡的膜细胞的受控成熟。卵泡的生长是一个动态的过程，需要精细的调控。卵泡在腔前阶段被抑制，直到它们被垂体激素卵泡刺激素(FSH)刺激。作为对FSH的反应，GCs产生类固醇、蛋白质激素和生长因子，调节下丘脑/脑垂体轴和子宫容受性，促进卵母细胞成熟和卵泡发育到排卵前表型。所有文献记载的对FSH的反应都是通过cAMP及其主要的细胞内靶标cAMP依赖的蛋白激酶(PKA)介导的。事实上，GC提供了由PKA协调响应的细胞模型的最佳范例之一。PKA的信号通过一系列定位PKA池、底物和相互连接的信号酶的A-激酶锚定蛋白(AKAP)被限制在细胞中的特定位置。这一应用重点是PKA整合转录网络以模拟GC成熟的机制。PKA通过磷酸化直接调节转录的底物或通过调节其靶标调节转录的途径来完成这种整合功能。共激活因子β-连环蛋白是一种潜在的PKA底物，激活FSH靶基因的一个子集是必需的。PKA还使一种未知底物磷酸化，该底物指导磷脂酰肌醇-3激酶(PI-3K)的激活，而PI-3K是GC生存、增殖和分化的基础。在PI-3K途径的许多靶点中，转录因子FOXO1(叉头盒O因子1)需要磷酸化/失活才能诱导至少一个FSH靶基因子集。我们推测，PKA既可以磷酸化β-连环蛋白来激活其共激活活性，也可以通过磷酸化底物来直接激活PI-3K通路，从而激活和失活FOXO1调节的靶基因网络。AIMS验证了以下假设：特定的AKAP以PKA池为靶点，形成多酶复合体，指导PI-3K的激活；FSH靶基因的诱导，如Lhcgr，需要激活β-catenin；PI-3K途径的靶标FOXO1调节直接靶基因网络，维持GC处于未成熟阶段。了解FSH如何发出信号引导卵泡成熟，可以转化为更安全、更有效的不孕不育和早孕丢失治疗方法，以及避孕药物的新方法。公共卫生相关性：卵泡刺激素向成熟卵泡发出排卵前表型的信号是生育所必需的。了解FSH如何发出信号引导卵泡成熟，可以转化为更安全、更有效的不孕不育和早孕丢失治疗方法，以及避孕药物的新方法。

DESCRIPTION (provided by applicant): Fertility in females requires controlled maturation of the oocyte, supporting granulosa cells (GCs), and thecal cells that comprise the ovarian follicle. Follicle growth is a dynamic process that demands exquisite regulation. Follicles are restrained at the preantral stage until they are stimulated by the pituitary hormone follicle stimulating hormone (FSH). In response to FSH GCs produce steroid and protein hormones and growth factors that regulate the hypothalamic/pituitary axis and uterine receptivity, and promote oocyte maturation and development of the follicle to a preovulatory phenotype. All of the documented responses to FSH are mediated via cAMP and it's predominate intracellular target, cAMP-dependent protein kinase (PKA). Indeed, GCs offer one of the best examples of a cellular model whose responses are orchestrated by PKA. Signaling by PKA is confined to specific locations in cells by virtue of a family of A-kinase anchoring proteins (AKAPs) that localize pools of PKA, their substrates, and interconnected signaling enzymes. This application focuses on the mechanisms by which PKA integrates transcriptional networks to imitate maturation of GCs. PKA accomplishes this integrating function by phosphorylating substrates that directly regulate transcription or by regulating pathways whose targets regulate transcription. The co-activator beta-catenin is emerging as one potential PKA substrate necessary for activation of a subset of FSH target genes. PKA also phosphorylates an unidentified substrate that directs activation of the phosphatidylinositol-3 kinase (PI-3K) pathway fundamental to GC survival, proliferation, and differentiation. Among the many PI-3K pathway targets, the transcriptional factor FOXO1 (forkhead box O factor 1) requires phosphorylation/inactivation to permit induction of at least a subset of FSH target genes. We postulate that PKA phosphorylates both beta-catenin to activate its co- activator activity and a substrate to direct activation of the PI-3K pathway to activate and inactivate a network of FOXO1-regulated target genes. Aims test the following hypotheses: that a specific AKAP targets a pool of PKA to a multi-enzyme complex that directs activation of PI-3K; that induction of FSH target genes like Lhcgr requires activation of beta-catenin; and that the PI-3K pathway target FOXO1 regulates a network of direct target genes that maintain GCs in an immature stage. Understanding how FSH signals to direct follicular maturation can translate into safer and more effective treatments of infertility and early pregnancy loss as well as new approaches for contraceptive drugs. PUBLIC HEALTH RELEVANCE: FSH signaling to mature follicles to the preovulatory phenotype is required for fertility. Understanding how FSH signals to direct follicular maturation can translate into safer and more effective treatments of infertility and early pregnancy loss as well as new approaches for contraceptive drugs.