Regulation of Follistatin Expression by Activin

激活素对卵泡抑素表达的调节

• 批准号: 6847803
• 负责人: Louise M Bilezikjian
• 金额: $ 33.8万
• 依托单位: SALK INSTITUTE FOR BIOLOGICAL STUDIES
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6847803
• 关键词: DNA binding protein; RNA interference; SDS polyacrylamide gel electrophoresis; activins; biological signal transduction; cell line; chromatin immunoprecipitation; enzyme linked immunosorbent assay; follistatin; gene expression; gene induction /repression; genetic regulation; genetic regulatory element; gonadotropins; hormone regulation /control mechanism; introns; laboratory rabbit; matrix assisted laser desorption ionization; pituitary gonadal axis; protein protein interaction; western blottings

DESCRIPTION (provided by applicant): The major objective of this research proposal is to gain an understanding of how activin-dependent Smad signaling leads to follistatin gene activation in anterior pituitary gonadotropes. Activins are widely expressed pleiotropic regulators of diverse tissues and cellular functions, including the differential production of FSH from gonadotropes of the anterior pituitary. Thus of necessity, the actions of activins are under the precise control of multiple mechanisms of functional inactivation or antagonism. Follistatins are secreted activin-binding glycoproteins that function extracellularly to modulate the bio-availability of activins in most tissues. Although first identified as FSH-suppressing components of gonadal fluids, numerous studies have since documented the presence of follistatin in many tissues, including gonadotropes and other cell types of the anterior pituitary. Activins are one of the most potent inducers of follistatin expression and it is now presumed that many of the demonstrated actions of follistatins reflect their local autocrine/paracrine influence on the bioactivity of activins and possibly other TGF-Beta family members. As testimony to the importance of their actions to counterbalance the diverse effects of activins, mice null for follistatin exhibit many embryonic defects and die shortly after birth. On the other hand, follistatin over-expression is associated with infertility because of functional disruptions at the level of the gonads and the pituitary. In the anterior pituitary, the inducible expression of follistatin establishes a feedback loop and a mechanism for activin to self-modulate further signaling. The focus of this proposal is to elucidate the poorly understood mechanism underlying the regulation of follistatin gene expression in gonadotropes. We have obtained strong evidence that elements in the fin'st intron of the rat follistatin gene mediate the transcriptional effects of activin, via Smad signaling, on this gene in gonadotrope-derived alphaT3-1 and LBetaT2 cells. We propose to use complementary approaches to define precisely the elements of the activin-responsive region located in the first intron of the rat follistatin gene, to characterize gonadotrope-derived factor(s) that mediate these effects of activin in conjunction with Smad3 and Smad4 and, finally, to determine the function of these factors as obligate mediators of this action of activin. The proposed studies also aim to determine if activin induces follistatin expression by the same mechanism in other pituitary and non-pituitary cell types. Altogether, these studies will provide important insights into the mechanism by which activin controls follistatin expression in gonadotropes and identify selective therapeutic targets for the management of reproductive and other endocrine disorders.

描述（由申请人提供）：本研究提案的主要目的是了解激活素依赖性Smad信号传导如何导致垂体前叶促性腺激素细胞中卵泡抑素基因激活。激活素是广泛表达的多种组织和细胞功能的多效性调节剂，包括垂体前叶促性腺激素差异产生的FSH。因此，激活素的作用必然受到多种功能失活或拮抗机制的精确控制。卵泡抑素是分泌的激活素结合糖蛋白，其在细胞外起作用以调节大多数组织中激活素的生物利用度。虽然最初被鉴定为性腺液的FSH抑制成分，但许多研究已经证明卵泡抑素存在于许多组织中，包括促性腺激素细胞和垂体前叶的其他细胞类型。激活素是卵泡抑素表达的最有效的诱导剂之一，现在推测卵泡抑素的许多已证实的作用反映了它们对激活素和可能的其他TGF-β家族成员的生物活性的局部自分泌/旁分泌影响。作为它们抵消激活素不同作用的重要性的证据，卵泡抑素无效的小鼠表现出许多胚胎缺陷，并在出生后不久死亡。另一方面，卵泡抑素过度表达与不孕症有关，因为性腺和垂体水平的功能中断。在垂体前叶中，卵泡抑素的诱导表达建立了一个反馈回路和激活素自我调节进一步信号传导的机制。该建议的重点是阐明促性腺激素细胞中卵泡抑素基因表达调控的机制。我们已经获得了强有力的证据表明，在促性腺激素衍生的α T3 -1和LBetaT 2细胞中，大鼠卵泡抑素基因的最后内含子中的元件通过Smad信号传导介导激活素对该基因的转录作用。我们建议使用互补的方法来精确地定义位于大鼠卵泡抑素基因的第一个内含子中的激活素反应区的元素，以表征促性腺激素衍生因子（S），介导这些激活素与Smad 3和Smad 4的作用，最后，确定这些因子作为激活素这种作用的专性介质的功能。拟议的研究还旨在确定激活素是否通过相同的机制在其他垂体和非垂体细胞类型中诱导卵泡抑素表达。总之，这些研究将提供重要的见解，激活素控制促性腺激素卵泡抑素表达的机制，并确定选择性治疗靶点的管理生殖和其他内分泌疾病。