Pituitary PACAP gene regulation by hypothalamic, pituitary and gonadal factors

描述(由申请人提供)：最近的研究表明，垂体腺苷酸环化酶激活肽(PACAP)在促性腺激素的生物合成和分泌中具有明显的调节作用。PACAP最初被定义为下丘脑释放因子，后来被确定具有广泛的分布和功能，包括在性腺、胎盘、中枢和外周神经系统、内分泌胰腺和肾上腺表达。与这一建议特别相关的是，已发现PACAP在垂体促性腺激素细胞中的表达，提示PACAP可能在该组织中起自分泌-旁分泌因子的作用。鉴于其在多种生理系统中的重要作用，对PACAP基因表达的调控知之甚少。本研究的主要目的是阐明调节垂体促性腺激素中PACAP表达的激素因子、细胞内信号系统、转录因子和顺式元件。在初步研究中，我们观察了促性腺激素释放激素(GnRH)刺激PACAP基因表达的能力，并已开始研究确定PACAP基因启动子中GnRH反应的DNA调控区。本研究的具体目的是：1)研究GnRH激活的PACAP基因表达的细胞内信号转导途径，重点是AP-1和Cre样顺式元件；2)鉴定介导GnRH刺激PACAP基因启动子活性的转录因子(S)；3)确定不同生理状态下原代培养的大鼠垂体细胞中PACAP基因的表达；4)研究脉动性GnRH、性腺激素和性腺肽对PACAP基因表达的调节作用。有关PACAP表达的分子和细胞调控的信息被预测为与PACAP发挥作用的一系列生理系统具有广泛的相关性。更直接的是，这些研究将为促性腺激素生理的微调提供重要的见解，促性腺激素是正常生殖功能的必要条件。从长远来看，预计这些研究将拓宽我们的理解，并最终改善与促性腺激素异常表达相关的多种疾病的治疗选择，包括青春期延迟和性早熟、多囊卵巢综合征和性腺激素减退症。

DESCRIPTION (provided by applicant): Recent studies have demonstrated a clear role for pituitary adenylate cyclase-activating peptide (PACAP) in the regulation of gonadotropin biosynthesis and secretion. First defined as a hypothalamic-releasing factor, PACAP subsequently has been determined to have widespread distribution and function, including expression in the gonads, placenta, central and peripheral nervous systems, endocrine pancreas, and adrenal gland. Of particular relevance to this proposal, PACAP expression has been identified in pituitary gonadotrope cells, suggesting that PACAP may act as an autocrine-paracrine factor in this tissue. In view of its critical role in multiple physiologic systems, remarkably little is known regarding the regulation of PACAP gene expression. The primary objective of this proposal is to elucidate the hormonal factors, intracellular signaling systems, transcription factors, and cis-elements which regulate PACAP expression in the pituitary gonadotrope. In preliminary studies, we have observed the ability of gonadotropin-releasing hormone (GnRH) to stimulate PACAP gene expression and have initiated studies to identify GnRH-responsive DNA- regulatory regions in the PACAP gene promoter. The Specific Aims are: 1) To characterize the intracellular signaling pathways which mediate GnRH-activated PACAP gene expression, with a focus on putative AP-1 and CRE-like cis-elements, 2) To identify the transcription factor(s) which mediate GnRH-induced stimulation of PACAP gene promoter activity, 3) To define pituitary PACAP gene expression in primary rat pituitary cells under various physiologic states in vivo, and 4) To characterize the role of pulsatile GnRH, gonadal steroids and gonadal peptides as regulators of PACAP gene expression in vitro. Information obtained regarding the molecular and cellular regulation of PACAP expression is predicted to have broad relevance for the array of physiologic systems in which PACAP functions. More immediately, these studies will provide important insight into the fine-tuning of gonadotrope physiology, a requirement for normal reproductive function. In the longer term, it is predicted that these investigations will broaden our understanding, and ultimately improve treatment options, for the multiple disorders associated with abnormal gonadotropin expression, including delayed and precocious puberty, polycystic ovarian syndrome, and hypogonadotropic hypogonadism.