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）在调节促性腺激素的生物合成和分泌中具有明确的作用。PACAP最初被定义为一种下丘脑释放因子，随后被确定具有广泛的分布和功能，包括在性腺、胎盘、中枢和周围神经系统、内分泌胰腺和肾上腺中表达。与此建议特别相关的是，在垂体促性腺细胞中发现了PACAP的表达，这表明PACAP可能在该组织中作为自分泌-旁分泌因子。鉴于其在多个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垂体促性腺激素中调节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，我们观察到促性腺激素释放激素（GnRH）刺激PACAP基因表达的能力，并启动了在PACAP基因启动子中鉴定GnRH应答性DNA调控区域的研究。具体目标是：1)确定介导GnRH激活的PACAP基因表达的细胞内信号通路，重点研究推测的AP-1和cre样顺式元件；2)确定介导GnRH诱导的PACAP基因启动子活性刺激的转录因子；3)确定不同生理状态下大鼠垂体原代细胞中PACAP基因在体内的表达；促性腺激素和促性腺肽作为PACAP基因体外表达的调节因子。获得的关于PACAP表达的分子和细胞调控的信息预计与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学的微调提供重要的见解，这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对与促性腺激素异常表达相关的多种疾病的认识，并最终改善治疗方案，包括青春期延迟和性早熟、多囊卵巢综合征和促性腺功能低下。

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.