SEX STEROID REGULATION OF IGF-I EXPRESSION IN BONE

描述：（改编自申请人摘要）骨量通过以下方式平衡： 吸收和形成的相反过程。胰岛素样生长因子-i （IGF-I）是一种重要的骨生长因子，可增强 分化的骨细胞和成骨细胞的基质胶原合成。 甲状旁腺激素和前列腺素E2增加成骨细胞中的cAMP水平， 并且间歇施用任一种药剂刺激骨形成。 这些激素部分通过依赖于cAMP依赖性的过程起作用。 蛋白激酶A，诱导成骨细胞表达IGF-I。研究者已 确定了一个C/EBP位点，这是必要的和足够的cAMP依赖性 IGF-I启动子激活，发现C/EBP δ是功能性的反式作用， 转录因子在胎鼠成骨细胞，也发现雌激素 直接抑制cAMP对C/EBP δ介导的 IGF-I激活，但不影响cAMP合成。这是雌激素受体 依赖性，不需要可识别的雌激素反应元件， AP-1结合序列。拟议的研究将检查蛋白质：蛋白质 影响C/EBP介导的IGF-I激活的相互作用， 雌激素对IGF-I基因激活的反调节抑制作用。的 研究者将确定PGE 2和17 β-雌二醇的分子作用 C/EBP δ和C/EBP β表达的影响， 调节其启动子功能的反式作用元件，并决定 这些试剂调节C/EBP mRNA稳定性的能力。他将决定 17 β-雌二醇对PKA活化的影响 共处理对C/EBP δ和β从细胞质易位到细胞质的影响 细胞核，并分析在这些条件下C/EBP磷酸化的变化。 最后，他将确定C/EBP δ和β在cAMP中的生理作用。 激活IGF-I的表达，与雌激素的相互作用，并最终在 调节C/EBP敲除动物的骨量。骨量研究将 使用周边定量计算机断层扫描进行，并将 与基础和激活的骨骼IGF-I表达相关。

DESCRIPTION: (Adapted from the applicant's abstract) Bone mass is balanced by opposing processes of resorption and formation. Insulin-like growth factor-I (IGF-I) is an important bone growth factor that enhances replication of less differentiated bone cells and matrix collagen synthesis by osteoblasts. Parathyroid hormone and prostaglandin E2 increase cAMP levels in osteoblasts, and intermittent administration of either agent stimulates bone formation. These hormones act in part through a process that relies on cAMP dependent protein kinase A, inducing osteoblasts to express IGF-I. The investigator has identified a C/EBP site that is necessary and sufficient for cAMP-dependent IGF-I promoter activation, found C/EBP delta to be the functional trans-acting transcription factor in fetal rat osteoblasts, and also found that estrogen directly suppresses the stimulatory effect of cAMP on C/EBP delta-mediated IGF-I activation, but not on cAMP synthesis. This is estrogen receptor dependent and does not require an identifiable estrogen response elements or AP-1 binding sequence. The proposed studies will examine protein:protein interactions that influence C/EBP mediated IGF-I activation, and the counter-regulatory suppressive effect of estrogen on IGF-I gene activation. The investigator will determine the molecular actions of PGE2 and l7beta-estradiol on C/EBP delta and C/EBP beta expression by characterizing functional cis- and trans-acting elements that regulate their promoter function, and determine the ability of these agents to modulate C/EBP mRNA stability. He will determine the influence of PKA activation in the absence or presence of l7beta-estradiol co-treatment on translocation of C/EBP delta and beta from the cytoplasm to the nucleus and analyze changes in C/EBP phosphorylation under these conditions. Finally, he will determine the physiologic role of C/EBP delta and beta in cAMP activated IGF-I expression, interactions with estrogen, and ultimately in regulating bone mass in C/EBP knockout animals. Bone mass studies will be conducted using peripheral quantitative computer tomography, and will be correlated with basal and activated skeletal IGF-I expression.