MOLECULAR BIOLOGY OF STEROIDOGENIC P450 ENZYMES

这个项目的长期目标是了解哪些基因 影响类固醇激素的合成，并了解它们是如何工作的。 类固醇激素是无处不在的生理调节剂：矿物质皮质激素 调节盐、水代谢和血压；糖皮质激素 调节碳水化合物代谢和其他功能；性类固醇调节 繁衍的许多方面。这些类固醇是按顺序生产的 将胆固醇转化为一系列类固醇激素；其中大多数 转化由四种特定的P450酶进行：P450scc转化 胆固醇到孕烯醇酮；P450c17介导17，20裂解酶活性 和17羟基酶活性；P450c21介导两者的21-羟基化 糖皮质激素和矿物皮质激素；P450c11介导11羟基酶，18 羟基酶和18种羟氧基酶活性。 该项目的第一阶段，自1987年以来由这笔赠款资助，目的是 获得类固醇合成P450酶的cdna和基因克隆，用于检测 它们的调控，并研究它们的突变导致先天性肾上腺 增生症(CAH)。到目前为止，这项工作非常成功。在 在研究CAH的过程中，我们发现了两个以前未知的基因 位于与P450c21基因相反的DNA链上。基因 重叠P450c21A假基因称为XA，重叠P450c21A假基因 功能性P450c21B基因被称为XB。我们还发现了第三个 Y基因位于XB内，与P450c21B和3‘T0位于同一链上 它。测序研究表明，XA和XB可能编码 与Tenascin相关的细胞外基质蛋白；Y的功能是 未知。Xa和Y仅在肾上腺表达，因此可能是 参与类固醇合成；XB在几乎所有的胎儿组织中都有表达 建议在发展中发挥更广泛的作用。 目前申请竞合续期的重点是建立 结构与功能基因XA、XB和Y及其继续研究的问题 导致各种形式的类固醇激素生成P450基因的突变 先天性肾上腺增生症。为此，我们建议：1)完成 XA、XB和Y基因座的结构特征；2)表征 这些基因编码的信使核糖核酸和蛋白质产物决定组织 它们的表达分布表征了它们的生物活性 这些基因编码的产物继续我们对 先天性肾上腺增生症的分子基础。成功 这项工作的完成将极大地扩大我们对角色的理解 这些新发现的肾上腺功能基因。

The long term objective of this project it to understand what genes influence steroid hormone synthesis, and to understand how they work. Steroid hormones are ubiquitous physiologic regulators: mineralcorticoids regulate salt and water metabolism and blood pressure; glucocorticoids regulate carbohydrate metabolism and other functions; sex steroids regulate numerous aspects of reproduction. These steroids are made by sequential conversions of cholesterol to a series of steroid hormones; most of these conversions are made by four specific P450 enzymes: P450scc converts cholesterol to pregnenolone; P450c17 mediates both 17, 20 lyase activity and 17 hydroxylase activity; P450c21 mediates the 21-hydroxylation of both glucocorticoids and mineralcorticoids; P450c11 mediates 11 hydroxylase, 18 hydroxylase, and 18 methyloxidase activities. The first phase of this project, funded by this grant since 1987, was to obtain cDNA and gene clones for the steroidogenic P450 enzymes, to examine their regulation, and to study their mutations causing congenital adrenal hyperplasia (CAH). This work has been highly successful to date. In the course of studying CAH, we have discovered two previously unknown genes lying on the opposite strand of DNA from the P450c21 genes. The gene overlapping the P450c21A pseudogene is termed XA and that overlapping the functional P450c21B gene is termed XB. We have also discovered a third gene termed Y, lying within XB, on the same strand as P450c21B and 3' to it. Sequencing studies indicate that XA and XB probably encode extracellular matrix proteins related to tenascin; the function of Y is unknown. XA and Y are expressed solely in the adrenal, and hence may be involved in steroidogenesis; XB is expressed in virtually all fetal tissues suggesting a more general role in development. The present application for competing renewal focuses on establishing the structure and function Genes XA, XB and Y and on continuing our studies of the mutations in the steroidogenic P450 genes causing various forms of congenital adrenal hyperplasia. To do this we propose to: 1) Complete the structural characterization of the XA, XB and Y loci; 2) characterize the mRNA and protein products encoded by these genes 3) determine the tissue distribution of their expression 4) characterize the biologic activities of the products encoded by these genes 5) continue our studies on the molecular basis of the congenital adrenal hyperplasia. Successful completion of this work will greatly expand our understanding of the roles of these newly discovered genes in adrenal function.