MOLECULAR BIOLOGY OF STEROIDOGENIC P450 ENZYMES

这个项目的长期目标是了解 影响类固醇激素合成，并了解它们是如何工作的。 类固醇激素是普遍存在的生理调节剂：盐皮质激素 调节盐和水的代谢和血压;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 繁殖的许多方面。 这些类固醇是由 胆固醇转化为一系列类固醇激素;其中大多数 转化由四种特异性P450酶进行：P450SCC转化 P450c17介导17，20裂解酶活性 和17羟化酶活性; P450c21介导两者的21-羟基化 糖皮质激素和盐皮质激素; P450c11介导11羟化酶，18 羟化酶和18甲基氧化酶活性。 自1987年以来，该项目的第一阶段由该赠款资助， 获得类固醇生成P450酶的cDNA和基因克隆，以进行检查 它们的调节，并研究它们的突变导致先天性肾上腺皮质激素缺乏。 增生（CAH）。 这项工作迄今为止非常成功。 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 与P450c21A假基因重叠的称为XA，与P450c21A假基因重叠的称为XA。 有功能的P450c21B基因称为XB。 我们还发现了第三种 命名为Y的基因，位于XB内，与P450c21B在同一条链上，3 '端至 了 测序结果表明XA和XB可能编码 与腱生蛋白相关的细胞外基质蛋白; Y的功能是 未知 XA和Y仅在肾上腺中表达，因此可能是 参与类固醇生成; XB几乎在所有胎儿组织中表达 这表明在发展中有更广泛的作用。 本竞争性续期申请的重点是建立 结构和功能基因XA，XB和Y，并继续我们的研究， 类固醇生成P450基因的突变导致各种形式的 先天性肾上腺增生 为此，我们建议：1）完成 XA、XB和Y基因座的结构表征; 2）表征 由这些基因编码的mRNA和蛋白质产物3）决定组织 4）表征其表达的生物活性 由这些基因编码的产物5）继续我们对 先天性肾上腺皮质增生的分子基础 成功 这项工作的完成将大大扩展我们对这些角色的理解， 这些新发现的基因在肾上腺功能中的作用。

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.