MECHANISM OF ACTION OF PEPTIDE HORMONES IN STEROIDOGENIC CELLS

本项目研究促性腺激素对类固醇的作用。 间质细胞的生物合成和分泌。我们正在表演 细胞色素P450-17α(CYP17)的结构功能研究 合成雄激素和糖皮质激素的酶，它催化 Delta4或Delta5内C-17的连续氧化反应 用于生产17α-羟化中间体(17α-羟基化中间体)的前体 羟基酶)和雄激素(17-20裂解酶)。大鼠的突变分析 CYP17揭示了保守结构域中的带电残基 残基343和363对裂解酶和羟基酶活性有贡献。 Arg346对Delta4和Delta5裂解酶活性都是必需的，并且 Arg363参与了羟基酶反应。我们还有 已确定的大鼠和大鼠的物种特异性差异 人/牛/猪的Delta4裂解酶活性与Delta5裂解酶活性的序列 (Phe343大鼠VS Ileu343人)。我们的发现强调了身体上的 羟基酶与裂解酶活力的分离及其重要性 CYP17裂解酶活性的结构域343-348与 治疗用雄激素形成选择性抑制剂的研究进展 前列腺癌和某些形式的男性的基础 假两性畸形。我们还演示了CRF充当 睾丸中的抗生殖激素并抑制黄体生成素诱导的信号转导 和雄激素的产生。促肾上腺皮质激素释放因子在脑内发挥自分泌抑制作用 间质细胞，其分泌是由促黄体生成素通过一种 高亲和力的5HT2 5-羟色胺受体。一种低亲和力的5HT2自身受体 并对5-羟色胺的释放进行负反馈调节。 心得安，一种抗高血压的β-肾上腺素能阻滞剂， 经常导致阳萎，通过其拮抗剂模拟CRF的分泌 5-羟色胺能自身受体的作用及抑制黄体生成素诱导的作用 间质细胞中的类固醇合成。

This project examines the actions of gonadotropins on steroid biosynthesis and secretion in Leydig cells. We are performing structure-function studies of cytochrome P450-17alpha (CYP17), the key enzyme for synthesis of androgen and glucocorticoids, which catalyses consecutive oxidation reactions at C-17 within delta4 or delta5 precursors to produce the 17alpha-hydroxylated intermediate (17alpha- hydroxylase) and androgens (17-20 lyase). Mutational analysis of rat CYP17 revealed that charged residues in the conserved domain between residues 343 and 363 contribute to lyase and hydroxylase activities. Arg346 is essential for both delta4 and delta5-lyase activities and Arg363 is involved in the hydroxylase reaction. We have also determined species-specific differences between rat and human/bovine/pig sequences for delta4 versus delta5-lyase activities (Phe343 rat vs Ileu343 human). Our findings emphasizing the physical separation of hydroxylase from lyase activity as well as the importance of domain 343-348 for lyase activity in CYP17 are relevant to the development of selective inhibitors of androgen formation for treatment of prostate cancer, and to the basis of certain forms of male pseudohermaphroditism. We also demonstrated that CRF acts as an antireproductive hormone in the testis and inhibits LH-induced signaling and androgen production. CRF exerts autocrine inhibitory actions in the Leydig cell, whence its secretion is stimulated by LH acting via a high-affinity 5HT2 serotonin receptor. A low-affinity 5HT2 autoreceptor is also present and exerts negative feedback regulation of 5HT release. Propranolol, an anti-hypertensive beta-adrenergic blocker that frequently causes impotence, simulates CRF secretion by its antagonist action of the serotonergic autoreceptor and inhibits LH-induced steroidogenesis in the Leydig cell.