MECHANISM OF ACTION OF PEPTIDE HORMONES IN STEROIDOGENIC CELLS

细胞色素P450- 17 α（CYP 17）是合成 雄激素和糖皮质激素，催化两个连续氧化 反应以产生17 α-羟基化（羟化酶）中间体， 雄烯产物（17-20裂解酶）。 在保守结构域（343至 363），带电荷的氨基酸有助于裂解酶和羟化酶活性。 Arg 346对于裂解酶活性是必需的，Arg 363对于裂解酶活性是重要的。 羟化酶活性 基因组分析显示，该结构域是 exon 6中的一个。 氨基酸序列中Arg 361和Glu 358的取代 含丙氨酸的保守结构域消除了所有羟化酶和裂合酶 活动 这些突变体显示出一种过早降解的模式， 转染研究。 虽然突变蛋白水平接近 野生型在早期的时候，突变蛋白是无活性的，在这些时间 时期 脉冲追踪研究显示， 10小时到2小时。 另外的取代表明负电荷 Glu 358侧链的延长长度对于 羟化酶和裂解酶活性。 我们的研究表明，Glu 358 和Arg 361可能有助于类固醇结合结构域的折叠， CYP 17，并且它们的取代导致错误折叠和降解。 在Leydig细胞中，5-羟色胺是CRF分泌的急性刺激物， 其作用通过高亲和力低容量5 HT 2受体发挥， 位于细胞膜上。 在最近的研究中， 调节培养的睾丸间质细胞中5-羟色胺的分泌。 成年莱迪希 细胞分泌大量的血清素。 释放是 人绒毛膜促性腺激素和环腺苷急性刺激 单磷酸，表明其在促性腺激素诱导的血清素中的主要作用 release. hCG刺激不需要细胞外钙。 但是，在这方面， 离子霉素是5-羟色胺释放的有效刺激物，表明 细胞质钙的增加也可诱导胺释放。 的 睾丸间质细胞5-羟色胺含量在刺激时下降， 血清素释放 免疫细胞化学研究显示， 成年大鼠睾丸间质细胞中的血清素。 睾丸5-羟色胺具有局部抗生殖作用， 一个自分泌微回路的触发器， 刺激。 睾丸内5-羟色胺浓度的增加 发生在已知增加睾丸（精索静脉曲张）和中央 （压力）血清素，并可能有助于破坏睾丸 在这些国家中观察到的功能。

Cytochrome P450-17alpha (CYP17), the key enzyme for the synthesis of androgens and glucocorticoids, catalyses two consecutive oxidation reactions to produce 17alpha-hydroxylated (hydroxylase) intermediate and androstene products (17-20 lyase). Within the conserved domain (343 to 363), charged amino acids contribute to lyase and hydroxylase activities. Arg 346 is essential for lyase activity and Arg 363 is of importance for hydroxylase activity. Genomic analysis revealed that this domain is contained in exon 6. Substitution of Arg 361 and Glu 358 within the conserved domain with alanine abolished all hydroxylase and lyase activities. These mutants showed a pattern of premature degradation in transfection studies. Although the mutant protein levels were close to wild type at early times, the mutant protein was inactive at these time periods. Pulse chase studies revealed marked decreases in half-life from 10 hours to 2 hours. Additional substitutions show that a negative charge and the extended length of the side chain of Glu 358 is of importance for the hydroxylase and lyase activities. Our studies indicate that Glu 358 and Arg 361 may contribute to the folding of the steroid binding domain of CYP17 and that their substitution results in misfolding and degradation. In the Leydig cells, serotonin is an acute stimulus of CRF secretion and its action is exerted via high-affinity low capacity 5HT2 receptors that are located in the plasma membrane. In recent studies we defined the regulation of serotonin secretion in cultured Leydig cells. Adult Leydig cells secrete considerable quantities of serotonin. The release was acutely stimulated by human chorionic gonadotropin and by cyclic adenosine monophosphate, indicating its major role in gonadotropin-induced serotonin release. hCG stimulation did not require extracellular calcium. However, ionomycin was a potent stimulus of serotonin release, indicating that increases in cytoplasmic calcium could also induce amine release. The serotonin content of Leydig cells decreased during stimulation of serotonin release. Immunocytochemical studies revealed specific staining of serotonin in the interstitial cells of the adult rat testis. Testicular serotonin has local antireproductive actions and may serve as the trigger of an autocrine microcircuit that buffers the gonadotropin stimulus. Intratesticular increases of serotonin concentration could occur in conditions known to increase testicular (varicocele) and central (stress) serotonin, and may contribute to the disruption of testicular function observed in these states.