Clyne C D, White P C, Rainey W E
Division of Reproductive Endocrinology, University of Texas, Southwestern Medical School, Dallas 75235-9032, USA.
Endocr Res. 1996 Nov;22(4):485-92. doi: 10.1080/07435809609043735.
The CYP11B2 gene encodes aldosterone synthase, a cytochrome P450 (P450aldo) expressed in high levels in the adrenal zona glomerulosa. While the primary physiologic regulators of aldosterone production are circulating angiotensin II (Ang II) and potassium (K+) the action of these agents on CYP11B2 gene transcription have not been examined. Because these factors increase intracellular calcium we have hypothesized that calcium signaling pathways are one mechanism controlling CYP11B2 transcription. Previously we demonstrated that increases in intracellular calcium increase P450aldo mRNA. Herein, we analyzed the role of calcium in the expression of the human CYP11B2 gene using transient transfection of a luciferase reporter construct containing 2017 bp of human CYP11B2 5'flanking DNA in mouse Y-1 and human H295R adrenocortical cell lines. When transfected into Y-1 cells, reporter gene expression was increased following treatment with ACTH or forskolin, but not with Ang II, the L-type calcium channel agonist BAYK8644, or ionomycin. In H295R cells, however, reporter gene expression was increased following treatment with Ang II, K+, BAYK8644 ionomycin or dibutyryl cAMP (Bu2cAMP). Activation of protein kinase C with TPA did not alter reporter gene expression in either cell line. These data demonstrate that both calcium and cAMP signaling pathways regulate human CYP11B2 gene expression. In addition, the H295R adrenal cell line appears to be an appropriate model to study regulation of CYP11B2 by calcium.
CYP11B2基因编码醛固酮合成酶，这是一种细胞色素P450（P450aldo），在肾上腺球状带中高水平表达。虽然醛固酮生成的主要生理调节因子是循环中的血管紧张素II（Ang II）和钾（K+），但尚未研究这些因子对CYP11B2基因转录的作用。由于这些因素会增加细胞内钙，我们推测钙信号通路是控制CYP11B2转录的一种机制。此前我们证明细胞内钙的增加会增加P450aldo mRNA。在此，我们使用含有2017 bp人CYP11B2 5'侧翼DNA的荧光素酶报告构建体瞬时转染小鼠Y-1和人H295R肾上腺皮质细胞系，分析了钙在人CYP11B2基因表达中的作用。当转染到Y-1细胞中时，用促肾上腺皮质激素（ACTH）或福斯可林处理后报告基因表达增加，但用Ang II、L型钙通道激动剂BAYK8644或离子霉素处理则没有增加。然而，在H295R细胞中，用Ang II、K+、BAYK8644、离子霉素或二丁酰环磷腺苷（Bu2cAMP）处理后报告基因表达增加。用佛波酯（TPA）激活蛋白激酶C在两种细胞系中均未改变报告基因表达。这些数据表明钙和环磷腺苷（cAMP）信号通路均调节人CYP11B2基因表达。此外，H295R肾上腺细胞系似乎是研究钙对CYP11B2调控的合适模型。
