Bird I M, Mason J I, Rainey W E
Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas 75235.
Endocrinology. 1994 Jun;134(6):2468-74. doi: 10.1210/endo.134.6.8194473.
We have studied the hormonal regulation of type 1 angiotensin-II receptor (AT1-R) mRNA expression and [125I]angiotensin-II ([125I]AII) binding in human adrenocortical carcinoma H295 cells, which exhibit predominantly AT1-subtype receptors. Activation of the cAMP signaling pathway with forskolin or (Bu)2cAMP caused a rapid decrease in AT1-R mRNA levels (decreased 65% within 3 h). This preceded a time-dependent (maximal, 70% within 12 h) and dose-dependent (IC50, 2 microM forskolin) loss of [125I]AII binding together with decreased phosphoinositidase-C activation (72% decrease) on subsequent AII challenge. Thus, the decreases in AT1-R mRNA levels and functional receptor expression parallel each other in response to activation of protein kinase-A. AII treatment also caused a rapid loss in AT1-R mRNA (maximal, 80% decrease within 3 h), but 48-h treatment caused both [125I]AII binding and the subsequent phosphoinositidase-C response to decrease by only 6% (P < 0.05) and 22% (P < 0.05), respectively. The effect of AII on AT1-R mRNA levels was fully reproduced by the combination of calcium ionophore (A23187) and phorbol ester (12-O-tetradecanoylphorbol 13-acetate), suggesting that AII action was through protein kinase-C and possibly other Ca(2+)-sensitive protein kinases. The effect of AII, but not forskolin, was reversed by treatment in the presence of cycloheximide. In conclusion, control of AT1-R expression is differentially regulated by adenylate cyclase and phosphoinositidase-C signaling pathways, which act at multiple levels in human adrenocortical cells.
我们研究了1型血管紧张素II受体（AT1-R）mRNA表达的激素调节以及[125I]血管紧张素II（[125I]AII）在人肾上腺皮质癌H295细胞中的结合情况，该细胞主要表达AT1亚型受体。用福斯可林或（Bu）2cAMP激活cAMP信号通路会导致AT1-R mRNA水平迅速下降（3小时内下降65%）。这先于[125I]AII结合的时间依赖性（最大，12小时内70%）和剂量依赖性（IC50，2 microM福斯可林）丧失，以及随后AII刺激时磷脂酶C激活的下降（72%下降）。因此，响应蛋白激酶A的激活，AT1-R mRNA水平的下降与功能性受体表达的下降相互平行。AII处理也导致AT1-R mRNA迅速丧失（最大，3小时内下降80%），但48小时处理导致[125I]AII结合和随后的磷脂酶C反应分别仅下降6%（P < 0.05）和22%（P < 0.05）。钙离子载体（A23187）和佛波酯（12-O-十四烷酰佛波醇13-乙酸酯）联合使用完全重现了AII对AT1-R mRNA水平的影响，表明AII的作用是通过蛋白激酶C以及可能其他对Ca(2+)敏感的蛋白激酶。AII的作用，但不是福斯可林的作用，在放线菌酮存在的情况下处理可被逆转。总之，AT1-R表达的调控受到腺苷酸环化酶和磷脂酶C信号通路的差异调节，这些通路在人肾上腺皮质细胞中作用于多个水平。
