Sasson R, Rimon E, Dantes A, Cohen T, Shinder V, Land-Bracha A, Amsterdam A
Department of Molecular Cell Biology, The Weizmann Institute of Science Rehovot, 76100, Israel.
Mol Hum Reprod. 2004 May;10(5):299-311. doi: 10.1093/molehr/gah041. Epub 2004 Mar 16.
Gonadotrophins exert a major effect on ovarian development and on the control of fertilization. By stimulating cells with forskolin (FK), it is possible to study which genes are activated by gonadotrophins via the cAMP cascade, and which by alternative pathways. Using RNA isolated from stimulated cells, we found that 59% of the total genes modulated by LH were also modulated by FK, while 69% of the genes modulated exclusively by FSH were also modulated by FK. Gene transcripts involved in steroidogenesis/progesterone production were highly elevated, while 17beta-hydroxysteroid dehydrogenase was down-regulated. This suggests that a decrease in the conversion of androstenedione to testosterone and estrone to estradiol occurs during luteinization. Down-regulation of genes coding for actin cytoskeleton proteins and cytokeratin 18 was observed in response to gonadotrophin and cAMP stimulation. Several of the genes coding for the microtubule network were also modulated, implying that rearrangement of the cytoskeletal proteins permits better coupling between organelles involved in steroidogenesis. A dramatic change in gene transcripts coding for signalling enzymes was observed following LH stimulation. This includes the down-regulation of adenylyl cyclase 7 and 9, elevation of cAMP-dependent phosphodiesterase, and the up-regulation of a negative regulator of G-protein signalling (RGS16) that may negate gonadotrophin signalling via guanine nucleotide binding proteins. Thus luteinized cells, despite increased gene transcripts to LH/chorionic gonadotrophin (CG) receptors, respond inefficiently to gonadotrophin stimulation, due to attenuation of signal transduction in the cAMP cascade at multiple steps. Novel genes involved in the regulation of apoptosis were found for the first time to be up-regulated by gonadotrophin stimulation, including: BAX inhibitor-1, granulysin and apoptosis repressor with caspase recruitment domain (ARC). These proteins may be involved in a unique alternative pathway of ovarian cell death. Such a pathway could temporarily preserve the mitochondria and progesterone production during the initial stages of granulosa cell apoptosis.
促性腺激素对卵巢发育和受精控制具有重要作用。通过用福司可林（FK）刺激细胞，能够研究哪些基因是通过环磷酸腺苷（cAMP）级联反应被促性腺激素激活的，哪些是通过其他途径激活的。利用从受刺激细胞中分离出的RNA，我们发现，促黄体生成素（LH）调节的全部基因中有59%也受FK调节，而仅由促卵泡生成素（FSH）调节的基因中有69%也受FK调节。参与类固醇生成/孕酮产生的基因转录本显著升高，而17β-羟基类固醇脱氢酶则被下调。这表明在黄体化过程中，雄烯二酮向睾酮以及雌酮向雌二醇的转化减少。在促性腺激素和cAMP刺激下，观察到编码肌动蛋白细胞骨架蛋白和细胞角蛋白18的基因被下调。几个编码微管网络的基因也受到调节，这意味着细胞骨架蛋白的重排能使参与类固醇生成的细胞器之间实现更好的偶联。在LH刺激后，观察到编码信号酶的基因转录本发生了显著变化。这包括腺苷酸环化酶7和9的下调、cAMP依赖性磷酸二酯酶的升高，以及G蛋白信号负调节因子（RGS16）的上调，RGS16可能通过鸟嘌呤核苷酸结合蛋白使促性腺激素信号失活。因此，黄体化细胞尽管对LH/绒毛膜促性腺激素（CG）受体的基因转录本增加，但由于cAMP级联反应中信号转导在多个步骤中被减弱，对促性腺激素刺激的反应效率低下。首次发现参与细胞凋亡调节的新基因在促性腺激素刺激下被上调，包括：BAX抑制因子-1、颗粒溶素和具有半胱天冬酶募集结构域的凋亡抑制因子（ARC）。这些蛋白质可能参与卵巢细胞死亡的独特替代途径。这样的途径可能在颗粒细胞凋亡的初始阶段暂时维持线粒体和孕酮的产生。
