Moore R K, Otsuka F, Shimasaki S
Department of Reproductive Medicine, University of California at San Diego, School of Medicine, La Jolla, California 92093-0633, USA.
Biochem Biophys Res Commun. 2001 Dec 14;289(4):796-800. doi: 10.1006/bbrc.2001.6052.
A major concept in mammalian ovarian physiology is that follicle-stimulating hormone (FSH) activates the granulosa cells (GCs) in the Graafian follicle to selectively produce estradiol, but not progesterone, during the follicular phase of the menstrual or estrous cycle. However, given the fact that FSH can induce production of both estradiol and progesterone by GCs cultured in vitro, it has been postulated for a long time that there is a factor present in the ovary that selectively prevents FSH-induced progesterone production. Here, we provide evidence that two members of the mitogen-activated protein kinase family, extracellular signal-regulated kinase-1 and -2 (ERK1/2) can differentially regulate FSH-stimulated estradiol and progesterone production. Using primary rat GCs from early antral follicles cultured in serum-free medium for 48 h, we found that the addition of a specific inhibitor of ERK1/2 activation, U0126, caused the attenuation or enhancement of FSH-induced progesterone or estradiol production, respectively, in a dose-dependent manner. Throughout the 48-h culture period in this culture system ERK1/2 molecules in their activated state (phospho-ERK1/2) were clearly detectable in GCs exposed to FSH. The addition of U0126 caused a decrease in the levels of phosphorylated but not unphosphorylated ERK1/2 which was maintained throughout the 48-h culture, suggesting that U0126 was continuously active to inhibit the phosphorylation of ERK1/2. The divergent regulation of FSH-induced progesterone and estradiol synthesis by U0126 was further supported by demonstrating that U0126 inhibits and stimulates FSH-induced mRNA levels of steroidogenic acute regulatory protein and P450 aromatase, respectively. Collectively, this study clearly identified ERK1/2 as the first intracellular signaling molecules that differentially regulate FSH-induced progesterone and estradiol synthesis in GCs.
哺乳动物卵巢生理学中的一个主要概念是，促卵泡激素（FSH）在月经周期或发情周期的卵泡期激活格拉夫卵泡中的颗粒细胞（GCs），使其选择性地产生雌二醇，而不产生孕酮。然而，鉴于FSH能诱导体外培养的GCs产生雌二醇和孕酮，长期以来人们推测卵巢中存在一种因子，可选择性地阻止FSH诱导的孕酮生成。在此，我们提供证据表明，丝裂原活化蛋白激酶家族的两个成员，细胞外信号调节激酶-1和-2（ERK1/2）可分别调节FSH刺激的雌二醇和孕酮生成。使用来自早期窦状卵泡的原代大鼠GCs在无血清培养基中培养48小时，我们发现添加ERK1/2激活的特异性抑制剂U0126，分别以剂量依赖的方式导致FSH诱导的孕酮或雌二醇生成减弱或增强。在该培养系统的整个48小时培养期间，在暴露于FSH的GCs中可清楚检测到处于活化状态（磷酸化ERK1/2）的ERK1/2分子。添加U0126导致磷酸化而非未磷酸化的ERK1/2水平降低，且在整个48小时培养过程中保持不变，这表明U0126持续发挥作用抑制ERK1/2的磷酸化。U0126对FSH诱导的孕酮和雌二醇合成的不同调节作用，通过证明U0126分别抑制和刺激FSH诱导的类固醇生成急性调节蛋白和P450芳香化酶的mRNA水平得到进一步支持。总的来说，本研究明确将ERK1/2鉴定为首个在GCs中分别调节FSH诱导的孕酮和雌二醇合成的细胞内信号分子。
