Zeleznik Anthony J, Saxena Deeksha, Little-Ihrig Lynda
Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Endocrinology. 2003 Sep;144(9):3985-94. doi: 10.1210/en.2003-0293.
Although FSH receptors are linked to the cAMP second messenger system, additional intracellular signaling pathways appear to be required for the induction of aromatase and the LH receptor during granulosa cell differentiation. We employed adenovirus vectors to modulate specific intracellular signaling systems in undifferentiated granulosa cells to identify the signaling pathway(s) that may be involved in the FSH-mediated induction of aromatase and the LH receptor. Expression of either the constitutively activated human LH receptor D578H or the constitutively active human G(s)alpha Q227L resulted in increased cAMP production without increasing aromatase activity or mRNA levels for the LH receptor. To explore the contributions of other pathways, we expressed the constitutively activated forms MAPK kinase (MEK) and protein kinase B (PKB). Neither MEK nor PKB alone increased estrogen or progesterone production by undifferentiated granulosa cells. Stimulation of granulosa cells by FSH in the presence of the constitutively active PKB, but not MEK, led to an amplification of FSH-induced aromatase and LH receptor mRNA levels, whereas a dominant negative PKB vector completely abolished the actions of FSH. The expression of the constitutively active PKB in combination with the constitutively active LH receptor D578H, the constitutively active G(s)alpha Q227L, or 8-bromo-cAMP led to an induction of aromatase as well as LH receptor mRNA comparable to that seen in cells stimulated with FSH alone. These results demonstrate that PKB is an essential component of the FSH-mediated granulosa cell differentiation and that both PKB and G(s)alpha signaling pathways are required.
尽管促卵泡激素（FSH）受体与环磷酸腺苷（cAMP）第二信使系统相关联，但在颗粒细胞分化过程中，诱导芳香化酶和促黄体生成素（LH）受体似乎还需要其他细胞内信号通路。我们使用腺病毒载体来调节未分化颗粒细胞中的特定细胞内信号系统，以确定可能参与FSH介导的芳香化酶和LH受体诱导的信号通路。组成型激活的人LH受体D578H或组成型激活的人G(s)α Q227L的表达导致cAMP产生增加，但未增加芳香化酶活性或LH受体的mRNA水平。为了探索其他通路的作用，我们表达了组成型激活形式的丝裂原活化蛋白激酶激酶（MEK）和蛋白激酶B（PKB）。单独的MEK或PKB均未增加未分化颗粒细胞产生的雌激素或孕酮。在存在组成型激活的PKB而非MEK的情况下，FSH刺激颗粒细胞会导致FSH诱导的芳香化酶和LH受体mRNA水平放大，而显性负性PKB载体则完全消除了FSH的作用。组成型激活的PKB与组成型激活的LH受体D578H、组成型激活的G(s)α Q227L或8-溴-cAMP联合表达会导致芳香化酶以及LH受体mRNA的诱导，其程度与单独用FSH刺激的细胞中所见相当。这些结果表明，PKB是FSH介导的颗粒细胞分化的重要组成部分，并且PKB和G(s)α信号通路都是必需的。
