Shinohara O, Knecht M, Catt K J
Proc Natl Acad Sci U S A. 1985 Dec;82(24):8518-22. doi: 10.1073/pnas.82.24.8518.
The induction of granulosa cell differentiation by follicle-stimulating hormone (FSH) is characterized by cellular aggregation, expression of luteinizing hormone (LH) receptors, and biosynthesis of steroidogenic enzymes. These actions of FSH are mediated by activation of adenylate cyclase and cAMP-dependent protein kinase and can be mimicked by choleragen, forskolin, and cAMP analogs. Gonadotropin releasing hormone (GnRH) agonists inhibit these maturation responses in a calcium-dependent manner and promote phosphoinositide turnover. The phorbol ester phorbol 12-myristate 13-acetate (PMA) also prevented FSH-induced cell aggregation and suppressed cAMP formation, LH receptor expression, and progesterone production, with an ID50 of 0.2 nM. In FSH-treated cells, PMA did not reduce the initial increase in cAMP formation during the first 24 hr of culture but prevented its secondary increase from 24 to 48 hr. PMA also inhibited LH receptor induction by cholera toxin, forskolin, and 8-bromo-cAMP, but it did not impair cAMP responses to the former two agents, indicating that the site of action of the phorbol ester is distal to adenylate cyclase. The early stimulation of cAMP-dependent protein kinase activity by FSH was also unaffected by PMA, consistent with its lack of effect on the initial cAMP response to FSH. However, PMA caused a marked decrease in cytosolic protein kinase C activity within 1 min of its addition to the cells. The permeant diacylglycerols, 1-oleoyl-2-acetoyl-sn-glycerol and sn-1,2-dioctanoyl glycerol, also inhibited LH receptor formation, while the nonpermeant diacylglycerol, diolein, was inactive. These results indicate that in situ activation of protein kinase C by PMA or permeant diacylglycerols inhibits cAMP-dependent granulosa cell differentiation, and suggest that the inhibitory actions of GnRH agonists on granulosa cell maturation are also mediated by protein kinase C.
促卵泡激素（FSH）诱导颗粒细胞分化的特征在于细胞聚集、黄体生成素（LH）受体的表达以及类固醇生成酶的生物合成。FSH的这些作用是由腺苷酸环化酶和cAMP依赖性蛋白激酶的激活介导的，并且可被霍乱毒素、福斯可林和cAMP类似物模拟。促性腺激素释放激素（GnRH）激动剂以钙依赖性方式抑制这些成熟反应并促进磷酸肌醇代谢。佛波酯佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）也可防止FSH诱导的细胞聚集，并抑制cAMP形成、LH受体表达和孕酮产生，半数抑制浓度（ID50）为0.2 nM。在FSH处理的细胞中，PMA在培养的最初24小时内并未降低cAMP形成的初始增加，但阻止了其在24至48小时的二次增加。PMA还抑制霍乱毒素、福斯可林和8 - 溴 - cAMP诱导的LH受体，但不损害对前两种试剂的cAMP反应，表明佛波酯的作用位点在腺苷酸环化酶的下游。FSH对cAMP依赖性蛋白激酶活性的早期刺激也不受PMA影响，这与其对FSH初始cAMP反应缺乏影响一致。然而，PMA在添加到细胞后1分钟内导致胞质蛋白激酶C活性显著下降。渗透性二酰基甘油1 - 油酰基 - 2 - 乙酰基 - sn - 甘油和sn - 1,2 - 二辛酰甘油也抑制LH受体形成，而非渗透性二酰基甘油二油精则无活性。这些结果表明，PMA或渗透性二酰基甘油对蛋白激酶C的原位激活抑制了cAMP依赖性颗粒细胞分化，并提示GnRH激动剂对颗粒细胞成熟的抑制作用也由蛋白激酶C介导。
