Follicle-Stimulating hormone (FSH) stimulates phosphorylation and activation of protein kinase B (PKB/Akt) and serum and glucocorticoid-lnduced kinase (Sgk): evidence for A kinase-independent signaling by FSH in granulosa cells.
Follicle-Stimulating hormone (FSH) stimulates phosphorylation and activation of protein kinase B (PKB/Akt) and serum and glucocorticoid-lnduced kinase (Sgk): evidence for A kinase-independent signaling by FSH in granulosa cells.
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DOI：
10.1210/mend.14.8.0500
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发表时间：
2000-08
影响因子：
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通讯作者：
I. GONZALEZ-ROBAYNA;Allison E. Falender;S. Ochsner;G. Firestone;J. Richards
中科院分区：
文献类型：
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作者：
I. GONZALEZ-ROBAYNA;Allison E. Falender;S. Ochsner;G. Firestone;J. Richards
卵泡刺激素刺激卵巢颗粒细胞多种分化依赖性反应，涉及特定细胞信号级联的激活。在这些研究中，研究了三种激酶，以确定它们与FSH， cAMP和A激酶信号传导的关系：蛋白激酶B (PKB/Akt)，血清和糖皮质激素诱导激酶（Sgk）和p38丝裂原活化蛋白激酶（p38MAPK）。使用选择性激动剂/抑制剂分析这些激酶的磷酸化（激活）：forskolin/H89用于camp依赖性蛋白激酶（A激酶），胰岛素样生长因子I (IGF-I)/LY294002和wortmannin用于磷脂酰肌醇依赖性激酶（PI3-K），肉豆蔻酸佛波酯(PMA)/GF109203X用于二酰基甘油和Ca++依赖性激酶（C激酶）。还使用了调节细胞外调节激酶（ERKs）的MEK1抑制剂（PD98059）和抑制p38MAPK的SB203580。此外，我们分析了最近描述的camp调节的鸟嘌呤核苷酸交换因子（cAMP-GEFI和GEFII）的表达，这些因子影响ras相关的gtpase和Raf激酶，已知的各种蛋白激酶级联反应的调节因子。我们提供的证据表明，FSH、forskolin和8-溴- camp通过涉及PI3-K （LY294002/wortmannin敏感）而不是A激酶（H89不敏感）的机制刺激PKB的磷酸化，这是一种模仿IGF-I的反应模式。相比之下，FSH诱导和Sgk蛋白磷酸化需要A激酶（H89敏感），但也涉及PI3-K （LY294002敏感）和p38MAPK （SB203580敏感）途径。PMA （C激酶）在PI3-K上游的一个步骤中消除了fsh介导的PKB磷酸化（而不是igf - i介导的），并且不依赖于a激酶。最后，fsh介导的p38MAPK磷酸化受到A激酶和PI3-K的负面影响，这表明它可能是cAMP-GEF/Rap/Raf通路特定成员的下游。我们认为，在颗粒细胞中，A激酶的cAMP激活对于Sgk的转录是必需的，而cAMP （IGF-I-like）介导的PKB和Sgk（通过PI3-K）以及p38MAPK的磷酸化（激活）涉及其他细胞事件。这些结果提供了新的和令人兴奋的证据，表明cAMP在颗粒细胞中通过激酶依赖和独立的机制起作用，每种机制都控制特定的激酶级联反应。
FSH stimulates in ovarian granulosa cells diverse, differentiation-dependent responses that implicate activation of specific cellular signaling cascades. In these studies three kinases were investigated to determine their relationship to FSH, cAMP, and A kinase signaling: protein kinase B (PKB/Akt), serum and glucocorticoid-induced kinase (Sgk), and p38 mitogen-activated protein kinase (p38MAPK). The phosphorylation (activation) of these kinases was analyzed by using selective agonists/inhibitors: forskolin/H89 for cAMP-dependent protein kinase (A kinase), insulin-like growth factor I (IGF-I)/LY294002 and wortmannin for phosphatidylinositol-dependent kinase (PI3-K), and phorbol myristate (PMA)/GF109203X for diacylglycerol and Ca++-dependent kinases (C kinases). An inhibitor (PD98059) of MEK1, which regulates extracellular regulated kinases (ERKs), and SB203580, which inhibits p38MAPK, were also used. In addition, we analyzed the expression of the recently described, cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFI and GEFII) that impact Ras-related GTPases and Raf kinases, known regulators of various protein kinase cascades. We provide evidence that FSH, forskolin, and 8-bromo-cAMP stimulate phosphorylation of PKB by mechanisms involving PI3-K (LY294002/wortmannin sensitive) not A kinase (H89 insensitive), a pattern of response mimicking that of IGF-I. In contrast, FSH induction and phosphorylation of Sgk protein requires A kinase (H89 sensitive) but also involves PI3-K (LY294002 sensitive) as well as p38MAPK (SB203580 sensitive) pathways. PMA (C kinase) abolished FSH-mediated (but not IGF-I-mediated) phosphorylation of PKB at a step(s) upstream of PI3-K and independent of A kinase. Lastly, FSH-mediated phosphorylation of p38MAPK is negatively affected by A kinase and PI3-K, suggesting that it may be downstream of specific members of the cAMP-GEF/Rap/Raf pathway. We propose that cAMP activation of A kinase is obligatory for transcription of Sgk in granulosa cells whereas cAMP (IGF-I-like)-mediated phosphorylation (activation) of PKB and Sgk (via PI3-K), as well as p38MAPK, involves other cellular events. These results provide new and exciting evidence that cAMP acts in granulosa cells by A kinase-dependent and -independent mechanisms, each of which controls specific kinase cascades.