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GT1-7神经元细胞中促性腺激素释放激素诱导的CREB和BAD磷酸化对表皮生长因子受体反式激活的依赖性。

Dependence of GnRH-induced phosphorylation of CREB and BAD on EGF receptor transactivation in GT1-7 neuronal cells.

作者信息

Neithardt Adrienne, Farshori M Parvaiz, Shah Farzana B, Catt Kevin J, Shah Bukhtiar H

机构信息

Section on Hormonal Regulation, Endocrinology and Reproduction Research Branch, NICHD, National Institutes of Health, Bethesda, Maryland 20892-4510, USA.

出版信息

J Cell Physiol. 2006 Sep;208(3):586-93. doi: 10.1002/jcp.20697.

Abstract

The hypothalamic neuropeptide, gonadotropin releasing hormone (GnRH), is a primary regulatory factor in the neuroendocrine control of reproduction. The GnRH decapeptide is released in an episodic manner from hypothalamic GnRH neurons, which are known to express GnRH receptors. Here we examined the signaling pathways by which autocrine GnRH stimulation generates cell survival and proliferative signals in hypothalamic GT1-7 cells. Both GnRH and epidermal growth factor (EGF) caused rapid phosphorylation of cyclic AMP response element binding protein (CREB) and BAD. The selective epidermal growth factor receptor (EGF-R) antagonist, AG1478, attenuates the phosphorylation of these proteins by GnRH and EGF. Inhibition of PKC and Src abolished the stimulatory effects of GnRH, but not that of EGF, consistent with a critical role of these signaling molecules upstream of the EGF-R. All of these effects of GnRH were mimicked by phorbol 12 myristate 13-acetate (PMA). Consistent with the prosurvival and mitogenic effects of phosphoinositide 3-kinase/Akt (P13-K/Akt) downstream of the EGF-R, inhibition of P13-K diminished the activation of these proteins following stimulation with GnRH, EGF, and PMA. Overexpression of dominant negative Akt attenuated agonist-induced phosphorylation of BAD, but not that of ERK1/2 and CREB. Moreover, overexpression of wild-type RSK-1 resulted in enhanced basal as well as agonist-induced phosphorylation of CREB and BAD, indicating a critical role of RSK-1 in activating cytosolic as well as nuclear proteins. These data reveal novel signaling mechanisms of GnRH-induced phosphorylation of CREB and BAD in GT1-7 neurons through transactivation of the EGF-R.

摘要

下丘脑神经肽促性腺激素释放激素(GnRH)是生殖神经内分泌控制中的主要调节因子。GnRH十肽从已知表达GnRH受体的下丘脑GnRH神经元以脉冲方式释放。在此,我们研究了自分泌GnRH刺激在下丘脑GT1-7细胞中产生细胞存活和增殖信号的信号通路。GnRH和表皮生长因子(EGF)均可引起环磷酸腺苷反应元件结合蛋白(CREB)和BAD的快速磷酸化。选择性表皮生长因子受体(EGF-R)拮抗剂AG1478可减弱GnRH和EGF对这些蛋白的磷酸化作用。抑制蛋白激酶C(PKC)和Src可消除GnRH的刺激作用,但不影响EGF的刺激作用,这与这些信号分子在EGF-R上游的关键作用一致。GnRH的所有这些作用均可被佛波酯12-肉豆蔻酸酯13-乙酸酯(PMA)模拟。与EGF-R下游的磷酸肌醇3-激酶/蛋白激酶B(P13-K/Akt)的促存活和促有丝分裂作用一致,抑制P13-K可减弱GnRH、EGF和PMA刺激后这些蛋白的激活。显性负性Akt的过表达可减弱激动剂诱导的BAD磷酸化,但不影响细胞外信号调节激酶1/2(ERK1/2)和CREB的磷酸化。此外,野生型核糖体S6激酶1(RSK-1)的过表达导致CREB和BAD的基础磷酸化以及激动剂诱导的磷酸化增强,表明RSK-1在激活胞质和核蛋白中起关键作用。这些数据揭示了GnRH通过EGF-R的反式激活诱导GT1-7神经元中CREB和BAD磷酸化的新信号机制。

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