Salt-Inducible Kinase Is Involved in the Regulation of Corticotropin-Releasing Hormone Transcription in Hypothalamic Neurons in Rats
Salt-Inducible Kinase Is Involved in the Regulation of Corticotropin-Releasing Hormone Transcription in Hypothalamic Neurons in Rats
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DOI：
10.1210/en.2011-1404
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发表时间：
2012-01-01
期刊：
影响因子：
4.8
通讯作者：
Aguilera, Greti
中科院分区：
文献类型：
--
作者：
Liu, Ying;Poon, Victoria;Aguilera, Greti
CRH转录的激活需要cAMP反应元件结合蛋白（CREB）的磷酸化和CREB辅激活因子（调节CREB活性的转导子（TORC））从细胞质到细胞核的易位。在基础条件下，转录是低的，因为TORC保留在细胞质中，通过AMP依赖性蛋白激酶（AMPK）家族的Ser/Thr蛋白激酶（包括盐诱导型激酶（SIK））的磷酸化而失活。为了确定哪种激酶负责CRH神经元中TORC磷酸化，我们通过原位杂交检测了大鼠下丘脑室旁核中的SIK 1和SIK 2 mRNA。在基础条件下，这两种激酶的低mRNA水平被发现在室旁背内侧核，在CRH神经元的位置一致。1小时的束缚应激增加了SIK 1 mRNA水平，而SIK 2 mRNA仅显示出轻微的增加。在4 B下丘脑神经元，或原代培养，SIK 1 mRNA（但不是SIK 2 mRNA）的cAMP刺激剂，毛喉素诱导。在4 B细胞中过表达SIK 1或SIK 2降低核TORC 2水平（Western印迹）并抑制毛喉素刺激的CRH转录（荧光素酶测定）。相反，非选择性的SIK抑制剂，staurosporine，增加核TORC 2含量和刺激CRH转录在4 B细胞和原代神经元培养物（异源RNA）。出乎意料的是，在4 B细胞中，内源性SIK 2而不是SIK 1的特异性短发夹RNA敲低诱导TORC 2和CRH转录的核转位，表明SIK 2介导基础条件下的TORC失活，而SIK 1的诱导限制转录激活。该研究提供了证据表明，SIK通过灭活TORC抑制CRH转录，为CRH转录的快速开/关控制提供了潜在的机制。（内分泌学153：223-233，2012）
Activation of CRH transcription requires phosphorylation of cAMP response element-binding protein (CREB) and translocation of the CREB coactivator, transducer of regulated CREB activity (TORC) from cytoplasm to nucleus. In basal conditions, transcription is low because TORC remains in the cytoplasm, inactivated by phosphorylation through Ser/Thr protein kinases of the AMP-dependent protein kinases (AMPK) family, including salt-inducible kinase (SIK). To determine which kinase is responsible for TORC phosphorylation in CRH neurons, we measured SIK1 and SIK2 mRNA in the hypothalamic paraventricular nucleus of rats by in situ hybridization. In basal conditions, low mRNA levels of the two kinases were found in the dorsomedial paraventricular nucleus, consistent with location in CRH neurons. One hour of restraint stress increased SIK1 mRNA levels, whereas SIK2 mRNA showed only minor increases. In 4B hypothalamic neurons, or primary cultures, SIK1 mRNA (but not SIK2 mRNA) was inducible by the cAMP stimulator, forskolin. Overexpression of either SIK1 or SIK2 in 4B cells reduced nuclear TORC2 levels (Western blot) and inhibited forskolin-stimulated CRH transcription (luciferase assay). Conversely, the nonselective SIK inhibitor, staurosporine, increased nuclear TORC2 content and stimulated CRH transcription in 4Bcells and primary neuronal cultures (heteronuclear RNA). Unexpectedly, in 4B cells specific short hairpin RNA knockdown of endogenous SIK2 but not SIK1 induced nuclear translocation of TORC2 and CRH transcription, suggesting that SIK2 mediates TORC inactivation in basal conditions, whereas induction of SIK1 limits transcriptional activation. The study provides evidence that SIK represses CRH transcription by inactivating TORC, providing a potential mechanism for rapid on/off control of CRH transcription. (Endocrinology 153: 223-233, 2012)