title: Salt-inducible kinase is involved in the regulation of corticotropin-releasing hormone transcription in hypothalamic neurons in rats.
abstract: 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.
authors: Section on Endocrine Physiology, Developmental Endocrinology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 10 Center Drive, Bethesda, Maryland 20892, USA.
authors: Ying
authors: Y
authors: Liu
authors: Victoria
authors: V
authors: Poon
authors: Graciela
authors: G
authors: Sanchez-Watts
authors: Alan G
authors: AG
authors: Watts
authors: Hiroshi
authors: H
authors: Takemori
authors: Greti
authors: G
authors: Aguilera
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000235:genetics*; D017931:DNA Primers / Q000235:genetics; D055785:Gene Knockdown Techniques; D017403:In Situ Hybridization; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D019311:Staurosporine / Q000494:pharmacology; D013312:Stress, Physiological; D015534:Trans-Activators; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: C545700:CRTC2 protein, rat; D017931:DNA Primers; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D015534:Trans-Activators; D014157:Transcription Factors; D005576:Colforsin; D003346:Corticotropin-Releasing Hormone; D017346:Protein Serine-Threonine Kinases; C120299:Sik1 protein, rat; D019311:Staurosporine