Glucocorticoids regulate the expression of the mouse urocortin II gene: a putative connection between the corticotropin-releasing factor receptor pathways.

Abstract

Peptides encoded by the urocortin II (Ucn II) gene were recently identified as new members of the corticotropin-releasing factor (CRF) family. Ucn II is a specific ligand for the type 2 CRF receptor. Using RT-PCR, DNA sequencing, and immunofluorescence staining, we report the expression of Ucn II mRNA in several human and mouse (m) neuronal cell lines. Using these neuronal cell lines, we provide evidence that exposure to glucocorticoid hormones increases mUcn II mRNA expression and promoter activation. The effect of glucocorticoids on mUcn II mRNA expression was tested in the Ucn II/glucocorticoid receptor-positive cell line NG108-15. The results demonstrate that mUcn II mRNA expression is up-regulated by dexamethasone in a dose- and time-dependent fashion. Computer analysis revealed the presence of 14 putative half-palindrome glucocorticoid response element sequences within 1.2 kb of the mUcn II 5' flanking region. Transfections with different fragments of the 5'-flanking region of the mUcn II gene fused to a luciferase reporter gene showed a promoter-dependent expression of the reporter gene and regulation by dexamethasone. Promoter deletion studies clarify the sufficient putative glucocorticoid response element site mediating this effect. The steroid hormone antagonist RU486 blocked the effect of dexamethasone on mUcn II mRNA expression and promoter activation, suggesting a direct glucocorticoid receptor-mediated effect of dexamethasone on mUcn II mRNA expression. Ucn II is expressed in vivo in the hypothalamus, brainstem, olfactory bulb, and pituitary. Low levels were also detected in the mouse cortex, hippocampus, and spinal cord. We demonstrated that mUcn II gene transcription was stimulated by glucocorticoid administration in vivo and inhibited by removal of glucocorticoids by adrenalectomy. Administration of dexamethasone to mice resulted in an increase of mUcn II levels in the hypothalamus and brainstem but not in the olfactory bulb region 12 h following ip injection. In light of our present data and the current literature, we propose a putative link between the CRF receptor 1 and CRF receptor 2 pathways.