Coordinate and Divergent Regulation of Corticotropin-Releasing Factor (CRF) and CRF-Binding Protein Expression in an Immortalized Amygdalar Neuronal Cell Line

Abstract

CRF is a 41-amino acid neuropeptide best known for its hypophysiotropic actions. CRF is widely distributed in the central nervous system in areas beyond the hypothalamus. CRF-binding protein (CRF-BP) regulates the bioavailability of CRF, and knowledge of the regulation of CRF-BP synthesis is an integral component of understanding the actions of CRF. To better study the regulation of CRF and CRF-BP, primary amygdalar cultures were immortalized by transfection with the SV 40 large T antigen. A clonal line that expresses CRF immunoreactivity and messenger RNA was selected. The production of CRF peptide and message by this line is regulated in a manner indistinguishable from primary cultures. We also observed that the immortalized cells express CRF-BP immunoreactivity and messenger RNA. The expression of both CRF and CRF-BP is positively regulated by forskolin and interleukin-6. Unlike CRF, the expression of CRF-BP message and peptide was increased by phorbol 12-myristate 13-acetate or dexamethasone. These results demonstrate that the synthesis of CRF and CRF-BP in this clonal cell line may be regulated in parallel by some agents but not by others. These data also suggest that dexamethasone may decrease the biological availability of CRF in the amygdala by increasing the expression of CRF-BP, rather than by decreasing CRF expression.

Systemic Adrenocorticotropic Hormone Administration Down-Regulates the Expression of Corticotropin-Releasing Hormone (CRH) and CRH-Binding Protein in Infant Rat Hippocampus

“…Both coordinate and divergent alterations in CRH and CRH-BP expression have been reported, and the biologic actions of CRH may be limited by steroidinduced expression of CRH-BP (40). The down-regulation of CRH in this study was accompanied by a similar reduction in the CRH-BP expression.…”

“…CRH RIA was performed using protocols and reagents from IgG Corp. (Nashville, TN, U.S.A.) as described previously (18,20). Briefly, tissue lysates (100 L) were incubated with 100 L of primary antibodies (1:100, IgG-hCRH; IgG Corp.) for 3 d at 4°C.…”

Comparative Study of gp130 Cytokine Effects on Corticotroph AtT-20 Cells – Redundancy or Specificity of Neuroimmunoendocrine Modulators?

“…However, these in vitro findings do not diminish the putative major role of IL-6 as an inflammatory cytokine stimulating HPA axis activation. Firstly, IL-6 has been shown to induce the secretion of arginine vasopressin from the hypothalamus [27] and corticotrophin-releasing hormone from immortalized cell lines [28], thus IL-6 probably indirectly stimulates corticotroph function via hypothalamic activation. However, IL-6 injection in mice deficient in corticotrophin-releasing hormone also results in a profound increase in ACTH levels, even higher than in wildtype animals [25].…”

Pituitary CRH-binding protein and stress in female mice

“…Other studies have examined the regulation of the CRH-BP promoter or endogenous CRH-BP expression. Numerous factors activated by the stress response, including CRH, downstream members of CRH-activated signaling pathways (i.e., cAMP), and glucocorticoids are all important regulators of CRH-BP gene expression and protein secretion (28–33). In vivo studies showed that restraint stress increased CRH-BP gene expression 3-fold in male rat pituitary, while adrenalectomy decreased pituitary CRH-BP mRNA to 8% of control levels (31).…”