Transcriptional regulation of the thyrotropin-releasing hormone gene by leptin and melanocortin signaling
Mark Harris, … , Jeffrey S. Flier, Anthony N. Hollenberg
Mark Harris, … , Jeffrey S. Flier, Anthony N. Hollenberg
Published January 1, 2001
Citation Information: J Clin Invest. 2001;107(1):111-120. https://doi.org/10.1172/JCI10741.
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Article

Transcriptional regulation of the thyrotropin-releasing hormone gene by leptin and melanocortin signaling

Abstract

Starvation causes a rapid reduction in thyroid hormone levels in rodents. This adaptive response is caused by a reduction in thyrotropin-releasing hormone (TRH) expression that can be reversed by the administration of leptin. Here we examined hypothalamic signaling pathways engaged by leptin to upregulate TRH gene expression. As assessed by leptin-induced expression of suppressor of cytokine signaling–3 (SOCS-3) in fasted rats, TRH neurons in the paraventricular nucleus are activated directly by leptin. To a greater degree, they also contain melanocortin-4 receptors (MC4Rs), implying that leptin can act directly or indirectly by increasing the production of the MC4R ligand, α-melanocyte stimulating hormone (α-MSH), to regulate TRH expression. We further demonstrate that both pathways converge on the TRH promoter. The melanocortin system activates the TRH promoter through the phosphorylation and DNA binding of the cAMP response element binding protein (CREB), and leptin signaling directly regulates the TRH promoter through the phosphorylation of signal transducer and activator of transcription 3 (Stat3). Indeed, a novel Stat-response element in the TRH promoter is necessary for leptin’s effect. Thus, the TRH promoter is an ideal target for further characterizing the integration of transcriptional pathways through which leptin acts.

Authors

Mark Harris, Carl Aschkenasi, Carol F. Elias, Annie Chandrankunnel, Eduardo A. Nillni, Christian Bjørbæk, Joel K. Elmquist, Jeffrey S. Flier, Anthony N. Hollenberg

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Figure 6

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Identification of the Stat binding site in the TRH promoter. (a) 293T ce...
Identification of the Stat binding site in the TRH promoter. (a) 293T cells were cotransfected with the indicated hTRH constructs. Leptin responsiveness was then determined. The data are expressed as percent of maximal response where the fold stimulation of the –150 construct is set at 100%. (b) EMSA was performed with a radiolabeled probe spanning the human Stat site and nuclear extract from leptin-treated or untreated cells. The specificity of the bound complex was discerned by using an anti-Flag (αF) antibody. (c) A similar EMSA paradigm was used on the canonical SIEm67 probe. (d) A similar EMSA paradigm was used on a probe spanning the murine Stat element. (d) EMSA was performed on the murine Stat element with the addition of cold oligonucleotides representing the murine (lanes 3 and 4) or human (lanes 5 and 6) Stat elements. A 10× cold competitor was added in lanes 3 and 5, and 100× in lanes 4 and 6.