Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 287, Issue 19, Pages 15489-15501Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M111.310763
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Funding
- Deutsche Forschungsgemeinschaft [SFB/TR3, KFO 177, SFB-645]
- GIF
- NGFNplus EMINET
- European Union
- Euroepinomics Network of the European Science Foundation
- Else Kroner-Fresenius-Stiftung
- BMBF Independent research groups in neurosciences
- University of Bonn Medical Center
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The pore-forming Ca2+ channel subunit Ca(V)3.2 mediates a low voltage-activated (T-type) Ca2+ current (I-CaT) that contributes pivotally to neuronal and cardiac pacemaker activity. Despite the importance of tightly regulated Ca(V)3.2 levels, the mechanisms regulating its transcriptional dynamics are not well understood. Here, we have identified two key factors that up-and down-regulate the expression of the gene encoding Ca(V)3.2 (Cacna1h). First, we determined the promoter region and observed several stimulatory and inhibitory clusters. Furthermore, we found binding sites for the transcription factor early growth response 1 (Egr1/Zif268/Krox-24) to be highly overrepresented within the CaV3.2 promoter region. mRNA expression analyses and dual-luciferase promoter assays revealed that the CaV3.2 promoter was strongly activated by Egr1 overexpression in vitro and in vivo. Subsequent chromatin immunoprecipitation assays in NG108-15 cells and mouse hippocampi confirmed specific Egr1 binding to the Ca(V)3.2 promoter. Congruently, whole-cell ICaT values were significantly larger after Egr1 overexpression. Intriguingly, Egr1-induced activation of the Ca(V)3.2 promoter was effectively counteracted by the repressor element 1-silencing transcription factor (REST). Thus, Egr1 and REST can bi-directionally regulate Ca(V)3.2 promoter activity and mRNA expression and, hence, the size of I-CaT. This mechanism has critical implications for the regulation of neuronal and cardiac Ca2+ homeostasis under physiological conditions and in episodic disorders such as arrhythmias and epilepsy.
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