Abstract
Serotonin (5-HT) transporter (5-HTT) plays a key role in the control of 5-HT neuronal activity by reuptaking extracellular 5-HT from the synapse cleft. We have previously demonstrated that 5-HTT mRNA expression levels and its uptake activity in the mouse midbrain are significantly higher in the dark phase than those in the light phase. However, the molecular mechanisms of time-dependent expression of 5-HTT have not been clarified. In this study, expression of 5-HTT mRNA in the mouse midbrain showed a significant 24-h rhythm and was higher in the dark phase. Although such an oscillation was eliminated by a Clock gene mutation, CLOCK and BMAL1 did not activate 5-HTT transcription in the luciferase reporter assay. Activating transcription factor-4 (ATF4), a member of the ATF/cAMP response element (CRE)-binding protein family, is a component responsible for sustaining circadian oscillations of CRE-mediated gene expression. ATF4 significantly activated 5-HTT transcription in vitro and time dependently bound to the CRE site in the 5-HTT promoter in the mouse midbrain. In addition, mutation of the Clock gene disrupted temporal binding of ATF4 to the CRE site in the 5-HTT promoter. These results indicated that the circuit of circadian-basis molecular regulation between the clockwork system and mouse 5-HTT gene was connected by the ATF4 signaling pathway.
Footnotes
↵ The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
This study was supported by the Ministry of Education, Culture, Sports, and Technology, Japan [Grant-in-Aid for Young Scientists (B) 22790166] (to K.U.); [Grant-in-Aid for Scientfic Research (B) 24390149] (to S.K.); and [Grant-in-Aid for Challenging Exploratory Research 24650946] (to S.K.).
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
ABBREVIATIONS:
- 5-HT
- serotonin
- 5-HTT
- serotonin transporter
- SCN
- suprachiasmatic nucleus
- CRE
- cAMP response element
- ATF
- activating transcription factor
- CREB
- cAMP response element-binding protein
- PCR
- polymerase chain reaction
- ZT
- zeitgeber time
- NIH
- National Institutes of Health
- MOPS
- 4-morpholinepropanesulfonic acid
- TEF
- thyrotroph embryonic factor
- DMEM
- Dulbecco's modified Eagle's medium
- FBS
- fetal bovine serum
- shRNA
- short hairpin RNA
- ANOVA
- analysis of variance
- PPARE
- PAR-bZip protein response element.
- Received April 1, 2012.
- Accepted May 9, 2012.
- Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics
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