title: Insulin-FOXO3 signaling modulates circadian rhythms via regulation of clock transcription.
abstract: Circadian rhythms are responsive to external and internal cues, light and metabolism being among the most important. In mammals, the light signal is sensed by the retina and transmitted to the suprachiasmatic nucleus (SCN) master clock [1], where it is integrated into the molecular oscillator via regulation of clock gene transcription. The SCN synchronizes peripheral oscillators, an effect that can be overruled by incoming metabolic signals [2]. As a consequence, peripheral oscillators can be uncoupled from the master clock when light and metabolic signals are not in phase. The signaling pathways responsible for coupling metabolic cues to the molecular clock are being rapidly uncovered [3-5]. Here we show that insulin-phosphatidylinositol 3-kinase (PI3K)-Forkhead box class O3 (FOXO3) signaling is required for circadian rhythmicity in the liver via regulation of Clock. Knockdown of FoxO3 dampens circadian amplitude, an effect that is rescued by overexpression of Clock. Subsequently, we show binding of FOXO3 to two Daf-binding elements (DBEs) located in the Clock promoter area, implicating Clock as a transcriptional target of FOXO3. Transcriptional oscillation of both core clock and output genes in the liver of FOXO3-deficient mice is affected, indicating a disrupted hepatic circadian rhythmicity. Finally, we show that insulin, a major regulator of FOXO activity [6-9], regulates Clock levels in a PI3K- and FOXO3-dependent manner. Our data point to a key role of the insulin-FOXO3-Clock signaling pathway in the modulation of circadian rhythms.
authors.affiliation: Department of Genetics, Center for Biomedical Genetics, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, the Netherlands.
authors.forename: Inês
authors.initials: I
authors.lastname: Chaves
authors.affiliation: Department of Genetics, Center for Biomedical Genetics, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, the Netherlands.
authors.forename: Gijsbertus T J
authors.initials: GT
authors.lastname: van der Horst
authors.affiliation: Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, PO Box 85060, 3508 TA Utrecht, the Netherlands.
authors.forename: Raymond
authors.initials: R
authors.lastname: Schellevis
authors.affiliation: Department of Genetics, Center for Biomedical Genetics, Erasmus University Medical Center, PO Box 2040, 3000 CA Rotterdam, the Netherlands.
authors.forename: Romana M
authors.initials: RM
authors.lastname: Nijman
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, PO Box 85060, 3508 AB Utrecht, the Netherlands.
authors.forename: Marian Groot
authors.initials: MG
authors.lastname: Koerkamp
authors.affiliation: Molecular Cancer Research, University Medical Center Utrecht, PO Box 85060, 3508 AB Utrecht, the Netherlands.
authors.forename: Frank C P
authors.initials: FC
authors.lastname: Holstege
authors.affiliation: Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, PO Box 85060, 3508 TA Utrecht, the Netherlands; Swammerdam Institute of Life Sciences, University of Amsterdam, PO Box 94232, 1090 GE Amsterdam, the Netherlands.
authors.forename: Marten P
authors.initials: MP
authors.lastname: Smidt
authors.affiliation: Department of Translational Neuroscience, Brain Center Rudolf Magnus, University Medical Center Utrecht, PO Box 85060, 3508 TA Utrecht, the Netherlands; Swammerdam Institute of Life Sciences, University of Amsterdam, PO Box 94232, 1090 GE Amsterdam, the Netherlands. Electronic address: m.f.m.hoekman@uva.nl.
authors.forename: Marco F M
authors.initials: MF
authors.lastname: Hoekman
mesh_terms: D000818:Animals; D056926:CLOCK Proteins / Q000235:genetics* / Q000378:metabolism; D002940:Circadian Rhythm; D005260:Female; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics* / Q000378:metabolism; D007328:Insulin / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D058539:Phosphatidylinositol 3-Kinase / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; D007328:Insulin; D056926:CLOCK Proteins; C538944:Clock protein, mouse; D058539:Phosphatidylinositol 3-Kinase