title: AKT and TOR signaling set the pace of the circadian pacemaker.
abstract: The circadian clock coordinates cellular and organismal energy metabolism. The importance of this circadian timing system is underscored by findings that defects in the clock cause deregulation of metabolic physiology and result in metabolic disorders. On the other hand, metabolism also influences the circadian clock, such that circadian gene expression in peripheral tissues is affected in mammalian models of obesity and diabetes. However, to date there is little to no information on the effect of metabolic genes on the central brain pacemaker which drives behavioral rhythms. We have found that the AKT and TOR-S6K pathways, which are major regulators of nutrient metabolism, cell growth, and senescence, impact the brain circadian clock that drives behavioral rhythms in Drosophila. Elevated AKT or TOR activity lengthens circadian period, whereas reduced AKT signaling shortens it. Effects of TOR-S6K appear to be mediated by SGG/GSK3beta, a known kinase involved in clock regulation. Like SGG, TOR signaling affects the timing of nuclear accumulation of the circadian clock protein TIMELESS. Given that activities of AKT and TOR pathways are affected by nutrient/energy levels and endocrine signaling, these data suggest that metabolic disorders caused by nutrient and energy imbalance are associated with altered rest:activity behavior.
authors.affiliation: Department of Neuroscience, Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Xiangzhong
authors.initials: X
authors.lastname: Zheng
authors.forename: Amita
authors.initials: A
authors.lastname: Sehgal
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000378:metabolism*; D004330:Drosophila / Q000502:physiology*; D029721:Drosophila Proteins; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases
chemical_list: D056925:Circadian Rhythm Signaling Peptides and Proteins; D029721:Drosophila Proteins; D011494:Protein Kinases; C416303:target of rapamycin protein, Drosophila; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases