title: Protein phosphatase 1 (PP1) is a post-translational regulator of the mammalian circadian clock.
abstract: Circadian clocks coordinate the timing of important biological processes. Interconnected transcriptional and post-translational feedback loops based on a set of clock genes generate and maintain these rhythms with a period of about 24 hours. Many clock proteins undergo circadian cycles of post-translational modifications. Among these modifications, protein phosphorylation plays an important role in regulating activity, stability and intracellular localization of clock components. Several protein kinases were characterized as regulators of the circadian clock. However, the function of protein phosphatases, which balance phosphorylation events, in the mammalian clock mechanism is less well understood. Here, we identify protein phosphatase 1 (PP1) as regulator of period and light-induced resetting of the mammalian circadian clock. Down-regulation of PP1 activity in cells by RNA interference and in vivo by expression of a specific inhibitor in the brain of mice tended to lengthen circadian period. Moreover, reduction of PP1 activity in the brain altered light-mediated clock resetting behavior in mice, enhancing the phase shifts in either direction. At the molecular level, diminished PP1 activity increased nuclear accumulation of the clock component PER2 in neurons. Hence, PP1, may reduce PER2 phosphorylation thereby influencing nuclear localization of this protein. This may at least partially influence period and phase shifting properties of the mammalian circadian clock.
authors.affiliation: Department of Biology, Unit of Biochemistry, University of Fribourg, Fribourg, Switzerland.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Schmutz
authors.forename: Sabrina
authors.initials: S
authors.lastname: Wendt
authors.forename: Anna
authors.initials: A
authors.lastname: Schnell
authors.forename: Achim
authors.initials: A
authors.lastname: Kramer
authors.forename: Isabelle M
authors.initials: IM
authors.lastname: Mansuy
authors.forename: Urs
authors.initials: U
authors.lastname: Albrecht
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism; D057906:Circadian Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009043:Motor Activity / Q000502:physiology; D041681:NIH 3T3 Cells; D009474:Neurons / Q000166:cytology / Q000502:physiology; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference
chemical_list: C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D054645:Protein Phosphatase 1