Role for Slimb in the degradation of Drosophila Period protein phosphorylated by Doubletime.
Protein phosphorylation has a key role in modulating the stabilities of circadian clock proteins in a manner specific to the time of day. A conserved feature of animal clocks is that Period (Per) proteins undergo daily rhythms in phosphorylation and levels, events that are crucial for normal clock progression. Casein kinase Iepsilon (CKIepsilon) has a prominent role in regulating the phosphorylation and abundance of Per proteins in animals. This was first shown in Drosophila with the characterization of Doubletime (Dbt), a homologue of vertebrate casein kinase Iepsilon. However, it is not clear how Dbt regulates the levels of Per. Here we show, using a cell culture system, that Dbt promotes the progressive phosphorylation of Per, leading to the rapid degradation of hyperphosphorylated isoforms by the ubiquitin-proteasome pathway. Slimb, an F-box/WD40-repeat protein functioning in the ubiquitin-proteasome pathway interacts preferentially with phosphorylated Per and stimulates its degradation. Overexpression of slimb or expression in clock cells of a dominant-negative version of slimb disrupts normal rhythmic activity in flies. Our findings suggest that hyperphosphorylated Per is targeted to the proteasome by interactions with Slimb.
Ko
Hyuk Wan
HW
Graduate Program in Physiology and Neurobiology, Rutgers University, Center for Advanced Biotechnology and Medicine, 679 Hoes Lane, Piscataway, New Jersey 08854, USA.
Jiang
Jin
J
Edery
Isaac
I
D000818:Animals; D030801:Animals, Genetically Modified; D001683:Biological Clocks; D048149:Casein Kinase 1 epsilon; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002940:Circadian Rhythm; D003546:Cysteine Endopeptidases / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D009043:Motor Activity; D009097:Multienzyme Complexes / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D056950:Period Circadian Proteins; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D013379:Substrate Specificity; D044767:Ubiquitin-Protein Ligases
D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D020033:Protein Isoforms; C113519:dco protein, Drosophila; C110233:slmb protein, Drosophila; C096445:tim protein, Drosophila; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; D048149:Casein Kinase 1 epsilon; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex