title: Shaggy/glycogen synthase kinase 3β and phosphorylation of Sarah/regulator of calcineurin are essential for completion of Drosophila female meiosis.
abstract: The Ca(2+)/Calmodulin-dependent phosphatase calcineurin is essential for exit from meiotic arrest at metaphases I and II in Drosophila and Xenopus oocytes. We previously found that Sarah, the Drosophila homolog of regulator of calcineurin, acts as a positive regulator of calcineurin and is required to complete anaphase I of female meiosis. Here, we undertook biochemical approaches, including MS and posttranslational modification analyses, to better understand the mechanism by which Sarah regulates calcineurin. A search for phosphorylated residues revealed that Sarah is highly phosphorylated at Ser100, Thr102, and Ser219 in both ovaries and activated eggs and that Ser215 is phosphorylated only in activated eggs. Functional analyses using mutant forms of Sarah showed that phosphorylation at Ser215, a consensus phosphorylation site for glycogen synthase kinase 3β (GSK-3β) and its priming kinase site Ser219, are essential for Sarah function. Furthermore, germ-line clones homozygous for a null allele of shaggy (Drosophila GSK-3β) both fail to complete meiosis and lack phosphorylation of Sarah at Ser215, suggesting that the phosphorylation of Sarah by Shaggy/GSK-3β is required to complete meiosis. Our findings suggest a mechanism in which Shaggy/GSK-3β activates calcineurin through Sarah phosphorylation on egg activation in Drosophila.
authors.affiliation: Stowers Institute for Medical Research, Kansas City, MO 64110, USA. sta@stowers.org
authors.forename: Satomi
authors.initials: S
authors.lastname: Takeo
authors.forename: Selene K
authors.initials: SK
authors.lastname: Swanson
authors.forename: Kavyasree
authors.initials: K
authors.lastname: Nandanan
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nakai
authors.forename: Toshiro
authors.initials: T
authors.lastname: Aigaki
authors.forename: Michael P
authors.initials: MP
authors.lastname: Washburn
authors.forename: Laurence
authors.initials: L
authors.lastname: Florens
authors.forename: R Scott
authors.initials: RS
authors.lastname: Hawley
mesh_terms: D000483:Alleles; D000818:Animals; D015153:Blotting, Western; D019703:Calcineurin / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D004330:Drosophila / Q000166:cytology*; D029721:Drosophila Proteins / Q000378:metabolism* / Q000502:physiology*; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism / Q000502:physiology*; D000071679:Glycogen Synthase Kinase 3 beta; D006720:Homozygote; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008540:Meiosis / Q000502:physiology*; D010053:Ovary / Q000378:metabolism; D010063:Ovum / Q000378:metabolism; D010766:Phosphorylation
chemical_list: D002135:Calcium-Binding Proteins; D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; C513393:Sra protein, Drosophila; D000071679:Glycogen Synthase Kinase 3 beta; C080335:Sgg protein, Drosophila; D038362:Glycogen Synthase Kinase 3; D019703:Calcineurin