title: Rab11-FIP3 is a cell cycle-regulated phosphoprotein.
abstract: BACKGROUND
  Rab11 and its effector molecule, Rab11-FIP3 (FIP3), associate with recycling endosomes and traffic into the furrow and midbody of cells during cytokinesis. FIP3 also controls recycling endosome distribution during interphase. Here, we examine whether phosphorylation of FIP3 is involved in these activities.
  
  
  RESULTS
  We identify four sites of phosphorylation of FIP3 in vivo, S-102, S-280, S-347 and S-450 and identify S-102 as a target for Cdk1-cyclin B in vitro. Of these, we show that S-102 is phosphorylated in metaphase and is dephosphorylated as cells enter telophase. Over-expression of FIP3-S102D increased the frequency of binucleate cells consistent with a role for this phospho-acceptor site in cytokinesis. Mutation of S-280, S-347 or S-450 or other previously identified phospho-acceptor sites (S-488, S-538, S-647 and S-648) was without effect on binucleate cell formation and did not modulate the distribution of FIP3 during the cell cycle. In an attempt to identify a functional role for FIP3 phosphorylation, we report that the change in FIP3 distribution from cytosolic to membrane-associated observed during progression from anaphase to telophase is accompanied by a concomitant dephosphorylation of FIP3. However, the phospho-acceptor sites identified here did not control this change in distribution.
  
  
  CONCLUSIONS
  Our data thus identify FIP3 as a cell cycle regulated phosphoprotein and suggest dephosphorylation of FIP3 accompanies its translocation from the cytosol to membranes during telophase. S102 is dephosphorylated during telophase; mutation of S102 exerts a modest effect on cytokinesis. Finally, we show that de/phosphorylation of the phospho-acceptor sites identified here (S-102, S-280, S-347 and S-450) is not required for the spatial control of recycling endosome distribution or function.
authors.affiliation: Henry Wellcome Laboratory of Cell Biology, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, Davidson Building, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
authors.forename: Louise L
authors.initials: LL
authors.lastname: Collins
authors.forename: Glenn
authors.initials: G
authors.lastname: Simon
authors.forename: Johanne
authors.initials: J
authors.lastname: Matheson
authors.forename: Christine
authors.initials: C
authors.lastname: Wu
authors.forename: M Clare
authors.initials: MC
authors.lastname: Miller
authors.forename: Tetsuhisa
authors.initials: T
authors.lastname: Otani
authors.forename: Xinzi
authors.initials: X
authors.lastname: Yu
authors.forename: Shigeo
authors.initials: S
authors.lastname: Hayashi
authors.forename: Rytis
authors.initials: R
authors.lastname: Prekeris
authors.forename: Gwyn W
authors.initials: GW
authors.lastname: Gould
mesh_terms: D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D002455:Cell Division; D045744:Cell Line, Tumor; D048749:Cytokinesis / Q000235:genetics; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007399:Interphase / Q000235:genetics; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D010750:Phosphoproteins; C439063:RAB11FIP3 protein, human