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Polo kinase mediates the phosphorylation and cellular localization of Nuf/FIP3, a Rab11 effector

Lotti Brose1, Justin Crest1,2, Li Tao3,4

  • 1Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064.

Molecular Biology of the Cell
|April 7, 2017
PubMed

Insights

Polo kinase directly phosphorylates Nuf, regulating its cell cycle-dependent localization during animal cytokinesis. This phosphorylation controls Nuf dispersal from the centrosome, crucial for proper furrow formation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Developmental Biology

Background:

  • Animal cytokinesis requires both contractile ring formation and membrane addition via vesicles.
  • Nuf/FIP3, a Rab11 effector, delivers recycling endosome-derived vesicles to the cleavage furrow in cells like *Drosophila* embryos.
  • Nuf's centrosomal localization and phosphorylation change dynamically throughout the cell cycle.

Purpose of the Study:

  • To investigate the cell cycle regulation of Nuf localization and its upstream regulators.
  • To identify the kinase responsible for Nuf phosphorylation and its role in cytokinesis.
  • To elucidate the mechanism by which Nuf localization is controlled during cell division.

Main Methods:

  • Analysis of Nuf localization and phosphorylation in *Drosophila* embryos.
  • Experimentation with ectopic Cdk1 activation to observe Nuf dispersal.
  • Kinase screening to identify Nuf-interacting kinases, focusing on Polo kinase.
  • In vitro binding and phosphorylation assays using purified proteins.

Main Results:

  • Maximal Nuf phosphorylation coincides with prophase, leading to its cytoplasmic dispersal from the centrosome.
  • Polo kinase activity is essential for Nuf phosphorylation and proper furrow formation; its inhibition causes Nuf underphosphorylation and sustained centrosomal localization.
  • Polo kinase directly binds and phosphorylates Nuf at specific sites (Ser-225 and Thr-227) in vitro.

Conclusions:

  • Polo kinase directly mediates the cell cycle-dependent phosphorylation and localization of Nuf.
  • This regulation by Polo kinase is critical for controlling Nuf's centrosomal dispersal and subsequent function in cytokinesis.
  • The findings reveal a novel mechanism controlling vesicle transport during cell division.

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