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Microtubule assembly by the Apc protein is regulated by importin-beta--RanGTP

Dina Dikovskaya1, Zhuoyu Li, Ian P Newton

  • 1Division of Cell and Developmental Biology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. d.dikovskaya@dundee.ac.uk

Journal of Cell Science
|February 11, 2010
PubMed

Insights

Importin-beta binds Adenomatous polyposis coli (Apc) protein, negatively regulating its microtubule dynamics and spindle assembly functions. This interaction, crucial for colorectal cancer, is modulated by RanGTP.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Mutations in Adenomatous polyposis coli (Apc) are key drivers of sporadic colorectal cancers.
  • Apc protein plays a role in regulating microtubule (MT) dynamics during cell division, but the mechanisms are unclear.

Purpose of the Study:

  • To investigate the mechanism by which Apc regulates MT dynamics.
  • To identify Apc binding partners that modulate its MT-associated functions.

Main Methods:

  • In vitro binding assays and Xenopus egg extracts were used to study Apc-importin-beta interactions.
  • Microtubule assembly and spindle formation assays were performed.
  • Apc's ability to rescue Apc-depleted cells was assessed with wild-type and importin-beta-bound Apc.

Main Results:

  • Importin-beta directly binds Apc, with binding inhibited by RanGTP.
  • Importin-beta binding reduces Apc's MT assembly and spindle-promoting activities.
  • Apc depletion impairs spindle formation, and importin-beta-bound Apc is less effective at rescuing this defect.

Conclusions:

  • Importin-beta negatively regulates Apc's microtubule-bundling and spindle-promoting functions in a Ran-GTP-dependent manner.
  • This interaction provides a novel regulatory mechanism for Apc's role in cell division and cancer initiation.

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