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Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
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Regulation of leading edge microtubule and actin dynamics downstream of Rac1

Torsten Wittmann1, Gary M Bokoch, Clare M Waterman-Storer

  • 1Department of Cell Biology and Institute for Childhood and Neglected Diseases, La Jolla, CA 92037, USA.

The Journal of Cell Biology
|June 11, 2003
PubMed

Insights

Rac1 regulates microtubule dynamics in migrating cells. This protein controls microtubule growth and turnover, coordinating with actin for cell movement.

Area of Science:

  • Cell Biology
  • Cytoskeletal Dynamics

Background:

  • Rho GTPases, including Rac1, are known regulators of actin dynamics in migrating cells.
  • The role of Rho proteins, particularly Rac1, in regulating microtubule (MT) behavior remains less understood.

Purpose of the Study:

  • To investigate the downstream effects of Rac1 on microtubule dynamics in vivo.
  • To elucidate the coordinated regulation between actin and microtubules at the leading edge of migrating cells.

Main Methods:

  • Time-lapse microscopy was employed using PtK1 cells.
  • The study manipulated Rac1 activity using constitutively active (Rac1(Q61L)) and dominant-negative (Rac1(T17N)) forms.
  • Inhibition of p21-activated kinases (Paks) was used to assess downstream signaling.

Main Results:

  • "Pioneer" microtubules at the leading edge showed decreased catastrophe and increased growth time.
  • Rac1 activation promoted pioneer MT behavior, while Rac1 inhibition abolished it, confirming Rac1's role in MT dynamics.
  • Rac1 also enhanced MT turnover via retrograde flow and breakage, and promoted actin polymerization.
  • Pak inhibition counteracted Rac1-induced MT growth and retrograde flow.

Conclusions:

  • Rac1 is a key regulator of microtubule dynamics in migrating cells.
  • Rac1 coordinates the behavior of both actin and microtubule cytoskeletal systems at the leading edge.
  • This coordinated regulation is mediated, in part, through p21-activated kinases (Paks).

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