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The Rho kinases I and II regulate different aspects of myosin II activity

Atsuko Yoneda1, Hinke A B Multhaupt, John R Couchman

  • 1Division of Biomedical Sciences, Faculty of Medicine, Imperial College London, London SW7 2AZ, England, UK.

The Journal of Cell Biology
|July 27, 2005
PubMed

Insights

Mammalian rho kinases (ROCK I and II) are not redundant. ROCK I regulates stress fibers and focal adhesions, while ROCK II is crucial for phagocytosis, indicating distinct cellular roles.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mammalian rho kinases (ROCK I and II) are downstream effectors of Rho GTPases.
  • They are implicated in microfilament bundle assembly and smooth muscle contractility.
  • ROCK I and II were previously assumed to be functionally redundant.

Purpose of the Study:

  • To investigate the distinct functions of endogenous ROCK I and ROCK II.
  • To elucidate the regulatory mechanisms and substrate specificity of ROCK I and II.

Main Methods:

  • Analysis of fibroblast adhesion to fibronectin.
  • Specific reduction of ROCK I and ROCK II using siRNA.
  • Assessment of microfilament cytoskeleton organization and phagocytic activity.
  • Investigation of lipid-binding preferences of ROCK pleckstrin homology domains.

Main Results:

  • ROCK II was more abundant but less active than ROCK I.
  • ROCK I depletion caused loss of stress fibers and focal adhesions.
  • ROCK II depletion enhanced the microfilament cytoskeleton.
  • Phagocytic uptake of fibronectin-coated beads was impaired in ROCK II-depleted cells.
  • Distinct lipid-binding preferences, particularly for phosphatidylinositol 3,4,5P(3), were observed for ROCK II but not ROCK I.

Conclusions:

  • Endogenous ROCK I and ROCK II are distinctly regulated and perform non-redundant functions.
  • ROCK I is essential for stress fiber and focal adhesion formation.
  • ROCK II plays a critical role in phagocytosis and is regulated by phosphatidylinositol 3,4,5P(3).
  • These findings reveal distinct roles for ROCK isoforms in cellular processes.

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