Activation of ROCK by RhoA is regulated by cell adhesion, shape, and cytoskeletal tension

Exp Cell Res. 2007 Oct 1;313(16):3616-23. doi: 10.1016/j.yexcr.2007.07.002. Epub 2007 Jul 10.


Adhesion to the extracellular matrix regulates numerous changes in the actin cytoskeleton by regulating the activity of the Rho family of small GTPases. Here, we report that adhesion and the associated changes in cell shape and cytoskeletal tension are all required for GTP-bound RhoA to activate its downstream effector, ROCK. Using an in vitro kinase assay for endogenous ROCK, we found that cells in suspension, attached on substrates coated with low density fibronectin, or on spreading-restrictive micropatterned islands all exhibited low ROCK activity and correspondingly low myosin light chain phosphorylation, in the face of high levels of GTP-bound RhoA. In contrast, allowing cells to spread against substrates rescued ROCK and myosin activity. Interestingly, inhibition of tension with cytochalasin D or blebbistatin also inhibited ROCK activity within 20 min. The abrogation of ROCK activity by cell detachment or inhibition of tension could not be rescued by constitutively active RhoA-V14. These results suggest the existence of a feedback loop between cytoskeletal tension, adhesion maturation, and ROCK signaling that likely contributes to numerous mechanochemical processes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cattle
  • Cell Adhesion
  • Cell Movement
  • Cell Shape*
  • Cytoskeleton / enzymology*
  • Endothelial Cells / cytology
  • Endothelial Cells / enzymology
  • Enzyme Activation
  • Extracellular Matrix / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Ligands
  • Models, Biological
  • Protein-Serine-Threonine Kinases / metabolism*
  • Stress Fibers / metabolism
  • rho-Associated Kinases
  • rhoA GTP-Binding Protein / metabolism*


  • Intracellular Signaling Peptides and Proteins
  • Ligands
  • Protein-Serine-Threonine Kinases
  • rho-Associated Kinases
  • rhoA GTP-Binding Protein