Rho associated coiled-coil kinase-1 regulates collagen-induced phosphatidylserine exposure in platelets

PLoS One. 2013 Dec 16;8(12):e84649. doi: 10.1371/journal.pone.0084649. eCollection 2013.


Background: The transbilayer movement of phosphatidylserine mediates the platelet procoagulant activity during collagen stimulation. The Rho-associated coiled-coil kinase (ROCK) inhibitor Y-27632 inhibits senescence induced but not activation induced phosphatidylserine exposure. To investigate further the specific mechanisms, we now utilized mice with genetic deletion of the ROCK1 isoform.

Methods and results: ROCK1-deficient mouse platelets expose significantly more phosphatidylserine and generate more thrombin upon activation with collagen compared to wild-type platelets. There were no significant defects in platelet shape change, aggregation, or calcium response compared to wild-type platelets. Collagen-stimulated ROCK1-deficient platelets also displayed decreased phosphorylation levels of Lim Kinase-1 and cofilin-1. However, there was no reduction in phosphorylation levels of myosin phosphatase subunit-1 (MYPT1) or myosin light chain (MLC). In an in vivo light/dye-induced endothelial injury/thrombosis model, ROCK1-deficient mice presented a shorter occlusion time in cremasteric venules when compared to wild-type littermates (3.16 ± 1.33 min versus 6.6 ± 2.6 min; p = 0.01).

Conclusions: These studies define ROCK1 as a new regulator for collagen-induced phosphatidylserine exposure in platelets with functional consequences on thrombosis. This effect was downstream of calcium signaling and was mediated by Lim Kinase-1 / cofilin-1-induced cytoskeletal changes.

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

  • Actins / metabolism
  • Amides / pharmacology
  • Animals
  • Blood Platelets / drug effects*
  • Blood Platelets / metabolism*
  • Blood Platelets / pathology
  • Cofilin 1 / metabolism
  • Collagen / pharmacology*
  • Humans
  • Lim Kinases / metabolism
  • Mice
  • Mice, Knockout
  • Phosphatidylserines / pharmacology*
  • Platelet Aggregation / drug effects
  • Platelet Aggregation / physiology
  • Pyridines / pharmacology
  • Thrombin / biosynthesis
  • Thrombosis / genetics
  • rho-Associated Kinases / genetics
  • rho-Associated Kinases / metabolism*


  • Actins
  • Amides
  • Cofilin 1
  • Phosphatidylserines
  • Pyridines
  • Y 27632
  • Collagen
  • Lim Kinases
  • Rock1 protein, mouse
  • rho-Associated Kinases
  • Thrombin