The PAK system links Rho GTPase signaling to thrombin-mediated platelet activation

Joseph Aslan, Sandra M. Baker, Cassandra P. Loren, Kristina Haley, Asako Itakura, Jiaqing Pang, Daniel L. Greenberg, Larry David, Ed Manser, Jonathan Chernoff, Owen McCarty

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Regulation of the platelet actin cytoskeleton by the Rho family of small GTPases is essential for the proper maintenance of hemostasis. However, little is known about how intracellular platelet activation from Rho GTPase family members, including Rac, Cdc42, and Rho, translate into changes in platelet actin structures. To better understand how Rho family GTPases coordinate platelet activation, we identified platelet proteins associated with Rac1, a Rho GTPase family member, and actin regulatory protein essential for platelet hemostatic function. Mass spectrometry analysis revealed that upon platelet activation with thrombin, Rac1 associates with a set of effectors of the p21-activated kinases (PAKs), including GIT1, βPIX, and guanine nucleotide exchange factor GEFH1. Platelet activation by thrombin triggered the PAK-dependent phosphorylation of GIT1, GEFH1, and other PAK effectors, including LIMK1 and Merlin. PAK was also required for the thrombin-mediated activation of the MEK/ERK pathway, Akt, calcium signaling, and phosphatidylserine (PS) exposure. Inhibition of PAK signaling prevented thrombin-induced platelet aggregation and blocked platelet focal adhesion and lamellipodia formation in response to thrombin. Together, these results demonstrate that the PAK signaling system is a key orchestrator of platelet actin dynamics, linking Rho GTPase activation downstream of thrombin stimulation to PAK effector function, MAP kinase activation, calcium signaling, and PS exposure in platelets.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume305
Issue number5
DOIs
StatePublished - Sep 1 2013

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p21-Activated Kinases
rho GTP-Binding Proteins
Platelet Activation
Thrombin
Blood Platelets
Actins
Calcium Signaling
Phosphatidylserines
Neurofibromin 2
Guanine Nucleotide Exchange Factors
Pseudopodia
Focal Adhesions
Monomeric GTP-Binding Proteins
MAP Kinase Signaling System
Hemostatics
Hemostasis
Actin Cytoskeleton
Platelet Aggregation
Mass Spectrometry
Proteins

Keywords

  • Actin
  • PAK
  • Platelets
  • Rac1
  • Rho GTPases

ASJC Scopus subject areas

  • Cell Biology
  • Physiology

Cite this

The PAK system links Rho GTPase signaling to thrombin-mediated platelet activation. / Aslan, Joseph; Baker, Sandra M.; Loren, Cassandra P.; Haley, Kristina; Itakura, Asako; Pang, Jiaqing; Greenberg, Daniel L.; David, Larry; Manser, Ed; Chernoff, Jonathan; McCarty, Owen.

In: American Journal of Physiology - Cell Physiology, Vol. 305, No. 5, 01.09.2013.

Research output: Contribution to journalArticle

Aslan, Joseph ; Baker, Sandra M. ; Loren, Cassandra P. ; Haley, Kristina ; Itakura, Asako ; Pang, Jiaqing ; Greenberg, Daniel L. ; David, Larry ; Manser, Ed ; Chernoff, Jonathan ; McCarty, Owen. / The PAK system links Rho GTPase signaling to thrombin-mediated platelet activation. In: American Journal of Physiology - Cell Physiology. 2013 ; Vol. 305, No. 5.
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