Thrombopoietin stimulates cortactin translocation to the cytoskeleton independently of tyrosine phosphorylation

Biochem J. 2001 Jun 15;356(Pt 3):875-81. doi: 10.1042/0264-6021:3560875.


Cortactin is an F-actin-binding protein expressed in platelets. During aggregation by thrombin, cortactin associates with Src, is tyrosine phosphorylated, and then translocates to the cytoskeleton. It is also found to associate with Syk during platelet shape change. Since cortactin undergoes tyrosine phosphorylation in platelets activated by thrombopoietin (TPO) that exhibit neither shape change nor aggregation, we investigated whether it could also relocalize to the detergent-insoluble fraction. We demonstrate that cortactin was present as a tyrosine-phosphorylated protein and co-localized with Syk in the Triton X-100-insoluble fraction of TPO-activated platelets. TPO stimulated Syk activation and association with cortactin. Conversely, cortactin associated with the kinases, Syk and Src. Cortactin tyrosine phosphorylation was blocked by Syk kinase inhibitor, piceatannol or Src family kinase inhibitor, PP2, suggesting that it depends on these two kinases. However, piceatannol or PP2 did not prevent cortactin translocation to the detergent-insoluble fraction. These data suggest that tyrosine phosphorylation is not required for cortactin translocation to the detergent-insoluble compartment. Furthermore, TPO activates, through its receptor c-Mpl, a signalling pathway to the cytoskeleton.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Platelets / drug effects
  • Blood Platelets / metabolism
  • Cortactin
  • Cytoskeleton / metabolism*
  • Enzyme Activation
  • Enzyme Precursors / metabolism
  • Humans
  • In Vitro Techniques
  • Intracellular Signaling Peptides and Proteins
  • Microfilament Proteins / metabolism*
  • Octoxynol
  • Phosphorylation
  • Protein Transport
  • Protein-Tyrosine Kinases / metabolism
  • Recombinant Proteins / metabolism
  • Stilbenes / pharmacology
  • Syk Kinase
  • Thrombopoietin / pharmacology*
  • Tyrosine / metabolism*
  • src-Family Kinases / metabolism


  • CTTN protein, human
  • Cortactin
  • Enzyme Precursors
  • Intracellular Signaling Peptides and Proteins
  • Microfilament Proteins
  • Recombinant Proteins
  • Stilbenes
  • Tyrosine
  • 3,3',4,5'-tetrahydroxystilbene
  • Octoxynol
  • Thrombopoietin
  • Protein-Tyrosine Kinases
  • SYK protein, human
  • Syk Kinase
  • src-Family Kinases