Tyrosine phosphorylation of focal adhesion kinase by PDGF is dependent on ras in human hepatic stellate cells

Hepatology. 2000 Jan;31(1):131-40. doi: 10.1002/hep.510310121.


Focal adhesion kinase (FAK) is a widely expressed nonreceptor tyrosine kinase found in focal adhesions. FAK has been indicated as a point of convergence of other signaling pathways including platelet-derived growth factor (PDGF) receptors, and recently, FAK tyrosine phosphorylation has been shown to be stimulated by PDGF. In the present study we assessed the role of Ras as a possible intermediate protein regulating PDGF-induced FAK tyrosine phosphorylation in human hepatic stellate cells (HSCs), liver-specific pericytes primarily involved in the pathogenesis of liver fibrosis. For this purpose, cells were first subjected to retroviral-mediated gene transfer with a dominant-negative mutant of Ras (N17Ras). This resulted in a marked inhibition of PDGF-induced FAK tyrosine phosphorylation together with the expected reduction of PDGF-induced extracellular signal-regulated kinase activity (ERK). Afterward, the effects of pharmacological agents potentially affecting Ras isoprenylation were evaluated. PDGF-induced FAK tyrosine phosphorylation, ERK activity and intracellular calcium increase, as well as the biological effects of this growth factor, (i.e., mitogenesis and cell migration) were effectively blocked by GGTI-298, an inhibitor of geranylgeranyltransferase I. Inhibition of Ras processing obtained with FTI-277, an inhibitor of farnesyltransferase, resulted in detectable effects only at high doses. Taken together, these results establish that Ras operates as a protein-linking PDGF-beta receptor to FAK in human HSCs, and that signaling molecules requiring geranylgeranylation may also be involved in this process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkyl and Aryl Transferases / antagonists & inhibitors
  • Becaplermin
  • Calcium / metabolism
  • Cell Adhesion Molecules / analysis
  • Cell Adhesion Molecules / metabolism*
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • Farnesyltranstransferase
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • Humans
  • Liver / enzymology*
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mutation
  • Phosphorylation
  • Phosphotyrosine / metabolism*
  • Platelet-Derived Growth Factor / pharmacology*
  • Protein Prenylation
  • Protein-Tyrosine Kinases / analysis
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins c-sis
  • Proto-Oncogene Proteins p21(ras) / genetics
  • Proto-Oncogene Proteins p21(ras) / physiology*
  • Receptors, Platelet-Derived Growth Factor / analysis
  • Receptors, Platelet-Derived Growth Factor / metabolism
  • Signal Transduction
  • Transfection
  • Type C Phospholipases / metabolism


  • Cell Adhesion Molecules
  • Enzyme Inhibitors
  • Platelet-Derived Growth Factor
  • Proto-Oncogene Proteins c-sis
  • Becaplermin
  • Phosphotyrosine
  • Alkyl and Aryl Transferases
  • geranylgeranyltransferase type-I
  • Farnesyltranstransferase
  • Protein-Tyrosine Kinases
  • Receptors, Platelet-Derived Growth Factor
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • PTK2 protein, human
  • Mitogen-Activated Protein Kinase 1
  • Type C Phospholipases
  • HRAS protein, human
  • Proto-Oncogene Proteins p21(ras)
  • Calcium