c-Src couples PI 3 kinase/Akt and MAPK signaling to PDGF-induced DNA synthesis in mesangial cells

Cell Signal. 2006 Nov;18(11):1854-64. doi: 10.1016/j.cellsig.2006.02.003.


Platelet-derived growth factor BB (PDGF) and PDGF receptor-beta (PDGFR) play critical roles in mesangial cell proliferation during embryonic development and in mesangioproliferative glomerulonephritis. We have shown previously that phosphatidylinositol (PI) 3 kinase/Akt and Erk1/2 mitogen-activated protein kinase (MAPK) contribute to PDGF-dependent proliferation of mesangial cells, but the mechanism by which these two enzyme cascades are activated by PDGFR signaling is not precisely known. We examined the role of c-Src tyrosine kinase in this process. PDGF increased phosphorylation of c-Src in a time-dependent manner indicating its activation. A pharmacologic inhibitor of c-Src, PP1, blocked PDGF-induced DNA synthesis with concomitant inhibition of c-Src phosphorylation. Immune-complex kinase assays of c-Src and PDGFR demonstrated inhibition of c-Src tyrosine kinase activity by PP1, without an effect on PDGFR tyrosine phosphorylation. Both PP1 and expression of dominant negative c-Src inhibited PDGF-induced PI 3 kinase, resulting in attenuation of Akt kinase activity. Expression of constitutively active c-Src increased Akt activity to the same extent as with PDGF. Constitutively active c-Src augmented PDGF-induced Akt activity, thus contributing to Akt signaling. Inhibition of c-Src tyrosine kinase blocked PDGF-stimulated MAPK activity and resulted in attenuation of c-fos gene transcription with concomitant prevention of Elk-1 transactivation. Furthermore, inhibition of c-Src increased p27(Kip1) cyclin kinase inhibitor, and attenuated PDGF-induced pRb phosphorylation and CDK2 activity. These data provide the first evidence in mesangial cells that PDGF-activated c-Src tyrosine kinase relays signals to PI 3 kinase/Akt and MAPK. Furthermore our results demonstrate that c-Src integrates signals into the nucleus to activate CDK2, which is required for DNA synthesis.

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
  • CSK Tyrosine-Protein Kinase
  • Cells, Cultured
  • Cyclin-Dependent Kinase 2 / metabolism
  • DNA / biosynthesis*
  • Mesangial Cells / metabolism*
  • Mitogen-Activated Protein Kinase Kinases / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Platelet-Derived Growth Factor / physiology*
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction
  • src-Family Kinases


  • Platelet-Derived Growth Factor
  • DNA
  • Protein-Tyrosine Kinases
  • CSK Tyrosine-Protein Kinase
  • src-Family Kinases
  • Proto-Oncogene Proteins c-akt
  • Cyclin-Dependent Kinase 2
  • Mitogen-Activated Protein Kinase Kinases