TGF-beta1-mediated activations of c-Src and Rac1 modulate levels of cyclins and p27(Kip1) CDK inhibitor in hepatoma cells replated on fibronectin

Biochim Biophys Acta. 2005 Mar 22;1743(1-2):151-61. doi: 10.1016/j.bbamcr.2004.09.014.

Abstract

Integrin-mediated cell adhesion transduces signals to regulate actin cytoskeleton and cell proliferation. While understanding how integrin signals cross-talk with the TGF-beta1 pathways, we observed lamellipodia formation and cyclin regulation in Hep3B cells, following TGF-beta1 treatment. To answer if integrin signaling via actin organization might regulate cell cycle progression after TGF-beta1 treatment, we analyzed cross-talk between the two receptor-mediated pathways in hepatoma cells on specific ECMs. We found that basal and TGF-beta1-mediated activation of c-Src and Rac1, expression of cyclins E and A, and suppression of p27Kip1 were significant in cells replated on fibronectin, but not in cells on collagen I, indicating a different integrin-mediated cellular response to TGF-beta1 treatment. Levels of tyrosine phosphorylation and actin-enriched lamellipodia on fibronectin were also more prominent than in cells on collagen I. Studies using pharmacological inhibitors or transient transfections revealed that the preferential TGF-beta1 effects in cells on fibronectin required c-Src family kinase activity. These observations suggest that a specific cross-talk between TGF-beta1 and fibronectin-binding integrin signal pathways leads to the activation of c-Src/Rac1/actin-organization, leading to changes in cell cycle regulator levels in hepatoma cells. Therefore, this study represents another mechanism to regulate cell cycle regulators when integrin signaling is collaborative with TGF-beta1 pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Blotting, Western
  • Bromodeoxyuridine / pharmacology
  • CSK Tyrosine-Protein Kinase
  • Carcinoma, Hepatocellular / metabolism*
  • Cell Adhesion
  • Cell Cycle
  • Cell Cycle Proteins / metabolism*
  • Cell Line
  • Cell Line, Tumor
  • Cell Proliferation
  • Collagen Type I / metabolism
  • Cyclin A / metabolism
  • Cyclin E / metabolism
  • Cyclin-Dependent Kinase Inhibitor p27
  • Cytoskeleton
  • Electrophoresis, Polyacrylamide Gel
  • Fibronectins / metabolism*
  • Flow Cytometry
  • Fluorescent Antibody Technique, Indirect
  • Gene Expression Regulation
  • Humans
  • Integrin alpha2 / metabolism
  • Integrins / metabolism
  • Microscopy, Phase-Contrast
  • Mutation
  • Phosphotransferases / metabolism*
  • Protein Binding
  • Protein-Tyrosine Kinases
  • Proto-Oncogene Proteins / metabolism*
  • Signal Transduction
  • Transfection
  • Transforming Growth Factor beta / metabolism*
  • Transforming Growth Factor beta1
  • Tumor Suppressor Proteins / metabolism*
  • rac1 GTP-Binding Protein / metabolism*
  • src-Family Kinases

Substances

  • Actins
  • Cell Cycle Proteins
  • Collagen Type I
  • Cyclin A
  • Cyclin E
  • Fibronectins
  • Integrin alpha2
  • Integrins
  • Proto-Oncogene Proteins
  • TGFB1 protein, human
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • Tumor Suppressor Proteins
  • Cyclin-Dependent Kinase Inhibitor p27
  • Phosphotransferases
  • Protein-Tyrosine Kinases
  • CSK Tyrosine-Protein Kinase
  • src-Family Kinases
  • CSK protein, human
  • rac1 GTP-Binding Protein
  • Bromodeoxyuridine