Disruption of fibronectin binding to the α5β1 integrin stimulates the expression of cyclin-dependent kinases and DNA synthesis through activation of extracellular signal-regulated kinase

Jian Gen Gong, Tien C. Ko, Michael G. Brattain

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38 Scopus citations


The α5α1 integrin, a fibronectin receptor, has been implicated in the control of cell growth and the regulation of gene expression. We report that disruption of ligation between α5α1 and fibronectin by integrin α5 subunit or fibronectin monoclonal antibodies stimulated DNA synthesis in growth-arrested FET human colon carcinoma cells. This stimulation only occurred when monoclonal antibody was added in the early G1 phase of the cell cycle after release from quiescence by fresh medium. Stimulation of DNA synthesis by α5 or fibronectin antibody was concentration- and time- dependent. FET cells expressed α4β1 integrin (another fibronectin receptor); however, addition of anti-human integrin α4 monoclonal antibody had no effect on DNA synthesis. Treatment with α5 monoclonal antibody led to a marked increase in the expression of CDK4 in G1 phase of the cell cycle and consequently increased the phosphorylation of retinoblastoma protein. α5 monoclonal antibody treatment increased both cyclin A- and cyclin E- associated kinase activity which was accompanied by increased protein levels of CDK2 and cyclin A. Western blotting of immunoprecipitates demonstrated increased CDK2-cyclin E and CDK2-cyclin A complexes in cells treated with α5 monoclonal antibody. Furthermore, disruption of α5α1/fibronectin ligation activated mitogen-activated protein kinase p44 and p42 (extracellular signal-regulated kinase 1 and 2). Pretreatment of the cells with a specific inhibitor of MEK-1, PD98059, blocked the α5 monoclonal antibody-induced mitogen-activated protein kinase activity. In addition PD98059 prevented α5 monoclonal antibody-induced DNA synthesis. Since α5α1 ligation to fibronectin is associated with decreased growth parameters, our results indicate that ligation of α5α1 integrin to fibronectin results in suppressed mitogen-activated protein kinase activity which in turn inhibits cyclin-dependent kinase activity in growth-arrested cells.

Original languageEnglish (US)
Pages (from-to)1662-1669
Number of pages8
JournalJournal of Biological Chemistry
Issue number3
StatePublished - Jan 16 1998

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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